Blog archive

Wed

24

Jun

2020

Latest research in football - week 20 -2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 How does mental fatigue affect soccer performance during small-sided games? A cognitive, tactical and physical approach
Reference: J Sports Sci. 2020 May 2:1-11. doi: 10.1080/02640414.2020.1756681. [Epub ahead of print]
Authors: Kunrath CA, Nakamura FY, Roca A, Tessitore A, Teoldo Da Costa I
Summary: We examine how mental fatigue (MF) influences peripheral perception, tactical behaviour, and physical performance of soccer players during a standardized small-sided game. Eighteen male university first-team soccer players participated. A modified Stroop task and the Vienna Test System were employed to induce MF and to evaluate players' peripheral perception, respectively. The FUT-SAT test was used to assess participants' tactical behaviour and physical performance was quantified using GPS technology. MF decreased players' visual field (pre-test = 189.9° and post-test = 181.6°). Additionally, MF constrained players to more frequently perform actions related to the tactical principles of penetration, depth mobility, and defensive unity, and less frequently perform actions of defensive coverage and balance. During MF, players showed decreased accuracy in actions related to the principles of offensive coverage, width and length, offensive unity, delay, balance, concentration, and defensive unity. Finally, under MF players covered higher total distance and at more moderate speed. MF decreased players' peripheral perception, making them prioritize actions towards the opposing goal and protecting their own goal, while displaying more errors for most tactical actions. In summary, MF impaired several aspects of players' cognitive and tactical behaviours, causing a compensatory increase in physical performance.


#2 Return to Play and Career Length After Anterior Cruciate Ligament Reconstruction Among Canadian Professional Football Players
Reference: Am J Sports Med. 2020 May 7:363546520918224. doi: 10.1177/0363546520918224. [Epub ahead of print]
Authors: Longstaffe R, Leiter J, Gurney-Dunlop T, McCormack R, MacDonald P
Summary: For many athletes, a tear of the anterior cruciate ligament (ACL) represents a significant injury that requires a prolonged period away from the sport with substantial rehabilitation. There will be no difference in return to play (RTP) and career length after hamstring tendon (HT) ACL reconstruction in a group of Canadian Football League professional players as compared with what has been already been reported in the literature among professional football players. Data on athletes who sustained an ACL injury were collected by team physicians and head athletic trainers from 2002 to 2017 from 2 Canadian Football League teams. Patient details included age at the time of injury, initial injury date, position, practice versus game injury, and primary versus rerupture with injury-specific data, such as affected limb, concomitant injuries, graft choice, and procedure performed. RTP rates and career length data were collected through publically available internet sources. Comparisons between the non-RTP and RTP groups were made with independent-sample t tests. Binomial logistic regression was performed to determine variables (ie, games preinjury, graft type, meniscal injury, collateral ligament injury) that contributed to players not being able to RTP. A total of 44 ACL reconstructions were performed over the study period (HT, n = 32 [72.7%]; bone-patellar tendon-bone [BPTB], n = 8 [18.2%]; allograft, n = 4 [9.1%]). Overall, 69.8% (n = 30) were able to RTP in at least 1 game, while 30.2% (n = 13) did not return. Mean time to return was 316.1 days (range, 220-427 days), or 10.4 months. For those players who did RTP, mean career length after ACL reconstruction was 2.8 seasons, or 34.4 games. The majority (56.8%) of injuries occurred early in the season. Breakdown by graft type demonstrated RTP rates among HT, BPTB, and allograft of 64.5% (n = 20), 87.5% (n = 7), and 75% (n = 3), respectively. Career length among HT, BPTB, and allograft was 2.9, 2.4, and 3 seasons. Logistic regression analysis found only concomitant medial collateral ligament (MCL) injuries to be a negative predictor for RTP. Meniscal injuries were associated with a decreased RTP rate and career length, but this was not statistically significant. The RTP rates after ACL reconstruction in this study are similar to those reported in National Football League players. A concomitant injury to the MCL injury was a negative predictor of RTP. Meniscal injuries demonstrated a trend for decreased RTP rate and career length, but this was not a significant predictor. A large portion of injuries occur early in the season, and further study should be done to examine potential preventative strategies to reduce ACL injuries.


#3 Comparing Psychopathological Symptoms in Portuguese Football Fans and Non-Fans
Reference: Behav Sci (Basel). 2020 May 1;10(5). pii: E85. doi: 10.3390/bs10050085.
Authors: Leite Â, Ramires A, Costa R, Castro F, Sousa HFPE, Vidal DG, Dinis MAP
Download link: https://www.mdpi.com/2076-328X/10/5/85/pdf
Summary: The present study aims to characterize football fans and non-fans and to compare their psychopathological symptoms with the latest normative values for the Portuguese population from Canavarro in 2007. Results showed that football fans and non-fans are mostly male, have an affective relationship, are childless, have secondary education or a high degree, and are employed or students; fans are more likely to be male, dating, unemployed, to have elementary education and be younger than non-fans. Football fans present significantly higher psychopathological symptoms than non-fans in somatization, interpersonal sensitivity, anxiety, hostility, paranoid ideation and psychoticism and all psychopathological indexes. Football fans present values very close to those of populations with emotional distress in hostility and are above the mean of the general population in obsession-compulsion, hostility, paranoid ideation and psychoticism.


#4 Barriers and Enablers to Implementing Mental Well-being Programs Through Australian Rural Football Clubs - A Qualitative Descriptive Study
Reference: Health Promot J Austr. 2020 May 3. doi: 10.1002/hpja.358. [Epub ahead of print]
Authors: Hutchesson H, Dollman J, Baker A, Kernot J
Summary: Suicide rates in rural Australia are almost twice as high as those in urban areas. In rural communities, football clubs are often the 'hub' of the community and are being explored as an avenue to deliver mental health and wellbeing promotion. The aim of this study was to explore barriers and enablers for programs promoting mental health and wellbeing through rural Australian football clubs. This qualitative descriptive study included 12 individuals of 10 rural clubs affiliated with the South Australian National Football League. Recruitment occurred via emails to club secretaries/presidents. Semi-structured telephone interviews explored mental health and wellbeing issues experienced in clubs, previous involvement with mental wellbeing programs, and potential barriers/enablers for future programs. Interviews were transcribed verbatim and analysed thematically. Thematic analysis identified three themes encompassing barriers and enablers: (1) more than a football club, (2) attitudes towards mental health, and (3) what is needed to implement a program. The third theme had subthemes of resources, importance of timing, mental health initiatives and components of a program. Key barriers included difficulty getting people involved due to individual attitudes towards mental health, and not having the finances/resources to implement a program. Major enablers included the important role the football club serves in the community, the inclusion of speakers with credibility, and making the program engaging. SO WHAT?: This study identifies key factors which may impact on community engagement and program effectiveness for mental health and wellbeing programs delivered via rural football clubs.


#5 Heart rate variability and pre-competitive anxiety according to the demanding level of the match in female soccer athletes
Reference: Physiol Behav. 2020 May 11:112926. doi: 10.1016/j.physbeh.2020.112926. [Epub ahead of print]
Authors: Ayuso-Moreno RM, Fuentes-García JP, Collado-Mateo D, Villafaina S
Summary: The present study aimed to evaluate the effects of a highly-demanding match and a lowly-demanding match on pre-competitive heart rate variability (HRV) and anxiety in semi-professional female soccer athletes. A total of 14 players, with a mean age of 23.78 (4.93), from the Cáceres Women Football Club of the Spanish Second National Division participated in our study. They were evaluated in two microcycles which correspond to a highly- and a lowly-demanding matches. For each microcycle a baseline and a pre-competitive measures were collected. Results indicated that HRV was significantly reduced before a highly demanding match whereas a lowly-demanding match did not lead to any change. Significant differences in HRV and cognitive anxiety were observed when compared the highly and the lowly demanding matches, which means an increase in the anxiety levels before the highly-demanding match. HRV could be an indicator of precompetitive anxiety in semi-professional female soccer players. This could be used by coaches or physical trainers as a tool to examine the precompetitive anxiety in athletes.


#6 The Increased Effectiveness of Resistance Training on Unstable vs. Stable Surfaces on Selected Measures of Physical Performance in Young Male Soccer Players
Reference: J Strength Cond Res. 2020 May 13. doi: 10.1519/JSC.0000000000003590. [Epub ahead of print]
Authors: Sanchez-Sanchez J, Raya-González J, Ramirez-Campillo R, Chaabene H, Petisco C, Nakamura FY
Summary: The purpose was to examine the effects of 10-week (2/wk) resistance training on stable vs. unstable surfaces on selected measures of physical performance in young male soccer players, national-level U19 players participated in this study. They were randomly allocated to an unstable resistance training group (uRT, n = 27) or a stable resistance training group (sRT, n = 28). Before and after the training, horizontal jumping with dominant (Hop D) and nondominant leg (Hop non-D), repeated sprint ability (RSA best time [RSAbest] and RSA mean time [RSAmean]), change-of-direction (COD) speed (Illinois COD test), and aerobic endurance (YoYo Intermittent Recovery Test Level 1 [YoYo IR1]) were assessed. To establish the effects of the interventions on the dependent variables, a 2 (group: uRT and sRT) × 2 (time: pre, post) analysis of variance with repeated measures on time was computed. A significant main effect of time was observed for Hop non-D, RSAbest, and RSAmean (p = 0.003-0.06, effect size [ES] = 0.06-0.15). Furthermore, significant group × time interactions were shown for RSAbest (p = 0.007, ES = 0.13) and RSAmean (p = 0.002, ES = 0.2). Post hoc analysis revealed significant pre- to post-training improvements for RSAbest (p = 0.002, ES = 0.35) and RSAmean (p = 0.0002, ES = 0.36) in the uRT. In the sRT, however, no significant pre-post performance changes were observed in RSAbest and RSAmean. In conclusion, 10 weeks of an in-season resistance training on unstable conditions in addition to regular soccer training was effective in improving repeated-sprint ability performance in youth male elite soccer players including maximal linear sprinting and the ability to perform repeated sprint.


#7 How and why do young soccer players change the Flow State?
Reference: PLoS One. 2020 May 14;15(5):e0233002. doi: 10.1371/journal.pone.0233002. eCollection 2020.
Authors: Castillo-Rodríguez A, Lopera CU, Onetti-Onetti W, Chinchilla-Minguet JL
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0233002&type=printable
Summary: Flow State (FS) as well as other psychological characteristics influence sports performance (SP) and could be relevant according to the playing position in team sports, such as the soccer where players have different specific functions within the team. The aim of this study was to evaluate the difference in FS dimensions in young soccer players between training time (TR) and official competition time (CM), according to the playing position and, to find relationships between FS dimensions and physical characteristics and academic performance. A total of 141 U16 soccer players were selected (14.7 ± 0.5 years). Data was collected for academic performance, physical and socio-demographic characteristics, and on two occasions, the dimensions of FS (before of a TR and CM). The results showed that the FS dimensions are higher before of the TR than before of the CM (p < 0.05) in all playing positions. In clear goals dimension, forwards showed lower scores than other playing positions, and various dimensions had a positive relationship with academic performance. In conclusion, the FS presented in CM is lower in U16 soccer players compared to that presented in TR. This work has contributed to increasing the knowledge of the fluctuation of the FS that negatively influence the soccer player in pre-competition states and the influence of various factors on this construct.
 

#8 Does the FIFA 11+ Program Prevent Hamstring Injuries in College-Aged Male Soccer Players? A Critically Appraised Topic
Reference: J Sport Rehabil. 2020 May 13:1-3. doi: 10.1123/jsr.2019-0390. [Epub ahead of print]
Authors: Street SB, Kaminski T.
Summary: Hamstring injuries are the most prevalent lower-extremity injury among soccer players. The Fédération Internationale de Football Association (FIFA) has addressed this issue by developing the FIFA 11+ program, which is focused on improving strength and decreasing the incidence of lower-extremity injuries in the sport. This critically appraised topic focuses on this program as well as one of its components, the Nordic hamstring exercise, in the prevention of hamstring injuries. Clinical Question: Does the FIFA 11+ program prevent hamstring injuries in college-aged male soccer players? Summary of Key Findings: Four studies were selected to be critically appraised. The PEDro checklist was used to score the articles on methodology and consistency. All 4 articles demonstrated support for the clinical question. Clinical Bottom Line: There is moderate evidence to support the use of the FIFA 11+ program and Nordic hamstring exercise as part of a college soccer team's warm-up routine. Strength of Recommendation: Grade B evidence exists in support of incorporating the FIFA 11+ program to reduce the incidence of hamstring injuries in male college soccer players.


#9 HIV knowledge, risky behaviours and public health care services attendance among adolescents from the Grassroot soccer Zimbabwe programme
Reference: BMC Health Serv Res. 2020 May 13;20(1):420. doi: 10.1186/s12913-020-05305-3.
Authors: Mzingwane ML, Mavondo GA, Mantula F, Mapfumo C, Gwatiringa C, Moyo B, Dube P, Chaibva CN
Download link: https://bmchealthservres.biomedcentral.com/track/pdf/10.1186/s12913-020-05305-3
Summary: Interventions aimed at improving accessing of health care services, including HIV testing, remain a priority in global HIV eradication efforts. Grassroot Soccer Zimbabwe (GRSZ) is an adolescent health organisation that uses the popularity of soccer to promote healthy behaviours. We assessed HIV knowledge levels, risky behaviours and attitudes in school going adolescents and young adults who attended GRSZ programmes and determined if HIV knowledge levels were associated with increased levels of accessing of health care services by youths. This was a cross-sectional study carried out on 450 participants aged 13-30 years who attended at least one of the three programmes offered by GRSZ. Self-administered and self-reporting questionnaires were used to collect information on participants' demographics, knowledge on HIV and reproductive health, sources of information, access to HIV and reproductive health services and attitudes and risky behaviours. A total of 392 (87.1%) responses were received. High HIV and reproductive health knowledge levels were recorded (77.7%) on our scale with females recording higher levels (81.1%) than males (71.1%). The majority of participants (72%) indicated willingness to abstain from risky behaviours such as use of drugs and attending youth sex parties. However about 33.3% of the participants who had sexual intercourse reported having condomless sex. There was marginal association between high HIV and reproductive health knowledge levels and accessing health care services in the past 24 months (p = 0.045). HIV and reproductive health knowledge levels were relatively high among adolescents and were associated with accessing health care services in the past 24 months. There however are some gaps associated with engaging in risky sexual behaviours such as condomless sex which could be addressed by using these findings to assist organizations working with adolescents, educators and policy makers in developing programmes that address adolescent sexual behaviours.


#10 Effects of Age and Maturation on Lower Extremity Range of Motion in Male Youth Soccer Players
Reference: J Strength Cond Res. 2020 May 8. doi: 10.1519/JSC.0000000000003642. [Epub ahead of print]
Authors: Robles-Palazón FJ, Ayala F, Cejudo A, De Ste Croix M, Sainz de Baranda P, Santonja F
Summary: Restricted joint range of motion (ROM) has been considered as a primary risk factor for some sport-related injuries. Consequently, preparticipation assessment of lower extremity joints ROM could help identify youth soccer players at high risk of injury and to aid in the design of tailored age and maturational specific training interventions. The purpose of this study was to analyze and compare the influence of chronological age and maturational stage on several lower extremity ROM measures, as well as to describe the lower extremity ROM profile using a comprehensive approach in youth soccer players. A total of 286 male youth soccer players' ROM were assessed including passive hip (extension [PHE], adduction with hip flexed 90° [PHADHF90°], flexion with knee flexed [PHFKF] and extended [PHFKE], abduction with hip neutral [PHABD] and flexed 90° [PHABDHF90°], external [PHER] and internal [PHIR] rotation), knee (flexion [PKF]) and ankle (dorsiflexion with knee flexed [ADFKF] and extended [ADFKE]) ROMs. Between-group differences were analyzed using a one-way analysis of variance (ANOVA) and magnitude-based decisions. The results only report statistically significant (p < 0.05; d > 0.5) and clinically relevant differences (>8°) for the PKF ROM between U12 vs. U19, and Pre-PHV vs. Post-PHV groups. Furthermore, approximately 40, 35, and 20% of players displayed restrictions in their PHFKE, PKF, and ADFKF ROM values, respectively. These findings emphasize the necessity of prescribing (across all age groups and periods of growth and maturation) compensatory measures in daily soccer training, and these exercises should be equally applied to both limbs with the aim of improving PHFKE, PKF and ADFKF ROM values.


#11 Bio-banding in junior soccer players: a pilot study
Reference: BMC Res Notes. 2020 May 12;13(1):240. doi: 10.1186/s13104-020-05083-5.
Authors: Romann M, Lüdin D, Born DP
Download link: https://bmcresnotes.biomedcentral.com/track/pdf/10.1186/s13104-020-05083-5
Summary: Bio-banding (BB) has been introduced to account for varying maturity and to improve the talent development of junior soccer players. To date, research that investigated the physiological and technical effects of BB is sparse. Therefore, the aim of the study was to compare effects of BB with CA on selected technical and tactical parameters in U13 and U14 soccer players. BB significantly increased the number of duels (p = 0.024) and set pieces (p = 0.025) compared to chronological age. The mean time of ball possession per action was reduced (p = 0.021) and the rate of successful passes was lower with BB (p = 0.001). Meanwhile, the total number of passes was unaffected (p = 0.796), and there was a trend towards a lower difference in ball possession between BB teams (p = 0.058). In addition, BB reduced the distances covered while jogging (p = 0.001), running (p = 0.038) and high-speed running (p = 0.035). With BB, an increased number of duels, unsuccessful passes and set pieces resulted in a quicker change of match play situations between teams. While physical demand was reduced, BB seems to result in a more technically and tactically challenging game. Benefits in long-term player development, however, require further investigation.

Thu

18

Jun

2020

Are “classical” tests of repeated-sprint ability in football externally valid

A new approach to determine in-game sprinting patterns

Wed

17

Jun

2020

Mesocycle load of European footballers

Also with regards to positional differences.

Mon

15

Jun

2020

Latest research in football - week 19 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The UEFA Heading Study: Heading incidence in children's and youth' football (soccer) in eight European countries
Reference: Scand J Med Sci Sports. 2020 Apr 26. doi: 10.1111/sms.13694. [Epub ahead of print]
Authors: Beaudouin F, Gioftsidou A, Larsen MN, Lemmink K, Drust B, Modena R, Espinola JR, Meiu M, Vouillamoz M, Meyer T
Summary: To assess the real-life magnitude of the heading incidence in children's and youth' football in eight European countries with different "football cultures" a cross-sectional observational design, in which one match per team in 480 different teams from eight European countries (2017/18-2018/19) was recorded by video. One training session was recorded in 312 teams. Clubs with Under-10, Under-12 (female/male/mixed) and Under-16 female and male teams were eligible to participate. Heading frequencies and types were analysed. Results are presented as headers per match/training and per team. Incidence rates (IR) per 1000 match/training hours were calculated. Under-10 teams carried out the lowest average number of headers per match (8.8), followed by Under-16 female (17.7), Under-12 (18.4), and Under-16 male (35.5). Total number of headers per match and team varied between countries. 80% of the total number of headers were single intentional headers, 12% heading duels, 3% unintentional headers by getting hit and 5% others (trends apparent in all age groups). Three head injuries occurred during match play corresponding to an IR of 0.70 (95% CI, 0.23-2.16). The lowest number of headers per training and team was found in Under-10 (21.3), followed by Under-16 females (34.1), Under-12 (35.8), and Under-16 males (45.0). In conclusion, this large-scale study presents novel data about the number and type of headers in youth' football throughout Europe. A more precise understanding of the heading incidence, specifically in young players, is mandatory for the debate of restrictions on heading in youth football


#2 Conservative treatment of Osgood-Schlatter disease among young professional soccer players
Reference: Int Orthop. 2020 Apr 28. doi: 10.1007/s00264-020-04572-3. [Epub ahead of print]
Authors: Bezuglov EN, Tikhonova АА, Chubarovskiy PV, Repetyuk АD, Khaitin VY, Lazarev AM, Usmanova EM
Summary: The present-day conservative treatment algorithms of Osgood-Shlatter Disease (OSD) are often inadequate for young athletes because they require extremity immobilization and avoidance of sports, and hence the longer duration of rehabilitation. Therefore, the development of safe and efficacious treatment protocols for young athletes is of great practical importance. The aim of the study was to assess the efficacy and safety of the conservative treatment of Osgood-Schlatter disease in young professional soccer players. Medical records of young soccer players from two different Russian soccer-academies from the period January 2016-July 2019 were analyzed in a retrospective cohort study. Trauma records of young soccer players aged 11-15 years were included in the analysis. Statistical analysis was performed using IBM SPSS Statistics software, 23.0. Descriptive statistics tools were applied for the analysis. A total of 280 soccer players were included in the study. The aged ranged between 11 and 15 years. Ten percent of players (n = 28, mean age 12.9 ± 1.3) were diagnosed with OSD during the observation period. The mean OSD treatment duration was 27.3 ± 13.9 days. Bilateral symptoms were observed in 42.9% of cases, and unilateral symptoms in 57.1%. In 53.6% of players, the first manifestation of OSD symptoms was observed during wintertime. All players were training on artificial turf playing fields. Conservative treatment without immobilization was applied to all patients. It included kinesiotherapy for quadriceps muscle lengthening and physiotherapy as well as gradual increase of physical activity. A total of 35.7% of players reported having discomfort upon resuming regular training, which caused some restrictions in exercise. However, the symptoms resolved spontaneously with time. Surgical treatment or complete avoidance of exercise was not used in any of the patients. High incidence of OSD was revealed among young soccer players of the leading Russian soccer academies. The OSD most commonly occurred during wintertime. Conservative treatment of OSD-i.e., physiotherapy and kinesiotherapy-enabled disease-free resuming of sports activity for the majority of patients.


#3 Comparison of the Physical Demands of Friendly Matches and Different Types On-Field Integrated Training Sessions in Professional Soccer Players
Reference: Int J Environ Res Public Health. 2020 Apr 22;17(8). pii: E2904. doi: 10.3390/ijerph17082904.
Authors: Giménez JV, Castellano J, Lipinska P, Zasada M, Gómez MÁ
Download link: https://www.mdpi.com/1660-4601/17/8/2904/pdf
Summary: The aim of this study was to investigate the relationships among physical demands of two friendly matches (FMs) and three task training sessions (TS1,2,3) combining in a different way: a Small-Sided Game (SSG), Mini-Goals (MG), a ball Circuit Training (CT) and a Large-Sided Game (LSG): SSG+MG+LSG (TS1), SSG+CT+LSG (TS2) and MG+CT+LSG (TS3). The TS and match demands in running intensities were monitored in fourteen professional soccer players (age = 23.2 ± 2.7 years, height = 178 ± 6 cm, body mass = 73.2 ± 6.9 kg, mean and SD, respectively) using 10-Hz global positioning system devices, and players' perception of exertion was recorded after each session or match using a visual analogue scale. A one-way repeated measures ANOVA with a Bonferroni correction coupled with magnitude-based inferences were used. A principal component (PC) analysis was conducted on all variables to account for covariance. Three PCs were retained, explaining 76% of the variance: Component 1 explained 46.9% with the associated variables: Total Distance (TD) and distance covered in ranges of speed from >2.2 to <5 m/s, Player Load and Work Rest Ratio; component 2 explained 19.7% and was composed of TD at > 5 m/s and maximal running speed (MRS); and component 3 explained 9.5% and was represented by TD < 2.2 m/s, decelerations and accelerations. The ANOVA results showed significant differences (p < 0.05) among TS vs. FM in TD3, TD4, TD5, and TD > 5, TD, deceleration rate, acceleration rate, maximal running speed, exertion index, work rest ratio, and self-reported exertion. Therefore, the training routines did not replicate the main set of high intensity efforts experienced in competitive conditions. Additionally, PC analysis could be applied in order to select the most representative training and competitive conditions.


#4 Phases of match-play in professional Australian Football: Distribution of physical and technical performance
Reference:  J Sports Sci. 2020 Apr 28:1-8. doi: 10.1080/02640414.2020.1754726. [Epub ahead of print]
Authors: Rennie MJ, Kelly SJ, Bush S, Spurrs RW, Austin DJ, Watsford ML
Summary: The current study aimed to describe the distribution of physical and technical performance during the different phases of play in professional Australian Football. The phases of play (offence, defence, contested play, umpire stoppages, set shots and goal resets) were manually coded from video footage for a single team competing in 18 matches in the Australian Football League. Measures of physical performance including total distance (m), average speed (m · min-1), low-speed running (LSR, <14.4 km h-1), high-speed running (HSR, >14.4 km h-1), accelerations (2.78 m · s-2) and decelerations (-2.78 m · s-2) were derived from each phase of play via global positioning system (GPS) devices. Technical skill data including tackles, handballs and kicks were obtained from a commercial statistics provider and derived from each phase of play. Linear mixed-effects models and effect sizes were used to assess and reflect the differences in physical and technical performance between the six phases of play. Activity and recovery cycles, defined as periods where the ball was in or out of play were also described using mean and 95% confidence intervals. The analysis showed that several similarities existed between offence and defence for physical performance metrics. Contested play involved the highest total distance, LSR, accelerations, decelerations and tackles compared to all other phases. Offence and defence involved the highest average speed and HSR running distances. Handballs and kicks were highest during offence, while tackles were highest during contested play, followed by defence. Activity and recovery cycles involved mean durations of ~110 and ~39 s and average speeds of ~160 and ~84 m · min-1, respectively. The integration of video, GPS and technical skill data can be used to investigate specific phases of Australian Football match-play and subsequently guide match analysis and training design.


#5 Anterior cruciate ligament injuries in Australian football: should women and girls be playing? You're asking the wrong question
Reference: BMJ Open Sport Exerc Med. 2020 Apr 9;6(1):e000778. doi: 10.1136/bmjsem-2020-000778. eCollection 2020.
Authors: Fox A, Bonacci J, Hoffmann S, Nimphius S, Saunders N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173994/pdf/bmjsem-2020-000778.pdf
Summary: Anterior cruciate ligament (ACL) injuries have been a rising concern in the early years of the women's Australian Football League (AFLW), eliciting headlines of a 'knee crisis' surrounding the league. There has been a focus on female biology as the primary factor driving the high rate of ACL injuries in the AFLW. Emphasising Australian football (AF) as being dangerous predominantly due to female biology may be misrepresenting a root cause of the ACL injury problem, perpetuating gender stereotypes that can restrict physical development and participation of women and girls in the sport. We propose that an approach addressing environmental and sociocultural factors, along with biological determinants, is required to truly challenge the ACL injury problem in the AFLW. Sports science and medicine must therefore strive to understand the whole system of women in AF, and question how to address inequities for the benefit of the athletes.


#6 English Football Players are not as Bad at Kicking Penalties as Commonly Assumed
Reference: Sci Rep. 2020 Apr 27;10(1):7027. doi: 10.1038/s41598-020-63889-6.
Authors: Brinkschulte M, Furley P, Memmert D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184592/pdf/41598_2020_Article_63889.pdf
Summary: The previous performance of the English men's national football team in penalty shootouts has led to the widespread stereotype that English football players are particularly bad at scoring penalties. Research has proposed possible reasons behind this alleged "penalty curse". When looking at these reasons, the question arises if English football players per se have trouble scoring penalty kicks. Therefore, we analyzed the performance of a large sample of penalty takers during all World- and European Championships (N = 696) and, additionally, in some of the highest European leagues over a ten-year period (N = 4,708). The results reveal no significant differences between the success rates (on average between 71-79%, depending on the type of penalty kick and on the type of competition) of penalty takers from different nations. Therefore, we conclude that English players perform as well as players from other nations and that poor performance in penalties lay beyond the factor nationality.


#7 Changes in Knee Extension and Flexion Maximal and Rapid Torque Characteristics During a Collegiate Women's Soccer Season
Reference: J Strength Cond Res. 2020 May 5. doi: 10.1519/JSC.0000000000003607. [Epub ahead of print]
Authors: Akehi K, Palmer TB, Conchola EC, Thompson BJ, Kasl A, Bice M, Unruh S
Summary: The purpose of this study was to assess the changes in maximal and rapid torque capacities of the knee extensor and flexor muscles over the course of a competitive season in NCAA Division II women's soccer players. Eighteen female soccer athletes performed 2 maximal voluntary isometric contractions (MVICs) of the knee extensor and flexor muscles before, during, and at the end of the competitive season. Peak torque (PT) and rate of torque development (RTD) at 50 (RTD50), 200 (RTD200), and 100-200 (RTD100-200) milliseconds were extracted from each MVIC for both legs. The rapid (RTD50) to maximal force ratio (RTD:PT), hamstring-to-quadriceps (H:Q) strength ratio, and bilateral strength differences were also calculated. Results indicated that PT, RTD50, and RTD200 decreased 11-21% from the preseason to the midseason for the knee extensors (p < 0.02) and RTD50 increased approximately 11% from the midseason to the end of season for the knee flexors (p < 0.01). Rate of torque development-to-PT ratios for the knee extensors and flexors increased 12-25% at the end of the season (p < 0.05). Also, H:Q strength ratios using PT, RTD50, and RTD200 increased 12.5-24% after the season started (p = 0.001-0.04). There were no bilateral strength differences (dominant vs. non-dominant limbs) across the season (p > 0.05). These findings suggest that participation in a soccer season can change maximal and rapid torque production of the knee extensors and flexors. Coaches and clinicians should consider incorporating a season-long strength training and maintenance plan for soccer players with the aim to improve athletic performance and minimize the risk of musculoskeletal injuries to the lower extremities.


#8 A survey of talent identification and development processes in the youth academies of professional soccer clubs from around the world
Reference: J Sports Sci. 2020 May 7:1-10. doi: 10.1080/02640414.2020.1752440. [Epub ahead of print]
Authors: Ford PR, Bordonau JLD, Bonanno D, Tavares J, Groenendijk C, Fink C, Gualtieri D, Gregson W, Varley MC, Weston M, Lolli L, Platt D, Di Salvo V
Summary: Talent identification (TID) and development (TDE) are large fields in professional soccer and in science. However,  TID and TDE processes in youth academies have not been assessed in detail. As such, our aim was to survey professional clubs from around the world about their youth academy TID and TDE processes, with 29 clubs responding to the survey. TID and TDE processes changed as a function of player age. TID processes involved finding the best players locally and regionally, but for older players the search widened to nationally and internationally for the needs of the first team. Clubs used a multidisciplinary approach to TID, but more so with older players. Median number of academy players was 80, 100, and 66 players at 8-11 years, 12-16 years, and 17-21 years, respectively. Annual player turnover in the most recent season (selections/de-selections) was 29% across all age groups, with competition from other clubs cited as a limitation to TID. TDE processes involved weekly matches and 3-5 training sessions per week led by experienced, well-qualified coaches, with most clubs providing players with academic education, residency and transportation services. Our findings extend previous research assessing professional soccer youth academy TID and TDE processes by quantifying worldwide practices.


#9 Influence of Sunlight and Oral D3 Supplementation on Serum 25(OH)D Concentration and Exercise Performance in Elite Soccer Players
Reference: Nutrients. 2020 May 4;12(5). pii: E1311. doi: 10.3390/nu12051311.
Authors: Michalczyk MM, Gołaś A, Maszczyk A, Kaczka P, Zając A
Download link: https://www.mdpi.com/2072-6643/12/5/1311/pdf
Summary: The aim of this study was to evaluate the influence of natural sun exposure and six weeks of a high dose of vitamin D supplementation on vitamin D, testosterone and cortisol serum concentrations as well as speed, power and VO2max in professional soccer players. The study was conducted from January to September. At the beginning of the study, 33 professional soccer players were enrolled; however, only 28 subjects (height 181.5 cm; body mass 77.81 ± 8.8 kg; body fat 12.38% ± 2.4% and muscle mass 40.27 ± 5.3 kg) completed the study. The research consisted of three stages. The first one, lasting 10 days, was conducted in January during a training camp in the south part of Cyprus at a latitude of 34 33°, where participants experienced natural sun exposure; it was called a winter sun exposure (WSE) period. The second stage, which was a supplementation period (SP), lasted 6 weeks, during which all subjects were randomly assigned either to an experimental group-EG (n = 15)-or a placebo group-PG (n = 13)-and were administered 6000 IU/d cholecalciferol or a placebo, respectively. The third stage took place in September, after summertime (summer sun exposure-SSE). The data of the 25(OH)D, free and total testosterone (fT, tT), cortisol as well as 5 and 30 m sprint tests (STs), power of the left leg (PLL) and VO2max were evaluated before and after the WSE period, the SP and SSE. In January, the baseline value of vitamin D in 12 subjects was ≤20 ng/mL, and 14 of them had levels between 20-30 ng/mL and 2 individuals >30 ng/mL. After the WSE period, significant changes in 25(OH)D, fT, tT and cortisol concentration, as well as in the 5 m ST, were observed. After the SP, in the EG, significant changes were found in 25(OH)D, fT, tT and the 5 m ST. Furthermore, a positive correlation between the concentration of 25(OH) fT and tT was observed. After SSE, 2 out of 28 players had <20 ng/mL 25(OH)D, 12 of them had 25(OH)D between 20 and 30 ng/mL and 14 of them had 25(OH)D between 30 and 50 ng/mL. Significant differences in 25(OH)D, fT, tT concentration and the 5 m ST performance were observed following SSE compared with the WSE period. Due to the serum level of 25(OH)D demonstrated by most participants at the beginning of the study and after summertime, all-year-round supplementation with high doses of vitamin D seems to be a reasonable solution to enhance high 25(OH)D concentration in blood and physical performance. In the middle of the winter, almost half of the soccer players were serum deficient of 25(OH)D. After ten days of sun exposure and 6 weeks of vitamin D supplementation, the concentration of 25(OH)D significantly increased, as did testosterone and results in the 5 m sprint test also improved. Therefore, athletes should be constantly monitored for serum levels of 25(OH)D throughout the year and should be supplemented if deficiencies or insufficient amounts of this vitamin occur.


#10 Does Low-Level Laser Therapy Decrease Muscle-Damaging Mediators After Performance in Soccer Athletes Versus Sham Laser Treatment? A Critically Appraised Topic
Reference: J Sport Rehabil. 2020 May 5:1-4. doi: 10.1123/jsr.2019-0421. [Epub ahead of print]
Authors: Bettleyon J, Kaminski TW.
Summary: Clinical Scenario: Low-level laser therapy (LLLT) is a controversial topic for its use in athletic recovery, mainly due to inconsistency in research regarding the application of LLLT. Articles on LLLT have assessed its effectiveness in untrained humans through pain scales, functional scales, and blood draws, and it has been found capable in nonathletic rehabilitative use. The controversy lies with LLLT in the recovering athlete. Not only do athletes need to perform at high levels, but each sport is unique in the metabolic demands placed on the athletes' bodies. This modality can alter chemical mediators of the inflammatory process, specifically blood lactate (BL) and creatine kinase (CK). During soccer contests, it is a common problem for athletes to have an average CK level of 800 U/L and BL of 8 mmol·L, increasing delayed-onset muscle soreness and fatigue. Micro-CK level elevation is associated with cellular membrane damage, localized hypoxia, and electrolyte imbalances, hindering the recovery process. Clinical Question: Does LLLT decrease muscle-damaging mediators effecting player fatigue and delayed-onset muscle soreness after performance in soccer athletes versus sham treatment? Summary of Key Findings: In 3 studies, preperformance, postperformance, or preperformance and postperformance LLLT was performed and evaluated BL (2 of 3) and CK (2 of 3). In each article, BL and CK showed a significant decrease (P < .05) when performed either preperformance or postperformance versus the control group. The greatest decrease in these mediators was noticed when postperformance laser therapy was performed. Clinical Bottom Line: LLLT at 10, 30, or 50 J performed at a minimum of 2 locations on the rectus femoris, vastus lateralis, and vastus medialis bilaterally for 10 seconds each is significant in decreasing blood serum levels of BL and CK when performed postexercise. Strength of Recommendations: All 3 articles obtained a Physiotherapy Evidence Database score of ≥8/10.


#11 Modifying the pre-pitch entry practices of professional soccer substitutes may contribute towards improved movement-related performance indicators on match-day: A case study
Reference: PLoS One. 2020 May 5;15(5):e0232611. doi: 10.1371/journal.pone.0232611. eCollection 2020.
Authors: Hills SP, Barrett S, Hobbs M, Barwood MJ, Radcliffe JN, Cooke CB, Russell M
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0232611&type=printable
Summary: Modifying a soccer substitute's pre-pitch-entry activities may represent an opportunity to maximise physical performance and minimise injury-risk following match-introduction. Using a professional team that has previously participated in substitute profiling research, this follow-up case study investigated the effects of a modified match-day protocol that included substitutes; 1) performing a new pre-match warm-up alongside members of the starting team (as opposed to a separate substitute-only warm-up), 2) participating in a staff-led half-time rewarm-up (as opposed to player-led half-time activities), and 3) receiving ongoing education focusing on the efficacy of (re)warm-up activities. English Championship substitutes (n = 15) were monitored using Micro-electromechanical Systems during 13 matches incorporating the modified practices (35 observations). On an individual player basis, data were organised into bouts of warm-up activity (pre-pitch-entry) and five min epochs of match-play (post-pitch-entry). Linear mixed modelling assessed the influence of 'bout' and 'epoch', position, and scoreline. Substitutes performed 3±1 rewarm-up bouts∙player-1∙match-1 between kick-off and pitch-entry, which were shorter (-17.2 to -27.1 min) and elicited less distance (-696 to -1257 m) than the pre-match warm-up (p≤0.001). Compared with previous data, heightened absolute movement responses were observed during the pre-match and staff-led half-time (re)warm-ups, alongside greater relative distances covered during player-led activities performed between kick-off and pitch-entry. Whilst less distance (-10%) was covered during the second versus first five min period following match-introduction, values remained higher than previously reported. Between pitch-entry and the end of the match, the scoreline improved and worsened following 26% and 11% of substitutions, respectively; a favourable record compared with existing observations. Acknowledging the likely contribution from external factors, this case study reports heightened movement profiles and improved match scorelines when pre-pitch-entry practices were modified. Practitioners should note the potential influence of match-day activities on the physical responses of soccer substitutes and, if deemed necessary, consider adapting their pre-pitch-entry routines accordingly.


#12 Age of First Exposure to Soccer Heading and Sensory Reweighting for Upright Stance
Reference: Int J Sports Med. 2020 May 4. doi: 10.1055/a-1141-3553. [Epub ahead of print]
Authors: Caccese JB, Santos FV, Yamaguchi F, Jeka JJ
Summary: US Soccer eliminated soccer heading for youth players ages 10 years and younger and limited soccer heading for children ages 11-13 years. Limited empirical evidence associates soccer heading during early adolescence with medium-to-long-term behavioral deficits. The purpose of this study was to compare sensory reweighting for upright stance between college-aged soccer players who began soccer heading ages 10 years and younger (AFE ≤ 10) and those who began soccer heading after age 10 (AFE > 10). Thirty soccer players self-reported age of first exposure (AFE) to soccer heading. Sensory reweighting was compared between AFE ≤ 10 and AFE > 10. To evaluate sensory reweighting, we simultaneously perturbed upright stance with visual, vestibular, and proprioceptive stimulation. The visual stimulus was presented at two different amplitudes to measure the change in gain to vision, an intra-modal effect; and change in gain to galvanic vestibular stimulus (GVS) and vibration, both inter-modal effects. There were no differences in gain to vision (p=0.857, η2=0.001), GVS (p=0.971, η2=0.000), or vibration (p=0.974, η2=0.000) between groups. There were no differences in sensory reweighting for upright stance between AFE ≤ 10 and AFE > 10, suggesting that soccer heading during early adolescence is not associated with balance deficits in college-aged soccer players, notwithstanding potential deficits in other markers of neurological function.

Fri

12

Jun

2020

Effect of opposition quality and match location on positional demands of a 4-2-3-1 in football

Are there positional differences playing a 4-2-3-1 with strong vs. weak oppositions?

Wed

10

Jun

2020

Postional differences in RSA in footballers

And their relation with other performance tests.

Tue

09

Jun

2020

Latest research in football - week 18 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Soccer-Specific Agility: Reliability of a Newly Developed Test and Correlates of Performance
Reference: J Strength Cond Res. 2020 Apr 21. doi: 10.1519/JSC.0000000000003635. [Epub ahead of print]
Authors: Altmann S, Neumann R, Ringhof S, Rumpf MC, Woll A
Summary: The purpose of this study was to examine the reliability of a newly developed soccer-specific agility test and to determine the correlation of different performance parameters with overall agility performance as measured by the total time. Twenty-two amateur soccer players (age, 25.1 ± 4.0 years) completed a newly developed agility test on 2 separate occasions. The test required the players to conduct 2 changes of direction, one in a preplanned manner and one in response to a stimulus that was provided by a live tester who performed different soccer-specific passing movements. Regarding reliability, very large Pearson's r and intraclass correlation coefficient values were obtained for the total time and the movement time, with moderate and large-to-very large values being evident for the response time and the decision-making time, respectively. The usefulness to detect moderate performance changes was rated as "good" for the total time, the response time, and the movement time. The decision-making time was rated as "OK." The movement time showed a very large relationship with overall agility performance as measured by the total time, while the response time and the decision-making time showed small to moderate relationships. In conclusion, the newly developed soccer-specific agility test is a reliable tool to assess the agility performance of soccer players and can be used by coaches and researchers to detect moderate performance changes. Because physical aspects, represented by the movement time, showed the greatest influence on total agility performance, they are advised to be included in soccer-specific agility training programs of amateur players.


#2 Seasonal Changes in the Sprint Acceleration Force-Velocity Profile of Elite Male Soccer Players
Reference: J Strength Cond Res. 2020 Feb 14. doi: 10.1519/JSC.0000000000003513. [Epub ahead of print]
Authors: Jiménez-Reyes P, Garcia-Ramos A, Párraga-Montilla JA, Morcillo-Losa JA, Cuadrado-Peñafiel V, Castaño-Zambudio A, Samozino P, Morin JB
Summary: This study aimed to describe the seasonal changes in the sprint force-velocity (Fv) profile of professional soccer players. The sprint Fv profile of 21 male soccer players competing in the first division of the Spanish soccer league was evaluated 6 times: preseason 1 (September 2015), in-season 1 (November 2015), in-season 2 (January 2016), in-season 3 (March 2016), in-season 4 (May 2016), and preseason 2 (August 2016). No specific sprint capabilities stimuli other than those induced by soccer training were applied. The following variables were calculated from the velocity-time data recorded with a radar device during an unloaded sprint: maximal force (F0), maximal velocity (v0), Fv slope, maximal power (Pmax), decrease in the ratio of horizontal-to-resultant force (DRF), and maximal ratio of horizontal-to-resultant force (RFpeak). F0 (effect size [ES] range = 0.83-0.93), Pmax (ES range = 0.97-1.05), and RFpeak (ES range = 0.56-1.13) were higher at the in-seasons 2 and 3 compared with both preseasons (p ≤ 0.006). No significant differences were observed for v0, Fv slope, and DRF (p ≥ 0.287). These results suggest that relevant Fv profile variables may be compromised (F0 more compromised than v0) toward the end of the competitive season when specific sprint stimuli are not systematically applied.


#3 Reliability of Change of Direction and Agility Assessments in Youth Soccer Players
Reference: Sports (Basel). 2020 Apr 18;8(4). pii: E51. doi: 10.3390/sports8040051.
Authors: Dugdale JH, Sanders D, Hunter AM
Summary: Considering the vast physical and neural developments experienced throughout adolescence, the reliability of physical performance may vary in youth populations. This study aimed to examine the reliability of change of direction (COD) and agility tests in youth soccer players. Altogether, 86 youth soccer players, aged 13.6 ± 2.0 years, volunteered to participate. Data were collected from a modified 505 COD test (m505COD) and the Y-sprint drill in both pre-planned (Y-SprintPRE) and reactive (Y-SprintREACT) conditions during 2 sessions, 7 days apart. Anthropometric data including body mass, standing stature, and sitting height were also collected. COD and agility tests demonstrated good reliability (ICC = 0.81-0.91; CV = 1.2-2.0; d = 0.00-0.31; p < 0.01) for our entire sample. However, we observed a small negative relationship between age and intersession differences for the Y-SprintPRE (r = -0.28; p = 0.04), and moderate negative relationships between both age (r = -0.41; p < 0.01), and maturity offset (r = -0.39; p < 0.01) for the Y-SprintREACT. Although the COD and agility tests adopted within this study possess good intersession reliability, we observed greater intersession differences for younger and less mature individuals. We suggest that while COD and agility tests may provide meaningful objective data for monitoring the development of youth soccer players, these tests should be used with caution when evaluating younger, more immature athletes.


#4 Influence of playing position and laterality in centripetal force and changes of direction in elite soccer players
Reference: PLoS One. 2020 Apr 23;15(4):e0232123. doi: 10.1371/journal.pone.0232123. eCollection 2020.
Authors: Granero-Gil P, Gómez-Carmona CD, Bastida-Castillo A, Rojas-Valverde D, de la Cruz E, Pino-Ortega J
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0232123&type=printable
Summary: The purpose of the present study was to: (a) assess centripetal force (CentF) and changes of direction (COD) in elite soccer players according to playing position (central defender, CD; lateral defender, LD; central midfielder, CM; lateral midfielder, LM; forward, FW), laterality (right-footed vs. left-footed) and field zone (central vs. lateral), and (b) analyze the relationship between anthropometric characteristics (age, weight, height, body mass and fat mass) and non-linear locomotion workload. Thirty professional soccer players (age: 26.57±5.56 years) were tracked during the 2017-2018 season during friendly, national and international matches (38 total games) using inertial measurement devices. CentF and COD were the variables extracted for analysis. A one-way ANOVA was used for playing position comparison, a t-test for laterality and field zone, and Pearson's correlation coefficient to analyze relationships between anthropometric characteristics and dependent variables. There were differences by playing position in COD (556.33-to-412.18), R20COD (484.36-to-354.81) and R60COD (48.38-to-38.61) (p < .01; ωp2 = 0.03-to-0.05; CD>CM>LD>LM = FW); in CODHIA (49.75-to-37.11), R20CODHIA (16.04-to-9.11) and R60CODHIA (10.64-to-9.11) (p < .01; ωp2 = 0.03-to-0.07; CM>FW>LM>CD = LD); in CODSPRINT (14.56-to-8.40) and R20CODSPRINT (3.29-to-1.40) (p < .01; ωp2 = 0.03-to-0.04; FW = LM = CM>CD = LD); and in CentFMAX both in clockwise (992.04-to-902.09N) and counterclockwise (999.24-to-872.61N) directions (p < .02; ωp2 = 0.02-to-0.07; FW = CD>CM = LM = LD). The highest values of counterclockwise CentF were performed by left-footed players in the central zone (p < .001; d = 0.71-to-1.44) and clockwise CentF by right-footed players (p < .001; d = 0.04-to-0.55) in the lateral field zone. Moderate correlations were found between age, body mass and high intensity/sprints COD and repeated COD ability (p < .05; r = 0.235-to-0.383). Therefore, team staff should consider anthropometric characteristics, playing position, laterality and field zone to individualize training workload related to non-linear locomotion in soccer.


#5 Seasonal Repeated Sprint Ability With Change of Direction Variations in U17 and U20 Elite Brazilian Soccer Players: A Comparative Study
Reference: J Strength Cond Res. 2020 May;34(5):1431-1439. doi: 10.1519/JSC.0000000000002361.
Authors: Jorge G, Garrafoli MT, Cal Abad CC
Summary: This study aimed to describe seasonal variations of repeated sprint with change-of-direction ability in young elite Brazilian soccer players. The Bangsbo sprint test (BST) was performed by 21 under-17 (U17) (176.9 cm; 68.2 kg) and 22 under-20 (U20) athletes (178.7 cm, 74.4 kg) at the start, middle, and end of the season. The fatigue index (FI) was calculated in seconds and in percentage of decrease (%D) for comparisons. Both age categories showed higher BST performance in the middle and end compared with the start of the season (p ≤ 0.05). The U20 players performed better at the start than the U17 players. The U17 soccer players showed higher FI at the start and in the middle in comparison with the U20 players (p ≤ 0.05). They also showed lower FI at the end of the season in comparison with the start and middle of the season (p ≤ 0.05). The U20 players showed significant reductions in the FI in the middle and at the end in comparison with the start of the season (p ≤ 0.05). Only the U17 soccer players showed lower %D at the end in comparison with the start of the season (p ≤ 0.05). To summarize, both U17 and U20 players performed BST poorly at the start, increased the BST performance until the middle, and maintained the BST performance until the end of the season. A difference in the magnitude of enhancement was observed between U17 and U20 soccer players, which was found to be dependent on the initial values. Finally, the mathematical model to calculate the FI requires caution.


#6 The feasibility and impact of instrument-assisted manual therapy (IAMT) for the lower back on the structural and functional properties of the lumbar area in female soccer players: a randomised, placebo-controlled pilot study design
Reference: Pilot Feasibility Stud. 2020 Apr 16;6:47. doi: 10.1186/s40814-020-00592-3. eCollection 2020.
Authors: Weber P, Graf C, Klingler W, Weber N, Schleip R
Download link: https://pilotfeasibilitystudies.biomedcentral.com/track/pdf/10.1186/s40814-020-00592-3
Summary: Myofascial (self-)treatments, such as foam rollers to therapeutic instruments in manual therapy, are utilized increasingly in prevention and therapy in healthy people, athletes, and patients suffering from chronic back pain. However, there is limited knowledge about the effectiveness of treatment and the underlying mechanisms of myofascial therapies, especially for instrument-assisted manual therapy (IAMT). Therefore, this pilot study will investigate the feasibility and impact of IAMT for the lumbar area compared with heat application and placebo treatment as a basis for calculating the sample size for further full studies. The primary outcomes will be a critical analysis of the feasibility of the measurement protocol in terms of time economy and expressiveness and of the short- and long-term effects on shear motion of the single tissue layers of the lower back obtained through ultrasound imaging. Secondary outcomes will include thickness and compressibility of the lumbar structures and flexibility of the dorsal structures, indentometry, and superficial skin temperature. A minimum of 60 healthy, competitive 15-35-year-old female soccer players will be recruited and randomised into three groups. Short-term effects of IAMT on thoracolumbar structures will be compared with heat application and pressure-less placebo treatment. Long-term effects in the IAMT group will be tested after nine further interventions over a 5-week period (2×/week) and compared with the placebo group, which will not receive further treatments but will serve as a control. Intermediate and final testing of both groups will occur in weeks three and five. This pilot study will assess the feasibility and the impact of IAMT for the lower back particularly by examining the structural and functional properties of myofascial tissue using diagnostic ultrasound. These outcomes could evaluate the feasibility of the measurements used, shall build a basis for sample size calculation of further full studies, and might generate a greater understanding of myofascial therapies, especially IAMT, for the lower back and its benefits. If this approach proves to be practicable, next steps will be further full studies with soccer players, other sports, and patients with low back pain.


#7 Increased risk and early onset of ALS in professional players from Italian Soccer Teams
Reference: Amyotroph Lateral Scler Frontotemporal Degener. 2020 Apr 22:1-7. doi: 10.1080/21678421.2020.1752250. [Epub ahead of print]
Authors: Pupillo E, Bianchi E, Vanacore N, Montalto C, Ricca G, Robustelli Della Cuna FS, Fumagalli F, Castellani M, Poli F, Romeo F, Tommasi D, Lazzaro P, Beghi E
Summary: Since the observation of several deaths from amyotrophic lateral sclerosis (ALS) among Italian professional soccer players, an association between ALS and soccer has been postulated. The objective of the study is to investigate the association between professional soccer and the risk of ALS in a large cohort of former professional soccer players with prolonged follow-up. All professional soccer players practicing in the period 1959-2000 were identified through the archives of an Italian soccer cards publisher. For each player, date and place of birth, playing role, and team history were recorded. Each player was followed since 15 years of age. Incident ALS cases were all soccer players first diagnosed during the period 1959-2018. The expected incidence rate was the number of ALS cases/100,000 person-years expected in the cohort. SIR was the ratio between observed and expected incidence rate. 34 ALS cases were detected. The number of expected cases was 17.8. The SIR was 1.91 (95% CI 1.32-2.67) in the entire sample and 4.66 (95% CI 2.66-7.57) in subjects aged less than 45 years. The mean age at diagnosis was 45.0 years. Compared to the mean age of onset of ALS in the general population (65.2 years), the disease in former soccer players occurred 20.2 years earlier. Professional soccer players are at higher risk of developing ALS than the general population. Soccer players with ALS develop the disease at a younger than expected age.


#8 A cross-sectional study on foot loading patterns in elite soccer players of different ages
Reference: J Back Musculoskelet Rehabil. 2020 Apr 7. doi: 10.3233/BMR-181436. [Epub ahead of print]
Authors: Hotfiel T, Golditz T, Wegner J, Pauser J, Brem M, Swoboda B, Carl HD
Summary: Alterations in plantar loading patterns are risk factors for stress injuries of the lower limb, particularly of the foot and ankle. Epidemiological studies have revealed a higher incidence of soccer-related stress fractures of the fifth metatarsal (MT V) in younger athletes than in their adult counterparts.The aim of the present study was to assess the plantar pressure distributions of members of four high-level soccer teams of different age groups to identify age-related differences in loading patterns. A total of 65 elite soccer players were included in the study. Data were computed with sensor-loaded insoles (pedar® X system, novel Inc., Munich, Germany) while the players ran in soccer shoes. Plantar pressures for nine defined regions on the preferred and nonpreferred foot were analyzed. The participants consisted of 17 elite male soccer professionals from the first national league (mean 23 years, height 184 cm, weight 81 kg), 14 players from the under-21 squad (U21, 20 years, 180 cm, 75 kg), 15 players from the U17 squad (16 years, 176 cm, 69 kg) and 19 players from the U16 squad (15 years, 179 cm, 70 kg). We detected statistically significantly elevated peak pressures on the lateral aspects of the nonpreferred foot compared with the preferred foot in the U16 and U17 players, corresponding to a relative increase by 29% (p= 0.044) in the lateral midfoot, a relative increase by 24% (p= 0.031) in MT heads 4-5 in the U16 players and a difference of 18% (p= 0.049) in the lateral midfoot in the U17 players. In contrast, the U21 and adult professional players displayed symmetric plantar pressure distributions in all foot regions. In contrast to adult elite soccer players, adolescents demonstrate asymmetric foot loading patterns with increased peak loads in the lateral aspects of the nonpreferred foot. Our results may provide some explanation for MT V stress fractures that occur in elite adolescents.


#9 The Effect of Training Experience and Leg Dominance on the Prevalence of Asymptomatic Intraarticular Changes of the Knee Joints in Adult Professional Male Soccer Players
Reference: Sports Med Open. 2020 Apr 19;6(1):19. doi: 10.1186/s40798-020-00248-9.
Authors: Bezuglov EN, Khaitin VY, Lyubushkina AV, Lazarev AM, Gorinov AV, Sivakova EY, Rumiantseva EI, Lychagin AV
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7167386/pdf/40798_2020_Article_248.pdf
Summary: Currently, no data is available regarding the association between professional experience or limb dominance and the prevalence of asymptomatic knee joint lesions in adult professional male soccer players. The prevalence of the accumulated changes increases with training experience. This is especially true for the dominant leg, which is involved in a large proportion of the athletes' movements.  MRI was used to assess the condition of 94 knee joints in 47 adult professional male soccer players (mean age 25.7 ± 4.6 years, BMI 22.8 ± 1.4). Previous surgery on joints was an exclusion criterion. No football player had knee injuries (including fresh bruises) for at least 3 months before the examination. All the scans were performed using a 1.5T MRI scanner and a slice thickness of 3 mm. The images were blindly analyzed by two experienced radiologists. We analyzed all the three compartments of the knee joint. We consider a chondral lesion already from grade I in modified Noyes and Stabler classification system. To assess the influence of soccer training experience, all players were divided into two groups: group 1 formed from players with less than 20 years of experience and group 2 with more than 20 years of experience. One hundred percent of the soccer players had at least one chondral and meniscal lesion. In both legs, the posterior horn of the medial meniscus (95.6%) was the most frequent site of injury. Most of the injuries were classified as grade II injuries (73.3% for the dominant and 75.6% for the non-dominant leg). Experience and age of the athletes significantly increased the probability of subcortical bone lesions. They were significantly positively correlated with the grades of patellar lesions and lesions of the patellar surface of the femur and significantly negatively correlated with the grades of lesions of posterior horn of lateral meniscus and anterior horn of medial meniscus. No statistically significant differences in the prevalence and grades of cartilage and meniscal lesions in the dominant and non-dominant limb were observed. Soccer practice is associated with the increased prevalence of asymptomatic chondral and meniscal lesions. The probability of subcortical bone lesions significantly increases with training experience and age. These factors are also positively correlated with the grades of patellar lesions and lesions of the patellar surface of the femur. The prevalence and grade of asymptomatic chondral and meniscal lesions is independent of leg dominance.


#10 Asymmetry of lower limb strength and jumping ability of young soccer players
Reference: Acta Bioeng Biomech. 2020;22(1):79-85.
Author: Rutkowska-Kucharska A
Summary: The aim of this study was to evaluate the potential correlation between asymmetry of lower limb muscle torque, asymmetry of vertical ground reaction force during take-off in young soccer players and their jumping abilities. Twenty-three young soccer player (16.9 ± 0.64 years old) participated in measurements. An isokinetic dynamometer, the Biodex System, was applied to test muscle torque (PT) of the knee flexors and extensors. The vertical ground reaction force (vGRF) was recorded from two Kistler plates. Jumping abilities were assessed with the horizontal (HJ) and vertical jump (VJ) tests. The asymmetry index (AI) was used to assess the asymmetry of the limbs. The asymmetry index showed the highest asymmetry (over 10%) for the PT under static conditions for knee flexors and extensors. The correlation (-0.432, p = 0.038) was found between the asymmetry of vGRF and the height of the VJ. There was no correlation between the muscle torque and the height of the vertical jump. However, a correlation between the HJ length and muscle torque for flexors and extensors of the right and left lower limb was found. The asymmetry of the muscle torque of the flexors and extensors of the knee joint does not correlate with the results of both jumping ability tests. There was a statistically significant correlation between the vGRF asymmetry index during take-off and the height of the VJ. In the HJ, such a relationship was not found.


#11 Seasonal Training Load Quantification and Comparison in College Male Soccer Players
Reference: J Strength Cond Res. 2020 Mar 17. doi: 10.1519/JSC.0000000000003589. [Epub ahead of print]
Authors: Ryan GA, Snarr RL, Eisenman ML, Rossi SJ.
Summary: Monitoring and quantification of training load (TL) throughout a competitive soccer season is important to ensure players are able to perform throughout the season. The intent of this study was to examine the positional demands and patterns of select measures of TL during a 14-week season in collegiate male soccer players. Heart rate (HR), running performance (SZ), and perceived recovery data were collected daily using a bioharness for each subject (n = 21). Data were grouped into 2- to 3-week training blocks (Pre1, Pre2, In1, In2, In3, and In4). Continuous variables were analyzed using a multivariate analysis of variance, with post hoc Least Squared Difference pairwise comparisons. Significant positional differences were observed across the season. During Pre1, center midfielders (CM) spent more time in %HRlow compared to center backs (CB) (p < 0.01), wide midfielders (p < 0.01), and center forwards (p = 0.04). Center midfielders spent greater time in SZlower than CB (p < 0.01) and wide backs (WB) (p = 0.01). Wide backs spent greater time in SZupper compared to other positions (all p < 0.01). During Pre2, WB spent more time in %HRhigh and SZupper compared to other positions (all p < 0.01). Positional differences were more varied throughout in-season comparisons, but generally, WB and CB demonstrated higher intensities in variables compared to other positions. Tracking variations in positional TLs across the season is important for coaching and training staffs to determine player readiness and plan future training sessions, while helping to mitigate overuse injuries during a long competitive season.

Mon

08

Jun

2020

Positional demands in various SSG according to demanding passages of play

Small-sided games (5 vs 5) to larg(er)-sided games (10 vs 10) vs. official match.

Thu

04

Jun

2020

Recovery of Neuromuscular Fatigue following Match-Play

The contribution and time-course of recovery of central and peripheral factors towards neuromuscular fatigue following soccer match-play.

Wed

03

Jun

2020

Latest research in football - week 17 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Influence of Match Status on Ball Possession in High Performance Women's Football
Reference: Front Psychol. 2020 Mar 23;11:487. doi: 10.3389/fpsyg.2020.00487. eCollection 2020.
Authors: Maneiro R, Losada JL, Casal CA, Ardá A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7104793/pdf/fpsyg-11-00487.pdf
Summary: The objective of this study was to examine the effect of the situational match status variable on the ball possession of the teams that participated in the 2015 FIFA Women's World Cup. The 52 games played during the championship have been collected, and 3,740 ball possessions made by the teams were analyzed. The teams have been divided into successful and unsuccessful. Three types of analysis have been carried out: a univariate analysis for both groups with the categorical and continuous variables selected; a bivariate analysis, using chi-square tests and the exact Fischer test; and finally, a multivariable technique such as the decision trees was incorporated. The available results show significant differences between the two groups considered. Specifically, there are significant differences between winning and losing teams in terms of match status. The results of the post hoc test have shown that unsuccessful teams make few ball possessions with a winning match status, most of the possessions are performed when they are losing. Instead, successful teams make more possessions when they are winning than when they are losing. Also, spend more time keeping the ball in their offensive zone, and completing a greater number of passes in it. The results of the decision tree identified that the unsuccessful teams have more ball possessions in forward and middle lines with a draw during the first half, while in the second, a large percentage of possessions are made with an unfavorable match status. Instead, the successful teams have more ball possessions in the first part with a draw, while in the second it happens with a favorable match status.


#2 Changes of Differential Urinary Metabolites after High-Intensive Training in Teenage Football Players
Reference: Biomed Res Int. 2020 Mar 18;2020:2073803. doi: 10.1155/2020/2073803. eCollection 2020.
Authors: Cao B, Liu S, Yang L, Chi A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7109581/pdf/BMRI2020-2073803.pdf
Summary: The mechanism underlying the fatigue of football players is closely related to the energy depletion and accumulation of metabolites; the present study tries to explore the metabolic mechanism in teenage football players during exercise-induced fatigue. 12 teenage football players were subjected to three groups of combined training by using a cycle ergometer, with the subjective Rating of Perceived Exertion (RPE) as a fatigue criterion. The following indicators were measured in each group after training: maximum oxygen uptake (VO2max), anaerobic power, and average anaerobic power. Urine samples were collected before and after the training. Gas chromatography-mass spectrometry (GC-MS) was performed for the metabonomics analysis of the samples. The metabolism data was analyzed by using principal component analysis (PCA) and orthogonal partial least squares analysis (OPLS-DA), through the Kyoto Encyclopedia of Genes and Genomes (KEGG) database to confirm the potential differences between metabolites, and the MetPA database was used to analyze the related metabolic pathways. There was no significant difference between the maximal oxygen uptakes among the three groups. Compared with group 1, the maximum and average anaerobic power in group 3 significantly decreased (p < 0.05) at the end of training. GC-MS detected 635 metabolites in the urine samples. Through PCA, OPLS-DA analysis, and KEGG matching, 25 different metabolites (3↑22↓) that met the conditions were finally selected. These different metabolites belonged to 5 metabolic pathways: glycine-serine-threonine metabolism, citrate cycle, tyrosine metabolism, nitrogen metabolism, and glycerophospholipid metabolism. During the combined exercise of aerobic and anaerobic metabolism, teenage football players show a significant decrease in anaerobic capacity after fatigue. The metabolic mechanism of exercise fatigue was related to disorders in amino acid and energy metabolism.


#3 Long-Term Recreational Football Training and Health in Aging
Reference: Int J Environ Res Public Health. 2020 Mar 21;17(6). pii: E2087. doi: 10.3390/ijerph17062087.
Authors: Imperlini E, Mancini A, Orrù S, Vitucci D, Di Onofrio V, Gallè F, Valerio G, Salvatore G, Liguori G, Buono P, Alfieri A
Download link: https://www.mdpi.com/1660-4601/17/6/2087/pdf
Summary: This narrative review aims to critically analyze the effects of exercise on health in aging. Here we discuss the main clinical and biomolecular modifications induced by long-term recreational football training in older subjects. In particular, the effects induced by long-term recreational football training on cardiovascular, metabolic and musculo-skeletal fitness, together with the modifications in the muscle expression of hallmarks related to oxidative metabolism, DNA repair and senescence suppression pathways and protein quality control mechanisms will be provided. All these topics will be debated also in terms of preventing non-communicable metabolic diseases, in order to achieve successful aging over time.


#4 Changes in countermovement jump performance and subjective readiness-to-train scores following a simulated soccer match
Reference: Eur J Sport Sci. 2020 Apr 17:1-25. doi: 10.1080/17461391.2020.1757764. [Epub ahead of print]
Authors: Lombard W, Starling L, Wewege L, Lambert M
Summary: The study investigated whether countermovement jump (CMJ) metrics and subjective responses to a readiness-to-train questionnaire (RTT-Q) tracked simulated match-induced acute fatigue. This was a randomized cross-over repeated measures study. Participants were assigned into one of two groups; CONTROL or LIST. The LIST group performed the Loughborough Intermittent Shuttle Run (LIST), which was designed to simulate the demands of a soccer match. The CONTROL performed light physical activity at an intensity of <65% of maximal heart rate. Each group performed three CMJ's and completed an RTT-Q before (PRE), and again at 24 h and 48 h after the LIST and/or CONTROL interventions. At 24 h there were significant differences in RTT-Q answers between the Pre and 24 h for the LIST group for questions; "Do you feel physically strong today?" and "Do you have muscle soreness today?" (p = 0.02 and 0.0008, respectively). The questions "Do you feel mentally strong today?" and "Do you have muscle soreness today?" (p=0.02 and p = 0.0001 respectively) were the only questions that had a significant difference between Pre and 48 h for the LIST group. None of the CMJ metrics (LIST or CONTROL) changed significantly at any stage of the experiment. Although fatigue was detected by changes in the RTT-Q at 24 h and 48 h after the LIST, none of the CMJ metrics changed. These findings suggest that subjective measures are more sensitive to low-level fatigue than objective measures, thus effective monitoring should include both.


#5 Unlocking the potential of big data to support tactical performance analysis in professional soccer: A systematic review
Reference: Eur J Sport Sci. 2020 Apr 16:1-16. doi: 10.1080/17461391.2020.1747552. [Epub ahead of print]
Authors: Goes FR, Meerhoff LA, Bueno MJO, Rodrigues DM, Moura FA, Brink MS, Elferink-Gemser MT, Knobbe AJ, Cunha SA, Torres RS, Lemmink KAPM
Download link: https://www.tandfonline.com/doi/abs/10.1080/17461391.2020.1747552?needAccess=true#aHR0cHM6Ly93d3cudGFuZGZvbmxpbmUuY29tL2RvaS9wZGYvMTAuMTA4MC8xNzQ2MTM5MS4yMDIwLjE3NDc1NTI/bmVlZEFjY2Vzcz10cnVlQEBAMA==
Summary: In professional soccer, increasing amounts of data are collected that harness great potential when it comes to analysing tactical behaviour. Unlocking this potential is difficult as big data challenges the data management and analytics methods commonly employed in sports. By joining forces with computer science, solutions to these challenges could be achieved, helping sports science to find new insights, as is happening in other scientific domains. We aim to bring multiple domains together in the context of analysing tactical behaviour in soccer using position tracking data. A systematic literature search for studies employing position tracking data to study tactical behaviour in soccer was conducted in seven electronic databases, resulting in 2338 identified studies and finally the inclusion of 73 papers. Each domain clearly contributes to the analysis of tactical behaviour, albeit in - sometimes radically - different ways. Accordingly, we present a multidisciplinary framework where each domain's contributions to feature construction, modelling and interpretation can be situated. We discuss a set of key challenges concerning the data analytics process, specifically feature construction, spatial and temporal aggregation. Moreover, we discuss how these challenges could be resolved through multidisciplinary collaboration, which is pivotal in unlocking the potential of position tracking data in sports analytics. Over the recent years, there has been a considerable growth in studies on tactical behaviour using position tracking data, especially in the domains of sports science and computer science. Yet both domains have contributed distinctly different studies, with the first being more focused on developing theories and practical implications, and the latter more on developing techniques. Considerable opportunities exist for collaboration between sports science and computer science in the study of tactics in soccer, especially when using position tracking data. Collaborations between the domains of sports science and computer science benefit from a stronger dialogue yielding a cyclical collaboration. We have proposed a framework that could serve as the foundation for the combination of sports science and computer science expertise in tactical analysis in soccer.


#6 The Federated Practice of Soccer Influences Hamstring Flexibility in Healthy Adolescents: Role of Age and Weight Status
Reference: Sports (Basel). 2020 Apr 13;8(4). pii: E49. doi: 10.3390/sports8040049.
Authors: Ponce-González JG, Gutiérrez-Manzanedo JV, De Castro-Maqueda G, Fernández-Torres VJ, Fernández-Santos JR
Download link: https://www.mdpi.com/2075-4663/8/4/49/pdf
Summary: The aim of this study was to compare the hamstring flexibility between federated soccer and non-federated adolescents, and also to evaluate the effect of age and weight status on hamstring flexibility. The participants were 234 students (11-18 years old) divided into: (i) G1: non-federated (n = 127), and (ii) G2: federated in soccer (n = 107). The deep flexion of the trunk (DF) test and the sit and reach test (SRT) were performed. G2 showed higher values for the DF and SRT compared to G1 (p < 0.05). Both flexibility tests correlated positively (r = 0.4, p < 0.001). Body mass index (BMI) was negatively correlated with the DF test (r = -0.3, p < 0.001), but not with the SRT. Divided by BMI, the underweight and normal weight groups had higher scores in the DF test compared with the overweight and obese groups (p < 0.001). BMI was negatively correlated with hamstring flexibility. Federated soccer students present higher scores of hamstring flexibility.


#7 Lower Limb Kinetic Asymmetries in Professional Soccer Players With and Without Anterior Cruciate Ligament Reconstruction: Nine Months Is Not Enough Time to Restore "Functional" Symmetry or Return to Performance
Reference: Am J Sports Med. 2020 Apr 15:363546520912218. doi: 10.1177/0363546520912218. [Epub ahead of print]
Authors: Read PJ, Michael Auliffe S, Wilson MG, Graham-Smith P
Summary: Residual between-limb deficits are a possible contributing factor to poor outcomes in athletic populations after anterior cruciate ligament reconstruction (ACLR). Comprehensive appraisals of movement strategies utilized by athletes at key clinical milestones during rehabilitation are warranted. The purpose was to examine kinetic parameters recorded during a countermovement jump with a force platform in healthy professional soccer players and to compare their performance with those who had undergone ACLR at different stages of their rehabilitation. A total of 370 male professional soccer players attended a physical screening assessment where they performed at counter jump movement protocol on dual force plates and were divided into 4 groups: group 1 (<6 months post-ACLR), group 2 (6-9 months post-ACLR), group 3 (>9 months post-ACLR), and group 4 (healthy matched controls). Players in the later phases of rehabilitation increased their jump performance; however, values were significantly lower than those of healthy matched controls (P > .05). Significant between-limb differences were present for both eccentric- and concentric-phase variables (P < .05), with effect sizes ranging from moderate to very large (d = 0.42-1.35). Asymmetries were lower in players who were further away from surgery; however, between-limb differences remained significantly greater in players >9 months after ACLR versus matched controls-specifically, for concentric impulse, concentric peak force, eccentric deceleration impulse, and eccentric deceleration rate of force development asymmetry (P < .05). Logistic regression identified concentric impulse asymmetry as being most strongly associated with a history of ACLR when group prediction analysis was performed (ACLR group 1, 2, or 3 vs matched controls), with odds ratios ranging from 1.50 to 1.91. Between-limb deficits in key eccentric and concentric loading parameters remain >9 months after ACLR, indicating a compensatory offloading strategy to protect the involved limb during an athletic performance task. Concentric impulse asymmetry could be considered an important variable to monitor during rehabilitation.


#8 Timing and Reasons Behind Single-Sport Specialization in Soccer: A Survey of 64 Major League Soccer Athletes
Reference: Sports Health. 2020 Apr 14:1941738120911373. doi: 10.1177/1941738120911373. [Epub ahead of print]
Authors: Knapik DM, Rizzone KH, Voos JE
Summary: Single-sport specialization at the exclusion of other sports has become increasingly popular in youth sporting culture. The purpose of this study was to survey Major League Soccer (MLS) athletes to examine factors influencing the timing of single-sport specialization in soccer. The hypothesis is that the majority of surveyed athletes will have participated in multiple sports prior to specialization and specialized primarily as a result of a coach's recommendation, with no significant impact on specialization timing stemming from birth or high school location, obtaining a collegiate scholarship, MLS experience, or position. Anonymous surveys were distributed to 3 MLS organizations and completed by MLS athletes during preseason physicals. Surveys evaluated the age and reason(s) behind an athlete's decision to specialize in soccer, birth location, geographic high school location for US-born athletes, participation in a developmental league, college scholarship, years in the MLS, and position played. Approximately 74% (64/86) of athletes returned completed surveys. Athletes reported beginning soccer at a mean age of 5.1 ± 2.1 years and specializing at age 12.6 ± 4.3 years. Athletes who participated in no other sports prior to specialization (P < 0.001), athletes reporting soccer to be their first sport played at an advanced level (P < 0.001), and athletes receiving a college scholarship (P = 0.02) specialized at a significantly younger age. Internationally born athletes specialized at significantly younger ages when compared with US-born athletes (P < 0.001). The majority of athletes participated in multiple sports prior to specialization and eventually specialized to focus exclusively on soccer. The timing of sport specialization in professional MLS athletes was not associated with multisport participation prior to specialization, playing soccer at an advanced level prior to other sports, receiving a college scholarship, or being born outside the United States. Timing of sport specialization is associated with multiple factors prior to athlete promotion to the MLS that warrant further investigation to better understand the impact of specialization on injury incidence, performance, and career length.


#9 Nutrition for Female Soccer Players-Recommendations
Reference: Medicina (Kaunas). 2020 Jan 10;56(1). pii: E28. doi: 10.3390/medicina56010028.
Authors: Dobrowolski H, Karczemna A, Włodarek D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7022222/pdf/medicina-56-00028.pdf
Summary: Soccer is one of the most popular sports in the world. As its number of players is increasing, the number of female players is also on the rise. However, there are limited data about how the diets of female soccer players should be designed. Thus, the aim of our work is to deliver concise nutritional recommendations for women practicing this sport. Based on a literature review, we emphasize that individual adjustment of the energy value of the diet is the key factor for the physical performance of female soccer players. Appropriate macronutrient intake makes it possible to achieve the proper energy value of the diet (5-10 g/kg body mass/day carbohydrates; 1.2-1.7 g/kg body mass/day proteins; <30% fats from energy). The micronutrients should be consumed in amounts corresponding to individual values recommended in national standards. Soccer players should pay special attention to the proper consumption of such micronutrients, as well as vitamins such as iron, calcium, and vitamin D. The right amount of fluid intake, consistent with the player's needs, is crucial in maximizing exercise performance. The diet of a female practicing soccer is usually characterized with low energy values, which increases the risk of various health consequences related to low energy availability. Monitoring the diets of female soccer players is, therefore, necessary.


#10 Scaling left ventricular mass in adolescent female soccer players
Reference: BMC Pediatr. 2020 Apr 13;20(1):157. doi: 10.1186/s12887-020-02043-7.
Authors: V Martinho D, Valente-Dos-Santos J, Coelho-E-Silva MJ, Gutiérrez AO, Duarte JP, Lourenço-Farinha P, Luz LGO, Gonçalves-Santos J, Machado DRL, Leite N, Conde J, Castanheira JM, Cumming SP, Sherar LB, Malina RM
Download link: https://bmcpediatr.biomedcentral.com/track/pdf/10.1186/s12887-020-02043-7
Summary: The aim of the study was to examine the contribution of chronological age (CA), skeletal maturation, training experience and concurrent body size descriptors, to inter-individual variance in left ventricular mass (LVM) among female adolescent soccer players. The sample included 228 female soccer players 11.8-17.1 years. Training experience defined as years of participation in competitive soccer (range 2-9 years), was obtained by interview. Stature, body mass and skinfolds (triceps, medial calf) were measured. Fat mass was estimated; Fat-free mass was derived. LVM was assessed by echocardiography. Skeletal maturity status was as the difference of skeletal age (SA, Fels method) minus CA. Fat-free mass was the most prominent single predictor of LVM (R2 = 36.6%). It was associated with an allometric coefficient close to linearity (k = 0.924, 95%CI: 0.737 to 1.112). A significant multiplicative allometric model including body mass, fat-free mass, CA, training experience and skeletal maturity status was also obtained (R = 0.684; R2 = 46.2%). Stature has limitations as a valid size descriptor of LVM. Body mass, fat-free mass, training experience, CA, body mass and skeletal maturity status were relevant factors contributing to inter-individual variability in LVM.


#11 Internal jugular vein compression applied during competitive female soccer season preserves functional and structural connectome organization
Reference: Brain Connect. 2020 Apr 13. doi: 10.1089/brain.2019.0729. [Epub ahead of print]
Authors: Dudley J, Yuan W, Diekfuss J, Barber Foss KD, DiCesare CA, Altaye M, Logan K, Leach J, Myer G
Summary: Characterization of, and evaluation of strategies to mitigate, the effects of sub-concussive impacts (SCI) on brain structure and function are crucial to understand potential long-term neurological risks associated with sports participation. In this study, we applied a graph theoretical framework to resting state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) data to evaluate the efficacy of a jugular vein compression collar for preserving functional and structural measures of brain network organization in a cohort of female high school soccer players throughout a season of competitive play. Athletes were assigned to a collar (N = 72) or non-collar (N = 56) group before engaging in a season of play, during which head impact data were recorded via accelerometer for every practice and competition. Participants completed neuroimaging sessions before and following the season. Non-collar-wearing athletes exhibited significantly increased rs-fMRI-derived global clustering coefficients (p = 0.032) and DTI-derived modularity (p = 0.042), compared to collar-wearing athletes. No longitudinal changes in any graph measures were observed for the collar group (p > 0.05). The observed increase in graph measures in the non-collar group is congruent with previous studies of SCI and is similar to graph theoretical studies of traumatic brain injury. The absence of alterations in graph metrics in the collar group indicates a potential ameliorating effect of the collar device against network reorganization, in line with previous literature.

Tue

02

Jun

2020

Influence of intense training cycle and psychometric status on technical and physiological aspects performed during the small-sided games in footballers

What is the effect of an intense training cycle and well-being on performance in SSGs?

Sat

30

May

2020

Order of concurrent training...

...does not really matter.

Fri

29

May

2020

Latest research in football - week 16 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Preliminary Validation of Mirrored Scales for Monitoring Professional Soccer Training Sessions
Reference: J Hum Kinet. 2020 Mar 31;72:265-278. doi: 10.2478/hukin-2019-0112. eCollection 2020 Mar.
Authors: Morandi RF, Pimenta EM, Andrade AGP, Serpa TKF, Penna EM, Costa CO, Júnior MNSO, Garcia ES
Summary: We aimed to create a single subjective method to assess both internal training loads and subsequent fatigue. This new training-fatigue (dose-response) scale (TFS) was composed of two similar scales with the same properties, metrics and construction criteria. These two scales were designed to rate the perceived exertion (RPETFS) and perceived fatigue (RPFTFS) in professional soccer players. Twenty-two athletes participated to establish reliability, and 15 participated to establish validity. For reliability, the intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were used. For criterion validity, the Spearman's correlation coefficient and linear regression analyses were applied. Associations between RPETFS and RPFTFS were verified by a chi square test, and a further factorial exploratory analysis was conducted. RPETFS and RPFTFS were found to be reliable (ICC 0.74 and 0.77, SEM 0.30 and 0.30, respectively) and valid. RPETFS was best explained by the internal load of the Banister training impulse (p < 0.001), while RPFTFS was best explained by the internal load of the Stagno training impulse (p < 0.001). An association was found between the scales (RPETFS and RPFTFS) in which training duration had a more substantial impact on these subjective perceptions than did training intensity (p < 0.01). RPETFS and RPFTFS scales are reliable and valid for monitoring training sessions in Brazilian professional soccer players. The simultaneous oscillations of the RPETFS and RPFTFS scores can be used by staff members to better plan weekly training programs based on dose-response ratings. Finally, training duration must be carefully controlled because it has a greater impact than intensity on subjective perceptions.


#2 Assessing Change of Direction Ability in a Spanish Elite Soccer Academy
Reference: J Hum Kinet. 2020 Mar 31;72:229-239. doi: 10.2478/hukin-2019-0109. eCollection 2020 Mar.
Authors: Arcos AL, Aramendi JF, Emparanza JI, Castagna C, Yanci J, Lezáun A, Martínez-Santos R
Summary: The aims of the study were: a) to analyze the reproducibility of the Modified Agility Test (MAT) according to two types of displacement (i.e. constrained [MATtop] vs. free [MATfree]), b) to examine the explanatory capacity of anthropometric characteristics and neuromuscular performance on the ability to change the direction (CODA), c) to look into the practical consequences of the types of displacement from the perspective of an elite soccer academy. 118 male soccer players (age: 16 (13-25) years old) from the same elite Spanish soccer academy (U13 to senior) were tested twice on two versions of the MAT (MATtop and MATfree), with 48 hours between testing sessions. Moreover, they were tested on linear-sprint performance, over 5 m (S5m) and 15 m (S15m), and the vertical jump (VJ) (countermovement jump with [ACMJ] and without an arm swing [CMJ]). The main findings were: a) the type of displacement did not affect the reliability of the CODA test; b) weight, S15m, ACMJ and CMJ variables explained close to 60% of CODA performance; c) MATtop (i.e. constrained displacement) and MATfree (i.e. free-displacement) CODA tests could show different profiles of development along the age groups; and d) the impact of the task's constraints was relatively higher in U16 and U17 groups. CODA seems to have a variable meaning depending on the characteristics of the test and the age of the participants.


#3 Match Performance Indicators that Discriminated Between Winning, Drawing and Losing Teams in the 2017 AFCON Soccer Championship
Reference: J Hum Kinet. 2020 Mar 31;72:215-221. doi: 10.2478/hukin-2019-0108. eCollection 2020 Mar.
Authors: Kubayi A, Toriola A
Summary: The purpose of this study was to examine match performance indicators that discriminated between winning, drawing and losing teams in the 2017 Total Africa Cup of Nations (AFCON) soccer championship. Data were collected from 32 matches during the AFCON soccer tournament using the InStat® system. The studied variables included the number of goals scored, the time period in which a goal was scored and the impact of the first goal on the match outcome, as well as total shots, shots on goal, total passes, accurate passes, corners, ball possession, fouls, offsides as well as yellow and red cards. The results showed that goals scored (1.80 ± 0.83), total shots (11.05 ± 4.83), shots on target (4.70 ± 2.62), fouls (18.60 ± 5.19), offsides (2.35 ± 1.76), yellow cards (1.55 ± 1.10), and red cards (0.05 ± 0.22) were discriminative performance indicators of winning teams. In contrast, losing teams yielded higher mean values in total passes (260.30 ± 49.10), accurate passes (69.28 ± 5.74), corners (5.10 ± 2.95), and ball possession (51.20 ± 5.52). In conclusion, these results have practical implications for coaches in planning and implementing team tactics for successful performance.


#4 Heart Rate Variability is Correlated with Perceived Physical Fitness in Elite Soccer Players
Reference: J Hum Kinet. 2020 Mar 31;72:141-150. doi: 10.2478/hukin-2019-0103. eCollection 2020 Mar.
Authors: Ravé G, Zouhal H, Boullosa D, Doyle-Baker PK, Saeidi A, Abderrahman AB, Fortrat JO
Summary: Heart Rate Variability (HRV) has been typically used to monitor athletes' physical fitness readiness. The supine position maximizes parasympathetic tone, which is important for monitoring in continuous aerobic sports, however, this is not the case of team sports that rely on anaerobic intermittent bouts, thus increasing sympathetic activation and vagal withdrawal. We hypothesized that HRV during sympathetic activation and vagal withdrawal would be a useful marker to evaluate perceived physical fitness in team sports. HRV was measured in both supine and standing positions during the mornings of 4 match days in 14 professional players. The supine Root Mean Square of the Successive Differences (RMSSD), as well as spectral analysis indices were recorded. Perceived physical fitness was assessed after each match by means of a visual analogue scale (VAS). Supine RMSSD was moderately correlated with perceived physical fitness (rho = 0.416), however, larger correlations were observed for supine and standing spectral indices (rho > 0.5). Correlation between RMSSD and Total Power was very large, thus questioning the usual interpretation of RMSSD (rho > 0.7). Standing Spectral HRV analyses may be a useful method for evaluating perceived physical fitness in the context of team sports. RMSSD may reflect the overall variability of HR and not only the parasympathetic influence, as observed in the current study.


#5 Corrigendum: Strength, Jumping, and Change of Direction Speed Asymmetries Are Not Associated With Athletic Performance in Elite Academy Soccer Players
Reference: Front Psychol. 2020 Mar 20;11:518. doi: 10.3389/fpsyg.2020.00518. eCollection 2020.
Authors: Raya-González J, Bishop C, Gómez-Piqueras P, Veiga S, Viejo-Romero D, Navandar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7100853/pdf/fpsyg-11-00518.pdf


#6 Effects of plyometric jump training in female soccer player's vertical jump height: A systematic review with meta-analysis
Reference: J Sports Sci. 2020 Apr 7:1-13. doi: 10.1080/02640414.2020.1745503. [Epub ahead of print]
Authors: Ramirez-Campillo R, Sanchez-Sanchez J, Romero-Moraleda B, Yanci J, García-Hermoso A, Manuel Clemente F
Summary: The purpose was to assess the effects of plyometric jump training (PJT) in female soccer player's vertical jump height, a review was conducted using the data sources PubMed, MEDLINE, Web Of Science and SCOPUS. Only peer-review articles were included. To qualify for inclusion in the meta-analysis, studies must have included (i) a PJT programme of at least 2 weeks, (ii) cohorts of healthy female soccer players with no restriction for age, (iii) a control group, (iv) a measure of countermovement jump (CMJ). The inverse variance random-effects model for meta-analyses was used. From 7,136 records initially identified through database searching, 8 were eligible for meta-analysis, comprising 9 training groups (n = 99) and 9 control groups (n = 94). The magnitude of the main effect was moderate (ES = 1.01 [95%CI = 0.36-1.66], Z = 3.04, p = 0.002). Sub-group analyses were performed (i.e., PJT frequency, duration and total number of sessions), revealing no significant subgroup differences (p = 0.34-0.96). Among the studies included in this review, none reported injury or other adverse effects. In conclusion, PJT is effective in female soccer players for the improvement of vertical jump height. In future, research must identify specific dose-response relationships following PJT, particularly in the long term.


#7 Making football safer for women: a systematic review and meta-analysis of injury prevention programmes in 11 773 female football (soccer) players
Reference: Br J Sports Med. 2020 Apr 6. pii: bjsports-2019-101587. doi: 10.1136/bjsports-2019-101587. [Epub ahead of print]
Authors: Crossley KM, Patterson BE, Culvenor AG, Bruder AM, Mosler AB, Mentiplay BF
Summary: The purpose was to evaluate the effects of injury prevention programmes on injury incidence in any women's football code; explore relationships between training components and injury risk; and report injury incidence for women's football. Randomised controlled trials evaluating any injury prevention programme (eg, exercise, education, braces) were included. Study inclusion criteria were: ≥20 female football players in each study arm (any age, football code or participation level) and injury incidence reporting. Twelve studies, all in soccer, met inclusion criteria, with nine involving adolescent teams (aged <18 years). All studies (except one) had a high risk of bias. Eleven studies examined exercise-based programmes, with most (9/11) including multiple (≥2) training components (eg, strength, plyometric, balance exercises). Multicomponent exercise programmes reduced overall (any reported) injuries (incidence rate ratio (IRR) 0.73, 95% CI 0.59 to 0.91) and ACL injuries (IRR 0.55, 95% CI 0.32 to 0.92). For exercise-based strategies (single-component and multicomponent), hamstring injuries were also reduced (IRR 0.40, 95% CI 0.17 to 0.95). While exercise-based strategies resulted in less knee, ankle and hip/groin injuries, and the use of multiple training components was associated with greater reductions in overall and knee injuries, further studies would be required to increase the precision of these results. The incidence of overall injuries in women's football was 3.4 per 1000 exposure hours; with ankle injuries most common. In women's football, there is low-level evidence that multicomponent, exercise-based programmes reduce overall and ACL injuries by 27% and 45%, respectively.


#8 The Effects of Low- and High-Glycemic Index Sport Nutrition Bars on Metabolism and Performance in Recreational Soccer Players
Reference: Nutrients. 2020 Apr 2;12(4). pii: E982. doi: 10.3390/nu12040982.
Authors: Kaviani M, Chilibeck PD, Gall S, Jochim J, Zello GA
Download link: https://www.mdpi.com/2072-6643/12/4/982/pdf
Summary: Consumption of low-glycemic index (GI) carbohydrates (CHO) may be superior to high-GI CHO before exercise by increasing fat oxidation and decreasing carbohydrate oxidation. We compared the effects of pre-exercise feeding of a low-GI lentil-based sports nutrition bar with a high-GI bar on metabolism and performance during a simulated soccer match. Using a randomized, double-blind, counterbalanced, crossover design, participants (n = 8) consumed 1.5 g/kg available CHO from a low-GI bar (GI = 45) or high-GI bar (GI = 101) two hours before a 90 min simulated soccer match, and 0.38 g/kg body mass during a 15 min half-time break. The test involved alternating 6 min intervals of paced jogging, running, walking, and sprinting, and 3 min intervals of soccer-specific skills (timed ball dribbling, agility running, heading, kicking accuracy). Carbohydrate oxidation rate was lower during the match after consuming the low-GI compared to high-GI bar (2.17 ± 0.6 vs. 2.72 ± 0.4 g/min; p < 0.05). Participants performed better during the low-GI versus high-GI bar condition on the agility test (5.7 ± 0.4 versus 6.1 ± 0.6 s; p < 0.01) and heading (i.e., jumping height 24.7 ± 4.3 versus 22.2 ± 4.5 cm; p < 0.01) late in the soccer match (72 min). A low-GI lentil-based sports nutrition bar provides a metabolic benefit (lower carbohydrate oxidation rate) and a modest improvement in agility running and jumping height (heading) late in the test.


#9 Do Changes in Fitness Status, Testosterone Concentration, and Anthropometric Characteristics Across a 16-Month Training Period Influence Technical Performance of Youth Soccer Players During Small-Sided Games?
Reference: J Strength Cond Res. 2020 Apr 3. doi: 10.1519/JSC.0000000000003614. [Epub ahead of print]
Authors: Rodrigues Lopes RA, Aoki MS, Carling C, Vaz Ronque ER, Moreira A
Summary: This study examined the influence of changes in physical capacity, testosterone concentration, and anthropometric characteristics across a 16-month training period on technical performance of youth players during small-sided games (SSG). Thirty-five elite youth players (14.3 ± 0.2 years, 170 ± 6.2 cm, and 61 ± 6 kg) were assessed on 3 occasions (T1, T2, and T3) over the period. A multivariate canonical correlation (MCC) was used to assess the multiple associations between the criterion variable (SSG technical performance) and the predictor variable (physical capacity represented by the Yo-Yo Intermittent Recovery Test Level 1 [Yo-Yo IRT1], testosterone concentration, and anthropometric characteristics). Changes between T1 and T3 were retained for MCC analysis. Multivariate canonical correlation analysis revealed 2 significant functions (R = 0.42 and 0.36) indicating a significant relationship between predictor and criterion variables. Changes in Yo-Yo IRT1 performance were the main contributor to the predictor variable, whereas the frequency of tackles/interceptions contributed mostly to the criterion variable (SSG technical performance). These results showed that technical performance in SSG was influenced by changes in Yo-Yo IRT1 performance, suggesting the importance of monitoring in conjunction, intermittent exercise capacity, and technical performance in SSG in youth soccer players. In addition, the stability in technical performance during SSG observed over the experimental period suggests that practitioners could use SSG as a tool for systematic real-world monitoring of technical performance rather than isolated practice drills.


#10 Player and Parent Experiences with Child and Adolescent Power Soccer Sport Participation
Reference: Phys Occup Ther Pediatr. 2020 Apr 5:1-14. doi: 10.1080/01942638.2020.1746946. [Epub ahead of print]
Authors: Bragg E, Spencer NLI, Phelan SK, Pritchard-Wiart L
Summary: Power soccer presents opportunities for young athletes who use power wheelchairs to experience competitive team sports. As the focus of rehabilitation is to enhance participation and quality of life, insight into the subjective experience of sport participation could broaden considerations for power wheelchair prescription and inform how therapists share information about community sports and other activities with families. The purpose was to  provide insight into the experiences of power soccer players and their parents to inform rehabilitation practice. Primary data for this Interpretive Description study were individual interviews with five power soccer athletes, ranging from 11 to 17 years of age, and three parents of power soccer players. Observational field notes were also used. Five inter-related themes were developed: 1) Level playing field, 2) I am an athlete, 3) Important "life lessons" are gained through team sports, 4) The value of belonging to a community, and 5) Role of the rehabilitation community in supporting power mobility sports. Findings of this study demonstrate the benefits and challenges of power sport participation. The results encourage therapists to share information about sport opportunities with families and to consider a broad range of contexts when assessing for power mobility.


#11 Indirect Assessment of Skeletal Muscle Glycogen Content in Professional Soccer Players before and after a Match through a Non-Invasive Ultrasound Technology
Reference: Nutrients. 2020 Apr 1;12(4). pii: E971. doi: 10.3390/nu12040971.
Authors: San-Millán I, Hill JC, Calleja-González J
Download link: https://www.mdpi.com/2072-6643/12/4/971/pdf
Summary: Skeletal muscle glycogen (SMG) stores in highly glycolytic activities regulate muscle contraction by controlling calcium release and uptake from sarcoplasmic reticulum, which could affect muscle contraction. Historically, the assessment of SMG was performed through invasive and non-practical muscle biopsies. In this study we have utilized a novel methodology to assess SMG through a non-invasive high-frequency ultrasound. Nine MLS professional soccer players (180.4 ± 5.9 cm; 72.4 ± 9.3 kg; 10.4% ± 0.7% body fat) participated. All followed the nutritional protocol 24 h before the official match as well as performing the same practice program the entire week leading to the match. The SMG decreased from 80 ± 8.6 to 63.9 ± 10.2; p = 0.005 on MuscleSound® score (0-100) representing a 20% ± 10.4% decrease in muscle glycogen after match. Inter-individual differences in both starting glycogen content (65-90) and in percentage decrease in glycogen after the match (between 6.2% and 44.5%). Some players may not start the match with adequate SMG while others' SMG decreased significantly throughout the game. Adequate pre-match SMG should be achieved during half-time and game-play in order to mitigate the decrease in glycogen. Further and more ample studies are needed before the application of this technology.


 #12 Analysis of the Variability of the Game Space in High Performance Football: Implementation of the Generalizability Theory
Reference: Front Psychol. 2020 Mar 25;11:534. doi: 10.3389/fpsyg.2020.00534. eCollection 2020.
Authors: Maneiro R, Blanco-Villaseñor Á, Amatria M
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2020.00534/pdf
Summary: The analysis of variability in sport has shown significant growth in recent years. Also, the study of space management in the game field has not been object of research yet. The present study pretends to describe the variability in the use of strategic space in high performance football. To do this, the spatial management of the Spanish men's soccer team when it is in possession of the ball has been analyzed, during its participation in the UEFA Euro 2012 championship. Specifically, 6861 events have been collected and analyzed. Different zoning of the field have been used, and the location of the ball has been recorded in each offensive action. Using the observational methodology as a methodological filter, two types of analysis have been carried out: first, a General Linear Model was implemented to know the variability of the strategic space. Models with two, three, four and five variables have been tested. In order to estimate the degree of accuracy and generalization of the data obtained, the Generalizability Theory was implemented. Next, and in order to estimate the degree of accuracy and generalization of the data obtained, the Generalizability Theory was implemented. The results showed that the model that produces greater variability and better explanation is the four-variable model (P = 0.019; r 2 = 0.838), with the inclusion of the variables match half, rival, move initiation zone and move conclusion zone. Next, an optimization plan was implemented to know the degree of generalization with the Rival, Start Zone (SZ) and Conclusion Zone (CZ) facets. The available results indicate that it is based on an adequate research design in terms of the number of observations. The results of the present study could have a double practical application. On the one hand, the inclusion of the game's space management in training sessions will potentially conceal the true tactical intention. On the other hand, knowing the variability of the strategic space will allow to exploit areas of the optimal playing field to attack the rival team.

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Heavy sled training improved sprint performance

Sprint training in footballers: sled vs. more sled vs. SSG

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Game style in football

What is it and are there quantifiable variables

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2020

Latest research in football - week 15 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Influence of Soccer Playing Surface on the Loading Response to Ankle (P)Rehabilitation Exercises
Reference: J Sport Rehabil. 2020 Mar 31:1-7. doi: 10.1123/jsr.2019-0199. [Epub ahead of print]
Authors: Jones A, Brogden C, Page R, Langley B, Greig M.
Summary: Contemporary synthetic playing surfaces have been associated with an increased risk of ankle injury in the various types of football. Triaxial accelerometers facilitate in vivo assessment of planar mechanical loading on the player. The aim was to quantify the influence of playing surface on the PlayerLoad elicited during footwork and plyometric drills focused on the mechanism of ankle injury. A total of 15 amateur soccer players (22.1 [2.4] y), injury free with ≥6 years competitive experience. Each player completed a test battery comprising 3 footwork drills (anterior, lateral, and diagonal) and 4 plyometric drills (anterior hop, inversion hop, eversion hop, and diagonal hop) on natural turf (NT), third-generation artificial turf (3G), and AstroTurf. Global positioning system sensors were located at C7 and the mid-tibia of each leg to measure triaxial acceleration (100 Hz). PlayerLoad in each axial plane was calculated for each drill on each surface and at each global positioning system location were used as main outcome measures.  Analysis of variance revealed a significant main effect for sensor location in all drills, with PlayerLoad higher at mid-tibia than at C7 in all movement planes. AstroTurf elicited significantly higher PlayerLoad in the mediolateral and anteroposterior planes, with typically no difference between NT and 3G. In isolated inversion and eversion hopping trials, the 3G surface also elicited lower PlayerLoad than NT. PlayerLoad magnitude was sensitive to unit placement, advocating measurement with greater anatomical relevance when using microelectromechanical systems technology to monitor training or rehabilitation load. AstroTurf elicited higher PlayerLoad across all planes and drills and should be avoided for rehabilitative purposes, whereas 3G elicited a similar mechanical response to NT.


#2 Impact Of Contextual Variables On The Representative External Load Profile Of Spanish Professional Soccer Match-Play: A Full Season Study
Reference:  Eur J Sport Sci. 2020 Apr 1:1-22. doi: 10.1080/17461391.2020.1751305. [Epub ahead of print]
Authors: Oliva-Lozano JM, Rojas-Valverde D, Gómez-Carmona CD, Fortes V, Pino-Ortega J
Summary: The aims of this study were to: 1) identify the representative external load profile of match-play in Spanish professional soccer players by principal components analysis (PCA), and 2) analyze the effect of match location (home vs away), match outcome (win vs draw vs loss) and length of the microcycle (5 vs 6 vs 7 vs 8 vs 9 days) on the external load profile. Data was collected during one season consisting of 42 matches in LaLiga 123 and eleven external load variables were selected after the PCA. TD, total distance covered; DIS0-6: distance from 0 to 6 km/h; DIS21-24: distance from 21 to 24 km/h; HSRD: high-speed running distance above 21 km/h; HSRA: total of high-speed running actions above 21 km/h; VMAX: maximum speed in km/h; Sprints: total of actions above 24 km/h; ACC: total of accelerations; ACCG-avg: average accelerometer G-force; ACCMAX: maximum acceleration (m/s2); DECMAX: maximum deceleration (m/s2). Match location had an impact on HSRD (p<0.01; ES=0.05), DIS0-6 (p<0.01; ES = 0.05), and ACCMAX (p<0.01; ES = 0.05). Match outcome had a relation to TD (p<0.01; ES = 0.05), DIS0-6 (p<0.01; ES = 0.05) and HSRD (p<0.01; ES=0.05). Length of the microcycle had an impact on TD (p<0.01; ES=0.05), DIS0-6 (p<0.01; ES=0.11), ACC (p<0.01; ES = 0.04) and VMAX (p<0.01; ES=0.04). This study provides coaches a selection of variables for match-play analysis, which could represented two-thirds of external load profile. Then, professionals should consider that these contextual variables could have an impact on the external load profile.


#3 Low energy availability in group of Polish female soccer players
Reference: Rocz Panstw Zakl Hig. 2020;71(1):89-96. doi: 10.32394/rpzh.2020.0106.
Authors: Dobrowolski H, Włodarek D
Summary: The most important element of a well-balanced diet is a proper energetic value. Energy deficiencies are often observed in athletes, especially women. Energy deficiencies can lead to low energy availability which can cause serious health problems and affect exercise capacities. There is, therefore, a risk of health complications and reduced physical performance among female soccer players. The aim of this study was to check the frequency of low energy availability appearance in a group of women training soccer, which could results in negative health effects due to Relative Energy Deficiency in Sport (RED-S). Thirty-one professional female soccer players practicing on different league levels (Extra-league, I league, II league) participated in the study. The participants had their height and body mass measured. To assess the Energy Intake the method of 3-day dietary food recording was used. Total Energy Expenditure (TEE) and Exercise Energy Expenditure (EEE) was measured by means of an Armband SenseWear Pro3 device. The content of fat free mass was assessed with Akern BIA 101 Anniversary Sport Edition device. The body mass median of participants was 58 kg. The average height was 166±5 cm, and the average BMI was 21.4±2 kg/m2. TEE was 2703±392 kcal/day, while EEE was 515 kcal (203-597 kcal). Energy intake was 1548±452 kcal/day. Energy availability was 25±11 kcal/kg fat free mass/day. Twenty of the study participants had low energy availability. The percentage of EEE in TEE was 17.93±3.14%. Low energy availability was demonstrated in the vast majority of studied group, which may lead to negative health consequences or reduction of exercise capacity.


#4 Masculinity and soccer: gender issues in a psychosocial rehabilitation experience with men in Brazil's Federal District
Reference: Salud Colect. 2020 Feb 17;16:e2247. doi: 10.18294/sc.2020.2247.
Authors: Albuquerque FP, Schraiber LB
Summary: This article presents a study of men's participation in soccer workshops at a mental health services facility (CAPS). The sport is considered a relevant practice in terms of men's sociability processes. Qualitative research was conducted at two CAPS facilities in Brasilia, Federal District from August 2017 to September 2018. Data were collected through observations of daily activities and with 10 semi-structured interviews with male participants who were selected during observations. The findings of this study demonstrate the potential of therapeutic soccer workshops for the psychosocial rehabilitation of men with mental disorders - the users of these mental health services - based on social and cultural re-insertion through an activity that materially and symbolically constructs masculinity and what it means to be a man in Brazil. As patients with mental disorders who are customarily marginalized from hegemonic masculinity, the users of CAPS services were able to access possible masculinities and reconstruct their new identities as men.


#5 The role of different directions of attention on the extent of implicit perception in soccer penalty kicking
Reference: Hum Mov Sci. 2020 Apr;70:102586. doi: 10.1016/j.humov.2020.102586. Epub 2020 Jan 29.
Authors: Memmert D, Noël B, Machlitt D, van der Kamp J, Weigelt M
Summary: The role of different directions of attention on the extent of the off-center effect (penalty takers kick to the bigger side of the goal more often, although they explicitly perceive the goalkeeper in the center of the goal) was investigated for soccer penalty kicking. Regarding the directions of attention of the striker, two conflicting assumptions (attention is paid to the goalkeeper vs. attention is only spent on target) were directly contrasted. Participants viewed a goalkeeper standing either in the middle of the goal or being displaced by different distances to the left or right. In the goal-side-related instruction condition, participants had to indicate the greater goal side and already did so at above chance-level for small displacements of 0.1%, although they were not confident in their perceptual judgments, hinting at the occurrence of the off-center effect. They became mindful of displacements of 0.8% and larger when they indicated the goal side for kicking with greater confidence. In the goalkeeper-related instruction condition, participants were asked to choose a goal side for kicking, but only when they perceived the goalkeeper in the middle of the goal. Participants chose the greater goal side at above chance-level for small displacements of 0.2%. They became mindful of the displacement for a difference of 0.8%. However, when comparing the results of both instruction conditions statistically it turned out that the effect of different directions of attention on the off-center's extent differs from those previously reported. Participants were implicitly influenced by comparably small goalkeeper displacements, but became earlier aware of goalkeeper displacements in the goal-side-related instruction condition.


#6 Concussion-Prevention Strategies Used in National Collegiate Athletic Association Divisions I and II Women's Soccer
Reference: J Athl Train. 2020 Mar 27. doi: 10.4085/1062-6050-142-19. [Epub ahead of print]
Authors: Jeffries KK, Girouard TJ, Tandy RD, Radzak KN
Summary: Whereas much attention has been paid to identifying mechanisms for decreasing concussion rates in women's soccer players, which strategies currently being used is unknown. In addition, athletic trainers' (ATs') knowledge and beliefs about the efficacy of concussion-prevention practices have not been studied. The aim was to evaluate the concussion-prevention strategies being used in National Collegiate Athletic Association Division I and Division II women's soccer and identify the beliefs of certified ATs regarding mechanisms for preventing concussion. A total of 223 women's soccer team ATs employed at Division I or II universities participated in this study. A survey instrument of structured questions and open-ended, follow-up questions was developed to identify the use of cervical-strengthening programs, headgear, and other techniques for preventing concussion. Questions also addressed ATs' beliefs regarding the effectiveness of cervical strengthening, headgear, and mouthguards in concussion prevention. Data were collected via questionnaire in Qualtrics survey software. Descriptive statistics of frequencies and percentages were calculated for close-ended questions. Open-ended questions were evaluated for common themes, which were then reported by response frequency. Cervical strengthening or stability for concussion prevention was reported by 38 (17.12%) respondents; 153 (69.86%) ATs believed that cervical strengthening would aid in concussion prevention. Seventy-eight (35.49%) reported that their players wore headgear. Nineteen (8.76%) believed that soccer headgear prevented concussions; 45 (20.74%) believed that mouthguards prevented concussions. Education in proper soccer technique was reported by 151 (69.59%) respondents. Fourteen (0.06%) respondents cited nutritional strategies for concussion prevention. Although ATs believed that cervical strengthening could help prevent concussions, few had implemented this strategy. However, the ATs whose teams used headgear outnumbered those who believed that headgear was an effective prevention strategy. Based on our findings, we saw a disconnect among the current use of concussion-prevention strategies, ATs' beliefs, and the available evidence.


#7 Effect of Two Strength Training Models on Muscle Power and Strength in Elite Women's Football Players
Reference: Sports (Basel). 2020 Mar 30;8(4). pii: E42. doi: 10.3390/sports8040042.
Authors: Pacholek M, Zemková E
Download link: https://www.mdpi.com/2075-4663/8/4/42/pdf
Summary: This study evaluates changes in power and strength after implementing two different models of 9-week strength training in elite women's football players. A group of 13 players (age 20.2 ± 3.3 years, body mass 57.2 ± 3.7 kg, height 163.6 ± 5.3 cm, VO2max 45.2 ± ml/min) underwent either a complex (the intermittent load type) or combined (the maximal strength and dynamic method) model of training. The training load was tailored to each athlete. Results showed that the complex model of training improved power (10 W/kg, p = 0.006) and height of vertical jump (5.3 cm, p = 0.001), weight of 1 Repeat Maximum (1RM) which was (5.8 kg, p = 0.015), power and speed in the acceleration phase of barbell half squats (BHS) at weights from 20 to 60 kg, and the number of repetitions in BHS (10.3%, p = 0.012). The combined model of training improved the time of shuttle run (0.44 s, p = 0.000), weight of 1RM in BHS (9.6kg, p = 0.000) and BP (4 kg, p = 0.000), power in the acceleration phase of BHS at weights from 50 to 60 kg, the number of repetitions in BP (14.3%, p = 0.000), BHS (9.4%, p = 0.002), barbell bench pulls (11.9%, p = 0.002) and sit-ups (7.7%, p = 0.001). These findings indicate that the complex model of training improves explosive abilities, whereas the combined model is effective for developing strength at weights close to players' 1RM and for repeatedly overcoming resistance. Therefore, coaches should choose the training model based on the needs of individual players.


#8 Urine metabolomic analysis for monitoring internal load in professional football players
Reference: Metabolomics. 2020 Mar 28;16(4):45. doi: 10.1007/s11306-020-01668-0.
Authors: Quintas G, Reche X, Sanjuan-Herráez JD, Martínez H, Herrero M, Valle X, Masa M, Rodas G
Summary: The design of training programs for football players is not straightforward due to intra- and inter-individual variability that leads to different physiological responses under similar training loads. The aim was to study the association between the external load, defined by variables obtained using electronic performance tracking systems (EPTS), and the urinary metabolome as a surrogate of the metabolic adaptation to training. Urine metabolic and EPTS data from 80 professional football players collected in an observational longitudinal study were analyzed by ultra-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry and assessed by partial least squares (PLS) regression. PLS models identified steroid hormone metabolites, hypoxanthine metabolites, acetylated amino acids, intermediates in phenylalanine metabolism, tyrosine, tryptophan metabolites, and riboflavin among the most relevant variables associated with external load. Metabolic network analysis identified enriched pathways including steroid hormone biosynthesis and metabolism of tyrosine and tryptophan. The ratio of players showing a deviation from the PLS model of adaptation to exercise was higher among those who suffered a muscular lesion compared to those who did not. There was a significant association between the external load and the urinary metabolic profile, with alteration of biochemical pathways associated with long-term adaptation to training. Future studies should focus on the validation of these findings and the development of metabolic models to identify professional football players at risk of developing muscular injuries.


#9 Sleep Dysfunction and Mood in Collegiate Soccer Athletes
Reference: Sports Health. 2020 Apr 9:1941738120916735. doi: 10.1177/1941738120916735. [Epub ahead of print]
Authors: Benjamin CL, Curtis RM, Huggins RA, Sekiguchi Y, Jain RK, McFadden BA, Casa DJ
Summary: Sleep and mood are critical factors that contribute to health and wellness and are of particular interest to collegiate athletes who are juggling high physical, academic, and social demands. The aim of this study was to examine how psychological measures, player status, and sex-related factors were associated with perceived sleep quality. Higher levels of global sleep dysfunction will be related to poor mood and increased anxiety, and there will be differences in sleep dysfunction in male compared with female athletes as well as regarding playing status. During the 2016 through 2018 National Collegiate Athletic Association (NCAA) seasons, the Pittsburgh Sleep Quality Index (PSQI), Profile of Mood States, and Sports Anxiety Scale-2 questionnaires were administered to 230 soccer athletes at 6 separate time points throughout each season. PSQI results yielded scores ≥5 in 54% of observations. Increased sleep dysfunction was significantly related to decreased vigor and increased tension, depression, anger, fatigue, somatic anxiety, worry, and concentration disruption, although effect sizes (ES) were trivial (ES, -0.03 to 0.15). The odds ratio (OR) of reporting global sleep dysfunction increased by 8%, 9%, and 25% for every 1-unit increase in tension (OR, 1.08; 95% CI, 1.02-1.16; P = 0.015), fatigue (OR, 1.09; 95% CI, 1.03-1.16; P = 0.002), and concentration disruption (OR, 1.25; 95% CI, 1.09-1.45; P = 0.002), respectively. The odds of reporting global sleep dysfunction were 55% lower for males than females (OR, 0.45; 95% CI, 0.25-0.79; P = 0.006). Global sleep dysfunction was prevalent in NCAA soccer players and was related to negative mental health outcomes. Female participants experienced increased odds of reporting global sleep dysfunction. Regular monitoring allows for a greater understanding of the interrelatedness between sleep and mental health in athletes.


#10 Eccentric hamstring strength is associated with age and duration of previous season hamstring injury in male soccer players
Reference: Int J Sports Phys Ther. 2020 Apr;15(2):246-253.
Authors: Vicens-Bordas J, Esteve E, Fort-Vanmeerhaeghe A, Clausen MB, Bandholm T, Opar D, Shield A, Thorborg K
Summary: Eccentric hamstring strength seems important in reducing the odds of future hamstring injuries. While age and previous injury are well-known risk factors for future hamstring injuries, the association of age and previous hamstring injury with eccentric hamstring strength in the following season is unknown. The purpose was to investigate the association of age and previous hamstring injury with preseason eccentric hamstring strength in soccer players, and to investigate the association between previous hamstring injury duration and preseason eccentric hamstring strength. A convenience sample of 284 male amateur soccer players (age 18-38 years) was included in the analyses. Self-reported information about previous season hamstring injury and its duration (three weeks or less; more than three weeks) was collected. Preseason eccentric hamstring strength was obtained during the Nordic hamstring exercise using a field-based device. Age had a negative association with preseason eccentric hamstring strength with 0.9% reduction per year. Players with a previous hamstring injury duration of more than three weeks (n=27) had 13% lower preseason eccentric hamstring strength compared to players without previous hamstring injury. Older players have lower preseason eccentric hamstring strength than younger players. Players with a previous hamstring injury duration of more than three weeks have lower preseason eccentric hamstring strength than the rest of the players. These results highlight the need to monitor and address the identified weaknesses in eccentric hamstring strength in amateur soccer players, with specific emphasis on older players with a previous hamstring injury of longer duration.


#11 Application of Individualized Speed Zones to Quantify External Training Load in Professional Soccer
Reference: J Hum Kinet. 2020 Mar 31;72:279-289. doi: 10.2478/hukin-2019-0113. eCollection 2020 Mar.
Authors: Rago V, Brito J, Figueiredo P, Krustrup P, Rebelo A
Summary: This study aimed to examine the interchangeability of two external training load (ETL) monitoring methods: arbitrary vs. individualized speed zones. Thirteen male outfield players from a professional soccer team were monitored during training sessions using 10-Hz GPS units over an 8-week competitive period (n = 302 observations). Low-speed activities (LSA), moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary speed zones as <14.4, 14.4-19.8, 19.8-25.1 and ≥25.2 km·h-1, and using individualized speed zones based on a combination of maximal aerobic speed (MAS, derived from the Yo-yo Intermittent recovery test level 1), maximal sprinting speed (MSS, derived from the maximal speed reached during training) and anaerobic speed reserve (ASR) as <80% MAS, 80-100% MAS, 100% MAS or 29% ASR and ≥30% ASR. Distance covered in both arbitrary and individualized methods was almost certainly correlated in all speed zones (p < 0.01; r = 0.67-0.78). However, significant differences between methods were observed in all speed zones (p < 0.01). LSA was almost certainly higher when using the arbitrary method than when using the individualized method (p < 0.01; ES = 5.47 [5.18; 5.76], respectively). Conversely, MSR, HSR and sprinting speed were higher in the individualized method than in the arbitrary method (p < 0.01; ES = 5.10 [4.82; 5.37], 0.86 [0.72; 1.00] and 1.22 [1.08; 1.37], respectively). Arbitrary and individualized methods for ETL quantification based on speed zones showed similar sensitivity in depicting player locomotor demands. However, since these methods significantly differ at absolute level (based on measurement bias), arbitrary and individualized speed zones should not be used interchangeably.

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Eccentric hamstring work during preseason

Was there any effect on injury occurrence and performance?

Tue

19

May

2020

Attacking and Defensive Styles of Play in Football

Analysis of Spanish and English teams.

Mon

18

May

2020

Latest research in football - week 14 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Understanding the presence of mental fatigue in English academy soccer players
Reference: J Sports Sci. 2020 Mar 25:1-7. doi: 10.1080/02640414.2020.1746597. [Epub ahead of print]
Authors: Thompson CJ, Noon M, Towlson C, Perry J, Coutts AJ, Harper LD, Skorski S, Smith MR, Barrett S, Meyer T
Summary: Research has demonstrated that induced mental fatigue impairs soccer-specific technical, tactical and physical performance in soccer players. The findings are limited by the lack of elite players and low ecological validity of the tasks used to induce mental fatigue, which do not resemble the cognitive demands of soccer. The current study collected survey data from English academy soccer players (n = 256; age groups - U14 - U23), with questions comprising of five themes (descriptors of physical and mental fatigue, travel, education, match-play and fixture congestion). The survey consisted of multiple choice responses, checkboxes and blinded/unblinded (for duration based questions) 0-100 arbitrary unit (AU) slider scales. Listening to music (81.6% of players), using social media (58.3%) and watching videos (34.3%) were the most common pre-match activities. Pre-match subjective mental fatigue was low (18.7±18.8 AU), and most frequently reported at the end of a match (47±26 AU) and remained elevated 24-hours post-match (36±27 AU). Travel (29±24 AU), fixture congestion (44±25 AU) and education (30±26 AU) demonstrated a low to moderate presence of subjective mental fatigue. These findings provide an overview of activities performed by English academy soccer players pre-match, and demonstrate that mental fatigue is experienced as a result of match-play.


#2 Small-Sided Games are More Enjoyable Than High-Intensity Interval Training of Similar Exercise Intensity in Soccer
Reference: Open Access J Sports Med. 2020 Mar 4;11:77-84. doi: 10.2147/OAJSM.S244512. eCollection 2020.
Authors: Selmi O, Ouergui I, Levitt DE, Nikolaidis PT, Knechtle B, Bouassida A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7069497/pdf/oajsm-11-77.pdf
Summary: High-intensity interval training (HIIT) and small-sided games (SSG) have been applied and tested for athletes in order to enhance the soccer performance. For this reason, this experimental study aimed to compare the effects of SSGs and HIIT on power, physiological responses and perceived enjoyment. Sixteen youth soccer players (age, 17.5±0.6 years, mean±standard deviation; height, 178.2±6.4 cm; body mass, 70.4±5.4 kg; body fat, 10.6±0.8%) completed one session each of HIIT and SSG on separate days with 1 week between sessions. Each session lasted 25 mins (4x4 mins work with 3 mins of passive recovery in-between). SSGs consisted of 4 versus 4 player games on a 25×35 m pitch, and HIIT consisted of intermittent 15-s runs at 110% maximal aerobic speed separated by 15 s of passive recovery. Psychological responses following each protocol were assessed using the Physical Activity Enjoyment Scale (PACES). Heart rate (HR) was continuously recorded, rating of perceived exertion (RPE) and lactate concentration [La] were measured after each training session. Lower body muscular power was assessed using the 5-jump test relative to leg length (5JT-relative) before and after each training session, where greater average distance per stride over five sequential jumping strides indicated greater muscular power. HIIT and SSG showed no significant difference in HR, RPE and [La] responses (p=0.70, ES=0.11; p=0.61, ES=0.08 and p=0.38, ES=0.21, respectively). 5JT-relative decreased significantly for SSG and HIIT (p<0.05, ES=0.50 and p<0.05, ES=0.40, respectively). PACES score was greater in SSG compared to HIIT (ES=5.35, p<0.001). HIIT and SSG sessions induced similar physiological responses; however, SSGs induced a higher enjoyment level than HIIT. Coaches could choose between these training modalities according to the objective of their training session, considering the enjoyment-related advantages of SSGs.


#3 Effects of muscular injuries on the technical and physical performance of professional soccer players
Reference: Phys Sportsmed. 2020 Mar 21:1-5. doi: 10.1080/00913847.2020.1744485. [Epub ahead of print]
Authors: Portillo J, Abián P, Calvo B, Paredes V, Abián-Vicén J
Summary: The aim of this study was to determine the effects of muscular injuries in the lower limbs on the technical and physical performance of professional soccer players when they return to the league competition. Seventy-six muscular injuries incurred by Spanish male professional soccer players (Age: 27.5 ± 3.5 years) were analyzed during two consecutive competitive seasons: 2014-2015 and 2015-2016. The players' performance was studied during Spanish First Division competitive matches using a multi-camera computerized tracking system (Mediacoach Desktop). After muscular injury relative total distance covered in sprints decreased by 8.6 ± 30.2% (P = 0.013) in the first half and 7.7 ± 36.6% (P = 0.038) in the second half. Similarly, maximal running speed decreased by 2.78 ± 6.91 km.h-1 (pre: 27.3 ± 6.4 km.h-1 vs. post: 24.5 ± 6.6 km.h-1, P = 0.013) in the first half, and 1.50 ± 5.68 km.h-1 (29.1 ± 3.9 km.h-1 vs. 27.6 ± 5.3 km.h-1, P = 0.043) in the second half. Muscle injury also affected technical performance significantly decreasing successful passes (P = 0.045). There were no differences in the number of possession gains (P = 0.277), and possession losses (P = 0.178). After a moderate or severe muscular injury (causing >8 days lay off), player performance is significantly lower in high-intensity efforts and technical skills such as sprints, maximal running speed, or successful passes.


#4 Age-related differences in torque in angle-specific and peak torque hamstring to quadriceps ratios in female soccer players from 11 to 18 years old: Α Cross-sectional study
Reference: Res Sports Med. 2020 Mar 22:1-13. doi: 10.1080/15438627.2020.1742713. [Epub ahead of print]
Authors: Andrade MS, Junqueira MS, Andre Barbosa De Lira C, Vancini RL, Seffrin A, Nikolaidis PT, Rosemann T, Knechtle B
Summary: The aim of this study was to evaluate and compare the hamstring (H) and quadriceps (Q) strength, bilateral difference and balance ratios in female soccer players. Ninety-three athletes from three age groups: under 13 (U13), 15 (U15) and 18 (U18) participated in the study performing isokinetic tests to measure peak torque, total work, average power and torque at 30º of thigh muscles. Conventional strength balance ratios, angle-specific balance ratio and bilateral strength difference were evaluated. There was bilateral strength difference for extensor muscles total work (p = 0.02) in U13 and flexor muscles peak torque (p = 0.02) in U15. All variables were superior in U15 than U13 (p <.05). There was no strength difference between U15 and U18. Balance ratios did not differ between sides or age groups. The study showed that although peak torque values were higher in U15 than in U13, balance ratios were similar.


#5 Acceleration intensity is an important contributor to the external and internal training load demands of repeated sprint exercises in soccer players
Reference: Res Sports Med. 2020 Mar 22:1-10. doi: 10.1080/15438627.2020.1743993. [Epub ahead of print]
Authors: Beato M, Drust B
Summary: The aim of this study was to evaluate the effect of acceleration on the external and internal load during repeated sprint exercises (RSE). This study used a cross-over design. Sixteen soccer players were included (mean ± SDs: age 21 ± 1 years; weight 71.1 ± 7.7 kg). RSE was 3 sets of 7 × 30 m sprints with 25 s and 3 min recovery between sprints and sets, respectively. RSE was performed using two protocols requiring either 10 m maximal acceleration (2.12 m.s-2 [RSE-MA]) or 10 m submaximal acceleration (1.66 m.s-2 [RSE-SA]). Global positioning systems (10 Hz; STATSports, Viper) were utilized to collect: high speed running (HSR), dynamic stress load (DSL), Heart Rate (HR) peak, time >85% HR peak, respiratory (RPEres) and muscular (RPEmus) rating of perceived exertion. RSE-MA induced higher load than RSE-SA in HSR (p = 0.037, ES = 0.20), DSL (p = 0.027, ES = 0.43), HR peak (p = 0.025, ES = 0.47), Time >85% HR peak (p = 0.028, ES = 1.11), RPEres (p = 0.001, ES = 1.10), and RPEmus (p = 0.001, ES = 0.73). This study shows that a different acceleration intensity in a RSE (MA vs. SA) impacts external and internal training load parameters.


#6 Perceptual-cognitive processes underlying creative expert performance in soccer
Reference: Psychol Res. 2020 Mar 21. doi: 10.1007/s00426-020-01320-5. [Epub ahead of print]
Authors: Roca A, Ford PR, Memmert D
Summary: Creativity is one of the key parts of expert performance in sport and other domains. The aim of this study was to determine the underlying perceptual and cognitive processes that underpin creative expert performance in the sport of soccer. Forty skilled adult soccer players participated. In the experimental task, they interacted with representative video-based 11 vs. 11 attacking situations whilst in possession of a ball. Clips were occluded at a key moment and participants were required to play the ball in response to each presented scenario as they would in a real-game situation. Moreover, they were required to name other additional actions they could execute for each situation. Their solutions on the task were measured using the three observation criteria for creativity of originality, flexibility, and fluency of decisions. Using these criteria, players were categorized into either high- or low-creative groups. Visual search and cognitive thought processes were recorded during the task using a portable eye-movement registration system and retrospective verbal reports. The creativity-based between-group differences in decision making were underpinned by differences in visual search strategy. Compared to the low-creative group, the high-creative players made more fixations of shorter duration in a different sequential order and to more task-relevant locations of the display, indicating a broader attentional focus. They also generated a greater number of verbal reports of thoughts related to the assessment of the current task situation and planning of future decisions when compared with the low-creative players. Our findings highlight the perceptual-cognitive processes that underlie creative expert performance in a sport-specific domain.


#7 Short-Term FIFA 11+ Improves Agility and Jump Performance in Young Soccer Players
Reference: Int J Environ Res Public Health. 2020 Mar 18;17(6). pii: E2017. doi: 10.3390/ijerph17062017.
Authors: Trajković N, Gušić M, Molnar S, Mačak D, Madić DM, Bogataj Š
Download link: https://www.mdpi.com/1660-4601/17/6/2017/pdf
Summary: Studies dealing with the effectiveness of the Fédération Internationale de Football Association (FIFA) 11+ prevention program to improve performance outcomes in children aged < 14 years are limited. This study aimed to point out the effects of the application of short-term FIFA 11+ warm-up program on physical performance in young football players. Participants were 36 youth male football players, divided into a FIFA 11+ (n = 19; mean (SD) age: 11.15 (0.79) y) and a control group (CG: n = 17; age: 10.87 (0.8) y) and trained for 4 weeks. Before and after the training period, standing long jump performance, agility, repeated sprint ability, sit and reach, and "30-15" intermittent fitness tests were assessed. A mixed ANOVA showed significant differences between the groups in the standing long jump test (FIFA 11+: 5.6% vs. CG: -1.9%) in favor of FIFA 11+ over CG. Additionally, the FIFA 11+ performance of the Illinois agility test was significantly better compared to the CG performance (FIFA 11+: -1.9% vs. CG: 0.03%). The main findings of this study suggest that just 4 weeks of implementation of the FIFA 11+ improves physical performance compared with traditional warm-up routines in young soccer players.


#8 Football cannot restart soon during the COVID-19 emergency! A critical perspective from the Italian experience and a call for action
Reference: Br J Sports Med. 2020 Mar 24. pii: bjsports-2020-102306. doi: 10.1136/bjsports-2020-102306. [Epub ahead of print]
Authors: Corsini A, Bisciotti GN, Eirale C, Volpi P
Download link: https://bjsm.bmj.com/content/bjsports/early/2020/03/26/bjsports-2020-102306.full.pdf


#9 Does a recent hamstring muscle injury affect the timing of muscle activation during high speed overground running in professional Australian Football players?
Reference: Phys Ther Sport. 2020 Mar 18;43:188-194. doi: 10.1016/j.ptsp.2020.03.005. [Epub ahead of print]
Authors: Crow J, Semciw A, Couch J, Pizzari T
Summary: The purpose was to investigate if the temporal characteristics of hamstring and gluteal muscle activation are altered during high speed overground running in professional Australian Football players following hamstring muscle injury. Elite professional Australian Football players who had sustained a hamstring muscle injury in the six months prior to testing (n = 7) and a group of players from the same club who had no history of hamstring muscle injury (n = 8) participated in this study. Muscle onset timing, muscle offset timing and muscle onset duration of the medial hamstrings, biceps femoris and gluteus maximus muscles during high-speed running using electromyographic data were used.  No significant differences in any of the temporal aspects of muscle activation were found between groups for any of the muscles tested (p > 0.05). Persistent alterations to the timing of muscle activation following hamstring muscle injury that have been reported in recreational athletes were not observed during high speed running in professional athletes who have completed comprehensive rehabilitation programs.


#10 The relationship between cam morphology and hip and groin symptoms and signs in young male football players
Reference: Scand J Med Sci Sports. 2020 Mar 22. doi: 10.1111/sms.13660. [Epub ahead of print]
Authors: van Klij P, Ginai AZ, Heijboer MP, Verhaar JAN, Waarsing JH, Agricola R
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13660
Summary: Conflicting and limited high quality prospective data is available on the associations between cam morphology and hip and groin symptoms and range of motion (ROM). This cross-sectional cohort study investigated associations between cam morphology presence, size and duration and symptoms and ROM. Academy male football players (n=49, 17-24 years) were included. Standardised anteroposterior pelvic and frog-leg lateral radiographs were obtained at baseline, 2.5 and 5-year follow-up. The femoral head-neck junction was quantified by: Visual score. Cam morphology (flattening or prominence), large cam (prominence). Alpha angle.Cam morphology (≥60°), large cam (≥78°). Cam morphology duration was defined as long (first present at baseline) or short (only from 2.5 or 5-year follow-up). Current symptoms at 5-year follow-up were assessed using a hip and groin pain question and by the 'Hip and Groin Outcome Score' (HAGOS). HAGOS-scores were categorised into: most symptoms (≥2 domains in lowest interquartile range [IQR]), least symptoms (≥2 domains in highest IQR). Hip ROM was measured by goniometry at 5-year follow-up. Large cam morphology based on visual score was associated with hip and groin pain (23.8% vs. 7.1%, OR: 3.17, CI: [1.15-8.70], P=.026), but not with HAGOS-scores. Cam morphology presence, size and duration were associated with limited flexion of around 6° and/or 3° to 6° for internal rotation. Cam morphology presence, size and duration were associated with limited hip flexion and/or internal rotation, but differences might not exceed the minimal clinical important difference. Whether cam morphology results in symptoms is uncertain.


#11 Novel Methodology for Football Rebound Test Method
Reference: Sensors (Basel). 2020 Mar 18;20(6). pii: E1688. doi: 10.3390/s20061688.
Authors: Colino E, Corral-Gómez L, Rodríguez-Rosa D, Juárez-Pérez S, García-Unanue J, González-Rodríguez A, Sánchez-Sánchez J, Felipe JL, Gallardo L, Castillo-García FJ
Download link: https://www.mdpi.com/1424-8220/20/6/1688/pdf
Summary: Assessing and keeping control of the mechanical properties of sport surfaces is a relevant task in sports since it enables athletes to train and compete safely and under equal conditions. Currently, different tests are used for assessing athlete- and ball-surface interactions in artificial turf pitches. In order to make these evaluations more agile and accessible for every facility, it is important to develop new apparatus that enable to perform the tests in an easier and quicker way. The existing equipment for determining the vertical ball behavior requires a complex and non-easily transportable device in which the ball must be fixed to the upper part of the frame in a very precise position by means of a magnet. The rebound height is determined by capturing the acoustic signal produced when the ball bounces on the turf. When extended tests are conducted, the time required to evaluate a single field is too high due to the non-valid trials. This work proposes a novel methodology which allows to notoriously decrease the time of testing fields maintaining the repeatability and accuracy of the test method together with a compact device for improving its mobility and transport. Simulations and experiments demonstrates the repeatability and accuracy of the results obtained by the proposed device, which decreases the non-valid trials and notoriously reduces the time for field evaluation.

Fri

15

May

2020

The influence of creativity on goal scoring

How important is a creative pass to score a goal?

Wed

13

May

2020

Motivation counteracts fatigue-induced performance degrement

More precisely, money as motivation counteracts fatigue.

Tue

12

May

2020

Latest research in football - week 13 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Off-Season Training Habits and BMI, Not Preseason Jump Measures, Are Associated with Time-Loss Injury in Female Collegiate Soccer Players
Reference: Sports (Basel). 2020 Mar 15;8(3). pii: E36. doi: 10.3390/sports8030036.
Authors: Brumitt J, Mattocks A, Engilis A, Sikkema J, Loew J
Download link: https://www.mdpi.com/2075-4663/8/3/36/pdf
Summary: The primary purpose of this study was to determine the effectiveness of the standing long jump (SLJ) and the single-leg hop (SLH) tests to discriminate lower quadrant (low back and lower extremities) injury occurrence in female collegiate soccer players. The secondary purpose of this study was to determine associations between injury and off-season training habits or anthropometric measures. SLJ, SLH, and anthropometric measures were collected during a preseason screening clinic. Each subject completed a questionnaire providing demographic information and off-season training habits. Each athlete performed three SLJ and three SLH per leg. SLJ and SLH scores were not associated with an increased risk of a noncontact time-loss lower quadrant (LQ) injury. Athletes with a higher BMI or who reported less time training during the off-season were two times more likely to sustain an injury. Athletes who had both a higher body mass index (BMI) and lower off-season training habits were three times (relative risk = 3.1 (95% CI: 1.7, 5.5) p-value = 0.0001) more likely to sustain a noncontact time-loss lower quadrant injury. Preseason SLJ and SLH scores do not discriminate injury risk in female collegiate soccer players. Higher BMI and lower off-season training habits are associated with an increased risk of LQ injury.


#2 Read-the-game: System for skill-based visual exploratory activity assessment with a full body virtual reality soccer simulation
Reference: PLoS One. 2020 Mar 17;15(3):e0230042. doi: 10.1371/journal.pone.0230042. eCollection 2020.
Authors: Rojas Ferrer CD, Shishido H, Kitahara I, Kameda Y
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0230042&type=printable
Summary: We present a novel virtual reality (VR) system to measure soccer players' read-the-game ability. Read-the-game is a term that encompasses a conglomerate of visual exploratory behavioral patterns and cognitive elements required to make accurate in-game decisions. Our technological approach in the Sports Science domain focuses on the visuomotor component of targeted skill development in a VR simulation because VR is a powerful perception-action coupling training solution for visuomotor coordination due to its high sense of immersion and its psychological byproduct presence. Additionally, we analyze two critical aspects: psychological (i.e., sense of presence) and the human-computer interaction (HCI) domain (i.e., suitable input device for full-body immersion). To measure head movements related to visual explorations, the system tracks the user's head excursions. Specifically, the engaged visual exploratory activity (VEA) during a VR simulation is measured frame-by-frame at runtime to study the behavior of players making passing decisions while experiencing pressure from rivals during in-game situations recreated with computer graphics (CG). Additionally, the sense of presence elicited by our system is measured via the Igroup Presence Questionnaire applied to beginner and amateur soccer players (n = 24). Regarding the HCI aspect, a comparison of input options reveals that a high presence can be achieved when using full body interactions that integrate head and body motions via a combination of an HMD and kinetic body tracking. During our system verification, a difference in the VEA performance is observed between beginner and amateur players. Moreover, we demonstrate the capacity of the system to measure the VEA while evoking immersive soccer in-match experiences with a portable VR setup.


#3 Streamlining Analysis of RR Interval Variability in Elite Soccer Players: Preliminary Experience with a Composite Indicator of Cardiac Autonomic Regulation
Reference: Int J Environ Res Public Health. 2020 Mar 12;17(6). pii: E1844. doi: 10.3390/ijerph17061844.
Authors: Lucini D, Fallanca A, Malacarne M, Casasco M, Galiuto L, Pigozzi F, Galanti G, Pagani M
Download link: https://www.mdpi.com/1660-4601/17/6/1844/pdf
Summary: It is well recognized that regular physical activity may improve cardiac autonomic regulation preventing chronic non-communicable diseases. Accordingly, the assessment of cardiac autonomic regulation (CAR) with non-invasive techniques, such as RR interval Variability (V) might be of practical interest. We studied 56 soccer players (21.2 ± 4.2 years.) and 56 controls (22.2 ± 1.5 years.) and used a ranked Autonomic Nervous System Index (ANSI), resulting from the combination of multivariate statistical methodologies applied to spectral analysis derived indices from RRV. We hypothesized that ANSI would be higher in soccer players as compared to controls (p < 0.001) and that values would be greatest in defenders and midfielders, who are known to run longer distances during competitions. Conversely in the intrinsically stationary goalkeepers ANSI would be similar to controls. Our data show that it is possible to assess the overall level of autonomic performance in soccer players as compared to the general population, using a ranked composite autonomic proxy (ANSI). This approach suggests as well that CAR is better in those players who during competitions run for a greater distance. We conclude that it is possible to highlight the differences in autonomic profile due to distinct exercise routines, using ANSI, a simple ranked, composite autonomic proxy.


#4 Sprint mechanical properties in soccer players according to playing standard, position, age and sex
Reference: J Sports Sci. 2020 Mar 16:1-7. doi: 10.1080/02640414.2020.1741955. [Epub ahead of print]
Authors: Haugen TA, Breitschädel F, Seiler S
Summary: The purpose of this study was to quantify possible differences in sprint mechanical outputs in soccer according to soccer playing standard, position, age and sex. Sprint tests of 674 male and female players were analysed. Theoretical maximal velocity (v0), horizontal force (F0), horizontal power (Pmax), force-velocity slope (SFV), ratio of force (RFmax) and index of force application technique (DRF) were calculated from anthropometric and spatiotemporal data using an inverse dynamic approach applied to the centre-of-mass movement. Players of higher standard exhibited superior F0, v0, Pmax, RFmax and DRF scores (small to large effects) than those of lower standard. Forwards displayed clearly superior values for most outputs, ahead of defenders, midfielders and goalkeepers, respectively. Male >28 y players achieved poorer v0, Pmax and RFmax than <20, 20-24 and 24-28 y players (small to moderate), while female <20 y players showed poorer values than 20-24 and >24 y players for the same measures (small). The sex differences in sprint mechanical properties ranged from small to very large. These results provide a holistic picture of the force-velocity-power profile continuum in sprinting soccer players and serve as useful background information for practitioners when diagnosing individual players and prescribing training programmes.


#5 Anabolic-catabolic hormonal responses in youth soccer players during a half-season
Reference: Res Sports Med. 2020 Mar 15:1-14. doi: 10.1080/15438627.2020.1734930. [Epub ahead of print]
Authors: Andrzejewski M, Podgórski T, Kryściak J, Chmura P, Konefał M, Chmura J, Marynowicz J, Adrian J, Pluta B
Summary: This study sought to evaluate the hormonal response (i.e. total testosterone, free testosterone, cortisol, and their ratios TT/C and FT/C) in the under-19 youth soccer team (n = 18) throughout a six-month period. All sport medical examinations were conducted four times: before the beginning of the preparation period (T1), just after preparation period (T2), in the middle of the competitive period (T3), and at the end of the season (T4). The cortisol concentration was decreased at the T3 (-16.9%; p = 0.014), then increased at the T2 (16.8%; p = 0.001) and at the T4 (12.7%; p = 0.062), respectively, compared to the initial value. The analyses for total and free testosterone demonstrated no differences between the measurements. Finally, values of the TT/C and FT/C ratios were increased during the T3 (25%; p = 0.017, 24.4%; p = 0.021) in comparison with the initial measurement and decreased at the T4 (-28.9%; p = 0.001, - 30.8%; p = 0.001) in comparison with the T3. The study results showed that the lowest level of peripheral fatigue was recorded in the T3, which may suggest that a correct selection of training loads does not affect the severity of catabolic processes in youth players.


#6 Fifth Metatarsal Fractures in Professional Soccer Players: Case Series
Reference: Foot Ankle Spec. 2020 Mar 14:1938640020911223. doi: 10.1177/1938640020911223. [Epub ahead of print]
Authors: Baumfeld T, Fernandes Rezende R, Nery C, Batista JP, Baumfeld D
Summary: Fifth metatarsal fractures occur mainly in young athletes, with an estimated incidence of 1.8 per 1000 individuals per year. This study aims to evaluate the functional outcome of professional soccer players undergoing surgical treatment of fifth metatarsal base fractures. We appraised 34 soccer players operated on from July 2001 to June 2016. All individuals were assessed by the American Orthopedic Foot and Ankle Score (AOFAS) and Visual Analog Scale (VAS) before and after surgery, with a mean 23-month follow-up. The need for grafting, fracture healing, Torg classification, and return to sports were also evaluated. There were 10 attackers, 7 offensive-defensive midfielders, 6 side defenders, 5 central defensive midfielders, 3 defenders, 2 goalkeepers, and 1 defensive midfielder, at an average age of 19 years. Preoperative and postoperative AOFAS averaged 42 and 99 points, respectively, whereas VAS scores were 6 and 0. The longer the time to get operated on, the greater was the need for grafting (P = .011). In our study, all fractures have consolidated. Return to sports occurred, on average, 73 days after surgical treatment, and it was not influenced by the time to get operated on, fracture healing, Torg classification, and grafting. Surgical treatment of the fifth metatarsal base fracture in professional soccer players presents good clinical results. Getting back to activities after surgery is not influenced by surgery time, fracture healing, Torg classification, and grafting.


#7 Comparison between Two Different Device Models 18 Hz GPS Used for Time-Motion Analyses in Ecological Testing of Football
Reference: Int J Environ Res Public Health. 2020 Mar 15;17(6). pii: E1912. doi: 10.3390/ijerph17061912.
Authors: Gimenez JV, Garcia-Unanue J, Navandar A, Viejo-Romero D, Sanchez-Sanchez J, Gallardo L, Hernandez-Martin A, Felipe JL
Download link: https://www.mdpi.com/1660-4601/17/6/1912/pdf
Summary: The aim of this study was to compare the validity of two different GPS device models used for time-motion analyses in ecological testing of football. Ten healthy male players from a Spanish university football team participated in this study. The team sport simulation circuit (TSCC) used was based on previous research examining the validity and interunit reliability of different GPS systems. Participants were required to complete eight laps of the TSSC, resulting in a total distance of 1320 m. The GPS units used for the current study were the 18 Hz StatsSport Apex Pro and 18 Hz RealTrack WIMU Pro. Participants were required to wear either of the two GPS units during the test. To establish the construct validity of GPS as a measure of Vmax, timing lights were used as a gold standard. The results clearly suggest that it is not possible to use the same 18 Hz GPS model or interchange it. The measurement can be considered precise when the noise is at least equal to or lower than the smallest worthwhile change. In this case, all standard deviation in measurement error was higher than the smallest worthwhile change. This is due to an inconsistency in the data processing of each trademark. It is important to prevent a club using different GPS trademarks at the same time, since it is not possible to compare in any case any type of result obtained between different trademarks.


#8 Eccentric knee flexor strength of professional football players with and without hamstring injury in the prior season
Reference: Eur J Sport Sci. 2020 Mar 17:1-26. doi: 10.1080/17461391.2020.1743766. [Epub ahead of print]
Authors: Ribeiro-Alvares JB, Oliveira GS, de Lima-E-Silva FX, Baroni BM
Summary: Both injury history and eccentric knee flexor strength have been associated with risk of football players sustaining hamstring strain injury (HSI). However, it remains unclear whether football players who sustained HSIs in the prior season present themselves for the next season with persistent eccentric strength deficits. Therefore, the aim of the present study was to verify the eccentric knee flexor strength of professional male football players with and without history of HSI in the prior season. This case-control study assessed 210 professional male football players from 10 Brazilian clubs: 182 included in the control group and 28 in the previously injured group. Players from the injured group had suffered unilateral HSI in the prior season. We measured the peak eccentric knee flexors force during the Nordic hamstring exercise and calculated the between-limb asymmetry. Groups were similar for age, body mass and height (p>0.05). Control group had similar strength values between left and right limbs (376.29 ± 61.77 N vs. 380.28 ± 61.77 N; p=0.27; d=0.06), while the previously injured limb was weaker than the contralateral uninjured limb in the injured group (350.87 ± 60.79 N vs. 385.75 ± 63.49 N; p<0.01; d=0.56). Thirty-seven percent of players in the control group and 50% in the injured group presented between-limb asymmetry >10%. This study demonstrates that players with history of HSI in the prior season present reduced eccentric knee flexor strength in the injured limb, but half of them have between-limb asymmetry within the most commonly adopted benchmark value of 10%.


#9 Height After Side: Goalkeepers Detect the Vertical Direction of Association-Football Penalty Kicks From the Ball Trajectory
Reference: Front Psychol. 2020 Feb 27;11:311. doi: 10.3389/fpsyg.2020.00311. eCollection 2020.
Authors: Higueras-Herbada A, Lopes JE, Travieso D, Ibáñez-Gijón J, Araújo D, Jacobs DM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7056909/pdf/fpsyg-11-00311.pdf
Summary: The present research analyzes the relation between the height of penalty kicks in association football and (a) the probability that goalkeepers stop the ball, (b) the kinematics of the kicker, and (c) the movements of the goalkeeper. We re-analyzed movement registration data that were collected in an experiment (with professional and semi-professional players) that focused on the horizontal direction of the penalties (Lopes et al., 2014). We also digitized and analyzed regular videos of the goalkeepers that were recorded by Lopes et al. (2014) but not analyzed. The present research complements the current understanding of the penalty kick with three main observations. First, goalkeepers save penalties at middle heights more often than low and high penalties. Second, the height of penalties is predicted less clearly than their horizontal direction from the kinematics of penalty takers. Third, goalkeepers tend to initiate the horizontal component of the saving action before the penalty taker contacts the ball, but they initiate the vertical component of the action about 245 ms after the contact. Taken together, these results support the view that goalkeepers make the left-right decision at least partly focusing on the kinematics of the kicker, and that they dynamically decide the vertical aspects of the movement later, focusing on the ball trajectory.


#10 Estimation of maximal heart rate in recreational football: a field study
Reference: Eur J Appl Physiol. 2020 Mar 14. doi: 10.1007/s00421-020-04334-4. [Epub ahead of print]
Authors: Póvoas S, Krustrup P, Castagna C
Summary: The purpose of the study was to examine the accuracy of practical indirect methods (i.e., recreational football match and estimation equations) in assessing individual maximal heart rate (HRmax) in recreational football players. Sixty-two untrained male participants engaged in a recreational football intervention (age 39.3 ± 5.8 years, VO2max 41.2 ± 6.2 ml·kg-1·min-1, body mass 81.9 ± 10.8 kg, height 173.2 ± 6.4 cm) were tested for HRmax using a multiple approach, at baseline and post-intervention (i.e., in the untrained and trained status, respectively). Observed HRmax was plotted against peak match HR (Match-HRpeak) and HRmax estimated from prediction equations (EstHRmax) at both time-points. In the untrained status, only the 211 - 0.64 × Age and 226 - Age equations showed non-significant (medium-to-small) differences with observed HRmax. The differences between observed HRmax and Match-HRpeak were large (P < 0.0001). At post-intervention, the observed HRmax (Post-HRmax) was significantly and largely lower than at baseline. The prediction equations under consideration provided EstHRmax values that were lower than Post-HRmax, with small-to-large differences (P > 0.05). The exception was for the 226 - Age and 211 - 0.64 × Age equations, with values largely higher than Post-HRmax. This study suggests caution when considering EstHRmax and Match-HRpeak in recreational football interventions to track HRmax. The accuracy of EstHRmax may vary according to training status, suggesting the need for different approaches and equations across training interventions.


#11 Cardiac adaptations in elite female football- and volleyball-athletes do not impact left ventricular global strain values: a speckle tracking echocardiography study
Reference: Int J Cardiovasc Imaging. 2020 Mar 13. doi: 10.1007/s10554-020-01809-5. [Epub ahead of print]
Authors: Zacher J, Blome I, Schenk A, Gorr E
Summary: Cardiac adaptations to exercise on an elite level have been well studied. Strain analysis by speckle tracking echocardiography has emerged as a tool for sports cardiologists to assess the nature of hypertrophy in athletes' hearts. In prior studies, strain values generally did not change in physiological adaptations to exercise but were reduced in pathological hypertrophy. However, research in this field has focused almost solely on male athletes. Purpose of the present study is to investigate strain values in the hearts of female elite athletes in football and volleyball. In this cross-sectional study echocardiography was performed on 19 female elite football-players, 16 female elite volleyball-players and 16 physically inactive controls. Conventional echocardiographic data was documented as well as left ventricular longitudinal, radial and circumferential strain values gained by speckle tracking echocardiography. The hearts of the female athletes had a thicker septal wall, a larger overall mass and larger atria than the hearts in the control group. Global longitudinal, radial and circumferential strain values did not differ between the athletes and controls or between sporting disciplines. No correlation between septal wall thickness and global strain values could be documented. Cardiac adaptations to elite level exercise in female volleyball and football players do not influence global strain values. This has been documented for male athletes of several disciplines. The present study adds to the very limited control-group comparisons of left ventricular strain values in elite female athletes. The findings indicate that global strain values can be used when assessing the cardiac health in female athletes.

Mon

11

May

2020

Straight sprinting - The most frequent action whilst scoring in professional football

The influence of speed and power abilities in goal scoring situations in professional football.

Sat

09

May

2020

Passing patterns before and after scoring in Premier League football

Are there differences in successful passes before and after a goal in football?

Wed

06

May

2020

Latest research in football - week 12 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Effect of an Inside Floater on Soccer Players Tactical Behaviour in Small Sided and Conditioned Games
Reference: J Hum Kinet. 2020 Jan 31;71:167-177. doi: 10.2478/hukin-2019-0080. eCollection 2020 Jan.
Authors: Moniz F, Scaglia A, Sarmento H, García-Calvo T, Teoldo I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052718/pdf/hukin-71-167.pdf
Summary: The aim of this study was to verify the effect of an inside floater on soccer players' tactical behaviour in small-sided and conditioned games (SSCGs). The sample comprised 54 Brazilian top-level academy players. The instrument used to assess players' tactical behaviour was the System of Tactical Assessment in Soccer (FUT-SAT). Tactical behaviour was analysed through the number of tactical actions and the percentage of correct actions regarding the core tactical principles of soccer. Repeated measures test was used to compare tactical behaviour between games (SSCGs) with and without an inside floater. Pearson's r was used to verify the effect size of the inside floater on tactical behaviour. As for tactical actions, SSCGs with an inside floater displayed significantly lower means for the tactical principles of penetration (2.76 ± 1.63; p < .001), delay (6.11 ± 2.68; p < .018), defensive coverage (1.64 ± 1.14; p < .001) and significantly higher means for the tactical principle of defensive unity (14.98 ± 4.57; p < .032). With respect to the percentage of correct actions, SSCGs with an inside floater displayed significantly lower means for all tactical principles, except for offensive coverage (90.5 ± 18.48; p < 1.000). It was concluded that the inside floater allowed players to modify their behaviour in such a way that they adapted to the constraints imposed by the presence of an inside floater. Furthermore, the inside floater provided more difficulty for players, and thus may be considered an important task constraint to be added in SSCGs.


#2 Eating Habits and Body Composition of International Elite Soccer Referees
Reference: J Hum Kinet. 2020 Jan 31;71:145-153. doi: 10.2478/hukin-2019-0078. eCollection 2020 Jan.
Authors: Mascherini G, Petri C, Ermini E, Pizzi A, Ventura A, Galanti G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052701/pdf/hukin-71-145.pdf
Summary: Soccer referees are a specific group of the athletes' population whose careers peak from 30 to 45 years old. An athlete's performance is not only determined by physical training but also by a lifestyle, e.g. eating habits. The purpose of this study was to verify current eating habits and resulting body composition of a group of elite international soccer referees. At an international FIFA seminar 60 elite international soccer referees (aged 39.2 ± 4.2 years) were enrolled. A body composition assessment was performed with skinfold thickness and bio impedance analysis, while eating habits were evaluated with a multi-pass 24-hour dietary recall. The body composition showed a normal weight condition with a fat content of 11.4 ± 2.5%. Macronutrients showed a low level of carbohydrates (43.6 ± 5.4%) and a high level of fat (40.0 ± 4.5%). Micronutrients showed a low level of calcium, potassium, zinc, magnesium, iodine, vitamin B12 and vitamin B9. Even though their body composition was within the normal range, the current eating habits of elite international soccer referees did not appear to follow the nutrition guidelines. Therefore, it would be advisable to provide knowledge on nutrition for this particular category of sports subjects, an individualized nutritional plan would be advisable, in order to achieve and maintain better performance and appropriate body composition for their role.


#3 A Longitudinal Investigation of Symptom Recovery following Concussion in Youth Soccer
Reference: J Pediatr. 2020 Mar 5. pii: S0022-3476(20)30141-4. doi: 10.1016/j.jpeds.2020.01.068. [Epub ahead of print]
Authors: Kirkwood MW, Crossland MM, Howell DR, Wilson JC, Peterson RL
Summary: The purpose was to prospectively evaluate symptom outcomes after youth soccer-related concussion. Using a prospective cohort design, we enrolled male and female competitive soccer players age 8-17 years into 3 groups: concussed (n = 23), matched control (n = 23), and orthopedic injury (n = 24). Postconcussive symptoms were monitored serially via both athlete and parent report at days 1-2, 4, 7, 10, 30, and 90. Repeated-measures analyses revealed a significant time by group interaction (F [12, 402] = 19.91, P < .001). In the initial days postinjury, the concussed group reported greater symptoms than the comparison groups, with more symptoms reported by athletes on average than parents. By 10 days, concussed athletes did not differ from the matched controls by either rater's report, but they did differ from the orthopedic injury group by parent report. At 30 days, no differences were apparent among groups. At 30 days, 100% of concussed youth and 91% of parents rated symptoms as back to preinjury levels using reliable change indices. At 30 days, 86% of athletes had been cleared to return to full game play. The natural clinical history of concussion symptoms in youth competitive soccer players was similar to that seen in older athletes, with resolution in days to a few weeks. Additional study will be required to investigate which factors best predict symptom outcomes for individual athletes and how symptom report relates to performance-based outcome measures and underlying neurophysiologic recovery.


#4 Football-specific validity of TRACAB's optical video tracking systems
Reference: PLoS One. 2020 Mar 10;15(3):e0230179. doi: 10.1371/journal.pone.0230179. eCollection 2020.
Authors: Linke D, Link D, Lames M
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0230179&type=printable
Summary: The present study aimed to validate and compare the football-specific measurement accuracy of two optical tracking systems engineered by TRACAB. The "Gen4" system consists of two multi-camera units (a stereo pair) in two locations either side of the halfway line, whereas the distributed "Gen5" system combines two stereo pairs on each side of the field as well as two monocular systems behind the goal areas. Data were collected from 20 male football players in two different exercises (a football sport-specific running course and small-sided games) in a professional football stadium. For evaluating the accuracy of the systems, measures were compared against simultaneously recorded measures of a reference system (VICON motion capture system). Statistical analysis uses RMSE for kinematic variables (position, speed and acceleration) and the difference in percentages for performance indicators (e.g. distance covered, peak speed) per run compared to the reference system. Frames in which players were obviously not tracked were excluded. Gen5 had marginally better accuracy (0.08 m RMSE) for position measurements than Gen4 (0.09 m RMSE) compared to the reference. Accuracy difference in instantaneous speed (Gen4: 0.09 m⋅s-1 RMSE; Gen5: 0.08 m⋅s-1 RMSE) and acceleration (Gen4: 0.26 m⋅s-2 RMSE; Gen5: 0.21 m⋅s-2 RMSE) measurements were significant, but also trivial in terms of the effect size. For total distance travelled, both Gen4 (0.42 ± 0.60%) and Gen5 (0.27 ± 0.35%) showed only trivial deviations compared to the reference. Gen4 showed moderate differences in the low-speed distance travelled category (-19.41 ± 13.24%) and small differences in the high-speed distance travelled category (8.94 ± 9.49%). Differences in peak speed, acceleration and deceleration were trivial (<0.5%) for both Gen4 and Gen5. These findings suggest that Gen5's distributed camera architecture has minor benefits over Gen4's single-view camera architecture in terms of accuracy. We assume that the main benefit of the Gen5 towards Gen4 lies in increased robustness of the tracking when it comes to optical overlapping of players. Since differences towards the reference system were very low, both TRACAB's tracking systems can be considered as valid technologies for football-specific performance analyses in the settings tested as long as players are tracked correctly.


#5 The association between adolescent football participation and early adulthood depression
Reference: PLoS One. 2020 Mar 10;15(3):e0229978. doi: 10.1371/journal.pone.0229978. eCollection 2020.
Authors: Deshpande SK, Hasegawa RB, Weiss J, Small DS
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0229978&type=printable
Summary: Concerned about potentially increased risk of neurodegenerative disease, several health professionals and policy makers have proposed limiting or banning youth participation in American-style tackle football. Given the large affected population (over 1 million boys play high school football annually), careful estimation of the long-term health effects of playing football is necessary for developing effective public health policy. Unfortunately, existing attempts to estimate these effects tend not to generalize to current participants because they either studied a much older cohort or, more seriously, failed to account for potential confounding. We leverage data from a nationally representative cohort of American men who were in grades 7-12 in the 1994-95 school year to estimate the effect of playing football in adolescent on depression in early adulthood. We control for several potential confounders related to subjects' health, behavior, educational experience, family background, and family health history through matching and regression adjustment. We found no evidence of even a small harmful effect of football participation on scores on a version of the Center for Epidemiological Studies Depression scale (CES-D) nor did we find evidence of adverse associations with several secondary outcomes including anxiety disorder diagnosis or alcohol dependence in early adulthood. For men who were in grades 7-12 in the 1994-95 school year, participating or intending to participate in school football does not appear to be a major risk factor for early adulthood depression.


#6 The relationship between training load and fitness indices over a pre-season in professional soccer players
Reference: J Sports Med Phys Fitness. 2020 Mar;60(3):329-337. doi: 10.23736/S0022-4707.20.10109-9.
Authors: Papadakis L, Tymvios C, Patras K
Summary: An association between training load and changes in aerobic fitness has been established but the effect of training load on changes in strength/power remains controversial. Internal (Banister's TRIMP) and external (total distance, high-speed running and sprint distance) training load was collected from sixteen professional soccer players during and aerobic fitness and strength/power variables were measured before and after a 9-week pre-season. Banister's TRIMP had a moderate correlation with changes in maximal oxygen uptake (r=0.46, 90% CI: 0.04; 0.74). Total distance had a large and a moderate correlation with changes in velocity at 2M (r=0.60, 90% CI: 0.23; 0.82) and changes in velocity at 4M (r=0.42, 90% CI: -0.01; 0.72). High-speed running had moderate correlations with changes in maximal oxygen uptake (r=0.45, 90% CI: 0.03; 0.74), velocity at 2M (r=0.45, 90% CI: 0.03; 0.74) and velocity at 4M (r=0.39, 90% CI: -0.00; 0.70). Sprint distance had a large and a moderate correlation with changes in maximal oxygen uptake (r=0.58, 90% CI: 0.20; 0.81) and velocity at 4M (r=0.46, 90% CI: 0.00; 0.74 respectively). High versus low total distance was associated with lower changes in squat jump and countermovement jump (ES=-0.90, 90% CI: -1.57; -0.24 and ES=-1.06, 90% CI: -1.89; -0.24) respectively. High versus low high-speed running was associated with higher changes in maximal oxygen uptake (ES=0.36, 90% CI: 0.02; 0.70) but lower changes in squat jump (ES=-0.58, 90% CI: -1.32; 0.15). External rather internal training load had more pronounced correlations with changes in aerobic fitness. Higher compared with lower volumes of total distance and high-speed running were associated with lower gains in strength/power indices. Establishing a "dose-response" association between external/internal training load and endurance as well as strength adaptations, may maximize endurance gains with the least possible interference on strength/power gains, thus better informing soccer training practice.


#7 Strength, Jumping, and Change of Direction Speed Asymmetries Are Not Associated With Athletic Performance in Elite Academy Soccer Players
Reference: Front Psychol. 2020 Mar 3;11:175. doi: 10.3389/fpsyg.2020.00175. eCollection 2020.
Authors: Raya-González J, Bishop C, Gómez-Piqueras P, Veiga S, Viejo-Romero D, Navandar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7063114/pdf/fpsyg-11-00175.pdf
Summary: The aims of the present study were 2-fold: (1) to measure interlimb asymmetries from a battery of fitness tests in youth soccer players and (2) to determine the association between asymmetry and measures of athletic performance. Sixteen elite youth soccer players (14.7 ± 0.2 years) performed a single-leg Abalakov test (ABK), change of direction (COD) test over 10 m (5 + 5) and 20 m (10 + 10), and an iso-inertial power test. Subjects also performed 10-, 20-, and 30-m sprints and a bilateral countermovement jump, which were correlated with all ABK, COD, and iso-inertial asymmetry scores. A one-way repeated-measures analysis of variance showed significant differences between interlimb asymmetry scores across multiple tests (p < 0.05), with the iso-inertial power test presenting the greatest magnitude of asymmetry, whereas individual data highlighted substantially greater interindividual differences in each test. Pearson r correlations showed no significant relationships (p > 0.05) between the different interlimb asymmetry scores, and between asymmetry scores and athletic performance. These findings show the test-specific nature of asymmetries in youth soccer players, with the iso-inertial power test being the most sensitive in detecting asymmetry. Moreover, the results obtained suggest that inherent asymmetry in young soccer players did not negatively impact their performance.


#8 Influence of competition on performance factors in under-19 soccer players at national league level
Reference: PLoS One. 2020 Mar 19;15(3):e0230068. doi: 10.1371/journal.pone.0230068. eCollection 2020.
Authors: Izquierdo JM, De Benito AM, Araiz G, Guevara G, Redondo JC
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0230068&type=printable
Summary: The aim of this study was to analyse and quantify the acute effects of competition on several performance factors in under-19 male soccer players. To this end, 198 national league players (17.56 ± 0.78 years) performed various tests to measure jump capacity, kicking velocity and sprint times immediately pre-match (T1), at half-time (T2) and post-match (T3). Tests included kicking the ball to measure ball velocity (KICK), sprinting for 40 meters, timing the first 30 meters (30mACCEL), the last 10 meters (10mACCEL) and the total distance (40mACCEL), and performing countermovement jumps (CMJ). For subsequent analysis, the sample was divided into 5 playing positions: goalkeepers (n = 24), defenders (n = 51), midfielders (n = 36), wingers (n = 54) and forwards (n = 33). For all positions, we found a significant decline in performance (p<0.05) for kicking velocity (2.91% - 6.51%) and sprinting (0.44%-5.85%). For the CMJ, all positions except defenders presented a significant decline in performance that ranged from 1.5% to 4.56%. These findings highlight the need to individualise fitness training, taking into account the match needs and demands of the different playing positions in order to minimise the effects of match fatigue and accelerate post-match recovery.


#9 Infrared Thermography Protocol on Reducing the Incidence of Soccer Injuries
Reference: J Sport Rehabil. 2020 Mar 17:1-6. doi: 10.1123/jsr.2019-0056. [Epub ahead of print]
Authors: Gómez-Carmona P, Fernández-Cuevas I, Sillero-Quintana M, Arnaiz-Lastras J, Navandar A.
Summary: Infrared thermography has been used to detect skeletal muscle overload and fatigue in athletes, but its use in injury prevention in professional soccer has not been studied to date. The purpose was to establish a novel injury prevention program based on infrared thermography and to determine its influence on the injury incidence in professional soccer players in the preseason. A cross-sectional, prospective study design was used to compare a conventional injury prevention program (CPP) applied over the first preseason and an infrared thermography injury prevention program (IRTPP) carried out in the following preseason. Twenty-four players belonging to a first division soccer team from Spain participated in this study.  Injury incidences of each player were recorded according to the Orchard Sports Injury Classification System (version 10.0) convention to determine the injury classification, location, and type were used as main outcome measures. The incidence of injuries decreased from 15 injuries in the CPP preseason (0.63 [0.77] injuries per player) to 6 injuries in the second preseason when the IRTPP was applied (0.25 [0.53] injuries per player). The days of absence due to injuries also decreased from the CPP preseason (156 d, 10.4 [11.0] d per injury) to the IRTPP preseason (14 d, 2.3 [2.8] d per injury). The injury severity also decreased from the first preseason to the second preseason, and fewer musculoskeletal injuries in the thigh, hip, and groin were reported. The implementation of an IRTPP can reduce the presence of injuries by identifying players potentially at risk and as a result, reducing the injury severity and days lost as a consequence.


#10 Influence of Maturation Status on Eccentric Hamstring Strength Improvements in Youth Male Soccer Players After the Nordic Hamstring Exercise
Reference: Int J Sports Physiol Perform. 2020 Mar 18:1-7. doi: 10.1123/ijspp.2019-0184. [Epub ahead of print]
Authors: Drury B, Green T, Ramirez-Campillo R, Moran J.
Summary: This study examined the effects of a 6-week Nordic hamstring exercise (NHE) program in youth male soccer players of less mature (pre-peak height velocity [PHV]) or more mature (mid/post-PHV) status. Forty-eight participants were separated into pre-PHV (11.0 [0.9] y) or mid/post-PHV (13.9 [1.1]) groups and further divided into experimental (EXP) and control groups with eccentric hamstring strength assessed (NordBord) both before and after the training program. Participants in the EXP groups completed a periodized NHE program performed once or twice weekly over a 6-week period. The NHE program resulted in moderate and small increases in relative eccentric hamstring strength (in newtons per kilogram) in the pre-PHV EXP (d = 0.83 [0.03-1.68]) and mid-PHV EXP (d = 0.53 [-0.06 to 1.12]) groups, respectively. Moderate increases in the same measure were also seen in the between-groups analyses in the pre-PHV (d = 1.03 [0.23-1.84]) and mid-PHV (d = 0.87 [0.22-1.51]) groups, with a greater effect observed in the former. The results from this study demonstrate that a 6-week NHE program can improve eccentric hamstring strength in male youth soccer players, with less-mature players achieving mostly greater benefits. The findings from this study can aid in the training prescription of NHE in youth male soccer players.


#11 Effect of acupuncture on heart rate variability during prolonged high-intensity training in soccer players
Reference: J Tradit Chin Med. 2017 Oct;37(5):636-642.
Authors: Lin S, Wichai E, Amonrat J, Somchai R
Summary: The purpose was to investigate the effects of acupuncture therapy compared with sham acupuncture on heart rate variability (HRV) in 24 elite soccer players during 4-week, high-intensity training sessions. The subjects were randomly divided into two groups: acupuncture group (AG) and sham acupuncture group (SG). In addition, AG had been implemented two times/week to stimulate Zusanli (ST 36), Hegu (LI 4), Shenshu (BL 23), and Chize (LU 5). While SG, had been applied to utilize a special ""placebo-needle"" technique on the same sites. What's more, the HRV parameters were calculated before and after interventions, respectively. First, stress index (SI) had a significantly increased in SG (P = 0.031) compare pre-test with post-test, however, no significantly difference in AG (P = 0.102). Secondly, standard deviation of N-N intervals (SNDD) have enormously significantly higher in AG when comparing baseline with post therapy (P = 0.001), while, declined in SG (P = 0.827). Meanwhile, the root mean square of successive differences (RMSSD) were significant differences in AG (P = 0.023). What's more, when the high-frequency (HF) were significantly higher in AG (P = 0.047) after receiving the acupuncture therapy, the lowe-frequency (LF) power were decreased but no significant in AG and SG. Comparing with pre-experiment, the ratio of LF/HF was lower in AG, but higher in SG. Furthermore, it was significant difference when compare the post-experiment parameters of AG with SG (P = 0.015). And HF parameters have significance (P = 0.005) compare between two groups during the post-experiment. Based on evidence, acupuncture therapy on special acupoints could strengthen the parasympathetic nervous activity and modulates the balance between parasympathetic and sympathetic activity in soccer players while they engage in high-intensity training.


#12 The influence of offside rule and pitch sizes on the youth soccer players' small-sided games external loads
Reference: Res Sports Med. 2020 Mar 18:1-15. doi: 10.1080/15438627.2020.1739687. [Epub ahead of print]
Authors: Castillo D, Raya-González J, Manuel Clemente F, Yanci J
Summary: The aim was to analyse the influence of the offside rule and pitch sizes on the external loads encountered by young soccer players during small-sided games (SSGs). Twenty-four U12 soccer players belonged to the same Spanish Performance Soccer Academy participated in the study. Each player participated in six different SSGs attending to the offside rule (i.e., offside not applicable [NOS] and with offside [WOS]) and the pitch sizes (i.e., individual interaction space [IIS] of 25, 50 and 75 m2 per player). The obtained data included measures of external loads by global positioning systems. Players covered higher total distance and greater distances at jogging (8-12.9 km·h-1), cruising (13.0-16.0 km·h-1) and sprinting (>16.0 km·h-1) in NOS75 and WOS75 SSGs (p < 0.01; d = 0.65-6.60). Besides, in the NOS75 SSG, the total distance and the distance at cruising were higher in respect to WOS75 (p < 0.01; d = 0.63-0.82). In addition, players performed lower sprints (p < 0.01; d = 1.17-1.71) and achieved lower Vmax (p > 0.05; d = 1.10-1.88) during NOS25 and WOS25 SSGs. These findings could provide relevant information for coaches in order to apply different pitch sizes and the inclusion/absence of the offside rule throughout the microcycle.

Tue

05

May

2020

Small-sided games: Goalkeepers vs. Possession

Metabolic and mechanical demands in small-sided games with goalkeepers vs. possession play.

Mon

04

May

2020

Concurrent (Strength and High-intensity running) Training in football

Concurrent training during pre-season. One example what was done.

Sat

02

May

2020

Latest research in football - week 11 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Warming Up With Lower-Body Wearable Resistance on Physical Performance Measures in Soccer Players Over an 8-Week Training Cycle
Reference: J Strength Cond Res. 2020 Mar 4. doi: 10.1519/JSC.0000000000003498. [Epub ahead of print]
Authors: Bustos A, Metral G, Cronin J, Uthoff A, Dolcetti J
Summary: Warm-ups provide an opportune time to integrate specific movements to improve performance. This study aimed to examine the effects of adding wearable resistance (WR) lower-limb loading to a warm-up on physical performance measures in soccer athletes. Thirty-one national-level soccer players (aged 16-18 years) were matched for speed and allocated to either a WR training (WRT = 15) or an unloaded (CON = 16) group. Both groups performed the same warm-up 2-3x·wk for 8 weeks with the WRT group wearing 200- to 600-g loads on their calves. Pre-training, mid-training, and post-training data were collected for 10- and 20-m sprint times, repeated sprint ability, and vertical countermovement jump (CMJ) and horizontal countermovement jump (standing long jump [SLJ]) performance. Wearable resistance training improved pre-training to post-training 10- and 20-m sprint times more than the unloaded training (effect size [ES] = -1.06 to -0.96, respectively; 60.0-66.7 vs. 18.8-37.5% > smallest worthwhile change [SWC]). Both groups decreased CMJ over the first 4 weeks (ES ≥ 0.45) and increased CMJ performance over the second 4 weeks of training (ES ≥ 0.27). Both the WRT and CON groups improved SLJ performance after the 8-week training block (ES = 0.85 and 0.93, respectively; 86.7 and 62.5% > SWC, respectively), yet no differences were identified between groups. These findings indicate that 8 weeks (23 sessions) of WR training appears to elicit practically meaningful improvements in accelerated sprinting and horizontal jumping performance. Strength and conditioning practitioners should consider including WR in sports where sprinting and horizontal force production are critical performance indicators.


#2 Magnitude or Direction? Seasonal Variation of Interlimb Asymmetry in Elite Academy Soccer Players
Reference: J Strength Cond Res. 2020 Mar 4. doi: 10.1519/JSC.0000000000003565. [Epub ahead of print]
Authors: Bishop C, Read P, Chavda S, Jarvis P, Brazier J, Bromley T, Turner A
Summary: Previous research has highlighted a distinct lack of longitudinal data for asymmetry. The aims of this study were to provide seasonal variation data for the magnitude and direction of asymmetry. Eighteen elite male academy soccer players (under-23) performed unilateral countermovement jumps (CMJs) and unilateral drop jumps (DJs) during pre-season, mid-season, and end of season time points. Recorded metrics for asymmetry included jump height and concentric impulse for the CMJ, and jump height and reactive strength index for the DJ. The magnitude of asymmetry showed trivial to small changes throughout the season (CMJ effect size [ES] range = -0.43 to 0.05; DJ ES range = -0.18 to 0.41). However, Kappa coefficients showed poor to substantial levels of agreement for the direction of asymmetry during the CMJ (Kappa = -0.06 to 0.77) and DJ (Kappa = -0.10 to 0.78) throughout the season. These data show that when monitoring asymmetry, the magnitude alone may provide a false impression of consistent scores over time. By contrast, monitoring the direction of asymmetry highlights its task and variable nature and is suggested as a useful tool for practitioners who wish to monitor asymmetry over the course of a competitive soccer season.


#3 Seasonal Effects of Strength Endurance vs. Power Training in Young Female Soccer Athletes
Reference: J Strength Cond Res. 2020 Mar 4. doi: 10.1519/JSC.0000000000003564. [Epub ahead of print]
Authors: Lesinski M, Prieske O, Chaabene H, Granacher U
Summary: This study examined the seasonal effects of strength endurance training (SET) vs. power training (PT) on physical fitness and body composition in young female soccer players. Thirty-six young female elite soccer players (15 ± 1 years; maturity offset +3 ± 1 years) were allocated to progressive SET (n = 19) or PT (n = 17). Over the course of one soccer season, SET performed slow movement velocity, moderate intensity (50-60% of the 1 repetition maximum [1RM]; 20-40 repetitions) strength exercises while PT performed moderate-to-high intensity (50-95% of the 1RM; 3-8 repetitions), high movement velocity strength exercises (2 sessions·wk). Before and after training, tests were performed for the assessment of muscle strength (1RM leg press), jump performance (countermovement jump [CMJ], drop jump [DJ]), muscular endurance (ventral Bourban test), linear speed (10 m, 20 m), change-of-direction (CoD) speed (T-test), dynamic balance (Y-balance test), sport-specific performance (kicking velocity), and body composition (lean body mass and fat mass). An analysis of covariance was used to test for between-group differences at post-test with baseline values as covariate. No significant between-group differences were observed in terms of total training volume over the respective soccer seasons (p = 0.069; d = 0.68). At post-test, SET showed significantly better ventral Bourban and T-test performances (d = 1.28-2.28; p = 0.000-0.001) compared with PT. However, PT resulted in significantly better 1RM leg press, DJ, 10-m, and 20-m sprint performances (d = 0.85-1.44; p = 0.000-0.026). No significant between-group differences were observed at post-test for CMJ, Y-balance test, kicking performance, and body composition (d = 0.20-0.74, p = 0.051-0.594). Our findings are mainly in accordance with the principle of training specificity. Both SET and PT are recommended to be implemented in young female elite soccer players according to the respective training period.


#4 Gonadal hormones may predict structural bone fragility in elite female soccer player
Reference: J Sports Sci. 2020 Mar 9:1-11. doi: 10.1080/02640414.2020.1735982. [Epub ahead of print]
Authors: Lanhers C, Courteix D, Valente-Dos-Santos J, Ferry B, Gracia-Marco L, Pereira B, Borda IM, Lespessailles E, Duclos M
Summary: This study determined the impact of menstrual status on bone tissue in elite post-pubertal female soccer players over an entire season. Fifty-one elite female soccer players participated. At baseline, forty-one were assigned to the low hormonal androgenic profile (low-HAPL) and 10 to the high hormonal androgenic profile (high-HAPL). An 8-month training program led to increased bone mineral density content (p<0.05). The low-HAPL athletes improved the Narrow neck average cortical thickness (ACT) by 1.4% and reduced the corresponding Buckling ratio (BR) by 2.6%, thus decreasing the fracture risk (p<0.05). The high-HAPL athletes decreased the Narrow neck ACT by 5.4% and increased the BR by 2.6%, increasing fracture risk (p<0.05). Differences were assigned as being "very likely beneficial" for the low-HAPL athletes, supported by very large (d=3.41) and large (d=1.58) effect sizes for the Narrow neck ACT and BR, respectively. A season of soccer training has induced bone geometry improvements in adolescent females. Bone health parameters improved in the two clusters. However, high-HAPL athletes decreased its resistance to loading compare to low-HAPL athletes. Even if female players do not present clinical symptoms related to their hormonal status, sport medicine physicians should pay attention to their structural bone fragility.


#5 Pre- and Post-Activity Stretching Practices of Collegiate Soccer Coaches in the United State
Reference: Int J Exerc Sci. 2020 Feb 1;13(6):260-272. eCollection 2020.
Authors: Judge LW, Avedesian JM, Bellar DM, Hoover DL, Craig BW, Langley J, Nordmann N, Schoeff MA, Dickin C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039475/pdf/ijes-13-6-260.pdf
Summary: Current pre- and post-activity stretching guidelines are designed to optimize performance and reduce injury risk. However, it is unclear whether soccer coaches adhere to these recommendations. The purpose of this study was to determine if collegiate soccer coaches' perceptions and practices align with current scientific recommendations. A total of 781 questionnaires were electronically distributed to soccer coaches from NCAA Division I and III universities. The questionnaire obtained demographic, professional, and educational information, as well as stretching practices. Statistical analysis consisted of computing frequency counts and means where applicable. Pearson's Chi-square tests were performed to assess the potential differences in stretching perceptions and practices among the cohort of soccer coaches. Results suggest that soccer coaches are choosing some forms of stretching more frequently than other coaches (χ2 = 342.7, p < 0.001). Further analysis failed to determine significant associations between stretching type and coaching certification, level, sex, years of experience, and age. Of the 209 respondents, 84.9% believed pre-activity stretching to be of greater than average importance on a seven-point Likert scale. Dynamic stretching (68.7%) or a combination of static and ballistic stretching (18.0%) prior to athletic events was the most typical stretching prescribed. Current post-activity practices demonstrate that most coaches (95.4%) are using some form of a general cool-down following practice or competition. This study is an important assessment of the extent to which collegiate coaches administer appropriate stretching techniques. Most coaches adhere to current recommendations; however, they should continue to evaluate their practices against ongoing research and the practices of their peers.


#6 Continued Play Following Sport-Related Concussion in United States Youth Soccer
Reference: Int J Exerc Sci. 2020 Feb 1;13(6):87-100. eCollection 2020.
Authors: Zynda AJ, Sabatino MJ, Ellis HB, Miller SM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039489/pdf/ijes-13-6-87.pdf
Summary: Medical guidelines and legislation in the US call for immediate removal from play and prohibit continued play on the same day if a concussion is suspected. However, there is limited literature examining whether these guidelines and laws are being followed in youth soccer. The purpose of this study was to identify the frequency at which youth soccer players continued play on the same day following sport-related concussion and factors that may be associated with this behavior. A retrospective review of youth soccer players diagnosed at the initial clinic visit with a sport-related concussion was performed. Participants were categorized into groups, those who continued play on the same day as their concussion (PLAY) and those who did not (NO PLAY). Records were reviewed for demographics, injury characteristics, SCAT3™ symptoms, mBESS and ImPACT® results, symptom resolution and return to play protocol initiation. Fifty-eight girls (mean age: 14 years, range: 7-18 years) and 29 boys (mean age: 14.4 years, range: 6-18 years) participated in this study. Thirty of 58 girls (51.7%) continued play the same day compared to only 5 of 29 boys (17.2%; p=0.002). The odds of continued play in girls were 5 times as high as the odds of continued play in boys (OR=5.05; 95% CI, 1.59-19.3). Overall, 35 (40.2%) soccer players continued play on the same day following a concussion. In conclusion, approximately 40% of youth soccer players continued play on the same day as their concussion. Girl soccer players demonstrated a significantly higher frequency of continued play than boys.


#7 A Comparison of Quadriceps-to-Hamstrings Ratios During Isokinetic Testing, Cutting, and Drop Landings in Male Soccer Players
Reference: Int J Exerc Sci. 2020 Feb 1;13(4):157-166. eCollection 2020.
Authors: O'Donnell SR, Eitan DN, Roper JL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039484/pdf/ijes-13-4-157.pdf
Summary: Collegiate soccer is not an unusual place to suffer a knee injury. The sport has many dynamic movements, such as cutting, jumping and shooting. Many professionals use quadriceps-to-hamstring (Q/H) ratios as a tool to determine when an injured player can to return to game play or use the ratio to investigate how predisposed a certain player is to sustaining a knee injury. However, many of these ratios are taken in isokinetic testing in a controlled environment and to our knowledge it is unknown if these ratios are similar to those measured during dynamic activity. Therefore, this study investigated if there was a relationship between Q/H ratios measured during isokinetic testing and drop landings and cutting. Fifteen Division 2 collegiate male soccer players (age: 19.79 ± 1.25 years; height: 176.74 ± 6.22 cm; weight: 77.24 ± 11.01 kg). Wearing Athlos© compression shorts participants performed isokinetic testing, drop landings and cutting drills while muscle activity was measured. A significant difference was found between the bilateral Q/H ratios during the drop landings (p = 0.04; η = 0.49). There were no significant bilateral differences measured during the cutting drills in either direction and isokinetic testing (p > 0.05). Additionally, there was so significant relationship in Q/H ratios between isokinetic testing and the dynamic movements (p > 0.05). This suggests that clinicians should use Q/H ratios during dynamic movements rather than isokinetic testing in a controlled environment to better assess player risk disposition and return-to-play criteria.


#8 In-Season Hip Thrust vs. Back Squat Training in Female High School Soccer Players
Reference: J Exerc Sci. 2020 Feb 1;13(4):49-61. eCollection 2020.
Authors: Millar NA, Colenso-Semple LM, Lockie RG, Marttinen RHJ, Galpin AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039497/pdf/ijes-13-4-49.pdf
Summary: The barbell back squat provides a highly effective training stimulus to improve lower body strength, speed, and power, which are considered key components of athletic performance in many sports. The barbell hip thrust exercise utilizes similar musculature, and is popular among practitioners, but has received far less scientific examination. The purpose of this study was to evaluate the effects of an in-season resistance training program with hip thrusts or back squats on physical performance in adolescent female soccer players. Fourteen players completed identical whole-body resistance training twice per week for 6 weeks, except one group used the barbell hip thrust (HT) (n = 6) and the other the back squat (SQ) (n = 8). Improvements were observed for both groups in hip thrust 3RM (HT = 34.0%, SQ = 23.8%), back squat 3RM (HT = 34.6%, SQ = 31.0%), vertical jump (HT = 5.4%, SQ = 4.9%), broad jump (HT = 10.5%, SQ = 8.1%), ball kicking distance (HT = 13.2%, SQ = 8.1%), and pro-agility (HT = -1.5%, SQ = -1.5%; faster), but not 36.6-m dash (HT = 2.9%, SQ = 1.9%; slower) with no significant between-group differences. These data indicate that both the hip thrust and the squat provide an effective stimulus to improve these sport-specific performance measures. Practitioners should consider these findings in combination with other factors (equipment availability, ability to coach the movement, training goals, injuries, etc.) when selecting exercises.


#9 The Use of Small-Sided Games as an Aerobic Fitness Assessment Supplement Within Elite Level Professional Soccer
Reference: J Hum Kinet. 2020 Jan 31;71:243-253. doi: 10.2478/hukin-2019-0086. eCollection 2020 Jan.
Authors: Owen AL, Newton M, Shovlin A, Malone S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052721/pdf/hukin-71-243.pdf
Summary: The purpose of this investigation was to quantify the association between 5 vs. 5 small sided games (SSG) running performance and physiological performance during the Yo-YoIR1 test to ascertain the utility of SSGs as a potential fitness test modality within elite professional soccer players. Twenty-three (n = 23) elite male professional soccer players (mean ± SD age 25.3 ± 3.1 yrs, mass: 76 ± 9 kg, height: 176 ± 9 cm) were assessed. Players completed an intermittent aerobic fitness test (Yo-YoIR1) and a 5 vs. 5 SSGs protocol for the purpose of the study. During all SSGs players wore GPS (Statsports 10-Hz, Viper Pod, Newry, Northern Ireland) and HR monitors (Polar, Oy Kemple, Finland) with these measures related to Yo-YoIR1 running performance. Results revealed SSGs running performance (TD; m) and physiological performance (HR) showed the lowest CV% (< 5%), with high speed movements, accelerations and decelerations highlighting higher CV% during SSGs. Possibly small to possibly very large associations were observed for running performance during 5 vs. 5 SSGs and Yo-YoIR1 performance, with negative associations observed between physiological performance during SSG and YoYoIR1 running performance. To conclude, the current study observed how running performance during a standardised 5 vs. 5 SSG protocol within elite soccer cohorts is associated with the Yo-YoIR1 running performance. Given the low CV%, repeatability and large association of global running performance and internal load measures during a 5 vs. 5 SSG with Yo-YoIR1 performance, this particular soccer specific SSG protocol potentially supplements traditional non-sport specific testing assessments.


#10 Spanish Elite Soccer Reserve Team Configuration and the Impact of Physical Fitness Performance
Reference: J Hum Kinet. 2020 Jan 31;71:211-218. doi: 10.2478/hukin-2019-0085. eCollection 2020 Jan.
Authors: Arcos AL, Martínez-Santos R, Castillo D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052712/pdf/hukin-71-211.pdf
Summary: The aim of this study was threefold: 1) to assess the configuration of an elite reserve soccer team, 2) to compare physical fitness performance of promoted and new players according to the playing position, and 3) to analyze the level of competitive participation attained by these players. We considered physical fitness tests (5 m and 15 m sprint, countermovement jump [CMJ] and aerobic endurance) performed by 192 players (age = 20.2 ± 2.3 years) enrolled in the reserve team of a Spanish La Liga club from 1994 to 2013. The players were classified according to the previous club criterion (promoted from the soccer academy and new players signed from other clubs), b) their playing position, and c) the competitive level attained until the 2016/2017 season (Spanish 1st and 2nd Divisions and the remaining competition levels). The proportion of promoted and new players was similar (p = 0.47). Overall, no substantial differences (unclear-small) were found in physical fitness performance between promoted and new players. Considering the playing position, promoted lateral defenders (LDs) showed better sprinting (ES = moderate) and CMJ (ES = moderate) performance than new LDs. In addition, promoted central midfielders (CMs) demonstrated better performance in the 5 m sprint and the CMJ (ES = moderate) than new CMs. The percentage of players who later competed in the Spanish 1st and 2nd Divisions was greater in promoted players compared to new players (p = 0.006). Physical fitness performance did not determine the selection of new players in a soccer elite reserve team. We may conclude that soccer academies should prioritize the selection and the training process of youth soccer players.

Wed

29

Apr

2020

Metabolic and mechanical demands with different pitch size in SSGs

Effect of number of players and pitch size on physical demands in football.

Wed

29

Apr

2020

Technical and physical demands of small vs. large sided games in football

1 touch vs. 2 touch vs. free-play in SSGs

Tue

28

Apr

2020

Latest research in football - week 10 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Player-surface interactions: perception in elite soccer and rugby players on artificial and natural turf
Reference: Sports Biomech. 2020 Mar 4:1-11. doi: 10.1080/14763141.2020.1720279. [Epub ahead of print]
Authors: Strutzenberger G, Edmunds R, Nokes LDM, Mitchell ID, Mellalieu SD, Irwin G
Summary: Artificial turf (AT) is common at all levels of soccer and rugby. Employing an interdisciplinary design, this study aimed to examine the extent to which the negative attitude commonly expressed by players concerning AT is based on the difference in technique between AT and natural turf (NT), or due to pre-existing biases. Thirty professional soccer and rugby players performed a defined set of movements with masked and normal perception conditions on NT and AT. Two-dimensional kinematic analysis (100 Hz) of characteristics in parallel to a psychological assessment of the impact of cognitive bias for a playing surface was assessed. No significant interaction effects between the level of perception and surface type were found. For AT, contact time (CT) was shorter across conditions, while for NT rugby players had longer CT during acceleration/deceleration phases and shorter flight times. Pre-existing negative bias against AT was found during the normal perception trials in the technology acceptance model (Usefulness and Ease of Use) and the general preference questions on how much the athlete would like to play a game on it. The results suggest that opinion was not driven by surface characteristics, but by a cognitive bias, players brought with them to the pitch.


#2 Chronic Beetroot Juice Supplementation Accelerates Recovery Kinetics following Simulated Match Play in Soccer Players
Reference: J Am Coll Nutr. 2020 Mar 3:1-9. doi: 10.1080/07315724.2020.1735571. [Epub ahead of print]
Authors: Daab W, Bouzid MA, Lajri M, Bouchiba M, Saafi MA, Rebai H
Summary: The purpose was to assess the effect of beetroot juice (BET) on recovery kinetics of physical performance, muscle damage and perceived muscle soreness after simulated soccer match play in soccer players. In a randomized, double-blind, crossover design, thirteen soccer players completed the Loughborough Intermittent Shuttle Test LIST. Players received either BET or placebo (PLA) (2*150) for 7 days (3 days pre-exercise, on the day trial, and 3 days post-exercise). Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 meters sprint: SP), blood markers of muscle damage (creatine kinase: CK, Lactate dehydrogenase: LDH), inflammatory parameter (C-reactive protein: CRP) and perceived muscle soreness (DOMS) were assessed at baseline, 0 h, 24 h, 48 h and 72 h following the exercise. Following the LIST, a decrease was observed in CMJ, MVC and SP at 0 h, 24 h, 48 h in both conditions (p < 0.05). However, compared to PLA session, this decrease was significantly attenuated with BET for CMJ at 24 h and at 48 h and for MVC at 0 h, 24 h, 48 h and for SP at 48 h after the LIST (p < 0.05). Likewise, DOMS values were significantly lower with BET compared to PLA condition immediately and at 24 h after exercise.CK, LDH and CRP levels increased at 0 h and at 24 h post exercise in both conditions (p < 0.05), but without any significant difference between the two condition (p > 0.05). The results of the present study suggest that chronic beetroot juice supplementation reduces post exercise perceived muscle soreness and maintain better performance during the recovery period in soccer players.


#3 The physical demands of professional soccer goalkeepers throughout a week-long competitive microcycle and transiently throughout match-play
Reference: J Sports Sci. 2020 Mar 2:1-7. doi: 10.1080/02640414.2020.1736244. [Epub ahead of print]
Authors: White A, Hills SP, Hobbs M, Cooke CB, Kilduff LP, Cook C, Roberts C, Russell M
Summary: The physical demands of English Premier League soccer goalkeepers were quantified during training and match-play in a two-part study. Goalkeeper-specific micromechanical electrical systems (MEMS) devices, profiled training and match-day activities throughout one competitive week (n=8; part A). Changes in MEMS-derived outputs were also profiled throughout match-play (100 matches; n=8, 18±14 observations per goalkeeper; part B). In part A, goalkeeping-training elicited the most dives (51±11) versus all activities (all p≤0.030) except shooting-training (p=0.069). Small-sided games elicited the fewest (5±3) dives (all p≤0.012). High-speed distance covered in match (103±72 m) was similar to goalkeeping-training (p=0.484), while exceeding shooting-training, small-sided games, pre-match shooting, and pre-match warm-up (all p=0.012). Most changes of direction (34±12) and explosive efforts (70±18) occurred during goalkeeping-training, with values exceeding match (both p=0.012). In part B, between-half reductions in total distance, but increased high-speed changes of direction and explosive efforts, occurred (both p≤0.05). Excluding the number of high jumps, all variables differed from 0-15-min during at least one match epoch, with more dives (1.3±1.4 vs 1.0±1.1) and explosive efforts (2.5±2.4 vs 2.0±1.8) performed between 75-90-min versus 0-15-min (all p<0.05). These data highlight the differing physical demands of various activities performed by professional soccer goalkeepers throughout a competitive week.


#4 Psychometric Analysis and Effectiveness of the Psychological Readiness of Injured Athlete to Return to Sport (PRIA-RS) Questionnaire on Injured Soccer Players
Reference: Int J Environ Res Public Health. 2020 Feb 27;17(5). pii: E1536. doi: 10.3390/ijerph17051536.
Authors: Gómez-Piqueras P, Ardern C, Prieto-Ayuso A, Robles-Palazón FJ, Cejudo A, Baranda PS, Olmedilla A
Download link: https://www.mdpi.com/1660-4601/17/5/1536/pdf
Summary: The decision-making process about when an athlete may safely return to training and competition after an injury is a difficult decision. Safe return to training and competition is characterised by physical and psychological readiness to return to the sport. The objectives of this study are (1) to assess the measurement properties of the Psychological Readiness of Injured Athlete to Return to Sport questionnaire (PRIA-RS), and (2) to analyse the effectiveness which the PRIA-RS questionnaire possesses when applied during four consecutive seasons on professional soccer players. One hundred and nine male soccer players from the Albacete Soccer Club (Spain) were involved during four consecutive seasons for the current study: 2012-2013, 2013-2014, 2014-2015 and 2015-2016. Psychometric analysis (validity, reliability, internal consistency and effectiveness) and external psychometric analysis (evaluating measures of patient-reported outcomes (EMPRO)) were confirmed and supported. The main results of the study reveal that the psychometric properties of this questionnaire are optimum for their application in a professional sports context.


#5 Validity of Field Methods to Estimate Fat-Free Mass Changes Throughout the Season in Elite Youth Soccer Players
Reference: Front Physiol. 2020 Feb 12;11:16. doi: 10.3389/fphys.2020.00016. eCollection 2020.
Authors: Núñez FJ, Munguía-Izquierdo D, Suárez-Arrones L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7029743/pdf/fphys-11-00016.pdf
Summary: The aim of this study was to determine the most effective anthropometric equations or bioelectrical impedance analysis (BIA) devices for quantifying the sensitivity to change in fat-free mass (FFM) in elite young soccer players, in comparison with measurements using dual-energy X-ray absorptiometry (DXA), between the pre- and mid-season. A total of 40 elite youth soccer players participated in this study. DXA values provided a criterion measure of FFM. Correlation coefficients, biases, limits of agreement, and differences were used as measures of sensitivity to change. All body density, skinfold, and anthropometric equations and BIA devices used to obtain FFM data showed positive and very large correlations (r from 0.70 to 0.89) with DXA. A significant increase in FFM was shown between time points using DXA, BIA, and all anthropometric equations (p < 0.01). The magnitudes of differences were small for DXA, BIA inbody and all anthropometric equations except those of Faulkner (1966), Durnin and Rahaman (1967), Brook (1971), and Sarría et al. (1998). Six anthropometric equations [Faulkner (1966), Durnin and Womersley (1974), Carter (1982), Slaughter et al. (1988), Reilly et al. (2009), and Munguia-Izquierdo et al. (2018)] and BIA Tanita showed no statistical differences compared to DXA, with a low bias. We concluded that the equations developed by Durnin and Womersley (1974), Carter (1982), Slaughter et al. (1988), Reilly et al. (2009), and Munguia-Izquierdo et al. (2018) showed the best sensitivity in assessing FFM changes between pre- and mid-season in elite youth soccer players.


#6 Psychometric properties of the standardized assessment of concussion in youth football: Validity, reliability, and demographic factors
Reference: Appl Neuropsychol Child. 2020 Mar 6:1-7. doi: 10.1080/21622965.2020.1726746. [Epub ahead of print]
Authors: Maerlender A, Smith E, Brolinson PG, Urban J, Rowson S, Ajamil A, Campolettano ET, Gellner RA, Bellamkonda S, Kelley ME, Jones D, Powers A, Beckwith J, Crisco J, Stitzel J, Duma S, Greenwald RM
Summary: The objective of this study was to determine the psychometrics (reliability, validity) of the original Standardized Assessment of Concussion (SAC) in a youth sample (ages 11 to 13). Demographic factors of race, level of vocabulary knowledge, mother's level of education were also considered. Over 150 youth football athletes completed the SAC and a brief battery of NIH Toolbox cognitive tests as part of a larger study on biomechanical factors in youth sport concussion. This was a within-subjects design (pre-season, post-season assessments), and correlational analysis of convergent and discriminant validity. Between groups analysis based on demographic differences was also employed. The pre-season SAC scores were not different by age; however, SAC scores were statistically different by race: t(155) = 3.162, p = .002, d = .519. Maternal level of education and participant vocabulary scores were related to racial group membership. Convergent and discriminant validity were established compared to NIH Toolbox tests of memory and speed. Pre-post-season tests for 108 participants established marginally acceptable test-retest reliability (ICC = .692). These data support the use of the original SAC in youth football although clinicians must be aware of racial differences in scores.


#7 Surgical excision of post-traumatic myositis ossificans of the adductor longus in a football player
Reference: BMJ Case Rep. 2020 Mar 3;13(3). pii: e233504. doi: 10.1136/bcr-2019-233504.
Authors: de Smet GHJ, Buijk SE, Weir A
Download link: https://casereports.bmj.com/content/bmjcr/13/3/e233504.full.pdf
Summary: A football player was diagnosed with myositis ossificans of his right adductor longus muscle after an acute injury. Conservative treatment failed and 1 year after the initial trauma the patient underwent surgical excision of a large ossification. Seven months postoperatively, the patient was fully recovered and returned to his preinjury activity levels. We present our approach to this case and discuss our considerations, referring to background information about this rare disease.


#8 Bone metabolism, bone mass and structural integrity profile in professional male football players
Reference: J Sports Med Phys Fitness. 2020 Feb 27. doi: 10.23736/S0022-4707.20.09913-2. [Epub ahead of print]
Authors: Filippella M, Altieri B, Falchetti A, Cosso R, Cena H, Musso C, Geronutti E, Rassat L, Cipriani G, Colao A, Di Somma C, Faggiano A
Summary: Physical exercise plays an important role in bone mineralization as well as factors involved in bone metabolism influence the athletic performance. In European countries, soccer is the most popular sport. The aim of the study was to investigate bone metabolism, bone mass and structural integrity profile in professional male adult football players. Sixteen professional male football players from a single team of the 2nd division Italian League (mean age 22.4±0.7 years) were enrolled. Bone biochemical parameters, including serum calcium, phosphorus, albumin, creatinine, alkaline phosphatase, intact plasma PTH, 25-hydroxy- vitamin D (25-OHD), 24-h urinary calcium and phosphorus, and calcaneal quantitative ultrasound (QUS), were evaluated at the beginning (October 2012) and at the end of the League (May 2013). 25-OHD levels were significantly lower at the end of the League compared to the beginning (27.1 ± 5.9 vs 36.6 ± 9.5 ng/ml, fold change (FC)=0.25, p=0.008), and the prevalence of 25-OHD deficiency increased from 25 to 73%. Moreover, higher rate of previous bone, cartilage or ligament injuries correlated with 25-OHD deficiencies (p=0.014). T-score and Z-score were at the upper limits of the normality ranges, without significant difference between the beginning and end of the League. Phosphaturia was slightly decreased at the end of the League [(691.0 ± 364.5 vs 934.0 ± 274.3 mg/24h, FC=0.26, p=0.06)]. A significant correlation was found between phosphaturia and BQI (R square=0.28, p=0.03), and both T-s and Z-s (R square=0.28, p=0.03) at the beginning of the League. With this pilot study, we demonstrated that vitamin D status significantly worsened at the end of the League. Therefore, vitamin D supplementation might be suggested in adult football players in order to prevent vitamin D deficiency and improve the athletic performance.


#9 Resisted Sprint Velocity in Female Soccer Players: Influence of Physical Capacities
Reference: Int J Sports Med. 2020 Mar 11. doi: 10.1055/a-1083-6724. [Epub ahead of print]
Authors: Loturco I, Jeffreys I, Kobal R, Reis VP, Fernandes V, Rossetti M, Pereira LA, McGuigan M
Summary: This study aimed to examine the effects of different sled overloads on maximum sprint velocity achieved by female soccer players with different strength, speed, and power levels. Twenty elite female soccer players from the same club participated. On the same day, athletes performed: linear and resisted-sprint tests with 30 and 60 % of body-mass over 5-, 10-, and 20-m; half-squat maximum bar-power output, and half-squat one-repetition maximum assessment. A median split analysis was used to divide players into two groups according to their velocity, half-squat one-repetition maximum, and half-squat power. Differences in percentage decreases between unresisted- and resisted-sprints comparing higher and lower groups were analyzed using magnitude-based inferences. Overall, the stronger, faster, and more powerful players were less affected by both loads, as demonstrated by their lower decreases in velocity over the different distances. However, half-squat power appeared to be more sensitive for indicating impairments in resisted-sprint performance, due to meaningful differences in percentage decreases observed between higher and lower power groups. Notably, overloads of 30 and 60% of body-mass provoked substantial reductions in resisted-sprint velocity (~22.9% for 30% and ~51.4% for 60% of body-mass, relative to unresisted-sprint velocity). Athletes with superior power levels are less affected by the progressive sled overloading.


#10 Genetic interplay with soccer ball heading
Reference: Nat Rev Neurol. 2020 Mar 9. doi: 10.1038/s41582-020-0334-6. [Epub ahead of print]
Authors: Smith DH, Stewart W
Download link: https://www.nature.com/articles/s41582-020-0334-6.pdf


#11 The Effects of a Mindfulness-Based Program on the Incidence of Injuries in Young Male Soccer Players
Reference: J Sport Exerc Psychol. 2020 Mar 9:1-11. doi: 10.1123/jsep.2019-0003. [Epub ahead of print]
Authors: Naderi A, Shaabani F, Gharayagh Zandi H, Calmeiro L, Brewer BW
Summary: The authors tested the effectiveness of a mindfulness-based program in reducing sport-injury incidence. A total of 168 young male elite soccer players were randomly assigned to mindfulness and control groups. The mindfulness group consisted of seven sessions based on the mindfulness-acceptance-commitment approach, while the control group consisted of seven presentations on sport-injury psychology. Athlete exposure and injury data were recorded during one season. State and trait mindfulness, sport anxiety, stress, and attention control of participants were assessed. Number of injuries, average of injuries per team, and days lost to injury in the mindfulness group were significantly lower than those in the control group. Mindfulness and attention control were lower and sport anxiety and stress were higher in injured players than in noninjured players. Psychological variables were associated with injury. Mindfulness training may reduce the injury risk of young soccer players due to improved mindfulness and attention control and reduced sport anxiety.

Tue

28

Apr

2020

The technical and physiological effect of goalkeepers in small-sided games in football

Goalkeepers in SSGs - their effect on technical and physiological parameters.

Sat

25

Apr

2020

Bout duration on intensity and technical parameters in SSG

Are there any differences in intensity and technical parameters in SSGs with different durations?

Thu

23

Apr

2020

Latest research in football - week 9 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Cognitive Ageing in Top-Level Female Soccer Players Compared to a Normative Sample from the General Population: A Cross-sectional Study
Reference: J Int Neuropsychol Soc. 2020 Feb 26:1-9. doi: 10.1017/S1355617720000119. [Epub ahead of print]
Authors: Prien A, Besuden C, Junge A, Feddermann-Demont N, Brugger P, Verhagen E
Summary: There is an ongoing debate on the potential negative effect of contact sport participation on long-term neurocognitive performance due to inherent exposure to concussive and subconcussive head impacts. The aim of the present study was to investigate whether cognitive ageing is exacerbated in elite soccer players compared to the general population. Neurocognitive performance in 6 domains was compared between 240 elite soccer players and a normative sample from the general population (n = 585) using the computerised test battery CNS Vital Signs. We used two-way factorial ANOVA to analyse the interaction between age groups (15-19, 20-29, 30-39, 40-49 years) and study population (female soccer players vs. norm sample) in their effects on neurocognitive performance. We found no significant interaction effect of age group and study population in five of six test domains. For processing speed, the effect of age was more pronounced in female soccer players (F = 16.89, p = .002). Further, there was a clear main effect of study population on neurocognitive performance with generally better scores in soccer players. Elite female soccer players generally performed better than the norm sample on tests of cognitive function, and further, cognitive ageing effects were similar in elite soccer players and controls in all but one domain. A lifespan approach may facilitate insightful future research regarding questions related to long-term neurocognitive health in contact sport athletes.


#2 Sex differences in mechanisms of head impacts in collegiate soccer athletes
Reference: Clin Biomech (Bristol, Avon). 2020 Feb 13;74:14-20. doi: 10.1016/j.clinbiomech.2020.02.003. [Epub ahead of print]
Authors: Saunders TD, Le RK, Breedlove KM, Bradney DA, Bowman TG
Summary: There has been growing interest in head impacts related to sports participation due to potential long- and short-term consequences of head injuries. Our purpose was to compare head impact magnitude and frequency between men's and women's intercollegiate soccer players based on head impact mechanism. 28 collegiate soccer players (16 women: age = 19.94 (1.06) years, height = 163.75 (5.15) cm, mass = 61.21 (5.09) kg; 12 men: age = 20.25 (1.14) years, height = 180.34 (6.03) cm, mass = 74.09 (9.32) kg) wore xPatch (X2 Biosystems, Seattle, WA) head impact sensors and participated in this study. Each practice and game was video recorded in order to confirm head impacts. The independent variable was impact mechanism (head to head, head to body (other than head), head to ground, ball to head, goal to head, and combination). Sensors collected linear and rotational accelerations and frequency of head impacts per 1000 athlete exposures. Men were more likely to sustain head impacts than women (IRR = 1.74, CI95 = 1.59-1.92). The highest head impact incidence rate for men was head to body (IR = 611.68, CI95 = 553.11-670.25) while the highest impact incidence rate for women was ball to head (IR = 302.29, CI95 = 270.93-333.64). The interaction between sex and mechanism was significant for rotational accelerations (F4, 1720 = 3.757, P = .005, ω2 = 0.013) but not for linear accelerations (F4,1720 = 0.680, P = .606, ω2 < 0.001, 1 - β = 0.223). To reduce the frequency of head impacts in men, perhaps rules governing player to player contact should be more strictly enforced as these data confirm frequent player-to-head contact during soccer practices and games. Prevention efforts for women should be focused on limiting the amount of purposeful heading (planned contact between the head and ball) occurring during play especially since these impacts had higher magnitudes compared to men.


#3 Neurofilament light and tau in serum after head-impact exposure in soccer
Reference: Brain Inj. 2020 Feb 25:1-8. doi: 10.1080/02699052.2020.1725129. [Epub ahead of print]
Authors: Sandmo SB, Filipcik P, Cente M, Hanes J, Andersen TE, Straume-Naesheim TM, Bahr R
Summary: Blood-based biomarkers can provide valuable information on the effects of repetitive head impacts in sports. This study investigated if repetitive headers or accidental head impacts in soccer could cause structural brain injury, detected as an increase in serum neurofilament light (NfL) or tau. NfL and tau were measured in professional soccer players in pre-season. Then, the effect of three short-term exposures on biomarker levels was assessed: (1) high-intensity exercise, (2) repetitive headers, and (3) head impacts in a match. We analyzed 354 samples and observed no effects on NfL from any of the three short-term exposures. Tau levels rose significantly from baseline to 1 h after (1) high-intensity exercise (Δ0.50 pg/mL, 95% CI 0.19-0.81, p < .01); the same was observed after (2) repetitive headers (Δ0.29 pg/mL, 95% CI 0.10-0.48, p < .01), but not after (3) accidental head-impact incidents (Δ0.36 pg/mL, 95% CI -0.02-0.74, p = .06). The highest absolute values were seen 1 h after high-intensity exercise (mean±SD, 1.92 ± 0.83 pg/mL). NfL and tau in serum were unaffected by head impacts in soccer. Importantly, tau levels seem to rise in response to exercise, emphasizing the need for control groups. Our findings highlight important characteristics and limitations when using these biomarkers in sports.


#4 Effect of chronotype on motor skills specific to soccer in adolescent players
Reference: Chronobiol Int. 2020 Feb 24:1-12. doi: 10.1080/07420528.2020.1729787. [Epub ahead of print]
Authors: Roveda E, Mulè A, Galasso L, Castelli L, Scurati R, Michielon G, Esposito F, Caumo A, Montaruli A
Summary: Circadian rhythms influence daily behavior, psychological and physiological functions, as well as physical performance. Three chronotypes are distinguished according to the preferences people typically display for activity at certain times of day: Morning, Neither, and Evening types (M-, N- and E-types). The chronotype changes with age: eveningness tends to be stronger in youth and morningness in older age. The progressive shift toward eveningness during adolescence creates misalignment with morning society schedules and can lead to a deterioration in intellectual and physical performance. Soccer is one of the world's most popular sports practiced by adolescents and soccer workouts are usually held after school in the afternoon or evening. Performance in soccer is related to a host of factors, including physiological variables and motor skills that have a circadian variation. The aim of this study was to determine the effect of chronotype on motor skills specific to soccer, specifically whether agility, aerobic endurance, and explosive power differ among the three chronotypes in relation to the time of day. For this study 141 adolescent soccer players filled in the Morningness-Eveningness Questionnaire (MEQ) for the assessment of chronotype. A subsample of 75 subjects, subdivided in M-types (n= 25), E-types (n= 25), and N-types (n= 25), performed three tests (Sargent Jump Test - SJT, Illinois Agility Test - IAT, and 6-Minutes Run Test - 6MRT) at a morning and an evening training session (9:00 am and 6:00 pm). Mixed ANOVA was used to test the interactions between chronotypes, physical performance, and time. On all tests, better performance during the morning than the evening session was observed for the M-types (p< .05), whereas the E-types performed better in the evening than in the morning session (p< .05), and no differences in test performance were detected for the N-types. These findings underline the importance of a correct chronobiological approach to sports training. Scheduling training sessions according to an athlete's circadian preferences could be a valid strategy to enhance performance.


#5 Can Participation in a Community Organized Football Program Improve Social, Behavioural Functioning and Communication in Children with Autism Spectrum Disorder? A Pilot Study
Reference: J Autism Dev Disord. 2020 Feb 27. doi: 10.1007/s10803-020-04423-5. [Epub ahead of print]
Authors: Howells K, Sivaratnam C, Lindor E, Hyde C, McGillivray J, Whitehouse A, Rinehart N
Summary: This pilot research investigated the effects of a community-based organized football program on behavioral, social and communicative outcomes in children with Autism Spectrum Disorder. In a non-randomized design, 19 children completed the football program and were compared pre- and post-intervention with 21 children who received no comparable intervention (ages 5-12 years). Caregiver-report using the child behavior checklist indicated a significant decrease in total, internalizing, DSM-oriented anxiety and social problems for children who participated in the program, with no change in the comparison group. There were no group differences in socialization and communication scores on the Vineland Adaptive Behavior scale. Results provide preliminary evidence in support of the program, justifying the need for further, more rigorous trials in this area.


#6 Effect of Acute Sleep Hygiene on Salivary Cortisol Level Following A Late Night Soccer-Specific Training Session
Reference: J Sports Sci Med. 2020 Feb 24;19(1):235-236. eCollection 2020 Mar.
Authors: Bonato M, Merati G, La Torre A, Saresella M, Marvetano I, Banfi G, Vitale JA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039028/pdf/jssm-19-235.pdf


#7 Isoinertial Eccentric-Overload Training in Young Soccer Players: Effects on Strength, Sprint, Change of Direction, Agility and Soccer Shooting Precision
Reference: J Sports Sci Med. 2020 Feb 24;19(1):213-223. eCollection 2020 Mar.
Authors: Fiorilli G, Mariano I, Iuliano E, Giombini A, Ciccarelli A, Buonsenso A, Calcagno G, di Cagno A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039027/pdf/jssm-19-213.pdf
Summary: The isoinertial training method owes its efficacy to an accommodated resistance and optimal individualized eccentric overload. The aim of this study was to assess the effects of a 6-week isoinertial eccentric-overload training program - using a flywheel inertial device during the execution of specific soccer exercises - on explosive and reactive strength, sprint ability, change of direction (COD) performance and soccer shooting precision. Thirty-four junior soccer players were randomly assigned to a plyometric training group (PT) (n = 16, aged 13.36 ± 0.80), which underwent a six-week traditional soccer training program, and a flywheel eccentric overload group (FEO) (n = 18, aged 13.21 ± 1.21), which received additional training consisting of two inertial eccentric-overload training sessions per week. Pre and post intervention tests were carried out to assess explosive and reactive strength, sprint ability, COD ability, agility using the Y-agility test (YT) and soccer shooting precision. The FEO showed significantly higher values than the PT in squat jump height (SJh) (p = 0.01), drop jump height (DJh) (p = 0.003), 7 repeated hop test heights (p = 0.001), the Illinois test (ILL) (p = 0.001), and the Loughborough Soccer Shooting Test (SHOT) (p = 0.02). Finally, the FEO showed significant between-group differences in DJh (p = 0.007), ILL (p = 0.0002), YT (p = 0.002), a linear sprint test (SPRINT) (p = 0.001), and SHOT (p = 0.003). These results confirmed the positive effect of isoinertial training. The use of an isoinertial device to overload multidirectional movements in specific sport conditions leads to greater performance improvements than conventional soccer training. The absence of knowledge of the eccentric overload applied by the isoinertial device, which is different in any exercise repetition, may stimulate the athlete's neural adaptations, improving their soccer skills and in particular their soccer shooting precision.


#8 Match Situations Leading to Head Injuries in Professional Male Football (Soccer)-A Video-Based Analysis Over 12 Years
Reference: Clin J Sport Med. 2020 Mar;30 Suppl 1:S47-S52. doi: 10.1097/JSM.0000000000000572.
Authors: Beaudouin F, Aus der Fünten K, Tröß T, Reinsberger C, Meyer T
Summary: The purpose was to identify risk situations promoting head injuries in professional male football (soccer) and to investigate the impact of a rule change in 2006 punishing elbow-head contacts. Professional football players of the first male German Bundesliga participated in this investigation. Observational criteria of head impacts on video recordings (players' actions preceding head injuries, foul play-referee's decision and assessment of rater, ball possession, on-pitch medical treatment, and consequences of head impact) were used as outcome measures. Three hundred thirty-four head injuries were reported in kicker Sportmagazin corresponding to an incidence rate of 2.25 (95% confidence interval 2.01-2.51) per 1000 player match hours. The injured player predominantly jumped (60%), headed the ball (36%), or ran forwards (20%); the noninjured players mainly jumped (64%), headed the ball (27%), or raised the elbow to the head (23%). Free ball situations (2 players challenge for the ball) caused most of the head injuries (81%). The players' action "raising the elbow" during a head injury seemed to be lower after the rule change. Jumping for the ball with the intention of heading is the predominant action associated with head injury risk. Head injuries occur most often when players challenge for the ball in a header duel. As head injuries bear the potential risk of long-term health sequelae, the identification of situational circumstances is essential to develop preventative means in the future.


#10 Sex differences in bone density, geometry, and bone strength of competitive soccer players

Reference: J Musculoskelet Neuronal Interact. 2020 Mar 3;20(1):62-76.
Authors: Baker BS, Chen Z, Larson RD, Bemben MG, Bemben DA
Download link: http://www.ismni.org/jmni/pdf/79/jmni_20_062.pdf
Summary: The purpose was to examine sex differences in bone characteristics in competitive soccer players. 43 soccer players (male, n=23; female, n=20), and 43 matched controls (males, n=23; females, n=20), completed the study. Areal BMD (aBMD) of the total body, lumbar spine, and dual femur and tibiae volumetric BMD (vBMD), bone geometry, and bone strength variables (pQCT) were measured. Bone-specific physical activity and training history were assessed. Male soccer players had significantly greater (p≤0.05) total body and hip aBMD, hip strength indices and 4% and 38% tibia variables than females. Regression analyses determined that BFLBM, not sex, was the strongest predictor of bone variables. Female soccer players exhibited significantly greater percent differences from controls for tibiae variables than males (p≤0.05). Soccer players had greater aBMD and hip strength indices than controls (p≤0.040). Soccer-specific asymmetries were found for 38% total area (2.1%) and pSSI (3.8%), favoring the non-dominant leg (both p≤0.017). Bone characteristics adjusted for body size were greater in male versus female soccer players. However, body composition variables were more important predictors of bone characteristics than sex. There were no sex differences in the magnitude of limb asymmetries, suggesting skeletal responsiveness to mechanical loading was similar in males and females.


#11 Video Confirmation of Head Impact Sensor Data From High School Soccer Players
Reference: Am J Sports Med. 2020 Mar 4:363546520906406. doi: 10.1177/0363546520906406. [Epub ahead of print]
Authors: Patton DA, Huber CM, McDonald CC, Margulies SS, Master CL, Arbogast KB
Summary: Recent advances in technology have enabled the development of head impact sensors, which provide a unique opportunity for sports medicine researchers to study head kinematics in contact sports. Studies have suggested that video or observer confirmation of head impact sensor data is required to remove false positives. In addition, manufacturer filtering algorithms may be ineffective in identifying true positives and removing true negatives. The aims were to (1) identify the percentage of video-confirmed events recorded by headband-mounted sensors in high school soccer through video analysis, overall and by sex; (2) compare video-confirmed events with the classification by the manufacturer filtering algorithms; and (3) quantify and compare the kinematics of true- and false-positive events. Adolescent female and male soccer teams were instrumented with headband-mounted impact sensors (SIM-G; Triax Technologies) during games over 2 seasons of suburban high school competition. Sensor data were sequentially reduced to remove events recorded outside of game times, associated with players not on the pitch (ie, field) and players outside the field of view of the camera. With video analysis, the remaining sensor-recorded events were identified as an impact event, trivial event, or nonevent. The mechanisms of impact events were identified. The classifications of sensor-recorded events by the SIM-G algorithm were analyzed. A total of 6796 sensor events were recorded during scheduled varsity game times, of which 1893 (20%) were sensor-recorded events associated with players on the pitch in the field of view of the camera during verified game times. Most video-confirmed events were impact events (n = 1316, 70%), followed by trivial events (n = 396, 21%) and nonevents (n = 181, 10%). Female athletes had a significantly higher percentage of trivial events and nonevents with a significantly lower percentage of impact events. Most impact events were head-to-ball impacts (n = 1032, 78%), followed by player contact (n = 144, 11%) and falls (n = 129, 10%) with no significant differences between male and female teams. The SIM-G algorithm correctly identified 70%, 52%, and 66% of video-confirmed impact events, trivial events, and nonevents, respectively. Video confirmation is critical to the processing of head impact sensor data. Percentages of video-confirmed impact events, trivial events, and nonevents vary by sex in high school soccer. Current manufacturer filtering algorithms and magnitude thresholds are ineffective at correctly classifying sensor-recorded events and should be used with caution.

Thu

23

Apr

2020

Rules change in small-sided games in football

The effect of using an end-zone vs. a small goal on physiological parameters (such as heart rate).

Wed

22

Apr

2020

Manipulating task constraints in small-sided games

What are the effects of task constraints (for example number of touches) on different game indicators in football?

Sun

19

Apr

2020

Latest research in football - week 8 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Oxygen therapy in patients with ST elevation myocardial infarction based on the culprit vessel: results from the randomized controlled SOCCER trial
Reference: BMC Emerg Med. 2020 Feb 18;20(1):12. doi: 10.1186/s12873-020-00309-y.
Authors: Mokhtari A, Akbarzadeh M, Sparv D, Bhiladvala P, Arheden H, Erlinge D, Khoshnood A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7027294/pdf/12873_2020_Article_309.pdf
Summary: Oxygen (O2) treatment has been a cornerstone in the treatment of patients with myocardial infarction. Recent studies, however, state that supplemental O2 therapy may have no effect or harmful effects in these patients. The aim of this study was thus to evaluate the effect of O2 therapy in patients with ST Elevation Myocardial Infarction (STEMI) based on the culprit vessel; Left Anterior Descending Artery (LAD) or Non-LAD. This was a two-center, investigator-initiated, single-blind, parallel-group, randomized controlled trial at the Skåne university hospital, Sweden. A simple computer-generated randomization was used. Patients were either randomized to standard care with O2 therapy (10 l/min) or air until the end of the primary percutaneous coronary intervention. The patients underwent a Cardiac Magnetic Resonance Imaging (CMRI) days 2-6. The main outcome measures were Myocardium at Risk (MaR), Infarct Size (IS) and Myocardial Salvage Index (MSI) as measured by CMRI, and median high-sensitive troponin T (hs-cTnT). A total of 229 patients were assessed for eligibility, and 160 of them were randomized to the oxygen or air arm. Because of primarily technical problems with the CMRI, 95 patients were included in the final analyses; 46 in the oxygen arm and 49 in the air arm. There were no significant differences between patients with LAD and Non-LAD as culprit vessel with regard to their allocation (oxygen or air) with regards to MSI, MaR, IS and hs-cTnT. The results indicate that the location of the culprit vessel has probably no effect on the role of supplemental oxygen therapy in STEMI patients.


#2 ALCAPA syndrome in an asymptomatic young soccer player
Reference: Turk Gogus Kalp Damar Cerrahisi Derg. 2019 Jun 14;27(3):388-391. doi: 10.5606/tgkdc.dergisi.2019.16320. eCollection 2019 Jul.
Authors: Ramoğlu MG, Bulut MO, Epçaçan S, Dedemoğlu M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021416/pdf/TurkGogusKalpDama-27-388.pdf
Summary: Anomalous origin of left coronary artery from pulmonary artery syndrome is a rare, but severe congenital cardiac malformation. It is an important cause of dilated cardiomyopathy and left heart failure during infancy and, if left untreated, the prognosis is poor with an overall mortality rate over 90%. About 15% of patients can survive beyond the first year of life, depending on the development of collateral circulation and may present with angina, dyspnea, syncope, and arrhythmias. Myocardial infarction and sudden cardiac death may be the only and the first symptom in some cases. The treatment of choice for this syndrome is urgent surgical intervention with favorable long-term outcomes. Herein, we present an asymptomatic adolescent active sportsman who was diagnosed with anomalous origin of left coronary artery from pulmonary artery syndrome and underwent a successful surgery.


#3 Does Recreational Soccer Change Metabolic Syndrome Status in Obese Adolescents? A Pilot Study
Reference: Res Q Exerc Sport. 2020 Feb 21:1-9. doi: 10.1080/02701367.2019.1711007. [Epub ahead of print]
Authors: Vasconcellos F, Cunha FA, Gonet DT, Farinatti PTV
Summary: The purpose was to evaluate whether a soccer program (RSP) might lower risk factors related to metabolic syndrome (MetS) in obese adolescents. A 12-week randomized controlled trial [RSP: n = 6 (2 girls), age = 13.9 ± 1.6 yr, body mass index = 30.5 ± 2.1 kg/m2; Control: n = 7 (2 girls); age = 14.7 ± 2.3 yr, body mass index: 30.8 ± 3.1 kg/m2] was conducted. Participants underwent anthropometric, body fractioning, blood pressure, lipid profile, and glucose tolerance assessments at baseline and post-intervention. MetS status was determined based on waist circumference and at least two additional criteria: high blood pressure, hypertriglyceridemia, dyslipidemia, and hyperglycemia. RSP included eutrophic and overweight adolescents and consisted of small-sided games (85 ± 4% maximal heart rate) performed three times/week. High-density lipoprotein increased [(HDL) ∆15.5 ± 5.2 mg·dL-1; p = .01] and triglycerides lowered [(TG) ∆-34.7 ± 7.1 mg·dL-1; p = .02] after RSP intervention. Between-group differences were also detected for changes in HDL (∆13.0 ± 6.1 mg·dL-1; p = .04) and TG (∆-47.1 ± 7.7 mg·dL-1; p = .05). The presence of MetS lowered in RSP (5 in 6 participants; p = .02), but not Control (1 in 7 participants; p = .32). A 12-week RSP was effective to reduce MetS risk factors and status in obese adolescents.


#4 Return to play after three ipsilateral anterior cruciate ligament reconstructions in an elite soccer player: A case report
Reference: Int J Surg Case Rep. 2020 Feb 19;68:1-3. doi: 10.1016/j.ijscr.2020.02.027. [Epub ahead of print]
Authors: Noronha JC, Oliveira JP, Brito J
Download link: https://www.sciencedirect.com/science/article/pii/S2210261220301012/pdfft?isDTMRedir=true&download=true
Summary: Despite the reasonable success of ACL reconstruction, some athletes are not able to regain the level of play they once had. Here, we report the case of a 32-year-old male professional soccer player who sustained an ACL injury in his right knee. The patient had a history of two prior ipsilateral ACL injuries, which was reconstructed with ipsilateral hamstring autograft (first surgery) and ipsilateral patellar tendon autograft (revision surgery). Imaging examination revealed a small narrowing of the medial femoro-tibial compartment, a complete ACL rupture, partial medial meniscectomy, small cartilage lesions in the medial condyle, a 7° varus knee, an enlarged tibial tunnel, and a femoral tunnel positioned high above the intercondylar roof. A one-step re-revision surgery using a fresh-frozen, cadaveric, non-irradiated Achilles tendon allograft was planned. After surgery, physiotherapy was conducted once per day during 4 months. The patient started running at the 6th month, and returned to full training 8 months after surgery. The player returned to full competitive play 9 months after surgery and has been competing for the last 36 months at the highest level of play without any limitation, inflammation, pain, or perception of instability. In professional sports, when re-revision ACL reconstruction is indicated and the patient expects to return to competition, surgery should not be delayed. In these cases, the usefulness of Achilles tendon allograft should be taken into consideration for re-revision ACL reconstruction.


#5 The Association Between Interlimb Asymmetry and Athletic Performance Tasks: A Season-Long Study in Elite Academy Soccer Players
Reference: J Strength Cond Res. 2020 Feb 27. doi: 10.1519/JSC.0000000000003526. [Epub ahead of print]
Authors: Bishop C, Read P, Bromley T, Brazier J, Jarvis P, Chavda S, Turner A
Summary: The aims of this study were to determine the association between asymmetry and measures of speed and change of direction speed (CODS) performance throughout a competitive soccer season and, determine whether any observed changes in asymmetry were associated with changes in speed and CODS performance. Eighteen elite male under-23 academy soccer players performed unilateral countermovement jumps, unilateral drop jumps (DJ), 10- and 30-m sprints, and 505 CODS tests at pre, mid, and end of season. No significant relationships were evident during preseason or midseason between asymmetry and speed or CODS performance. Significant correlations were shown at the end of season between DJ height asymmetry and 10-m sprint time (ρ = 0.62; p = 0.006) and 505 time on the right limb (ρ = 0.65; p = 0.003). No significant correlations between changes in asymmetry and changes in speed or CODS were evident at any time point. Although numerous studies have reported associations between asymmetry and reduced athletic performance, it seems that these associations with speed and CODS do not track consistently over time. Thus, suggestions for the reduction of asymmetry that may indirectly enhance athletic performance cannot be made.


#6 The prevalence of disordered eating in elite male and female soccer players
Reference: Eat Weight Disord. 2020 Feb 27. doi: 10.1007/s40519-020-00872-0. [Epub ahead of print]
Authors: Abbott W, Brett A, Brownlee TE, Hammond KM, Harper LD, Naughton RJ, Anderson L, Munson EH, Sharkey JV, Randell RK, Clifford T
Download link: https://link.springer.com/content/pdf/10.1007/s40519-020-00872-0.pdf
Summary: The purpose was to examine the prevalence of disordered eating (DE) in elite male and female soccer players and the influence of perfectionism. Using a cross-sectional design, elite male (n = 137) and female (n = 70) soccer players and non-athlete controls (n = 179) completed the clinical perfectionism questionnaire (CPQ-12) and the eating attitudes test (EAT-26) to assess perfectionism and DE risk, respectively. Male soccer players had higher EAT-26 scores than controls (10.4 ± 9.9 vs. 6.8 ± 6.7; P = 0.001), but there were no differences in the prevalence of clinical levels of DE (EAT-26 score ≥ 20) (15 vs. 5%, respectively; X2 = 0.079) The proportion of females with DE risk was higher in controls [EAT-26: 13.9 ± 11.6 (25% of population)] than female players [EAT-26: 10.0 ± 9.0% (11% of population)] (X2 = 0.001). With linear regression, perfectionism explained 20% of the variation in DE risk in males (P = 0.001); in females, athletic status (player vs. control) and perfectionism were significant predictors of DE risk, explaining 21% of the variation (P = 0.001). Male reserve team players had higher EAT-26 (+ 3.5) and perfectionism (+ 2.7) scores than first-team players (P < 0.05). There were no differences in the prevalence of DE risk between the male and female soccer players (X2 = 0.595). The prevalence of DE risk was not different in elite male and female soccer players; in fact, the prevalence was greatest in non-athlete female controls. Perfectionism is a significant predictor of DE risk in males and females.


#7 Effect of Forefoot and Midfoot Bending Stiffness on Agility Performance and Foot Biomechanics in Soccer
Reference: J Appl Biomech. 2020 Feb 25:1-7. doi: 10.1123/jab.2019-0115. [Epub ahead of print]
Authors: Brinkmann DJ, Koerger H, Gollhofer A, Gehring D
Summary: Footwear bending stiffness is known to positively affect performance in agility maneuvers due to improved energy storage and propulsion based on a stiffer foot-shoe complex. However, the functional properties of the forefoot and midfoot differ. Therefore, the present study investigates the effect of the interface of longitudinal bending stiffness and the ratio of forefoot to midfoot bending stiffness on agility performance and foot biomechanics. A total of 18 male soccer players performed 2 agility tasks in footwear conditions that were systematically modified in forefoot and midfoot bending stiffness. Results revealed that higher longitudinal bending stiffness caused more foot exorotation at the initial ground contact (P < .05), less torsion (P < .001), and an anterior shift in the point of force application during push off (P = .01). In addition, the authors observed decreased forefoot bending (P < .05) and increased torsion (P < .01) in footwear with a higher forefoot-midfoot ratio. Finally, the agility performance was significantly impaired by 1.3% in the condition with the highest forefoot-midfoot ratio (P < .01). The high forefoot-midfoot ratio, that is, a stiff forefoot in combination with a soft midfoot, seemed to shift the flex line from anterior to posterior that may explain the performance impairment.


#8 Twelve eyes see more than eight. Referee bias and the introduction of additional assistant referees in soccer
Reference: PLoS One. 2020 Feb 26;15(2):e0227758. doi: 10.1371/journal.pone.0227758. eCollection 2020.
Authors: Albanese A, Baert S, Verstraeten O
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0227758&type=printable
Summary: This study is the first to investigate whether the introduction of additional assistant referees in the UEFA Europa League (2009-2010 season) and the UEFA Champions League (2010-2011 season) was associated with lower referee bias in terms of home and "big" team favouritism. To this end, we analyse a unique database with pre- and within-game characteristics of all games in seven recent seasons in these leagues by means of bivariate probit regression models. We find evidence for substantial referee bias before the introduction of additional referees, while no such evidence is found after the introduction. Furthermore, additional assistants go hand in hand with more yellow cards for both home and away teams. We show that these findings are robust to multiple operationalisations of referee bias and that they are not just picking up a general time evolution towards less referee bias or the effect of parallel reforms.


#9 Significant differences in dietary intake of NCAA Division III soccer players compared to recommended levels
Reference: J Am Coll Health. 2020 Feb 26:1-8. doi: 10.1080/07448481.2020.1728279. [Epub ahead of print]
Authors: Gomez-Hixson K, Biagioni E, Brown ML
Summary: This study evaluated dietary intake patterns of NCAA Division III soccer players compared to recommended levels. NCAA Division III soccer players (n = 75) participated in this study. Actual dietary intake was determined by the analysis of a 3-day food record. Results indicate that total energy, carbohydrate, and dietary fiber intake was significantly below the recommended levels. In addition, added sugar and total fat consumption were significantly above recommended levels. Potassium, magnesium, and vitamin D levels were consumed in levels significantly below the recommended levels. Sodium, iron, and vitamin C were consumed in significantly higher levels than the recommended target. Female athletes had significantly higher intakes of added sugar, saturated fat and vitamin C compared to male athletes. Female athletes had significantly lower intakes of calcium, potassium, sodium, iron, magnesium and vitamin D compared to male athletes. Based on the results of the present study, increased efforts should be put into development of nutrition education programs for NCAA Division III athletes.


#10 Concussion incidence and recovery in Swedish elite soccer - prolonged recovery in female players
Reference: Scand J Med Sci Sports. 2020 Feb 26. doi: 10.1111/sms.13644. [Epub ahead of print]
Authors: Vedung F, Hänni S, Tegner Y, Johansson J, Marklund N
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13644
Summary: Sport-related concussions are an increasingly recognized health problem. Soccer is the most popular sport in the world although recent studies on concussion incidence are scarce. Here, a nation-wide prospective study on concussion incidence, symptom severity, risk factors, gender differences and return-to-play after concussion was performed in 51 Swedish elite soccer teams during the 2017 season. In the first and second soccer leagues for men and women, a Sport Concussion Assessment Tool (SCAT) -based questionnaire study was performed at pre-season (baseline) and from 48h up to three months post-concussion. We followed 959 players (389 women, 570 men) for 25146 player game hours (9867 h for women, 15279 h for men). Concussion incidence (n= 36) was 1.19/1000 player game hours (females 1.22/1000 h, males 1.18/1000 h; p= 0.85). Twenty-seven percent (females 8%, males 40%) of players continued to play immediately after the concussion. When compared to male players, female players had worse initial symptom severity scores (median and IQR 30 (17-50.5) vs. 11 (4-26.25), p=0.02) and longer return to play (p=0.02). Risk factors for concussion were baseline symptoms and previous concussion. In Swedish elite soccer, the concussion incidence was 1.19/1000 without gender differences. Most players recovered to play within four weeks post-injury. Almost one third of players continued to play at time of concussion. Female players had worse initial symptoms and longer return-to-play time than males, and a prolonged recovery beyond three months was only observed among female players.


#11 The Impact of Sleep on the Relationship between Soccer Heading Exposure and Neuropsychological Function in College-Age Soccer Players
Reference: J Int Neuropsychol Soc. 2020 Feb 26:1-12. doi: 10.1017/S1355617720000211. [Epub ahead of print]
Authors: Levitch CF, McConathey E, Aghvinian M, Himmelstein M, Lipton ML, Zimmerman ME
Summary: Soccer is the most popular sport worldwide and is the only sport where athletes purposely use their head to deflect the ball during play, termed "heading" the ball. These repetitive head impacts (RHI) are associated with worse neuropsychological function; however, factors that can increase risk of injury following exposure to such head impacts have been largely unexamined. The present study provided a novel examination of the modifying role of sleep on the relationship between RHI exposure and neuropsychological function in college-age soccer players. Fifty varsity and intramural college soccer players completed questionnaires assessing recent and long-term heading exposure, a self-report measure of sleep function, and a battery of neuropsychological tests. A high level of recent heading exposure was significantly associated with poorer processing speed, independent of concussion history. With reduced sleep duration, a high level of recent heading exposure was related to worse sustained attention. However, with greater hours of sleep duration, heading exposure was related to preserved neuropsychological outcome in sustained attention. We replicated our earlier finding of an association between recent head impact exposure and worse processing speed in an independent sample. In addition, we found that sleep may serve as a risk or protective factor for soccer players following extensive exposure to head impacts. Ultimately, this study furthers the understanding of factors impacting neuropsychological function in soccer players and provides empirical support for sleep interventions to help ensure safer soccer play and recovery from injury.

Fri

17

Apr

2020

Small-sides games are more enjoyable compared to running...

...but does it have the same cardiovascular effect for players?

Fri

17

Apr

2020

Positional differences in the most demanding passages of play in football competition

Are there any differences for midfielders vs. strikers with regards to meters covered per minute in demanding passages of games?

Tue

14

Apr

2020

Latest research in football - week 7 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Sprint versus isolated eccentric training: Comparative effects on hamstring architecture and performance in soccer players
Reference: PLoS One. 2020 Feb 11;15(2):e0228283. doi: 10.1371/journal.pone.0228283. eCollection 2020.
Authors: Mendiguchia J, Conceição F, Edouard P, Fonseca M, Pereira R, Lopes H, Morin JB, Jiménez-Reyes P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7012429/pdf/pone.0228283.pdf
Summary: The purpose of this study was to compare the effects of hamstring eccentric (NHE) strength training versus sprint training programmed as complements to regular soccer practice, on sprint performance and its mechanical underpinnings, as well as biceps femoris long head (BFlh) architecture. In this prospective interventional control study, sprint performance, sprint mechanics and BFlh architecture variables were compared before versus after six weeks of training during the first six preseason weeks, and between three different random match-pair groups of soccer players: "Soccer group" (n = 10), "Nordic group" (n = 12) and "Sprint group" (n = 10). For sprint performance and mechanics, small to large pre-post improvements were reported in "Sprint group" (except maximal running velocity), whereas only trivial to small negative changes were reported in "Soccer group" and "Nordic group". For BFlh architecture variables, "Sprint" group showed moderate increase in fascicle length compared to smaller augment for the "Nordic" group with trivial changes for "Soccer group". Only "Nordic" group presented small increases at pennation angle. The results suggest that sprint training was superior to NHE in order to increase BFlh fascicle length although only the sprint training was able to both provide a preventive stimulus (increase fascicle length) and at the same time improve both sprint performance and mechanics. Further studies with advanced imaging techniques are needed to confirm the validity of the findings.


#2 Acute effects of two different initial heart rates on testing the repeated sprint ability in elite women's soccer players
Reference: J Sports Med Phys Fitness. 2020 Feb 5. doi: 10.23736/S0022-4707.19.10311-8. [Epub ahead of print]
Authors: Ruscello B, Esposito M, Fusco C, Ceccarelli C, Pomponi S, Filetti C, Pantanella L, Gabrielli P, D'ottavio S
Summary: Repeated Sprint Ability (RSA) in women's soccer is crucial to ensure high level of performance during the game. Aim of this study is to investigate the acute effects of two different initial heart rates intensities on fatigue when testing the RSA. Since there are many kinds of pre-match warming-ups, the heart rate reached at the end of two different warm-up protocols (~90vs.≈60%HRmax) as an indicator of internal load has been selected and the respective RSA performances were compared. RSA tests were performed by 19 elite women soccer players (Age: 22.5±3.3 years, height 163.9±7.3 cm, body mass 54.3±6.4 kg, BMI 20.6±1.5 kg·m-2) with two sets of ten shuttle-sprints (15+15m) with a 1:3 exercise to rest ratio, in different days (randomized order) with different initial HR% (60 & 90% HRmax). In order to compare the different sprint performances a Fatigue Index (FI%) was computed; the blood lactate concentrations (BLa-) were measured before and after testing, to compare metabolic energy. Significant differences among trials within each sets (P<0.01) were found, as evidence of fatigue. Differences between sets were not found, (Factorial ANOVA 2x10; P>0.05). Although the BLa- after warm-up was higher between 90% vs. 60% HRmax (P<0.05), at the completion of RSA tests - after 3 minutes - the differences were considerably low and not significant (P>0.05). This study shows that, contrary to male soccer, the initial heart rates, induced by different modes of warming-up, do not affect the overall performance while testing RSA in women's soccer players.


#3 Tactical Variables Related to Gaining the Ball in Advanced Zones of the Soccer Pitch: Analysis of Differences Among Elite Teams and the Effect of Contextual Variables
Reference: Front Psychol. 2020 Jan 21;10:3040. doi: 10.3389/fpsyg.2019.03040. eCollection 2019.
Authors: Fernandez-Navarro J, Ruiz-Ruiz C, Zubillaga A, Fradua L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6985566/pdf/fpsyg-10-03040.pdf
Summary: Attacking tactical variables have been commonly studied in soccer to analyze teams' performance. However, few studies investigated defensive tactical variables during match-play and the influence of contextual variables on them. The aims of the present study were (1) to examine the defensive behaviors of soccer teams when gaining the ball in advanced zones of the pitch and (2) to evaluate the effect of contextual variables on these defensive behaviors. A sample of 1,095 defensive pieces of play initiated in the opposing half of the pitch obtained from 10 matches of the season 2010/11 of La Liga and involving 13 teams was collected using the semiautomated tracking system Amisco Pro. Five defensive tactical variables, the outcome of defensive pieces of play, and contextual variables (i.e., match status, venue, quality of opposition, and match period) were recorded for every defensive piece initiated in the opposing half of the pitch. Results showed that there were significant differences among teams in the outcome of defensive pieces of play originating from the opposing half (χ2 = 111.87, p < 0.01, φc = 0.22), and in the outcome of offensive pieces of play following ball gains (χ2 = 49.92, p < 0.001, φc = 0.22). Cluster analysis revealed four groups describing different defensive behaviors from high-pressure to a defense close to their own goal. Match status (χ2 = 25.87, p < 0.05, φc = 0.11) and quality of opposition (χ2 = 21.19, p < 0.05, φc = 0.10) were the contextual variables that showed a significant effect on defensive pieces of play initiated in the opposite half of the pitch. Teams winning gained more balls in the zone close to their own goal, and losing teams gained more balls in advanced zones of the pitch. Moreover, the greater the quality of the opponent the lesser the chance of gaining the ball in advanced zones of the pitch. Neither venue or match period influenced the defensive pieces of play analyzed. Soccer teams could employ a similar analysis to improve their performance and prepare for opposition teams in competition.


#4 Individualized Breakfast Programs or Glycogen Super-Compensation: Which Is the Better Performing Strategy? Insights from an Italian Soccer Referees Cohort

Reference: Int J Environ Res Public Health. 2020 Feb 5;17(3). pii: E1014. doi: 10.3390/ijerph17031014.
Authors: Regnoli R, Rovelli M, Gianturco V, Pregliasco FE, Bodini BD, Gianturco L
Download link: https://www.mdpi.com/1660-4601/17/3/1014/pdf
Summary: The role of soccer referees has grown in importance in the last decades, as has attention to their performance, which may be influenced and improved with specific and evolved training programs. Today, multiple specialists are working as a team in order to develop effective training programs. Moreover, for athletes, it is becoming more and more important to be attentive to nutrition. By considering such items, in this study, we aimed to investigate the nutritional habits of a group of referees belonging to the Italian Soccer Referees' Association (on behalf of AIA-FIGC). Our main aim was to spread a "culture of nutrition" in refereeing, starting with a survey on referees' breakfast attitudes and in order to disseminate such a "culture", we chose top-level elite referees who were younger subjects (despite the average 4 years' experience). Therefore, we enrolled 31 subjects (aged 22.74 ± 1.79, BMI 22.30 ± 1.53) and asked them about their breakfast habits. Then, for measuring their performance, we used the conventional fitness test named Yo-Yo (YYiR1), performed in three different sessions (test 1, test 2, test 3). Test 1 was carried out without any nutritional indications, test 2 was given after individualized breakfast suggestions by a designed dietician, and test 3 after an individualized glycogen super-compensation strategy. The Wilcoxon statistical analysis indicates that following an individualized breakfast strategy may enhance referees' performance (p < 0.0001), whereas no significant effects were observed with the glycogen super-compensation option. However, further studies will be necessary to better address this topic and clarify whether high-carbohydrates (high-CHO) intake may be useful in other sports.


#5 Influence of Contextual Variables in the Changes of Direction and Centripetal Force Generated during an Elite-Level Soccer Team Season
Reference: Int J Environ Res Public Health. 2020 Feb 4;17(3). pii: E967. doi: 10.3390/ijerph17030967.
Authors: Granero-Gil P, Bastida-Castillo A, Rojas-Valverde D, Gómez-Carmona CD, de la Cruz Sánchez E, Pino-Ortega J
Download link: https://www.mdpi.com/1660-4601/17/3/967/pdf
Summary: The study of the contextual variables that affect soccer performance is important to be able to reproduce the competition context during the training sessions. Therefore, the aim of the present study was to evaluate the effect of match outcome as related to goal difference (large win, >2 goals, LW; narrow win, 1-2 goals, NW; drawing, D; narrow loss, 1-2 goals, NL; or large loss, >2 goals, LL), match location (home, H; away, A; neutral, N), type of competition (international, INT; national, NAT; friendly, F), phase of the season (summer preseason, SPS; in-season 1, IS1; winter preseason, WPS; in-season 2), and the field surface (natural grass, NG; artificial turf, TF) on the change of direction (COD) and centripetal force (CentF) generated during official games. Thirty male elite-level soccer players (age: 26.57 ± 5.56 years) were assessed while using WIMU PROTM inertial devices (RealTrack Systems, Almeria, Spain) in 38 matches during the 2017-2018 season, selecting for analysis the number of COD at different intensities and the CentF, depending on the turn direction. Statistical analyses comprised a one-way ANOVA with the Bonferroni post-hoc and t-test for independent samples. The main results showed that the match outcome (ωp² = 0.01-0.04; NW = D = NL > LL), match location (ωp² = 0.01-0.06; A = N > H), type of competition (ωp² = 0.01-0.02; INT > NAT > F), and period of the season (ωp² = 0.01-0.02; SPS = IS1 = WPS > IS2) all exert some influence. No effect was found for the playing surface. Therefore, match outcome, match location, type of competition, and period of the season influence the demands of centripetal force and changes of direction. These aspects should be considered in the design of training sessions and microcycle workload planning during the season to improve competitive success.


#6 Experience as a Determinant of Declarative and Procedural Knowledge in School Football
Reference: Int J Environ Res Public Health. 2020 Feb 7;17(3). pii: E1063. doi: 10.3390/ijerph17031063.
Authors: García-Ceberino JM, Gamero MG, Feu S, Ibáñez SJ
Download link: https://www.mdpi.com/1660-4601/17/3/1063/pdf
Summary: The study of declarative and procedural knowledge makes it possible to ascertain what cognitive processes are like during motor learning. This study aimed to compare, according to the methodology, gender and experience (football practise), and the levels of declarative and procedural knowledge after the implementation of two intervention programmes on school football including one based on the tactics learning and the other on the technique learning. A total of 41 students in the 5th year of primary education from a state school from Spain, distributed in two class groups, participated in the study. Each class group participated in a different intervention programme. The sample of subjects was equal (tactical programme (n = 20) and technical programme (n = 21)). A panel of 13 experts validated both programmes. Levels of knowledge were measured using the Tactical Knowledge Assessment test in football. A descriptive analysis was performed to characterise the sample. Moreover, a t-test for independent samples, a t-test for related samples, and a 2 × 2 ANOVA (analysis of variance) were performed to compare the levels of knowledge between the pre-test and the post-test, according to the methodology, gender, and experience of the students. Results indicate that both intervention programmes induced higher levels of declarative and procedural knowledge in the post-test. Similarly, there were no significant differences with regard to the applied methodology. This fact is due to the heterogeneous character of the class groups with gender and experience showing effects on the levels of knowledge. The boys possessed greater experience and a higher level of knowledge compared to the girls.


#7 Measures of PHV and the effect on directional dynamic stability to identify risk factors for injury in elite football
Reference: J Sports Med Phys Fitness. 2020 Feb 5. doi: 10.23736/S0022-4707.20.10352-9. [Epub ahead of print]
Authors: Rhodes D, Alexander J, Jeffrey J, Birdsall D, Maden-Wilkinson J
Summary: The purpose was to analyse the relationship between Peak Height Velocity (PHV) and Dynamic Balance (Y-Balance) vs non-peak growth to identify risk factors for non-contact lower limb injuries using a retrospective study design in elite youth footballers. Ninety-Three elite category 1 academy football players completed Y-Balance assessment during the preseason screening assessment. Data in relation to Y-Balance and Peak Height Velocity measures was than analysed retrospectively and correlated against injury audit data to identify relationships between the variables. A significant correlation was identified between Peak Height Velocity (PHV) and measures of directional dynamic stability utilising Y-Balance assessment (p ≤ 0.001). No significant correlations were identified between PHV and injury or injury and dynamic stability scores (p > 0.05). Injury occurrence for players within predicted periods of PHV was represented as 45%, within the cohort contained within the study. Evidently periods of growth and maturation within elite academy footballers has a detrimental effect on directional dynamic stability performance. However, caution must be taken with interpreting the significance of this relationship and the effect it has on injury occurrence. Consideration must be given to quantifying key aetiological factors associated with injury during adolescence and refrain from reliance on measures of PHV.


#8 Selecting Training-Load Measures to Explain Variability in Football Training Games
Reference: Front Psychol. 2020 Jan 24;10:2897. doi: 10.3389/fpsyg.2019.02897. eCollection 2019.
Authors: Zurutuza U, Castellano J, Echeazarra I, Guridi I, Casamichana D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992576/pdf/fpsyg-10-02897.pdf
Summary: The purpose of this study was to investigate the structure of interrelationships among external (eT) and internal (iT) training intensity metrics and how these vary depending on game format in soccer. The variables were collected from 16 semi-professional players in seven types of small, medium, large-sided, and simulated games (SG). The eT variables were (per min): peak velocity (Vmax), total distance (DTmin), distance covered at velocities less than 60% (D < 60%min), between 60 and 80% (D > 60%min), and more than 80% (D > 80%min) of the maximal velocity, player load (PLmin), and distance covered accelerating at more than 2 m⋅s-2 (Daccmin) and decelerating at less than -2 m⋅s-2 (Ddecmin). The iT variables were: Edwards arbitrary units (EDWmin) and time spent at more than 80% of the maximal heart rate (T > 80% HRmin). All game formats were represented by three principal components (PC), explaining from 66.9 to 76.0% of the variance. The structure of the interrelationships among variables involved similar distributions in the PCs that are related to energetic production systems, such as the strength/neuromuscular dimension (PLmin and/or Daccmin and Ddecmin, complemented by DTmin and D < 60%min), the endurance/cardiovascular dimension (EDWmin), and the velocity/locomotion dimension (Vmax, D > 60%min, or D > 80%min). A particular combination of external and internal intensity measures is required to describe the training load of game formats.


#9 Navigation ability test: a new specific test to asses spatial orientation ability in football players and healthy
Reference: J Sports Med Phys Fitness. 2020 Feb 4. doi: 10.23736/S0022-4707.20.10110-5. [Epub ahead of print]
Authors: Gamba P, Guidetti R, Guidetti G
Summary: This paper describes a new specific test to asses spatial and orientation abilities: Navigation Ability Test (NAT). The goal of this study was to determine if football players and normal subjects use vestibular information to keep track of their positions while walking through the Navigation Ability Test. This study was conducted total of 120 patients, underwent to Navigation Ability Test (NAT): 60 football players and 60 of normal subjects recruited on the basis of no history of vertigo/balance disorders and a negative otoneurological instrumental examination and the second group of the football players and were recruited from Division B, Division Under-21 and Women's League. Patients were enrolled in the study of the met all the following inclusion criteria. Our results showed differences between sexes during navigation tasks are not related to spatial learning per se, but appear to be the consequence of difference in ability to effectively use specific types of distal information such as room geometry. The Navigation Ability Test showed the route- times walked with eyes closed are always longer than in normal people and the mistakes improved with training. These results suggest that Navigation Ability Test could suggest to the coach and trainers valuable information about the characteristics of the players and how they should play in the field. Although there are some intrinsic difficulties, for example in creating patient-specific versions of the test, preliminary normative data indicate that this original test is workable and provides important information in therapy rehabilitation for vestibular disorder.


#10 Lower-Limb Biomechanics in Football Players with and without Hip-related Pain
Reference: Med Sci Sports Exerc. 2020 Feb 18. doi: 10.1249/MSS.0000000000002297. [Epub ahead of print]
Authors: King MG, Semciw AI, Schache AG, Middleton KJ, Heerey JJ, Sritharan P, Scholes MJ, Mentiplay BF, Crossley KM.
Summary: The purpose was to evaluate the differences in lower-limb biomechanics between adult sub-elite competitive football players with and without hip-related pain during two contrasting tasks: walking and the single-leg drop jump (SLDJ); and to determine whether potential differences, if present, are sex-dependent. Eighty-eight football players with hip-related pain (23 women, 65 men) and 30 asymptomatic control football players (13 women, 17 men) who were currently participating in competitive sport were recruited. Biomechanical data were collected for the stance phase of walking and the SLDJ. Pelvis, hip, knee and ankle angles, as well as the impulse of the external joint moments, were calculated. Differences between groups and sex-specific effects were calculated using linear regression models. Compared to their asymptomatic counterparts, football players with hip-related pain displayed a lower average pelvic drop angle during walking (P =0.03) and greater average pelvic hike angle during the SLDJ (P <0.05). Men with hip-related pain displayed a smaller total range of motion (excursion) for the transverse plane pelvis angle (P = 0.03) and a smaller impulse of the hip external rotation moment (P <0.01) during walking compared to asymptomatic men. Women with hip-related pain displayed a greater total range of motion (excursion) for the sagittal plane knee angle (P = 0.01) during walking compared to asymptomatic women. Overall, few differences were observed in lower-limb biomechanics between football players with and without hip-related pain, irrespective of the task. This outcome suggests that, despite the presence of symptoms, impairments in lower-limb biomechanics during function do not appear to be a prominent feature of people with hip-related pain who are still participating in sport.


#11 A Machine Learning Approach to Assess Injury Risk in Elite Youth Football Players
Reference: Med Sci Sports Exerc. 2020 Feb 19. doi: 10.1249/MSS.0000000000002305. [Epub ahead of print]
Authors: Rommers N, Rössler R, Verhagen E, Vandecasteele F, Verstockt S, Vaeyens R, Lenoir M, D'Hondt E, Witvrouw E
Summary: The purpose was to assess injury risk in elite-level youth football players based on anthropometric, motor coordination and physical performance measures with a machine learning approach. A total of 734 players in the U10 to U15 age categories (mean age: 11.7 +/- 1.7 years) from seven Belgian youth academies were prospectively followed during one season. Football exposure and occurring injuries were monitored continuously by the academies' coaching and medical staff, respectively. Preseason anthropometric measurements (height, weight, and sitting height) were taken and test batteries to assess motor coordination and physical fitness (strength, flexibility, speed, agility, and endurance) were performed. An extreme gradient boosting algorithms (XGBoost) was used to predict injury based on the preseason test results. Subsequently, the same approach was used to classify injuries as either overuse or acute. During the season, half of the players (n = 368) sustained at least one injury. Of the first occurring injuries, 173 were identified as overuse and 195 as acute injuries. The machine learning algorithm was able to identify the injured players in the hold-out test sample with 85% precision, 85% recall (sensitivity) and 85% accuracy (f1-score). Furthermore, injuries could be classified as overuse or acute with 78% precision, 78% recall and 78% accuracy. Our machine learning algorithm was able to predict injury and to distinguish overuse from acute injuries with reasonably high accuracy based on preseason measures. Hence, it is a promising approach to assess injury risk among elite-level youth football players. This new knowledge could be applied in the development and improvement of injury risk management strategies, to identify youth players with the highest injury risk.


#12 Quantitative assessment of the effect of acute anaerobic exercise on macular perfusion via swept-source optical coherence tomography angiography in young football players
Reference: Int Ophthalmol. 2020 Feb 15. doi: 10.1007/s10792-020-01303-w. [Epub ahead of print]
Authors: Karakucuk Y, Okudan N, Bozkurt B, Belviranlı M, Sezer T, Gorçuyeva S
Summary: The purpose was to evaluate the effect of acute anaerobic exercise on macular perfusion measured by swept-source optical coherence tomography angiography (SS-OCTA) in young football players. Football players with ages between 18 and 20 years were included into the study. After a detailed ophthalmological examination, physiological parameters including height (cm), body weight (kg), body fat percentage (%), systemic blood pressure (BP) (mmHg), hematocrit values (%), oxygen saturation pO2 (%) and heart rate (bpm) were recorded. Intraocular pressure (IOP) (mmHg) and SS-OCTA using DRI OCT Triton (Topcon, Tokyo, Japan) were measured immediately before and after Wingate test. Out of 20, 16 participants completed the study. All participants were males with a mean age of 18.12 ± .34 years. Systolic BP, hematocrit and heart rate increased, while pO2 and IOP decreased remarkably after Wingate test (p < .01). After anaerobic exercise, there was an increase in mean FAZ area in superficial capillary plexus (FAZs) which was not significant (p = .13), while decrease in FAZ area in deep capillary plexus (FAZd) (mm2) was remarkable (p = .04). No changes were observed in mean vessel density (VD) (%) in superficial capillary plexus (VDs), deep capillary plexus (VDd), choriocapillaris (VDcc), central macular thickness (CMT) (μm) and subfoveal choroidal thickness (SFCT) (μm) after Wingate test (p > .05). FAZd and some of the VD parameters showed a significant correlation with BP (p < .05). Acute anaerobic exercise seems not to alter either mean VD in retina and choroid or CMT and SFCT. Among OCTA parameters, only FAZd decreased remarkably.


#13 Playing tactics, contextual variables and offensive effectiveness in English Premier League soccer matches. A multilevel analysis
Reference: PLoS One. 2020 Feb 18;15(2):e0226978. doi: 10.1371/journal.pone.0226978. eCollection 2020.
Authors: González-Rodenas J, Aranda-Malaves R, Tudela-Desantes A, Nieto F, Usó F, Aranda R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7028361/pdf/pone.0226978.pdf
Summary: The aim of this study was to investigate the combined effects of tactical and contextual indicators on achieving offensive penetration and scoring opportunities in English Premier League (EPL) soccer matches. A total of 1971 team possessions from 20 random matches were evaluated by means of multidimensional observation. The EPL matches had a great proportion of fast attacks (36.0%) followed by combinative (29.6%), direct attacks (24.1%) and counterattacks (9.5%). Multilevel logistic regression models revealed that counterattacks (OR = 3.428; 95% CI: 2.004-5.864; P<0.001) were more effective to create goal scoring opportunities than combinative attacks, while direct attacks showed to be less effective (OR = 0.472; 95% CI: 0.264-0.845; P<0.05). Playing at home increased the probability (OR = 1.530; 95% CI: 1.097-2.135; P<0.05) of creating goal scoring opportunities compared with playing away. These findings show the multifactorial character of soccer and how different contextual and tactical indicators can influence the creation of offensive penetration and goal scoring opportunities in the English Premier League.

Sun

05

Apr

2020

Latest research in football - week 6 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Hip and Groin Injuries in National Collegiate Athletic Association Women's Soccer Players
Reference: Orthop J Sports Med. 2020 Jan 22;8(1):2325967119892320. doi: 10.1177/2325967119892320. eCollection 2020 Jan.
Authors: Ralston B, Arthur J, Makovicka JL, Hassebrock J, Tummala S, Deckey DG, Patel K, Chhabra A, Hartigan D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6977238/pdf/10.1177_2325967119892320.pdf
Summary: Hip and groin injuries are common in competitive soccer players and have been shown to be significant sources of time loss. There are few studies describing the epidemiology of hip and groin injuries in female National Collegiate Athletic Association (NCAA) soccer players. The purpose was to describe the epidemiology of hip and groin injuries in women's collegiate soccer players. The NCAA Injury Surveillance System/Program (ISS/ISP) was analyzed from 2004 through 2014 for data related to hip and groin injuries in female collegiate soccer players. Injuries and athlete-exposures (AEs) were reported by athletic trainers. Data were stratified by time of season, event type, injury type, treatment outcome, time loss, and player field position. Between 2004 and 2014, there were 439 recorded hip or groin injuries in female soccer players and an overall rate of injury of 0.57 per 1000 AEs. Injuries were 12.0 times more likely to occur during the preseason (4.41/1000 AEs) as opposed to during the regular season (0.37/1000 AEs) (injury rate ratio [IRR], 12.01; 95% confidence interval [CI], 9.92-14.55) or postseason (0.38/1000 AEs) (IRR, 11.55; 95% CI, 7.06-18.91). Rates of injury were similar during the regular season and postseason (IRR, 0.96; 95% CI, 0.59-1.58). Rates of injury were higher during competition (0.69/1000 AEs) than during practice (0.52/1000 AEs) (IRR, 1.33; 95% CI, 1.08-1.63). Most injuries were new (87.5%; n = 384) and unlikely to recur (12.5%; n = 55). Hip and groin injuries in female NCAA soccer players are uncommon, and fortunately, most players return to play quickly without recurrence. Future prospective studies should evaluate the effectiveness of strength and conditioning programs in preventing these injuries.


#2 The Influence of Playing Surface on the Loading Response to Soccer-Specific Activity
Reference: J Sport Rehabil. 2020 Feb 5:1-5. doi: 10.1123/jsr.2019-0327. [Epub ahead of print]
Authors: Jones A, Page R, Brogden C, Langley B, Greig M.
Summary: The influence of playing surface on injury risk in soccer is contentious, and contemporary technologies permit an in vivo assessment of mechanical loading on the player. The objective was to quantify the influence of playing surface on the PlayerLoad elicited during soccer-specific activity. Fifteen amateur soccer players (22.1 [2.4] y), injury free with ≥6 years competitive experience participated in this study. Each player completed randomized order trials of a soccer-specific field test on natural turf, astroturf, and third-generation artificial turf. GPS units were located at C7 and the mid-tibia of each leg to measure triaxial acceleration (100 Hz). Total accumulated PlayerLoad in each movement plane was calculated for each trial. Ratings of perceived exertion and visual analog scales assessing lower-limb muscle soreness were measured as markers of fatigue. Analysis of variance revealed no significant main effect for playing surface on total PlayerLoad (P = .55), distance covered (P = .75), or postexercise measures of ratings of perceived exertion (P = .98) and visual analog scales (P = .61). There was a significant main effect for GPS location (P < .001), with lower total loading elicited at C7 than mid-tibia (P < .001), but with no difference between limbs (P = .70). There was no unit placement × surface interaction (P = .98). There was also a significant main effect for GPS location on the relative planar contributions to loading (P < .001). Relative planar contributions to loading in the anterioposterior:mediolateral:vertical planes was 25:27:48 at C7 and 34:32:34 at mid-tibia. PlayerLoad metrics suggest that playing surface does not influence mechanical loading during soccer-specific activity (not including tackling). Clinical reasoning should consider that PlayerLoad magnitude and axial contributions were sensitive to unit placement, highlighting opportunities in the objective monitoring of load during rehabilitation.


#3 Anticipation and Situation-Assessment Skills in Soccer Under Varying Degrees of Informational Constraint
Reference: J Sport Exerc Psychol. 2020 Feb 6:1-11. doi: 10.1123/jsep.2019-0118. [Epub ahead of print]
Authors: Basevitch I, Tenenbaum G, Filho E, Razon S, Boiangin N, Ward P
Summary: The authors tested the notion that expertise effects would be more noticeable when access to situational information was reduced by occluding (i.e., noncued) or freezing (i.e., cued) the environment under temporal constraints. Using an adaptation of tasks developed by Ward, Ericsson, and Williams, the participants viewed video clips of attacking soccer plays frozen or occluded at 3 temporal points and then generated and prioritized situational options and anticipated the outcome. The high-skill players anticipated the outcomes more accurately, generated fewer task-irrelevant options, and were better at prioritizing task-relevant options than their low-skill counterparts. The anticipation scores were significantly and positively correlated with the option prioritization and task-relevant options generated but not with the total options generated. Counter to the authors' prediction, larger skill-based option-prioritization differences were observed when the play was frozen than when it was occluded. These results indicate that processing environmental information depends on temporal and contextual conditions.


#4 Determinant Factors of the Match-Based Internal Load in Elite Soccer Players
Reference: Res Q Exerc Sport. 2020 Feb 6:1-8. doi: 10.1080/02701367.2019.1710445. [Epub ahead of print]
Authors: Enes A, Oneda G, Alves DL, Palumbo DP, Cruz R, Moiano Junior JVM, Novack LF, Osiecki R
Summary: The purpose was to analyze the contribution of physical measures and external load in the match-based internal load of elite soccer players. Twenty-three elite soccer players (n = 23, age 26.69 ± 3.93 years, body mass 78.04 ± 5.03 kg, height 178.04 ± 5.19 cm, body fat 10.98 ± 1.25%) from a first division soccer team of the Brazilian Championship were evaluated first with anthropometric and physical measures (flexibility and muscle power of lower limbs), and after 24 hrs they were asked to perform an incremental treadmill test (VO2max and ventilatory thresholds). Subsequently, athletes were monitored for 6 weeks during nine official matches of a regional championship. On match days, the external load data (e.g., player load) were collected by triaxial accelerometers with GPS systems and post 30 min after the end of the match the internal load was assessed with the Session Rating of Perceived Exertion method (Session-RPE). Our main findings showed significant contributions of the Player Load (r = .62, p < .001; 42.3%) and Anaerobic Threshold (r = - .199, p = .05, 17%) for the predictive model of Session-RPE. Physical measures and external load have a significant influence on the internal load in elite soccer players. Our findings suggest that sport scientists can use the Session-RPE as a low-cost method for prescribing and monitoring training loads, by the influence of physical measures and external load on the match-based internal load, in order to optimize athletes' performance.


#5 Practitioner perceptions regarding the practices of soccer substitutes
Reference: PLoS One. 2020 Feb 7;15(2):e0228790. doi: 10.1371/journal.pone.0228790. eCollection 2020.
Authors: Hills SP, Radcliffe JN, Barwood MJ, Arent SM, Cooke CB, Russell M
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0228790&type=printable
Summary: Despite empirical observations suggesting that practitioners value the use of substitutions during soccer match-play, limited research has sought to substantiate such claims. This study used online surveys to assess the perceptions of practitioners within professional soccer about the use and practices of substitutes. Thirty-three practitioners completed one of two surveys (each requiring both open and closed questions to be answered), depending upon whether their primary role related mostly to tactical ('tactical practitioners'; n = 7) or physical ('physical practitioners'; n = 26) aspects of player/team management. Thematic content analysis of responses identified four higher-order themes: 'impact of substitutions', 'planning and communication', 'player preparation and recovery' and 'regulations'. Eighty-five percent of practitioners believed that substitutes are important in determining success during soccer match-play, with the primary justification being the perceived ability of such players to provide a physical and/or tactical impact. However, contextual factors such as the match situation, timing of introduction, and players undergoing adequate pre-pitch-entry preparation, may be important for realising such aims. Although many practitioners believed that there was a need for substitutes to engage in bespoke non-match-day preparations and recovery strategies that differ from starting players, logistical considerations, such as scarcity of resources, often limit their scope. Notwithstanding, 96% of respondents indicated that substitutes frequently perform extra conditioning sessions to account for deficits in high-speed running loads compared with players exposed to a longer period of match-play. Substitutes' pre-match warm-ups are typically led by team staff, however practitioners reported providing varying levels of input with regards to the practices adopted between kick-off and pitch-entry. Uncertainty exists as to the efficacy of current pre-pitch-entry practices, and 100% of practitioners highlighted 'preparatory strategies' as at least a 'moderately important' direction for future research. This study presents novel insights and highlights areas that are considered future research priorities amongst those working in the field.


#6 The Effect of Transition Period on Performance Parameters in Elite Female Soccer Players
Reference: Int J Sports Med. 2020 Feb 14. doi: 10.1055/a-1103-2038. [Epub ahead of print]
Authors: Parpa KP, Michaelides MA.
Summary: The purpose of this study was to examine the effect of a 4-week off-season period (transition period) on the anthropometric and performance parameters in elite female soccer players who participated in the UEFA women's Champions league. Eighteen female players (age 23.6±4.3 years) underwent testing at the end of the competitive period and right after the transition period. An incremental cardiopulmonary testing, body composition assessment and isokinetic testing at 60 °/sec were performed on both occasions. The cardiopulmonary exercise testing revealed that VO2max (p=0.001) and time on the treadmill (p=0.000) were significantly reduced after the transition period that included a 2 times/week exercise regimen. Furthermore, the quadriceps torque production at 60 °/s was significantly reduced for both the right (p=0.013) and left quadriceps (p=0.004) following the transition period. Finally, body weight (p=0.001) and body fat (p=0.000) significantly increased after 4 weeks of significantly reduced training volume. It is concluded that the transition period negatively affected the anthropometric and performance parameters of the female players. These data maybe informative for coaches and trainers as they demonstrate that despite the efforts to keep the players physically active the performance parameters decreased significantly.


#7 Relative age effects in Elite Chinese soccer players: Implications of the 'one-child' policy
Reference: PLoS One. 2020 Feb 14;15(2):e0228611. doi: 10.1371/journal.pone.0228611. eCollection 2020.
Authors: Li Z, Mao L, Steingröver C, Wattie N, Baker J, Schorer J, Helsen WF
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0228611&type=printable
Summary: The relative age effect (RAE) refers to the asymmetrical distribution of birthdates in a cohort found in many achievement domains, particularly in sports with many participants like soccer. Given the uniqueness of the one-child policy in China, this study examined the existence of the RAE in elite Chinese male and female soccer players generally and relative to their playing position on the field. Results showed a clear and obvious RAE for all age groups (U20 male, U18 male, adult female and U18 female) with the observed birthdate distributions for each age group significantly different from expected distributions (p<0.05). Additionally, we noticed a differential RAE according to the players' position on the field as reflected in different effect sizes. In male players, the RAE was significantly greater in Defenders (DF) and Goalkeepers (GK) compared to Midfielders (MF) and Forwards (FW) (VDF = 0.266>VGK = 0.215>VMF = 0.178>VFW = 0.175). In female players, GKs had a larger RAE (VGK = 0.184>0.17, VDF = 0.143, VMF = 0.127, VFW = 0.116). To reduce the negative consequences associated with RAEs throughout player development systems, potential solutions are discussed.


#8 Anthropometric and Body Composition Profile of Young Professional Soccer Players
Reference: J Strength Cond Res. 2020 Feb 13. doi: 10.1519/JSC.0000000000003416. [Epub ahead of print]
Authors: Bernal-Orozco MF, Posada-Falomir M, Quiñónez-Gastélum CM, Plascencia-Aguilera LP, Arana-Nuño JR, Badillo-Camacho N, Márquez-Sandoval F, Holway FE, Vizmanos-Lamotte B
Summary: The purpose was to describe the anthropometric and body composition profile of young professional soccer players and to compare the players profiles between different competitive divisions and playing positions. A retrospective cross-sectional study was carried out with anthropometric data obtained from the records of soccer players of Club Deportivo Guadalajara, S.A. de C.V. (Mexico) in the under-17, under-20, second, third, and fourth division categories. Body mass, height, sitting-height, skinfolds, girths, and bone breadths were measured by certified anthropometrists from September 2011 to March 2015, following the procedures recommended by the International Society for the Advancement of Kinanthropometry. Body composition was determined using the 5-way fractionation method. Comparisons between playing positions in each division and between divisions were performed using analysis of variance, and Bonferroni's post-hoc analyses (SPSS version 22 for Windows, p < 0.05 considered as significant). Data from 755 subjects were analyzed. The mean age was 18.1 ± 1.7 years old (minimum 14.8, maximum 23.2). The under-20 division registered higher anthropometric and body composition values than all other competitive divisions. In addition, goalkeepers were taller, heavier, and obtained the highest values for adipose mass, whereas forwards presented higher percentages of muscle mass. These tables can be used during nutritional assessment and nutritional monitoring of players to establish body composition goals. In addition, the strength and conditioning practitioner may also use these data to design effective and specific training programs most suitable to the anthropometric and body composition profile of each player, taking into consideration his competitive division and playing position.


#9 Anthropometric, Body Composition, and Morphological Lower Limb Asymmetries in Elite Soccer Players: A Prospective Cohort Study
Reference: Int J Environ Res Public Health. 2020 Feb 11;17(4). pii: E1140. doi: 10.3390/ijerph17041140.
Authors: Mala L, Maly T, Cabell L, Hank M, Bujnovsky D, Zahalka F
Download link: https://www.mdpi.com/1660-4601/17/4/1140/pdf
Summary: The aim of this study was to identify and compare parameters related to anthropometry, body composition (BC), and morphological asymmetry in elite soccer players in nine age categories at the same soccer club (n = 355). We used a bio-impedance analyzer to measure the following indicators of BC: body height (BH); body mass (BM); relative fat-free mass (FFMr); percentage of fat mass (FM); and bilateral muscle mass differences in the lower extremities (BLD∆). Age showed a significant influence on all parameters observed (F64,1962 = 9.99, p = 0.00, λ = 14.75, η2p = 0.25). Adolescent players (from U16 through adults) had lower FM values (<10%) compared to players in the U12-U15 categories (>10%). The highest FFMr was observed in the U18 category. Players in the U12 and U13 categories showed more homogenous values compared to older players. With increasing age, significantly higher FFMr was observed in the lower extremities. An inter-limb comparison of the lower extremities showed significant differences in the U17 category (t27 = 2.77, p = 0.01) and in adult players (t68 = 5.02, p = 0.00). Our results suggest that the end of height growth occurs around the age of 16 years, while weight continues to increase until 20 years. This increase is not linked to decreasing FM, nor to the FFMr, which remains stable. We found morphological asymmetries between limbs in players of the U17 category and in adult players.


#10 The effect of low back pain and lower limb injury on lumbar multifidus muscle morphology and function in university soccer players
Reference: BMC Musculoskelet Disord. 2020 Feb 12;21(1):96. doi: 10.1186/s12891-020-3119-6.
Authors: Nandlall N, Rivaz H, Rizk A, Frenette S, Boily M, Fortin M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7017535/pdf/12891_2020_Article_3119.pdf
Summary: The lumbar multifidus muscle (LMM) plays a critical role to stabilize the spine. While low back pain (LBP) is a common complaint in soccer players, few studies have examined LMM characteristics in this athletic population and their possible associations with LBP and lower limb injury. Therefore, the purpose of this study was to 1) investigate LMM characteristics in university soccer players and their potential association with LBP and lower limb injury; 2) examine the relationship between LMM characteristics and body composition measurements; and 3) examine seasonal changes in LMM characteristics. LMM ultrasound assessments were acquired in 27 soccer players (12 females, 15 males) from Concordia University during the preseason and assessments were repeated in 18 players at the end of the season. LMM cross-sectional area (CSA), echo-intensity and thickness at rest and during contraction (e.g. function) were assessed bilaterally in prone and standing positions, at the L5-S1 spinal level. A self-reported questionnaire was used to assess the history of LBP and lower limb injury. Dual-energy x-ray absorptiometry (DEXA) was used to acquire body composition measurements. Side-to-side asymmetry of the LMM was significantly greater in males (p = 0.02). LMM thickness when contracted in the prone position (p = 0.04) and LMM CSA in standing (p = 0.02) were also significantly greater on the left side in male players. The LMM % thickness change during contraction in the prone position was significantly greater in players who reported having LBP in the previous 3-months (p < 0.001). LMM CSA (r = - 0.41, p = 0.01) and echo-intensity (r = 0.69, p < 0.001) were positively correlated to total % body fat. There was a small decrease in LMM thickness at rest in the prone position over the course of the season (p = 0.03). The greater LMM contraction in players with LBP may be a maladaptive strategy to splint and project the spine. LMM morphology measurements were correlated to body composition. The results provide new insights with regards to LMM morphology and activation in soccer players and their associations with injury and body composition measurements.


#11 Seven Weeks of Jump Training with Superimposed Whole-Body Electromyostimulation Does Not Affect the Physiological and Cellular Parameters of Endurance Performance in Amateur Soccer Players
Reference: Int J Environ Res Public Health. 2020 Feb 10;17(3). pii: E1123. doi: 10.3390/ijerph17031123.
Authors: Wirtz N, Filipovic A, Gehlert S, Marées M, Schiffer T, Bloch W, Donath L
Download link: https://www.mdpi.com/1660-4601/17/3/1123/pdf
Summary: Intramuscular density of monocarboxylate-transporter (MCT) could affect the ability to perform high amounts of fast and explosive actions during a soccer game. MCTs have been proven to be essential for lactate shuttling and pH regulation during exercise and can undergo notable adaptational changes depending on training. The aim of this study was to evaluate the occurrence and direction of potential effects of a 7-weeks training period of jumps with superimposed whole-body electromyostimulation on soccer relevant performance surrogates and MCT density in soccer players. For this purpose, 30 amateur soccer players were randomly assigned to three groups. One group performed dynamic whole-body strength training including 3 x 10 squat jumps with WB-EMS (EG, n = 10) twice a week in addition to their daily soccer training routine. A jump training group (TG, n = 10) performed the same training routine without EMS, whereas a control group (CG, n = 8) merely performed their daily soccer routine. 2 (Time: pre vs. post) x 3 (group: EG, TG, CG) repeated measures analyses of variance (rANOVA) revealed neither a significant time, group nor interaction effect for VO2peak, Total Time to Exhaustion and Lamax as well as MCT-1 density. Due to a lack of task-specificity of the underlying training stimuli, we conclude that seven weeks of WB-EMS superimposed to jump exercise twice a week does not relevantly influence aerobic performance or MCT density.

 

Sun

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2020

Repeated high-intensity running in professional soccer

Are there any positional differences? Are there any consequences for training - more specifically for conditioning...

Wed

01

Apr

2020

Latest research in football - week 5 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Pedagogical Function of Referees in Youth Sport: Assessment of the Quality of Referee-Player Interactions in Youth Soccer
Reference: Int J Environ Res Public Health. 2020 Feb 1;17(3). pii: E905. doi: 10.3390/ijerph17030905.
Authors: Firek W, Płoszaj K, Czechowski M
Download link: https://www.mdpi.com/1660-4601/17/3/905/pdf
Summary: We assume that all institutions and individuals involved in the organization of sport for children and young people should utilize the educational potential of sport. We assessed the quality of referee interactions with children during sports competitions in soccer. Based on the developmental theory and research suggesting that interactions between kids and adults are the primary mechanism of their development and learning, we focused on the quality of the referee-player interactions in terms of (1) emotional support, (2) game organization, and (3) instructional support. Twenty-five soccer referees who refereed matches for children aged 9-12 years were recruited. The Referee Educational Function Assessment Scoring System (REFASS) was used to assess the quality of the referee-player interactions. This tool was developed based on Classroom Assessment Scoring System-Upper Elementary. Regarding the REFASS dimensions, the mean scores for positive climate, Sensitivity, behavior management, content understanding and quality of feedback were in the medium range, while productivity and negative climate in the high range. In the case of the positive climate variable, the lowest mean ratings were recorded compared to other assessed dimensions. The assessments of the quality of referee-player interactions obtained for particular dimensions translated into the ratings for the specified domains. The highest ratings were given to game organization (6.0 ± 0.8; Me = 6.0), whereas the emotional support and instructional support were in the medium range (4.6 ± 1.5; Me = 4.5, and 5.2 ± 1.8; Me = 6.0, respectively). Referees are usually not aware of their pedagogical function and the complexity of their respective responsibilities. They are commonly considered to be ordinary technicians and evaluators of performance in competition. Based on the results, a postulate was formulated that referees should consciously perform a pedagogical function in the youth sport. Therefore, it is necessary to train them in educational methods and techniques appropriate to the age and needs of the child. The referees will then be prepared to take actions to prevent negative behavior of players on the field and to encourage prosocial behavior.


#2 Biomechanical and Physiological Responses to 120 min of Soccer-Specific Exercise
Reference: Res Q Exerc Sport. 2020 Feb 5:1-13. doi: 10.1080/02701367.2019.1698698. [Epub ahead of print]
Authors: Field A, Corr LD, Haines M, Lui S, Naughton R, Page RM, Harper LD
Summary: The purpose of the study is to investigate biomechanical and physiological responses to soccer-specific exercise incorporating an extra-time period (ET) and assess the test-retest reliability of these responses. Twelve soccer players performed 120 min of soccer-specific exercise. Tri-axial (PLTotal) and uni-axial PlayerLoad™ in the vertical (PLV), anterior-posterior (PLA-P), and medial-lateral (PLM-L) planes were monitored using a portable accelerometer. Likewise, respiratory exchange ratio (RER) was recorded throughout exercise. At the end of each 15-min period, players provided differential ratings of perceived exertion for legs (RPE-L), breathlessness (RPE-B) and overall (RPE-O), and capillary samples were taken to measure blood lactate (BLa) concentrations. The soccer-specific exercise was completed twice within 7 days to assess reliability. A main effect for time was identified for PLTotal (p = 0.045), PLV (p = 0.002), PLA-P (p = 0.011), RER (p = 0.001), RPE-L (p = 0.001), RPE-O (p = 0.003), and CMJ (p = 0.020). A significant increase in PLTotal (234 ± 34 au) and decrease in RER (0.87 ± 0.03) was evident during 105-120 versus 0-15 min (215 ± 25 au; p = 0.002 and 0.92 ± 0.02; p = 0.001). Coefficients of variations were <10% and Pearson's correlation coefficient demonstrated moderate-to-very strong (0.33-0.99) reliability for all PL variables, RPE-B, BLa, and RER. These results suggest that mechanical efficiency is compromised and an increased rate of lipolysis is observed as a function of exercise duration, particularly during ET. These data have implications for practitioners interested in fatigue-induced changes during ET.


#3 Constraints on visual exploration of youth football players during 11v11 match-play: The influence of playing role, pitch position and phase of play
Reference: J Sports Sci. 2020 Feb 2:1-11. doi: 10.1080/02640414.2020.1723375. [Epub ahead of print]
Authors: McGuckian TB, Cole MH, Chalkley D, Jordet G, Pepping GJ
Summary: Visual exploratory action, in which football players turn their head to perceive their environment, improves prospective performance with the ball during match-play. This scanning action, however, is relevant for players throughout the entire match, as the information perceived through visual exploration is needed to guide movement around the pitch during both offensive and defensive play. This study aimed to understand how a player's on-pitch position, playing role and phase of play influenced the visual exploratory head movements of players during 11v11 match-play. Twenty-two competitive-elite youth footballers (M = 16.25 years) played a total of 1,623 minutes (M = 73.8). Inertial measurement units, global positioning system units and notational analysis were used to quantify relevant variables. Analyses revealed that players explored more extensively when they were in possession of the ball, and less extensively during transition phases, as compared to team ball-possession and opposition ball-possession phases of play. Players explored most extensively when in the back third of the pitch, and least when they were in the middle third of the pitch. Playing role, pitch position and phase of play should be considered as constraints on visual exploratory actions when developing training situations aimed at improving the scanning actions of players.


#4 Analyzing the effects of combined small-sided games and strength and power training on the fitness status of under-19 elite football players
Reference: J Sports Med Phys Fitness. 2020 Jan;60(1):1-10. doi: 10.23736/S0022-4707.19.09818-9.
Authors: Querido SM, Clemente FM
Summary: The purpose of this study was twofold: 1) to characterize a common microcycle considering both internal and external training loads; and 2) to identify the effects of small-sided games (SSGs) and of power and strength training on the fitness status of football players. Fifteen male football players (age: 18.55±0.39 years) participated in this study. Ninety-two consecutive training sessions were monitored and analyzed over a period of nineteen weeks. Rating of perceived exertion (RPE ) was used as an internal load marker, and the distances covered at different speed thresholds and accelerations/decelerations were used as external load markers to characterize the common microcycle. Participants' body composition, vertical jumping ability, maximal strength, speed, and agility were assessed twice before and after the training monitoring process. The results revealed that match day -5 (MD-5) and MD-1 were associated with the lowest RPE scores (4.2 and 3.8 A.U., respectively). MD-4 and MD-3 were associated with the highest RPE values (9.2 and 8.8 A.U., respectively). Meaningful changes in RPE were found between training days. External load monitoring revealed that MD-4 had the highest values of accelerations and decelerations >2 m/s2/min (4.22 and 3.17, respectively) and MD-3 had the highest values of distance covered at high intensity (6.11 m/s2/min). Meaningful moderate improvements in jumping performance (d=0.90) and maximal strength parameters (d=0.83) were also found between assessments. It was identified that the concurrent approach had meaningful impacts on the fitness development of players and should be considered by coaches for future training interventions.


#5 Soccer Matches but Not Training Sessions Disturb Cardiac-Autonomic Regulation During National Soccer Team Training Camps
Reference: Res Q Exerc Sport. 2020 Feb 6:1-9. doi: 10.1080/02701367.2019.1708843. [Epub ahead of print]
Authors: Muñoz-López A, Nakamura F, Naranjo Orellana J
Summary: Heart rate variability (HRV) can be used to monitor changes in autonomic nervous system (ANS) function. Monitoring HRV via the natural log of the root-mean-square difference of successive normal RR intervals (lnRMSSD), a decrease was related to lower parasympathetic activity and a fatigued state, and an increase was related to higher parasympathetic activity and better physical conditioning. This study analyzed daily ANS function changes among professional soccer players at national team training camps during preparation for the UEFA Eurocup 2016. 23 professional soccer players were distributed into two groups: First eleven (players who played more than 60 minutes per soccer match) and Reserves (the rest of the players). HRV and session training load (s-TL) were monitored. Between-group daily differences were assessed using two-way mixed repeated measures ANOVA. s-TL significantly increased (p < .05) at the beginning of each camp and significantly decreased the day before the soccer match (p < .001). There was a significant time by group interaction in lnRMSSD (p = .024). Changes were found in the First eleven group from match day +1 to match day +2 (+0.523 ms, p = .003). After the soccer match, there were between-group differences (p < .05) at +24h and +72h in lnRMSSD. During national team training camps, ANS function was only modified 24h and 72h after playing soccer matches, in players who played a minimum of 60 minutes. This knowledge can help coaches to monitor the impact of soccer matches during training camps to detect fatigue and improve recovery.


#6 Global and region-specific patient-reported outcomes pre and post a division I football season
Reference: Phys Ther Sport. 2020 Jan 25;42:146-150. doi: 10.1016/j.ptsp.2020.01.014. [Epub ahead of print]
Authors: Parcell B, Simon JE
Summary: Determine the change in global and region-specific PROMs among athletes from one NCAA Division I football team during one season. Fifty-three Division I collegiate football athletes (n = 54) were eligible (20.1 ± 1.4 years, 187.7 ± 8.3 cm, and 113.5 ± 25.6 kg) for analyses participated in this study. Participants completed five PROMs (Disablement in the Physically Active Scale [DPA], Epworth Sleep Score [ESS], Headache Impact Test [Hit-6], Disabilities of the Arm, Shoulder, and Hand [DASH], and the Lower Extremity Functional Scale [LEFS]) before the season and the same five PROMs after the season. A multivariate repeated measure analysis of variance (ANOVA) was conducted for all dependent variables. Alpha level was set at ɑ = 0.05. The overall multivariate repeated measures ANOVA was significant for time (p = 0.01). Follow up one-way ANOVA's indicated the DPA (p < 0.01, mean decrease/worse of 6.6 points) and LEFS (p = 0.01, mean decrease/worse of 4.1 points) were statistically significant between time points. Division I football can be detrimental to the physical, mental, and emotional health of the athletes. From these data, global and one region-specific PROM decreased over one season in one NCAA Division I football team.


#7 Understanding the relative contribution of technical and tactical performance to match outcome in Australian Football
Reference: J Sports Sci. 2020 Feb 7:1-6. doi: 10.1080/02640414.2020.1724044. [Epub ahead of print]
Authors: Young CM, Luo W, Gastin PB, Dwyer DB
Summary: The aim of this study was to assess if tactical and technical performance indicators (PIs) could be used in combination to model match outcomes in Australian Football (AF). A database of 101 technical PIs and 14 tactical PIs from every match in the 2009-2016 Australian Football League (AFL) seasons was merged. Two outcome measures Win-loss and Score margin were used as dependent variables. The top 45 ranked technical and tactical PIs from a feature selection process were used to model match outcome using decision tree and Generalised Linear Models (GLMs). Of the top 45 selected features, this included seven tactical PIs. The Win-loss-based Decision tree model achieved a classification accuracy of 89.0% and GLM 93.2%. A Score margin-based GLM achieved a root mean squared error (RMSE) of 6.9 points. A combined approach to the classification of match outcomes provided no improvement in model accuracy compared with previous literature. However, this study has established the relative importance of technical and tactical measures of performance in relation to successful team performance in AF.


#8 Reproducibility of Internal and External Training Load During Recreational Small-Sided Football Games
Reference: Res Q Exerc Sport. 2020 Feb 5:1-6. doi: 10.1080/02701367.2019.1697794. [Epub ahead of print]
Authors: Milanović Z, Rađa A, Erceg M, Trajković N, Stojanović E, Lešnik B, Krustrup P, Randers MB
Summary: The aim of this study was to evaluate the reproducibility of internal and external load parameters during recreational small-sided football games. Ten healthy untrained young adult males (age: 20.2 ± 1.9 yr, body mass: 69.2 ± 6.3 kg, height: 175.4 ± 5.9 cm, body fat: 19.7 ± 5.2%) performed two 2 × 20-min sessions of four versus four plus goalkeeper small-sided games (SSG) 1 week apart on a standard, outdoor, 40 × 20-m artificial grass pitch. Twelve external (total distance, peak speed, player load, work rate and distance covered at 0-2, 2-5, 5-7, 7-9, 9-13, 13-16, 16-20 and >20 km/h) and seven internal load parameters (heart rate and time spent in different heart rate zones [<70%, 71-80%, 81-90%, 91-95%, 96-100%, 91-100%]) were measured. Reproducibility was reported as intraclass coefficient correlation (ICC), the coefficient of variation (CV), and the typical error of measurements (TE). No statistical differences (p> .05) between sessions were found in any measures. Minimal test-retest variability was noted for mean and peak heart rate (HRpeak) relative to HRpeak with CV values of 3.4% and 2.6%, respectively. Acceptable variability (CV<10%) was demonstrated for total distance covered, distance covered at 2-5 km/h, and peak speed. Distance covered in different speed zones (CV = 15.7-47.6%) and percentage of time in each HR zone showed large-to-very large variability (CV = 36.2-128.4%). Mean heart rate (HRmean), HRpeak, distance covered at 5-7, 13-16 and >20 km/h, and percentage of time above 95%HRpeak were the most reliable variables (ICC = 0.74-0.79), followed by total distance covered, peak speed, and percentage of time at 80-90% HRpeak (ICC = 0.39-0.67). The lowest reliability was observed for distance covered in the moderate speed zones 7-9 km/h (ICC = 0.12) and 9-13 km/h (ICC = -0.09), and percentage of time at 70-80% HRpeak (ICC = -0.01). Small-sided games can be used when planning training-induced exercise responses in relation to total distance covered, peak speed, and mean heart rate. This evidence further supports the use of SSG when organizing recreational football training, in young adult males, with the purpose of improving health profile due to the high reproducibility of HRmean and total distance covered.


#9 Uncovering EEG Correlates of Covert Attention in Soccer Goalkeepers: Towards Innovative Sport Training Procedures
Reference: Sci Rep. 2020 Feb 3;10(1):1705. doi: 10.1038/s41598-020-58533-2.
Authors: Jeunet C, Tonin L, Albert L, Chavarriaga R, Bideau B, Argelaguet F, Millán JDR, Lécuyer A, Kulpa R
Download link: https://www.nature.com/articles/s41598-020-58533-2.pdf
Summary: Advances in sports sciences and neurosciences offer new opportunities to design efficient and motivating sport training tools. For instance, using NeuroFeedback (NF), athletes can learn to self-regulate specific brain rhythms and consequently improve their performances. Here, we focused on soccer goalkeepers' Covert Visual Spatial Attention (CVSA) abilities, which are essential for these athletes to reach high performances. We looked for Electroencephalography (EEG) markers of CVSA usable for virtual reality-based NF training procedures, i.e., markers that comply with the following criteria: (1) specific to CVSA, (2) detectable in real-time and (3) related to goalkeepers' performance/expertise. Our results revealed that the best-known EEG marker of CVSA-increased α-power ipsilateral to the attended hemi-field- was not usable since it did not comply with criteria 2 and 3. Nonetheless, we highlighted a significant positive correlation between athletes' improvement in CVSA abilities and the increase of their α-power at rest. While the specificity of this marker remains to be demonstrated, it complied with both criteria 2 and 3. This result suggests that it may be possible to design innovative ecological training procedures for goalkeepers, for instance using a combination of NF and cognitive tasks performed in virtual reality.


#10 Prevalence of Asymptomatic Intra-articular Changes of the Knee in Adult Professional Soccer Players
Reference: Orthop J Sports Med. 2019 Nov 27;7(11):2325967119885370. doi: 10.1177/2325967119885370. eCollection 2019 Nov.
Authors: Bezuglov EN, Lyubushkina AV, Khaitin VY, Tokareva AV, Goncharov EN, Gorinov AV, Sivakova EY, Sereda AP
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6967194/pdf/10.1177_2325967119885370.pdf
Summary: Currently, there are few data on the association between participation in soccer and the condition of the knee joints in adult professional players. The hypothesis was that a high percentage of professional soccer players will have asymptomatic intra-articular changes of the knee. The condition of the intra-articular structures (osteophytes, cartilage, and menisci) in 94 knee joints of 47 adult professional soccer players (mean ± SD age, 25.7 ± 4.6 years; body mass index, 22.8 ± 1.4 kg/m2) was analyzed. A 1.5-T magnetic resonance imaging scanner was used to perform the imaging, and the anonymized data were analyzed by 2 experienced radiologists. Cartilage of both knee joints was affected in 97.9% of soccer players. Meniscal lesions were detected in 97.8% of joints, affecting both joints in 93.6% of athletes. Grade 2 cartilage lesions were the most prevalent (36%-60% depending on the lesion site), and grade 4 lesions were detected in 12.7% of joints. The medial femoral condyle and medial tibial plateau were most frequently affected by cartilage lesions (85.1%). Among meniscal lesions, grade 2 lesions were the most prevalent, being detected in 71% of the cases. Grade 3 lesions were detected in 13.8% of the joints. The posterior horn of the lateral meniscus was the most common site of meniscal lesions (affected in 95.7% of the joints). Osteophytes were detected in 4.2% of joints. The prevalence of asymptomatic cartilage and meniscal lesions in the knees of adult professional soccer players is extremely high and is not associated with the reduction of sports involvement. This research should promote the correct interpretation of magnetic resonance imaging data obtained from soccer players with acute trauma and the reduction of the number of unwarranted surgical procedures.


#11 Injury epidemiology in Australian male professional soccer
Reference: J Sci Med Sport. 2020 Jan 24. pii: S1440-2440(19)31442-2. doi: 10.1016/j.jsams.2020.01.006. [Epub ahead of print]
Authors: Lu D, McCall A, Jones M, Kovalchik S, Steinweg J, Gelis L, Duffield R
Summary: The purpose was to describe the injury epidemiology of the Australian male professional soccer league (A-League) over 6 consecutive seasons. Match-loss injury data was collected from each A-League club (n=10) for each competition match (n=27/season) over 6 seasons (2012/13-2017/18). Injuries were collected weekly through a standardised protocol and were classified by setting, mechanism, severity, the type and location on the body. Generalised Linear Models were used to estimate the injury incidences (injury/round/season), whilst rate ratios were reported for total injuries and within abovementioned injury classifications. Overall injury incidence was not significantly different ranging from 4.8 (95%CI:4.1-5.8) to 6.7 (95%CI:5.8-7.8) between seasons 2012/13 to 2017/18 (p>0.05). Match injuries remained stable whilst training injuries decreased across the 6 seasons (exp(β) 0.59[95%CI:0.36-1.0]; p=0.04). Respectively, contact and non-contact injuries were not significantly different across the 6 seasons, although non-contact injuries were more common than contact injuries (p>0.05). Mild severity injuries decreased (exp(β) 0.64 [95%CI:0.4-0.9];p=0.02), whilst moderate severity injuries increased (exp(β) 1.7 [95%CI:1.0-2.8];p=0.04) in season 2017/18 compared to 2012/13. The most common injuries were at thigh (23-36%), of which the majority were hamstring injuries (54%-65%) of muscle/tendon type (50-60% of total injuries/season). Injuries remained stable across the seasons by type and location (p>0.05 and p>0.05, respectively). Injury rates, mechanisms, locations and types have remained relatively stable over recent seasons of the A-League. Current Australian professional soccer league medical practices may have contributed to the stability of injury rates.

Thu

26

Mar

2020

Latest research in football - week 4 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Train Like You Compete? Physical and Physiological Responses on Semi-Professional Soccer Players
Reference: Int J Environ Res Public Health. 2020 Jan 24;17(3). pii: E756. doi: 10.3390/ijerph17030756.
Authors: Castillo-Rodríguez A, Cano-Cáceres FJ, Figueiredo A, Fernández-García JC
Download link: https://www.mdpi.com/1660-4601/17/3/756/pdf
Summary: Decision-making in soccer has repercussions and depends on the environment of training or competition. The demands on the players can reveal if the decision-making is similar or different from that required during competition. The aim of this study was to assess the physical and physiological responses of players in training matches (TM) and official competition matches (CM) according to the playing position (external defenders, internal defenders, midfielders, and forwards/extremes). Twenty semi-professional male soccer players and 10 CM (n = 40) and 10 TM (n = 40) were studied using global positioning system technology, and paired and one-way ANOVA tests were carried out to compare physical (distances and number of sprints) and physiological (heart rates) responses with the factors a) match environments (TM and CM) and b) the playing position, respectively. The results revealed that during CM, players covered higher total distance, partial distances, and sprints at different speeds (0-21 km/h) and produced higher physiological responses. Midfielders covered the greatest total distance in both TM (7227.6 m) and CM (11,225.9 m), in comparison to the other playing positions. However, forwards and extremes spent more time (56.8% of the CM [d = 0.78]) at 76% to 84% of their maximal heart rates. First, the physical and physiological responses in TM were significantly lower than in CM. Second, these responses were different according to the playing position, so this study was able to verify the exact amount of variation between the load produced in TM and CM. These results will help the coach and technical staff to design training tasks to complement the responses found in TM.


#2 T helper cell-related changes in peripheral blood induced by progressive effort among soccer players
Reference: PLoS One. 2020 Jan 28;15(1):e0227993. doi: 10.1371/journal.pone.0227993. eCollection 2020.
Authors: Kostrzewa-Nowak D, Nowak R
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0227993&type=printable
Summary: The regulatory mechanisms affecting the modulation of the immune system accompanying the progressive effort to exhaustion, particularly associated with T cells, are not fully understood. We analysed the impact of two progressive effort protocols on T helper (Th) cell distribution and selected cytokines. Sixty-two male soccer players with a median age of 17 (16-29) years performed different protocols for progressive exercise until exhaustion: YO-YO (YYRL1) and Beep. Blood samples for all analyses were taken three times: at baseline, post-effort, and in recovery. The percentage of Th1 cells increased post-effort and in recovery. The post-effort percentage of Th1 cells was higher in the Beep group compared to the YYRL1 group. Significant post-effort increase in Th17 cells was observed in both groups. The post-effort percentage of regulatory T cells (Treg) increased in the Beep group. An increased post-effort concentration of IL-2, IL-6, IL-8 and IFN-γ in both groups was observed. Post-effort TNF-α and IL-10 levels were higher than baseline in the YYRL1 group, while the post-effort IL-17A concentration was lower than baseline only in the Beep group. The recovery IL-2, IL-4, TNF-α and IFN-γ levels were higher than baseline in the YYRL1 group. The recovery IL-4, IL-6, IL-8, TNF-α and IFN-γ values were higher than baseline in the Beep group. The molecular patterns related to cytokine secretion are not the same between different protocols for progressive effort. It seems that Treg cells are probably the key cells responsible for silencing the inflammation and enhancing anti-inflammatory pathways


#3 Are Elite Soccer Teams' Preseason Training Sessions Associated With Fewer In-Season Injuries? A 15-Year Analysis From the Union of European Football Associations (UEFA) Elite Club Injury Study
Reference: Am J Sports Med. 2020 Jan 28:363546519899359. doi: 10.1177/0363546519899359. [Epub ahead of print]
Authors: Ekstrand J, Spreco A, Windt J, Khan KM
Summary: Preseason training develops players' physical capacities and prepares them for the demands of the competitive season. In rugby, Australian football, and American football, preseason training may protect elite players against in-season injury. However, no study has evaluated this relationship at the team level in elite soccer. The aim of this study was to investigate whether the number of preseason training sessions completed by elite soccer teams was associated with team injury rates and player availability during the competitive season. It was hypothesized that elite soccer teams who participate in more preseason training will sustain fewer injuries during the competitive season. We used the Union of European Football Associations (UEFA) injury dataset to analyze 44 teams for up to 15 seasons (total, 244 team-seasons). Separate linear regression models examined the association between the number of team preseason training sessions and 5 in-season injury measures. Injury-related problems per team were quantified by totals of the following: (1) injury burden, (2) severe injury incidence, (3) training attendance, (4) match availability, and (5) injury incidence. Teams averaged 30 preseason training sessions (range, 10-51). A greater number of preseason training sessions was associated with less injury load during the competitive season in 4 out of 5 injury-related measures. Our linear regression models revealed that for every 10 additional preseason training sessions that the team performed, the in-season injury burden was 22 layoff days lower per 1000 hours (P = .002), the severe injury incidence was 0.18 severe injuries lower per 1000 hours (P = .015), the training attendance was 1.4 percentage points greater (P = .014), and the match availability was 1.0 percentage points greater (P = .042). As model fits were relatively low (adjusted R2 = 1.3%-3.2%), several factors that contribute to in-season injury outcomes were unaccounted for. Teams that performed a greater number of preseason training sessions had "healthier" in-season periods. Many other factors also contribute to in-season injury rates. Understanding the benefit of preseason training on in-season injury patterns may inform sport teams' planning and preparation.


#4 Effects of Small-Sided Soccer Games on Physical Fitness, Physiological Responses, and Health Indices in Untrained Individuals and Clinical Populations: A Systematic Review
Reference: Sports Med. 2020 Jan 27. doi: 10.1007/s40279-019-01256-w. [Epub ahead of print]
Authors: Zouhal H, Hammami A, Tijani JM, Jayavel A, de Sousa M, Krustrup P, Sghaeir Z, Granacher U, Ben Abderrahman A
Summary: Small-sided soccer games (SSSG) are a specific exercise regime with two small teams playing against each other on a relatively small pitch. There is evidence from original research that SSSG exposure provides performance and health benefits for untrained adults. The aim of this systematic review was to summarize recent evidence on the acute and long-term effects of SSSG on physical fitness, physiological responses, and health indices in healthy untrained individuals and clinical populations. This systematic literature search was conducted in four electronic databases (PubMed, Web of Science, SPORTDiscus) from inception until June 2019. The following key terms (and synonyms searched for by the MeSH database) were included and combined using the operators "AND", "OR", "NOT": ((soccer OR football) AND ("soccer training" OR "football training" OR "soccer game*" OR "small-sided soccer game*") AND ("physical fitness" OR "physiological adaptation*" OR "physiological response*" OR health OR "body weight" OR "body mass" OR "body fat" OR "bone composition" OR "blood pressure")). The search syntax initially identified 1145 records. After screening for titles, abstracts, and full texts, 41 studies remained that examined the acute (7 studies) and long-term effects (34 studies) of SSSG-based training on physical fitness, physiological responses, and selected alth indices in healthy untrained individuals and clinical populations. No training-related injuries were reported in the 41 acute and long-term SSSG studies. Typically, a single session of SSSG lasted 12-20 min (e.g., 3 × 4 min with 3 min rest or 5 × 4 min with 4 min rest) involving 4-12 players (2 vs. 2 to 6 vs. 6) at an intensity ≥ 80% of HRmax. Following single SSSG session, high cardiovascular and metabolic demands were observed. Specifically, based on the outcomes, the seven acute studies reported average heart rates (HR) ≥ 80% of HRmax (165-175 bpm) and mean blood lactate concentrations exceeding 5 mmol/l (4.5-5.9 mmol/l) after single SSSG sessions. Based on the results of 34 studies (20 with healthy untrained, 10 with unhealthy individuals, and 4 with individuals with obesity), SSSG training lasted between 12 and 16 weeks and was performed 2-3 times per week. SSSG had positive long-term effects on physical fitness (e.g., Yo-Yo IR1 performance), physiological responses including maximal oxygen uptake (VO2max) [+ 7 to 16%], and many health-related markers such as blood pressure (reductions in systolic [- 7.5%] and diastolic [- 10.3%] blood pressure), body composition (decreased fat mass [- 2 to - 5%]), and improved indices of bone health (bone mineral density: [+ 5 to 13%]; bone mineral content: [+ 4 to 5%]), and metabolic (LDL-cholesterol [- 15%] as well as cardiac function (left-ventricular internal diastolic diameter [+ 8%], end diastolic volume [+ 21%], left-ventricular mass index [+ 18%], and left-ventricular ejection fraction [+ 8%]). Irrespective of age or sex, these health benefits were observed in both, untrained individuals and clinical populations. In conclusion, findings from this systematic review suggest that acute SSSG may elicit high cardiovascular and metabolic demands in untrained healthy adults and clinical populations. Moreover, this type of exercise is safe with positive long-term effects on physical fitness and health indices. Future studies are needed examining the long-term effects on physical fitness and physiological adaptations of different types of SSSG training (e.g., 3 vs. 3; 6 vs. 6) in comparison to continuous or interval training in different cohorts.


#5 Pubic stress fracture presenting as a strain of adductor longus in a 16-year-old elite soccer player with Crohn's disease: a case report
Reference: J Can Chiropr Assoc. 2019 Dec;63(3):197-204.
Authors: Marshall C, Gringmuth R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6973759/pdf/jcca-63-197.pdf
Summary: Adductor strains are the most commonly reported muscle injuries in adolescent soccer players and the second most common muscle injuries in adult players. Health practitioners should be aware of possible differential diagnoses, such as a pubic stress fracture or pubic apophysitis when athletes present with chronic groin pain. The purpose was to present a rare case of a unilateral pelvic stress fracture of a 16-year old elite soccer player with a history of Crohn's disease. Case notes of two sports-based practitioners were reviewed and compiled retrospectively. Following activity restriction, a period of rest, conservative care, and progressive rehabilitation, this athlete was able to achieve a pain-free state with near equal iso-kinetic strength bilaterally as measured by Cybex 6000 (Cybex International Inc., Medway, MA, USA) muscle testing. Full activity was resumed 10 months after initial presentation and the athlete was able to return to playing professional soccer. This case report presents a rare diagnosis of a unilateral pubic stress fracture presenting as a strain of adductor longus. Although quite rare, differential diagnoses such as a potential underlying stress fracture should be considered when presented with chronic or recurrent groin pain.


#6 Associations of Apolipoprotein E ε4 Genotype and Ball Heading With Verbal Memory in Amateur Soccer Players
Reference: JAMA Neurol. 2020 Jan 27. doi: 10.1001/jamaneurol.2019.4828. [Epub ahead of print]
Authors: Hunter LE, Freudenberg-Hua Y, Davies P, Kim M, Lipton RB, Stewart WF, Srinivasan P, Hu S, Lipton ML
Summary: Emerging evidence suggests that long-term exposure to ball heading in soccer, the most popular sport in the world, confers risk for adverse cognitive outcomes. However, the extent to which the apolipoprotein E ε4 (APOE ε4) allele, a common risk factor for neurodegeneration, and ball heading are associated with cognition in soccer players remains unknown. The purpose was to determine whether the APOE ε4 allele and 12-month ball heading exposure are associated with verbal memory in a cohort of adult amateur soccer players. A total of 379 amateur soccer players were enrolled in the longitudinal Einstein Soccer Study from November 11, 2013, through January 23, 2018. Selection criteria included participation in soccer for more than 5 years and for more than 6 months per year. Of the 379 individuals enrolled in the study, 355 were genotyped. Three players were excluded for reporting extreme levels of heading. Generalized estimating equation linear regression models were employed to combine data across visits for a cross-sectional analysis of the data. At each study visit every 3 to 6 months, players completed the HeadCount 12-Month Questionnaire, a validated, computer-based questionnaire to estimate 12-month heading exposure that was categorized as low (quartiles 1 and 2), moderate (quartile 3), and high (quartile 4). Verbal memory was assessed at each study visit using the International Shopping List Delayed Recall task from CogState was used as outcome measures.  A total of 352 soccer players (256 men and 96 women; median age, 23 years [interquartile range, 21-28 years]) across a total of 1204 visits were analyzed. High levels of heading were associated with worse verbal memory performance (β = -0.59; 95% CI, -0.93 to -0.25; P = .001). There was no main association of APOE ε4 with verbal memory (β = 0.09; 95% CI, -0.24 to 0.42; P = .58). However, there was a significant association of APOE ε4 and heading with performance on the ISRL task (χ2 = 7.22; P = .03 for overall interaction). In APOE ε4-positive players, poorer verbal memory associated with high vs low heading exposure was 4.1-fold greater (APOE ε4 negative, β = -0.36; 95% CI, -0.75 to 0.03; APOE ε4 positive, β = -1.49; 95% CI, -2.05 to -0.93), and poorer verbal memory associated with high vs moderate heading exposure was 8.5-fold greater (APOE ε4 negative, β = -0.13; 95% CI, -0.54 to 0.29; APOE ε4 positive, β = -1.11, 95% CI, -1.70 to -0.53) compared with that in APOE ε4-negative players. This study suggests that the APOE ε4 allele is a risk factor for worse memory performance associated with higher heading exposure in the prior year, which highlights that assessing genetic risks may ultimately play a role in promoting safer soccer play.


#7 Effects of Soccer Match-Play on Unilateral Jumping and Interlimb Asymmetry: A Repeated-Measures Design
Reference: J Strength Cond Res. 2020 Jan 24. doi: 10.1519/JSC.0000000000003389. [Epub ahead of print]
Authors: Bishop C, Read P, Stern D, Turner A
Summary: The aims of this study were two-fold: (a) determine the effects of repeated soccer match-play on unilateral jump performance and interlimb asymmetries and (b) examine associations between asymmetry and commonly reported external load variables collected during competition. Single-leg countermovement jumps and drop jumps were collected before and immediately after 5 soccer matches in elite academy soccer players. Global positioning system data were also collected during each match as part of the routine match-day procedures. Single-leg countermovement jump height and concentric impulse showed significant reductions after matches (p < 0.01; effect size [ES]: -0.67 to -0.69), but peak force did not (p > 0.05; ES: -0.05 to -0.13). Single-leg drop jump height and reactive strength also showed significant reductions after matches (p < 0.01; ES: -0.39 to -0.58). No meaningful reductions in asymmetry were present at the group level, but individual responses were highly variable. Significant associations between postmatch reactive strength asymmetry and explosive distance (r = 0.29; p < 0.05), relative explosive distance (r = 0.34; p < 0.05), high-speed running (r = 0.35; p < 0.05), and relative high-speed running (r = 0.44; p < 0.01) were observed. These findings show that unilateral jump tests are more appropriate than asymmetry to detect real change after soccer competition, and practitioners should be cautious about using asymmetry to inform decision-making during the temporal recovery period.


#8 Maturity Related Differences in Body Composition Assessed by Classic and Specific Bioimpedance Vector Analysis among Male Elite Youth Soccer Players
Reference: Int J Environ Res Public Health. 2020 Jan 22;17(3). pii: E729. doi: 10.3390/ijerph17030729.
Authors: Toselli S, Marini E, Maietta Latessa P, Benedetti L, Campa F
Download link: https://www.mdpi.com/1660-4601/17/3/729/pdf
Summary: The aim of this study was to analyze the efficiency of classic and specific bioelectrical impedance vector analysis (BIVA) in the assessment of maturity related differences in body composition among male elite youth soccer players, and to provide bioelectrical impedance reference data for this category. A group of 178 players (aged 12.1 ± 1.6 years) were registered in a professional Italian soccer team participating in the first division (Serie A). They were divided into three groups according to their maturity status while bioelectrical resistance and reactance were obtained. The classic and specific BIVA procedures were applied, which correct bioelectrical values for body height and body geometry, respectively. Percentage of fat mass (FM%) and total body water (TBW (L)) were estimated from bioelectrical values. Age-specific z-scores of the predicted age at peak height velocity identified 29 players as earlier-, 126 as on time-, and 23 as later-maturing. TBW was higher (p < 0.01) in adolescents classified as "early" maturity status compared to the other two groups and classic BIVA confirmed these results. Conversely, no differences in FM% were found among the groups. Specific vector length showed a higher correlation (r = 0.748) with FM% compared with the classic approach (r = 0.493). Classic vector length showed a stronger association (r = -0.955) with TBW compared with specific (r = -0.263). Specific BIVA turns out to be accurate for the analysis of FM% in athletes, while classic BIVA shows to be a valid approach to evaluate TBW. An original data set of bioelectric impedance reference values of male elite youth soccer players was provided.


#9 Spatio-temporal investigation of surface soil hardness on professional football field
Reference: Environ Monit Assess. 2020 Jan 30;192(2):151. doi: 10.1007/s10661-020-8087-7.
Authors: Biraderoglu M, Kaplan S, Basaran M
Summary: The present study was conducted to identify the minimum number of sampling points to monitor surface hardness of the pitches through geostatistical methods and to determine spatial and temporal distribution of surface hardness in autumn, winter, spring, and summer periods. Initial samplings were performed from 126 points and with data reduction, the optimum number of sampling points was identified as 77. In upcoming sampling periods, surface hardness and soil temperature were directly measured in situ and disturbed soil samples taken from 77 points were subjected to moisture content, bulk density, and texture analyses (clay-C, silt-Si, and sand-S). In autumn period, surface hardness highly correlated with soil temperature and moisture content (r2 = - 0.438 and - 0.344, p < 0.01). Surface hardness significantly correlated only with soil temperature in winter period and only with bulk density in summer period (respectively r2 = - 0.366 and 0.234, p < 0.01). Average surface hardness values in autumn, winter, spring, and summer periods were respectively measured as 5.99, 6.55, 5.84, and 5.92%. Semivariograms generated for hardness were modeled with spherical model in all periods and a certain nugget effect was detected in all periods. Maximum likelihood distance for autumn, winter, spring, and summer periods was respectively measured as 65, 40, 45, and 46 m. It was concluded based on present findings that geostatistical methods could reliably be used to monitor surface hardness of football pitches and then proper and timely interventions could be made to sections not complying with FIFA standards.


#10 The Influence of Time of Season on Injury Rates and the Epidemiology of Canadian Football Injuries
Reference: Clin J Sport Med. 2020 Feb 6. doi: 10.1097/JSM.0000000000000824. [Epub ahead of print]
Authors: Robbins SM, Bodnar C, Donatien P, Mirza R, Zhao ZY, Hoeber S, Naidu D, Redelmeier A, Steele RJ, Shrier I
Summary: The purpose was to describe injury rates and injury patterns in the Canadian Football League (CFL) according to time during the season, player position, injury type, and injury location. Depending on the analysis, time of season (preseason, regular, and playoffs), player position, injury type, and injury location. Medical attention and time-loss injury rates per 100 athletes at risk (AAR), and prevalence of time-loss injuries per week. The average game injury rate was 45.2/100 AAR medical attention injuries and 30.7/100 AAR time-loss injuries. Injury rates declined by 1% per week over the season for both medical attention (rate ratio = 0.99) and time-loss (rate ratio = 0.99) injuries, with a substantial decline during the playoffs compared with preseason (rate ratio = 0.70-0.77). The number of ongoing time-loss injuries increased over the course of the regular season. Quarterbacks, offensive backs, and linebackers had the highest game injury rates. Joint/ligament and muscle/tendon injuries were the most common injury types for games and practices, respectively. The lower extremity was the most commonly affected area, specifically the lower leg/ankle/foot and hip/groin/thigh. There was a 1% decline in injury rate per week during the season and a 30% decline during the playoffs. The number of ongoing time-loss injuries increased over the regular season. Current results can aid league officials and medical staff in making evidence-based decisions concerning player safety and health.


#11 A systematic review of genitourinary injuries arising from rugby and football
Reference: J Pediatr Urol. 2020 Jan 7. pii: S1477-5131(19)30443-7. doi: 10.1016/j.jpurol.2019.12.019. [Epub ahead of print]
Authors: Kim JK, Koyle MA, Lee MJ, Nason GJ, Ren LY, O'Kelly F
Summary: Genitourinary injuries in athletes engaging in high-impact sports such as football and rugby may have catastrophic consequences, especially in individuals with pre-existing urologic concerns, such as a solitary kidney. The purpose was to summarize the current literature on football-related or rugby-related genitourinary organ injuries in both adult and pediatric populations in an effort to risk stratify the likelihood of these injuries. An independent systematic literature search for records reporting football-related or rugby-related injuries was conducted by a certified librarian and reviewer in March 2019. The search electronic databases included Medline, EMBASE, Scopus, and Web of Science. All studies reporting football-related or rugby-related genitourinary injuries were included. Twenty-two records (11 research studies, 11 case reports) were identified. In the pediatric population, the reported football-related kidney injuries were 0.1-0.7% of all football-related injuries, 0.07-0.5% of all sports-related injuries, and 1.5-37.5% of all sports-related genitourinary injuries, with incidence ranging from 0.00000084 to 0.0000092 injuries per exposure (five studies). Pediatric football-related testicular injuries were reported to be 0.11% of all football injuries, 0-0.07% of all sports-related injuries, and 0-37.5% of all sports-related genitourinary injuries; injury per exposure was 0.0000092 (four studies). In adults, there was no proportion of genitourinary injuries that could be determined, and football-related kidney injury incidence was 0.000012 injuries per exposure (one study). No adult literature investigated testicular injuries. Eleven case reports were additionally identified. Review of the case reports suggests that patients with previously existing urologic abnormalities such as ureteropelvic junction obstruction may predispose an individual to kidney injuries. There is little to suggest that those engaged in football or rugby have a significant risk of genitourinary injury; therefore, future guidelines should reflect this.


#12 Injury in elite women's soccer: a systematic review
Reference: Phys Sportsmed. 2020 Feb 6:1-7. doi: 10.1080/00913847.2020.1720548. [Epub ahead of print]
Authors: Alahmad TA, Kearney P, Cahalan R
Summary: The objective was to summarize risk factors for injury in elite women's soccer. Ten electronic databases were searched for studies that explored risk factors for injury in elite women soccer players. Study cohorts were required to consist of adult (?18 years) elite players defined as 'the best performers in their country in a certain sport who are competing at national or international levels' [1]. Two reviewers independently assessed articles for eligibility. The CASP checklist was used for quality assessment of included studies, and the Oxford Center of Evidence-Based Medicine guidelines were used to determine their level of evidence. Eight studies were included in this review. Findings indicated an association between an increased injury risk and previous injury and increased joint laxity. There is additional evidence to support a relationship between injuries and higher soccer exposure, playing position, increased BMI, low H/Q ratio, player's level of balance and co-ordination, as well as various psychological issues. However, there were conflicting findings for the effect of postural control. Individual differences in Q-angle, intercondylar notch width or pelvic width measurements were not found to be associated with injury. The incidence of injury was higher in the dominant limb. The risk of injury in elite female soccer players is multifactorial, complex, and associated with a range of intrinsic, and extrinsic factors. More high-quality studies are needed to investigate each identified risk factor in order to inform effective injury screening.

Fri

13

Mar

2020

Latest research in football - week 3 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Effect of Respiratory Muscle Training on the Pulmonary Function, Lung Ventilation, and Endurance Performance of Young Soccer Players
Reference: Int J Environ Res Public Health. 2019 Dec 28;17(1). pii: E234. doi: 10.3390/ijerph17010234.
Authors: Mackała K, Kurzaj M, Okrzymowska P, Stodółka J, Coh M, Rożek-Piechura K
Download link: https://www.mdpi.com/1660-4601/17/1/234/pdf
Summary: This study investigated whether the addition of eight weeks of inspiratory muscle training (IMT) to a regular preseason soccer training program, including incremental endurance training (IET), would change pulmonary function, lung ventilation, and aerobic performance in young soccer players. Sixteen club-level competitive junior soccer players (mean age 17.63 ± 0.48 years, height 182 ± 0.05 cm, body mass 68.88 ± 4.48 kg) participated in the study. Participants were randomly assigned into two groups: experimental (n = 8) and control (n = 8). Both groups performed regular preseason soccer training, including endurance workouts as IET. In addition to this training, the experimental group performed additional IMT for eigght weeks with a commercially available respiratory muscle trainer (Threshold IMT), with a total of 80 inhalations (twice per day, five days per week). Pre- and post-intervention tests of pulmonary function, maximal inspiratory pressure, and the Cooper test were implemented. Eight weeks of IMT had a positive impact on expiratory muscle strength (p = 0.001); however, there was no significant effect on respiratory function parameters. The results also indicate increased efficiency of the inspiratory muscles, contributing to an improvement in aerobic endurance, measured by VO₂max estimated from running distance in the cardiorespiratory Cooper test (p < 0.005).


#2 Effects of Nordic Hamstring Exercise on Hamstring Injuries in High School Soccer Players: A Randomized Controlled Trial
Reference: Int J Sports Med. 2020 Jan 5. doi: 10.1055/a-1034-7854. [Epub ahead of print]
Authors: Hasebe Y, Akasaka K, Otsudo T, Tachibana Y, Hall T, Yamamoto M
Summary: We evaluated a range of physical characteristics related to hamstring injuries, as well as the Nordic Hamstring Exercise compliance rate, and whether this influenced the rate hamstring injury. Subjects comprised 259 male soccer players from seven high schools randomly clustered into two groups, a Nordic Hamstring Exercise group and a control group. Training and match time were logged, as well as details of hamstring injury, and subsequent time lost to hamstring injury recorded over a period of 27 weeks. The Nordic Hamstring Exercise compliance rate, injury rate per 10000 playing hours and time-lost-to-sport-injury rate were calculated. The relative risk and hamstring injury severity were also calculated. The hamstring injury rate was 1.04/10 000 h in the control group and 0.88/10 000 h in the intervention group. The relative risk for hamstring injury was 1.14. The time-lost to injury rate was 1116.3/10 000 h in the control group and 113.7/10 000 h in the intervention group; with relative risk 9.81. The Nordic Hamstring Exercise in high school soccer players significantly reduced hamstring injury severity compared to a control intervention. Our results indicate that the time-lost to injury rate should be taken into account when analyzing the severity of hamstring injury.


#3 Taking the First Steps Toward Integrating Testing and Training Cognitive Abilities Within High-Performance Athletes; Insights From a Professional German Football Club
Reference: Front Psychol. 2019 Dec 13;10:2773. doi: 10.3389/fpsyg.2019.02773. eCollection 2019.
Authors: Beavan A, Spielmann J, Mayer J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6923669/pdf/fpsyg-10-02773.pdf


#4 Corrigendum: Observational Studies in Male Elite Football: A Systematic Mixed Study Review
Reference: Front Psychol. 2019 Dec 16;10:2682. doi: 10.3389/fpsyg.2019.02682. eCollection 2019.
Authors: Preciado M, Anguera MT, Olarte M, Lapresa D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927414/pdf/fpsyg-10-02682.pdf


#5 Rapid hamstrings to quadriceps ratio at long muscle lengths in professional football players with previous hamstring strain injury
Reference: Eur J Sport Sci. 2020 Jan 9:1-16. doi: 10.1080/17461391.2020.1714741. [Epub ahead of print]
Authors: Correia P, Santos P, Mil-Homens P, Gomes M, Dias A, Valamatos MJ
Summary: Hamstring strain injuries (HSI) are the most common injury in male professional football and are potentially a primary risk factor to re-injury. Although the isokinetic strength ratios have often been used to identify strength imbalances that can augment the risk of injury in football players, the rate of torque development hamstring to quadriceps ratio (RTD H/Q) has rarely been considered in previous reports. Furthermore, little consideration has been given to selective hamstring lengths (30° of knee flexion) and its influence on torque production. The aim of this study was to investigate the RTD H/Q at long hamstring lengths, conventional (concentric/concentric) and functional (eccentric/concentric) H/Q ratios in football players with and without previous HSI. Twenty-four professional male football players (12 with and 12 without previous HSI) performed maximal voluntary isometric contractions at long hamstring lengths (knee and hip flexed at 30° and 85°, respectively) and isokinetic concentric and eccentric contractions at 180°.s-1 and 60°.s-1. Conventional and functional H/Q ratios based on peak torque throughout the entire isokinetic range of motion and at long hamstring lengths were calculated. The RTD H/Q was extracted at long hamstring lengths in incrementing time periods of 50 milliseconds (ms) from the onset of contraction (50-250ms). No significant differences were found between groups in any H/Q ratios studied. However, small effects (d=0.4) were found in previously injured hamstrings to lower RTD H/Q at 50ms and flexor eccentric torque. Previous HSI group showed small to moderate (0.4>d<0.6) higher RTD H/Q in late time intervals (>100ms).


#6 Hill on a mountaintop: A longitudinal and cross-sectional analysis of the relative age effect in competitive youth football
Reference: J Sports Sci. 2020 Jan 9:1-7. doi: 10.1080/02640414.2019.1706830. [Epub ahead of print]
Authors: Jackson RC, Comber G
Summary: The aim of this study was to examine the origin and persistence of the relative age effect (RAE) in competitive youth football. To examine its origin, birthdates of 121 category one Premier League academy players recruited over 6 years were compared with 691 Under 8 (U8) players in one of the regional grassroots leagues from which academy players are selected. To examine the persistence of the RAE we conducted a longitudinal comparison of retention rates in early-birth and late-birth academy players from U9 to U15, and made a cross-sectional comparison of birthdate distributions from U7 to U18 in 10,857 regional league players. The results revealed birthdate asymmetry in both the academy and grassroots players but a much larger RAE in the academy. Longitudinal analysis revealed that the cumulative probability of retention at the academy was higher for early-birth than late-birth players. A small to medium RAE persisted across grassroots football age groups though it declined somewhat from U15 to U18. The implication of these results for academy player recruitment is discussed.


#7 Agility Testing in Youth Football (Soccer)Players; Evaluating Reliability, Validity, and Correlates of Newly Developed Testing Protocols
Reference: Int J Environ Res Public Health. 2020 Jan 1;17(1). pii: E294. doi: 10.3390/ijerph17010294.
Authors: Krolo A, Gilic B, Foretic N, Pojskic H, Hammami R, Spasic M, Uljevic O, Versic S, Sekulic D
Download link: https://www.mdpi.com/1660-4601/17/1/294/pdf
Summary: Reactive agility (RAG) and change of direction speed (CODS) are important determinants of success in football (soccer), but there is an evident lack of information on reliable and valid football-specific testing procedures which will be applicable in defining sport-specific RAG and CODS in youth players. This study evaluated reliability and construct validity of newly developed tests of football-specific RAG (FS_RAG) and CODS (FS_CODS), which involved the ball kicking football technique. Additionally, factors associated with FS_RAG and FS_CODS were evaluated. The participants were youth football players (n = 59; age: 13.40 ± 1.25 years) divided according to their age into U13 (11-12 years of age; n = 29), and U15 (13-14 years of age; n = 30) categories. Additionally, performance levels (starters [first-team] vs. non-starters [substitutes]) were observed in each age category. The dependent variables were newly developed FS_RAG and FS_CODS tests. The independent variables were sprinting capacities over 10 and 20 meters (S10M, S20M), countermovement jump (CMJ), the reactive strength index (RSI), and a generic CODS test of 20 yards (20Y). The newly developed FS_CODS and FS_RAG were observed as dependent variables. Results showed appropriate intra-testing and inter-testing reliability of the FS_RAG and FS_CODS, with somewhat better reliability of the FS_CODS (ICC=0.82 and 0.79, respectively). Additionally, better reliability was evidenced in U15 than in U13 (ICC: 0.82-0.85, and 0.78-0.80 for U15 and U13, respectively). Independent samples t-test indicated significant differences between U13 and U15 in S10 (t-test: 3.57, p < 0.001), S20M (t-test: 3.13, p < 0.001), 20Y (t-test: 4.89, p < 0.001), FS_RAG (t-test: 3.96, p < 0.001), and FS_CODS (t-test: 6.42, p < 0.001), with better performance in U15. Starters outperformed non-starters in most capacities among U13, but only in FS_RAG among U15 (t-test: 1.56, p < 0.05). Multiple regression calculations indicated nonsignificant association between independent and dependent variables in U13 (FS_CODS: 19%, FS_RAG: 21% of the explained variance, both p > 0.05), but independent variables explained significant proportion of both dependent variables in U15 (FS_CODS: 35%, FS_RAG: 33% explained variance, both p < 0.05). The study confirmed the applicability of newly developed tests in distinguishing studied age categories of players. Results indicate that superiority in all studied fitness capacities is translated into performance level in U13. Meanwhile, FS_RAG seems to be important determinant of quality in U15.


#8 BDNF Val66Met Positive Players Demonstrate Diffusion Tensor Imaging Consistent With Impaired Myelination Associated With High Levels of Soccer Heading: Indication of a Potential Gene-Environment Interaction Mechanism
Reference: Front Neurol. 2019 Dec 11;10:1297. doi: 10.3389/fneur.2019.01297. eCollection 2019.
Authors: Hunter LE, Freudenberg-Hua Y, Davies P, Kim M, Fleysher R, Stewart WF, Lipton RB, Lipton ML
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6918922/pdf/fneur-10-01297.pdf
Summary: The purpose of this study was to examine the potential effect modifying role of the BDNF Val66Met polymorphism on the association of soccer heading with white matter microstructure. We studied 312 players enrolled in the ongoing Einstein Soccer Study, a longitudinal study of amateur soccer player in New York City and surrounding areas. At enrollment and 2 years later, total heading in the prior 12 months (12-mo.) was estimated using an established self-report instrument and diffusion tensor imaging (DTI) was performed. Generalized Estimating Equations (GEE) logistic regression models were employed to test effect modification by the BDNF Val66Met polymorphism on the association between 12-mo. heading exposure and DTI. We identified a significant interaction of 12-mo heading*BDNF Val66Met genotype on the presence of low Radial Diffusivity, a DTI marker associated with myelination. Only Met (+) players demonstrated significantly reduced odds of low RD [OR (95 % CI): -2.36 (-3.53, -1.19)] associated with the highest vs. lowest quartile of 12-mo heading exposure. BDNF Val66Met (+) soccer players with long-term exposure to high levels of heading exhibit less low Radial Diffusivity, suggesting impaired re-myelination may be a substrate of the previously reported association between heading and poor functional outcomes in soccer players.


#9 Effect of deep transverse friction massage vs stretching on football players' performance
Reference: World J Orthop. 2020 Jan 18;11(1):47-56. doi: 10.5312/wjo.v11.i1.47. eCollection 2020 Jan 18.
Fakhro MA1, Chahine H2, Srour H2, Hijazi K2.
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6960298/pdf/WJO-11-47.pdf
Summary: Flexibility, agility and muscle strength are key factors to either win or lose a game. Recently the effect of a new technique, deep transverse friction massage (DTFM) on muscle extensibility as compared to traditional stretching techniques has been examined. The aim was to compare the effect of DTFM vs static and dynamic stretching techniques on the hamstring's extensibility, agility, and strength amongst Lebanese and Syrian football players. Recording the incidence of non-contact hamstring muscle injury was a secondary objective. This study is a single-blinded prospective longitudinal randomized controlled trial. The experiment took place over a period of four weeks. Football players were randomized into three intervention groups (static stretching; dynamic stretching; DTFM). Participants of each group were followed-up carefully by assessors during their intervention sessions three times per week, for a total of 12 sessions and during the data collection. Extensibility, agility, and strength were compared between intervention groups at (baseline; acute; and chronic) phases. Straight leg raise and 1 repetition maximum tests were used to measure the dominant leg hamstring muscle extensibility and maximal strength respectively. T-drill test was used to assess the lower extremities agility. Of 103 Lebanese and Syrian male football players aged between 18 and 35 were sampled from Damascus-Syria and South of Lebanon to participate in this study. Between-groups measures of acute strength (P = 0.011) and chronic extensibility (P = 0.000) solely showed a significant difference, and the static group showed to be superior as compared to the other groups. No loss to follow-up or protocol violation was recorded. Static stretching is showing to be superior to the other techniques used, regarding gaining long-term extensibility and short-term maximal muscle strength. In addition, DTFM showed improvements but did not outweigh the effects on footballers' performance when comparing it to static and dynamic techniques. Finally, no difference between the interventions is recorded regarding the rate of muscle injuries incidence.


#10 Evaluation of the Technical Performance of Football Players in the UEFA Champions League
Reference: Int J Environ Res Public Health. 2020 Jan 17;17(2). pii: E604. doi: 10.3390/ijerph17020604.
Authors: Yi Q, Gómez-Ruano MÁ, Liu H, Zhang S, Gao B, Wunderlich F, Memmert D
Download link: https://www.mdpi.com/1660-4601/17/2/604/pdf
Summary: This study aimed to assess the technical match performance of top-class football players in a long-term perspective. Technical performance profiles of players according to five playing positions (central defender, full back, wide midfielder, central midfielder, forward) and five situational variables (competition stage, match location, quality of team, quality of opponent, match outcome) were established. Technical match data of players in the UEFA Champions League from season 2009-2010 to 2016-2017 were analyzed. The true effects of positional and situational variables on players' technical performance were evaluated by the non-clinical magnitude-based inference. Results showed that the effect of competition stage on player's performance was negligible. Quality of team, quality of opponent and match outcome revealed the strongest effects on player's performance (ES: -0.42 ± 0.10-0.59 ± 0.10) while the effect of match location was relatively lower (ES: -0.32 ± 0.10-0.23 ± 0.07). The number of variables that showed statistical differences under five competing contexts for wide midfielders and forwards were higher than those of central defenders, full backs, and central midfielders. Differences of players' match performance could mainly be identified in variables related to goal scoring, passing, and organizing, these findings may provide important insights for coaches and analysts during the match preparation and training session.


#11 Scale-Up and Scale-Out of a Gender-Sensitized Weight Management and Healthy Living Program Delivered to Overweight Men via Professional Sports Clubs: The Wider Implementation of Football Fans in Training (FFIT)
Reference: Int J Environ Res Public Health. 2020 Jan 16;17(2). pii: E584. doi: 10.3390/ijerph17020584.
Authors: Hunt K, Wyke S, Bunn C, Donnachie C, Reid N, Gray CM
Download link: https://www.mdpi.com/1660-4601/17/2/584/pdf
Summary: Increasing prevalence of obesity poses challenges for public health. Men have been under-served by weight management programs, highlighting a need for gender-sensitized programs that can be embedded into routine practice or adapted for new settings/populations, to accelerate the process of implementing programs that are successful and cost-effective under research conditions. To address gaps in examples of how to bridge the research to practice gap, we describe the scale-up and scale-out of Football Fans in Training (FFIT), a weight management and healthy living program in relation to two implementation frameworks. The paper presents: the development, evaluation and scale-up of FFIT, mapped onto the PRACTIS guide; outcomes in scale-up deliveries; and the scale-out of FFIT through programs delivered in other contexts (other countries, professional sports, target groups, public health focus). FFIT has been scaled-up through a single-license franchise model in over 40 UK professional football clubs to 2019 (and 30 more from 2020) and scaled-out into football and other sporting contexts in Australia, Canada, New Zealand, England and other European countries. The successful scale-up and scale-out of FFIT demonstrates that, with attention to cultural constructions of masculinity, public health interventions can appeal to men and support them in sustainable lifestyle change.

Fri

13

Mar

2020

Latest research in football - week 2 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Groin Injuries in Soccer: Investigating the Effect of Age on Adductor Muscle Forces
Reference: Med Sci Sports Exerc. 2019 Dec 31. doi: 10.1249/MSS.0000000000002243. [Epub ahead of print]
Authors: Dupré T, Lysdal FG, Funken J, Mortensen KRL, Müller R, Mayer J, Krahl H, Potthast W
Summary: The sudden rise in the injury incidence during adolescence, is also evident in soccer related injuries to the groin. Submaximal passing applies high stress on the adductor muscles and pubic symphysis and is therefore likely to be connected to the occurrence of groin injuries. Therefore, the purpose of the study was to compare hip joint kinematics and adductor muscle forces of different adolescent age groups during submaximal soccer passing. Sixty participants, in four groups, below 12, 15, 16 and 23 years (U12, U15, U16, U23), were analyzed. A Footbonaut, equipped with a 3D motion capture system consisting of 16 cameras, was used to capture kinematic data of short passes. Inverse dynamic analysis was performed to calculate muscle forces of ten passes of each subject. The U15 group showed reduced angular velocities. A rise in hip adductor muscle forces was evident from the youngest group up to the oldest groups. The largest increase (49%) was found between U12 and U15. Lower limb mass was identified as the best predictor for the increasing adductor force. The reduced angular velocities of the U15 and the increase in muscle forces between all age groups was attributed to the increasing segment masses and length. This increases the moments of inertia of the leg segments thereby demanding higher forces to accelerate the segments. Most likely, the stress put upon the adductors apophyses increases during adolescence, as tendons are known to adapt slower than muscles, increasing the risk for overuse injuries. Coaches could use lower limb mass as an indicator for fast increases in the force demand to identify players who would benefit from a reduced training volume.


#2 Pathoanatomy of the Jones Fracture in Male University Soccer Players
Reference: Am J Sports Med. 2019 Dec 30:363546519893365. doi: 10.1177/0363546519893365. [Epub ahead of print]
Authors: Fujitaka K, Tanaka Y, Taniguchi A, Ogawa M, Isomoto S, Otuki S, Okubo M
Summary: Jones fractures are relatively common in soccer players and require an extended recovery period because this type of fracture has a high incidence of delayed union, nonunion, and refracture. There has been some previous research on risk factors for Jones fracture, but no study has yet investigated the effect of the length of the fifth metatarsal bone and the positional relationship of the articular surface of the fifth metatarsal bones and the tarsal bones. Clarification of the characteristics of the foot structure that predispose soccer players to Jones fracture may aid in the prevention of this injury. The purpose was to investigate the association between Jones fracture and foot structure as assessed with a mapping system on weightbearing dorsoplantar and lateral foot radiographs. We used a mapping system to evaluate the radiographs of 60 feet from 30 university soccer players with Jones fractures and a control group of 60 feet from 60 male university soccer players without Jones fracture. The groups were compared regarding the length of the fifth metatarsal and the positions of the metatarsal and tarsal bones. Analysis of weightbearing dorsoplantar foot radiographs showed that the fifth metatarsal was significantly longer and that its proximal tip was positioned more proximally in the Jones fracture group as compared with the control group. Analysis of weightbearing lateral foot radiographs showed that the reference points for the medial arch were significantly higher in the Jones fracture group than in the control group. This study indicated that the proximally longer fifth metatarsal may cause greater stress at the base of the fifth metatarsal bone because the lever arm becomes long. In addition, high medial longitudinal arch may contribute to increased load on the lateral side of the foot. Thus, these anatomic features may be useful to identify soccer players at high risk of Jones fracture at medical checkup.


#3 Multidirectional Plyometric Training: Very Efficient Way to Improve Vertical Jump Performance, Change of Direction Performance and Dynamic Postural Control in Young Soccer Players
Reference: Front Physiol. 2019 Dec 9;10:1462. doi: 10.3389/fphys.2019.01462. eCollection 2019.
Authors: Jlid MC, Racil G, Coquart J, Paillard T, Bisciotti GN, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6913538/pdf/fphys-10-01462.pdf
Summary: The aim of the study was to assess the effects of multidirectional plyometric training (MPT) on vertical jump height, change of direction performance (CODP), and dynamic postural control (DPC) in young soccer players. Twenty-eight young male soccer players were randomly assigned to an experimental group (EG, n = 14; age: 11.8 ± 0.4 years) and a control group (CG, n = 14; age: 11.6 ± 0.5 years). The EG introduced 8-week MPT, two days per week into their in-season training, while CG continued training without change. Measurements of vertical jump height, CODP, and DPC were completed at the beginning and end of the 8-week MPT. A significant group × time interaction was observed for Squat-Jump (p < 0.05), for Counter-Movement Jump (p < 0.05), and for CODP test (p < 0.05). In addition, a significant group × time interaction was observed for DPC in seven axes for the dominant- (anterior, lateral, postero-lateral, posterior, postero-medial, medial, and antero-medial; p < 0.05 for all) and in seven axes for the non-dominant- (anterior, antero-lateral, lateral, posterior, postero-medial, medial and antero-medial; p < 0.05 for all) legs. The rest of the axes of both legs did not show any significant group × time interaction (p > 0.05). In conclusion, incorporating MPT into the in-season regimen of young male soccer players improved performance of various indices related to soccer activity (i.e., vertical jump height, CODP, and DPC). MPT has the potential to be appealing to coaches, as it requires little time while yielding valuable results in the physical preparation of young soccer players.


#4 Predictive modelling of the physical demands during training and competition in professional soccer players
Reference: J Sci Med Sport. 2019 Dec 17. pii: S1440-2440(19)31238-1. doi: 10.1016/j.jsams.2019.12.008. [Epub ahead of print]
Authors: Giménez JV, Jiménez-Linares L, Leicht AS, Gómez MA
Summary: The present study aimed to predict the cut-off point-values that best differentiate the physical demands of training and competition tasks including friendly matches (FM), small sided games (SSG), large sided games (LSG), mini-goal games (MG) and ball circuit-training (CT) in professional soccer players. Fourteen professional players participated in all tasks with the CT, SSG and MG consisting of 8 repetitions of 4-min game play, interspersed by 2-min of active recovery. The training data were compared to the first 32-min of the LSG and two competitive FM per player. All movement patterns from walking to sprint running were recorded using 10Hz GPS devices while player perception of exertion was recorded via a visual analogue scale, post-task. Decision tree induction was applied to the dataset to assess the cut-off point-values from four training drills (SSG, LSG, MG, and CT) and FM for every parameter combination. Distance covered during jogging (2.3-3.3m/s; >436m), number of decelerations (≤730.5) and accelerations (≤663), and maximum velocity reached (>5.48m/s) characterized the physical demands during competition (FM) with great variability amongst training drills. The use of these novel, cut-off points may aid coaches in the design and use of training drills to accurately prepare athletes for soccer competition.


#5 Technical-Tactical Analysis of the Players of the Left and Right Wing in Elite Soccer
Reference: J Hum Kinet. 2019 Nov 30;70:233-244. doi: 10.2478/hukin-2019-0045. eCollection 2019 Nov.
Authors: Amatria M, Dios RM, Pérez-Turpin JA, Gomis-Gomis MJ, Elvira-Aranda C, Suárez-Llorca C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942477/pdf/hukin-70-233.pdf
Summary: In today's soccer, teams are increasingly better trained both physically and tactically, hence different game styles can be identified and differences between them reduced. However, without an exhaustive analysis of reality, the view can lead to the extraction of erroneous conclusions, and what seems to be a team with a marked offensive profile is a mere illusion, resulting to be a team that develops a perfectly balanced game. In this paper, an analysis of technical-tactical performance of players who occupied both wings in an elite team was made, taking as reference the Spanish national soccer team as the model of international game to imitate in the last decade. The development of this paper was located within the observational methodology, using the polar coordinates technique for the analysis of the obtained data. The results showed how, despite identifying offensive profiles within technical-tactical performance of players that occupied the outer wings or lanes of the playing field, their tactical means and orientations diverged from each other. The results showed a more offensive profile and with higher technical complexity of players that occupied the left wing, while players that held the right wing showed a more defensive and recuperative profile, indicating a less vertical and complex style of play at a technical level with the forward as an offensive reference.


#6 External Load Variations Between Medium- and Large-Sided Soccer Games: Ball Possession Games Vs Regular Games with Small Goals
Reference: J Hum Kinet. 2019 Nov 30;70:191-198. doi: 10.2478/hukin-2019-0031. eCollection 2019 Nov.
Authors: Clemente FM, Praça GM, Bredt SDGT, van der Linden CMI, Serra-Olivares J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942466/pdf/hukin-70-191.pdf
Summary: This study compared external load variations between 5 vs 5 and 10 vs 10 sided game formats played under two conditions: (i) a ball possession game with two floaters, and (ii) a regular game with goalkeepers and small goals. Twenty-two professional soccer players participated in this study: four central defenders, four wide defenders, nine central midfielders, three wide forwards, and three strikers. Total distance (TD), running distance (RD), sprinting distance (SD), number of sprints (NS), and player's training load (PL) were recorded by GPS units. Within-format analyses revealed very likely large increases in TD (20.0%, [9.2; 31.9]; effect size (ES): 1.48, [0.71; 2.25]) and RD (130.9%, [20.2; 343.7]; ES: 1.32, [0.29; 2.35]) during the regular game when compared to the ball possession game in the 5 vs 5 format. In the 10 vs 10 format, large increases in TD (27.9%, [17.7; 39.1]; ES: 3.54, [2.34; 4.74]) and PL (27.4%, [12.6; 44.1]; ES: 2.46, [1.20; 3.72]) were observed in the regular condition when compared to the ball possession condition. Between-formats analyses revealed that, in the 10 vs 10 format, when compared to the 5 vs 5 format, RD was very likely larger (123.5%, [33.7; 273.7]), as was SD (195.8%, [20.5; 626.2]). However, very likely large decreases in PL were observed in the 10 vs 10 format (-19.6%; [-29.4; -8.3]) in the ball possession condition. Unclear differences were revealed based on variations in external load variables between formats in the regular condition. Smaller formats reduce the area available for running and sprinting and, thus, may be more adequate for increasing player's training load (based on accelerometer data).


#7 Short-Term Repeated-Sprint Training (Straight Sprint Vs. Changes of Direction) in Soccer Players
Reference: J Hum Kinet. 2019 Nov 30;70:183-190. doi: 10.2478/hukin-2019-0040. eCollection 2019 Nov.
Authors: Beato M, Coratella G, Bianchi M, Costa E, Merlini M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942460/pdf/hukin-70-183.pdf
Summary: Repeated-sprint training (RST) is considered a critical training method in team sports. It is well known that RST effects may depend on several variables such as the duration of the protocol and repeated-sprint methodology. Few studies have evaluated very short-term protocols and compared different RST modalities. The aim of this study was to compare the effectiveness of 2 week RST including straight sprints or changes of direction (CODs) on physical performance in a sample of soccer players. This study used a randomised pre-post parallel group trial design. The participants were assigned to either an RST group using straight sprints (RST-SS = 18 players) or an RST group using CODs (RST-COD = 18 players). The protocols were: 3 sets of 7 x 30 m sprints for the RST-SS and 7 x 20 + 20 m (one COD of 180°) for the RST-COD, with 20 s and 4 min recovery between sprints and sets, respectively. The following evaluations were performed: 10 and 20 m sprint, agility test, repeated sprint test (RSTbest and RSTmean), and Yo-Yo Recovery Level 1. After the training period, the RST-SS did not report any performance variation, while the RST-COD showed improvements in the 10 m sprint and RSTbest (effect size = 0.70 and 0.65, respectively). The between-group analysis did not report any statistical difference between the RST-SS and the RST-COD. In conclusion, this study did not support the utilisation of a very short-term RST protocol with soccer players, however, the RST-COD presented some additional benefits in sprint performance compared to the RST-SS.


#8 Analysis of Match Dynamics of Different Soccer Competition Levels Based on the Player Dyads
Reference: J Hum Kinet. 2019 Nov 30;70:173-182. doi: 10.2478/hukin-2019-0030. eCollection 2019 Nov.
Authors: Caetano FG, da Silva VP, Torres RDS, Anido RO, Cunha SA, Moura FA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942461/pdf/hukin-70-173.pdf
Summary: The purpose of this study was to analyse the dynamics of play based on dyads during soccer matches, according to the competition level, period of the matches, and playing positions. We recorded eight Brazilian soccer matches (four of the national and four of the regional level), using up to six digital cameras (30 Hz). The position information of the 204 players in the eight matches was obtained using an automatic tracking system. The Euclidean distance between the nearest opponents was calculated over time to define the dyads. The interaction between the components of dyads was assessed by the distances between players and was compared among the different positions (defender, full-back, defensive midfielder, midfielder, and forward), match periods (15, 30, 45, 60, 75, and 90 min), and competition levels. Results showed smaller distances for the national level dyads, compared to the regional matches. Greater distances between the players were found in the last 15 minutes of the matches, compared to the other periods. The full-backs were more distant from opposing players compared to players from other playing positions. Thus, coaches should consider the characteristics of each playing position and the greater proximity between opponents' players in top-level competition for the development of tactical proficiency of the players.


#9 Different Cleat Models Do Not Influence Side Hop Test Performance of Soccer Players with and Without Chronic Ankle Instability
Reference: J Hum Kinet. 2019 Nov 30;70:156-164. doi: 10.2478/hukin-2019-0029. eCollection 2019 Nov.
Authors: Silva DCF, Santos R, Vilas-Boas JP, Macedo R, Montes AM, Sousa ASP
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942480/pdf/hukin-70-156.pdf
Summary: The lateral ankle sprain is one of the most common sport injury, representing 10-30% of all musculoskeletal disorders. The lateral ankle sprain is induced by sport gestures involving changes of direction and landing manoeuvres and constitutes a risk factor for the occurrence of chronic ankle instability. Although cleat models and performance have been already explored, no study has evaluated this relationship in athletes with chronic ankle instability. Therefore, the purpose of the study was to analyse the influence of different soccer cleat models on Side Hop Test performance of athletes with and without chronic ankle instability. Thirty-nine athletes were divided into two groups, a chronic ankle instability group (n = 20) and a healthy group (n = 19). Each participant performed the Side Hop Test, executing 10 consecutive jumps on dry artificial grass with 4 cleat models. The Qualisys System and two force platforms were used to analyse the test runtime, the distance travelled and the mean velocity. No statistically significant interaction was observed between the group and the cleat model for all variables evaluated. In addition, no differences were observed between models or groups. In this specific test, performance does not seem to be influenced by different cleat models on dry artificial grass in athletes with and without chronic ankle instability.


#10 Assessment of Lower Body and Abdominal Strength in Professional Soccer Players
Reference: J Hum Kinet. 2019 Nov 30;70:15-23. doi: 10.2478/hukin-2019-0035. eCollection 2019 Nov.
Authors: Michaelides MA, Parpa KM, Zacharia AI
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6942483/pdf/hukin-70-015.pdf
Summary: The purpose of this study was to evaluate abdominal strength in professional soccer players and compare the findings to their lower body strength. An observational design was used to examine abdominal and lower body strength using two functional performance tests (a lower body isokinetic test and an isometric abdominal test, respectively). One hundred and thirty-two professional male soccer players from Cyprus's first and second divisions participated in this study. Testing included three and twenty-five maximal concentric flexion and extension repetitions at angle speeds of 60°/s (degrees/second) and 300°/s, respectively. On a separate occasion, participants completed two trials on an isometric device (ABTEST Gen. 3 system) for evaluation of abdominal strength. At both isokinetic speeds of 300°/s and 60°/s, abdominal strength had low to moderate significant correlations (p < .05) with quadriceps and hamstring strength. Coefficients of determination (R2) demonstrated that the variability in isokinetic variables accounted for only 14-16% of the variability of abdominal strength. Abdominal strength appears to be high in professional soccer players, but is not dependent on the sports level and/or a playing position. The results of this study demonstrate that abdominal strength and knee joint strength need to be evaluated separately.


#11 Effects of fatigue induced by repeated-sprint on kicking accuracy and velocity in female soccer players
Reference: PLoS One. 2020 Jan 7;15(1):e0227214. doi: 10.1371/journal.pone.0227214. eCollection 2020.
Authors: Torreblanca-Martínez V, Nevado-Garrosa F, Otero-Saborido FM, Gonzalez-Jurado JA
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0227214&type=printable
Summary: The aim of this study was to investigate the effects of fatigue induced by repeated sprint in the kicking accuracy and velocity in female soccer players. Eighteen Under-23 female soccer players from a Spanish professional club were subjected to a fatigue protocol based on a repeated-sprint ability (RSA) test. Measurements of the kicking velocity (maximal ball velocity) and accuracy (Loughborough Soccer Shooting Test) were taken before and after fatigue induction. Correlations between the change in the maximal ball velocity/accuracy and the heart rate (HR), the fatigue index (FI), the sprint decrement (Sdec) and the rating of perceived exertion (RPE) were made. There was a significant difference between maximal ball velocity under fatigue conditions with respect to non-fatigue conditions (p = 0.001; ES = 0.89). However, despite a lower kicking accuracy punctuation with fatigue, this was not statistically significant (p = 0.433; ES = 0.22). Significant correlations were found between the maximal kicking velocity and the FI (r = 0.632, p < 0.01) and the Sdec (r = -0.554, p < 0.05) and between the kicking accuracy and the RPE (r = -0.506, p < 0.05). In conclusion, there was a significant reduction in the maximal kicking velocity, but not in the kicking accuracy, under fatigued conditions. The RSA-related FI and Sdec were the best predictors of the maximal kicking velocity and the RPE for the kicking accuracy.


#12 Agility Testing in Youth Football (Soccer)Players; Evaluating Reliability, Validity, and Correlates of Newly Developed Testing Protocols
Reference: Int J Environ Res Public Health. 2020 Jan 1;17(1). pii: E294. doi: 10.3390/ijerph17010294.
Authors: Krolo A, Gilic B, Foretic N, Pojskic H, Hammami R, Spasic M, Uljevic O, Versic S, Sekulic D
Download link: https://www.mdpi.com/1660-4601/17/1/294/pdf
Summary: Reactive agility (RAG) and change of direction speed (CODS) are important determinants of success in football (soccer), but there is an evident lack of information on reliable and valid football-specific testing procedures which will be applicable in defining sport-specific RAG and CODS in youth players. This study evaluated reliability and construct validity of newly developed tests of football-specific RAG (FS_RAG) and CODS (FS_CODS), which involved the ball kicking football technique. Additionally, factors associated with FS_RAG and FS_CODS were evaluated. The participants were youth football players (n = 59; age: 13.40 ± 1.25 years) divided according to their age into U13 (11-12 years of age; n = 29), and U15 (13-14 years of age; n = 30) categories. Additionally, performance levels (starters [first-team] vs. non-starters [substitutes]) were observed in each age category. The dependent variables were newly developed FS_RAG and FS_CODS tests. The independent variables were sprinting capacities over 10 and 20 meters (S10M, S20M), countermovement jump (CMJ), the reactive strength index (RSI), and a generic CODS test of 20 yards (20Y). The newly developed FS_CODS and FS_RAG were observed as dependent variables. Results showed appropriate intra-testing and inter-testing reliability of the FS_RAG and FS_CODS, with somewhat better reliability of the FS_CODS (ICC=0.82 and 0.79, respectively). Additionally, better reliability was evidenced in U15 than in U13 (ICC: 0.82-0.85, and 0.78-0.80 for U15 and U13, respectively). Independent samples t-test indicated significant differences between U13 and U15 in S10 (t-test: 3.57, p < 0.001), S20M (t-test: 3.13, p < 0.001), 20Y (t-test: 4.89, p < 0.001), FS_RAG (t-test: 3.96, p < 0.001), and FS_CODS (t-test: 6.42, p < 0.001), with better performance in U15. Starters outperformed non-starters in most capacities among U13, but only in FS_RAG among U15 (t-test: 1.56, p < 0.05). Multiple regression calculations indicated nonsignificant association between independent and dependent variables in U13 (FS_CODS: 19%, FS_RAG: 21% of the explained variance, both p > 0.05), but independent variables explained significant proportion of both dependent variables in U15 (FS_CODS: 35%, FS_RAG: 33% explained variance, both p < 0.05). The study confirmed the applicability of newly developed tests in distinguishing studied age categories of players. Results indicate that superiority in all studied fitness capacities is translated into performance level in U13. Meanwhile, FS_RAG seems to be important determinant of quality in U15.

Thu

12

Mar

2020

Latest research in football - week 1 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Evaluation of soccer players under the Moneyball concept
Reference: J Sports Sci. 2019 Dec 26:1-27. doi: 10.1080/02640414.2019.1702280. [Epub ahead of print]
Authors: Gavião LO, Sant'Anna AP, Alves Lima GB, de Almada Garcia PA
Summary: The recruitment of athletes with limited resources is a global problem in professional sports. In US Major League Baseball, the experience of the Oakland Athletics' general manager in the last decade turned his "Moneyball" model into a synonym of quantitative analysis in the transfer market of baseball players. His strategy focused on hiring players with outstanding technical skills but relatively low market value. This study adapted this model to the framework of a multiple criteria decision aid (MCDA), by selecting undervalued players who have complementary abilities. The novelty here refers to the joint use of four algorithms explored by the composition of probabilistic preferences (CPP) (i.e., ranking, classification, dynamic evaluation and regularity analysis) and their application to soccer player performance evaluation. The new model analysed the recent transfer of a left-back soccer player to Europe. The results indicated 12 opportunities for better investment, among 32 left and right-back players considered. Two years later, the value of the same player was considerably lower. He played only five matches in the 2018-2019 season, without scoring or providing any assists. On the other hand, the players better classified by the CPP-MB model presented higher performances and market values.


#2 Treatment of Anterior Cruciate Ligament Injuries in Professional Soccer Players by Orthopedic Surgeons
Reference: Rev Bras Ortop (Sao Paulo). 2019 Dec;54(6):703-708. doi: 10.1055/s-0039-1697017. Epub 2019 Dec 13.
Authors: Arliani GG, Pereira VL, Leão RG, Lara PS, Ejnisman B, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6923647/pdf/10-1055-s-0039-1697017.pdf
Summary: The purpose was to describe the treatment provided by specialists for ACL lesions in professional soccer players. A cross-sectional study in which orthopedic surgeons affiliated to soccer teams competing in the Brazilian Soccer Championship answered a questionnaire about the treatment of ACL injuries in professional soccer players. The specialists wait between one to four weeks after the ACL injury to perform the surgical treatment. They use a single incision and single-bundle reconstruction, assisted by arthroscopy, femoral tunnel drilling by an accessory medial portal, and quadruple flexor tendon autografts or patellar tendon autografts. After three to four months, the players are allowed to run in a straight line; after four to six months, they begin to practice exercises with the ball without contact with other athletes; and, after six to eight months, they return to play. The main parameter used to determine the return to play is the isokinetic strength test. The specialists estimate that more than 90% of elite soccer players return to playing professionally after an ACL reconstruction, and 60 to 90% return to play at their prior or at a greater level of performance. The present article successfully describes the main surgical practices and post-surgery management adopted by specialists in this highly-specific population of patients.


#3 Improvements in Match-Related Physical Performance of Professional Soccer Players After the Application of an on-Field Training Program for Hamstring Injury Rehabilitation
Reference: J Sport Rehabil. 2019 Dec 22:1. doi: 10.1123/jsr.2019-0033. [Epub ahead of print]
Authors: Jiménez-Rubio S, Navandar A, Rivilla-García J, Paredes-Hernández V, Gómez-Ruano MÁ.
Summary: Although there are multiple, validated return-to-play programs following hamstring strain injuries, no studies have evaluated their changes in match performance parameters. The aim of this study was twofold as follows: (1) to determine the changes in match-based physical performance parameters in professional soccer players before and after sustaining a hamstring strain injury and undergoing a soccer-specific rehabilitation program and (2) to observe the progress of these performance parameters 6 to 10 weeks after the player returned from injury. Nineteen players suffering a hamstring strain injury from 2 male professional teams playing in the Spanish professional football league (La Liga) were followed during the 2015-2016, 2016-2017, and 2017-2018 seasons. The intervention was a participation in on-field training program following a hamstring injury. Match global positioning system data were collected in the following stages: prior to injury (PRE), after return to play (RTP), program, and 6 to 10 weeks following RTP (C2). Peak velocities and distances ran at sprint velocities showed most likely improvements in C2 versus PRE, and very likely improvements in RTP versus PRE. The distances ran at high and very high intensities, the average velocity, and work-to-rest ratio showed very likely improvements in C2 versus RTP and likely improvements in RTP versus PRE. Likely improvements were observed for all variables in C2 versus RTP. The authors' results showed an improvement of physical performance during competitive match after RTP, compared with PRE. There was a steady progression in the progress, and in 8 months following RTP, there was no injury reported in the players. The current findings may indicate that the hamstring muscle complex not only recovered completely from the injury but could also withstand a greater training and match load reducing the risk of reinjury.


#4 Seasonal variation in neuromuscular control in young male soccer players
Reference: Phys Ther Sport. 2019 Dec 16;42:33-39. doi: 10.1016/j.ptsp.2019.12.006. [Epub ahead of print]
Authors: Lloyd RS, Oliver JL, Myer GD, De Ste Croix M, Read PJ
Summary: Determine how lower limb neuromuscular control changes over the course of a competitive soccer season. 43 male youth soccer players (age 13.1 ± 2.2 yr; height 160.1 ± 15.7 cm; body mass 49.4 ± 14.3 kg; maturity offset 0.2 ± 1.9 yr) participated in this study.  Pre-, mid- and end of season assessments of peak landing forces during single leg 75% horizontal hop and stick (75%HOP) and a single leg countermovement jump (SLCMJ), single leg hop for distance (SLHD), knee valgus during the tuck jump assessment (TJA) and inter-limb symmetries. Hop distance increased significantly. Absolute peak landing forces in the left leg during the SLCMJ and 75%HOP increased significantly, with significant increases also present in the same leg for SLCMJ relative peak landing force. TJA knee valgus score was reduced in the right leg, but remained at a 'moderate' level in the left knee. Neuromuscular control, as evidenced by increased absolute and relative peak landing forces, appears to reduce over the course of a competitive season. Young soccer players should engage in neuromuscular training throughout the season to offset any decrements in neuromuscular control and to facilitate appropriate landing strategies.


#5 Normalized Hip and Knee Strength in Two Age Groups of Adolescent Female Soccer Players
Reference: J Strength Cond Res. 2019 Dec 20. doi: 10.1519/JSC.0000000000003420. [Epub ahead of print]
Authors: Hannon JP, Wang-Price S, Garrison JC, Goto S, Bothwell JM, Bush CA
Summary: Limb symmetry strength measures are used for clinical decision-making considering when an athlete is ready to return to sport after anterior cruciate ligament (ACL) injuries. However, changes in bilateral muscle strength occur after ACL injury resulting in potentially altered limb symmetry calculations. Adolescent female soccer players are at increased risk of sustaining ACL injuries. Published age and sex-matched strength values in this population may be of benefit to clinicians to improve clinical decision-making. The purpose of this study was to establish normative hip and knee strength data of both the dominant and nondominant limbs in adolescent female soccer players. Sixty-four female soccer players (ages 10-18) were enrolled in this study. Subjects were divided by age into 2 groups (group 1: 10-14 years; group 2: 15-18 years). Subjects underwent Biodex isokinetic strength testing at 60°·s and 180°·s to assess quadriceps and hamstring strength. Isometric hip strength (abduction and external rotation) was measured using a hand-held dynamometer. No significant differences were found between groups on either limb in regards to quadriceps or hamstring strength. No significant differences were found between groups on either limb for hip external rotation strength. Significant differences in hip abduction strength were found between groups on the dominant (group 1: 0.21 ± 0.04; group 2: 0.18 ± 0.04; p = 0.014) and nondominant (group 1: 0.21 ± 0.05; group 2: 0.18 ± 0.05; p = 0.019) limbs. The results of this study shed light on normative strength values for a high-risk injury population.


#6 Effects of Ramadan Fasting on Recovery Following a Simulated Soccer Match in Professional Soccer Players: A Pilot Study
Reference: Front Physiol. 2019 Dec 6;10:1480. doi: 10.3389/fphys.2019.01480. eCollection 2019.
Authors: Bouzid MA, Abaïdia AE, Bouchiba M, Ghattassi K, Daab W, Engel FA, Chtourou H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909883/pdf/fphys-10-01480.pdf
Summary: Assessing the effects of Ramadan fasting on recovery following a soccer match simulation. Eight elite soccer players (age: 21.0 ± 0.4 years) performed a modified Loughborough Intermittent Shuttle Test protocol (LISTmod) on two occasions: 1 week before (BR) and during the fourth week of Ramadan (End-R). At BR and End-R, soccer players performed squat jump, countermovement jump, maximal voluntary contraction, and 20 m sprint, and creatine kinase, uric acid, and subjective ratings (feelings scale, quality of sleep, fatigue, muscle soreness and stress) were assessed at baseline and 0, 24, 48, and 72 h following LISTmod. Following LISTmod, performance in squat jump (48 and 72 h) (p < 0.05), countermovement jump (48 and 72 h), maximal voluntary contraction (0, 24, 48, and 72 h), and 20 m sprint (0 and 48 h) decreased significantly on both occasions. Decreases were higher at End-R than BR. Creatine kinase levels increased significantly at 24 and 48 h at BR and End-R (p < 0.05). Uric acid increased at 0 and 24 h only on BR. Muscle soreness increased throughout the recovery period at both occasions, with a higher level at End-R. Stress rating increased only at 0 h on End-R, while fatigue rating increased at 24 h at BR and at 0, 24, and 48 h at End-R. Perturbations in physical performance and subjective ratings parameters were higher at the end of Ramadan. However, the results of this study showed that Ramadan fasting did not adversely affect the recovery following soccer match simulation in professional soccer players.


#7 Return to Play in Amateur Soccer Players Undergoing Hip Arthroscopy: Short- to Mid-Term Follow-Up
Reference: Arthroscopy. 2019 Dec 19. pii: S0749-8063(19)30727-3. doi: 10.1016/j.arthro.2019.08.027. [Epub ahead of print]
Authors: Ortiz-Declet V, Yuen LC, Schwarzman GR, Chen AW, Perets I, Domb BG
Summary: The purpose was to describe patient-reported outcomes (PROs) and return to play at any level in amateur soccer players undergoing hip arthroscopy for femoroacetabular impingement syndrome at short- to mid-term follow-up. Data were prospectively collected and retrospectively reviewed for patients who underwent hip arthroscopy between March 2009 and June 2014. Patients who participated in amateur soccer within 1 year prior to surgery and intended to return to their sport after hip arthroscopy for femoroacetabular impingement syndrome were considered for inclusion in our study. Patients were excluded if they had a preoperative Tönnis osteoarthritis grade of 2 or greater, previous ipsilateral hip conditions or hip surgical procedures, or Workers' Compensation status. The patients from the initial group who had preoperative and minimum 2-year postoperative measures for the modified Harris Hip Score, Non-Arthritic Hip Score, Hip Outcome Score-Sports Specific Subscale, and visual analog scale for pain were included in our final group. In addition to PROs, data regarding the patients' return to soccer, surgical complications, and secondary surgical procedures were collected. A total of 41 patients were eligible for inclusion in our study, of whom 34 (82.9%) had a mean follow-up period of 47.4 months. Five patients were not eligible because they did not intend to return to soccer. There were 15 male hips (44.1%) and 19 female hips (55.9%). The mean age at surgery was 20.8 ± 7.4 years. All PROs and the visual analog scale score improved significantly from preoperatively to latest follow-up. Of the 34 patients, 27 (79.4%) returned to soccer. Of the patients who returned to soccer, 19 (70.4%) were competing at the same level or a higher level compared with their highest level within 1 year of surgery. Regardless of competitive level, 21 patients (77.8%) reported that their athletic ability was the same as or higher than it was within 1 year of surgery. Hip arthroscopy was associated with significant improvements in PROs for amateur soccer players. There was a high level of return to soccer and a high proportion of patients whose competitive level was similar or improved. As such, hip arthroscopy is a good option for soccer players, in the absence of underlying osteoarthritis, presenting with hip pathology.


#8 Editorial Commentary: Anterior Cruciate Ligament Injury and Reconstruction in Soccer Players: The Major Challenge Is Always Going for Our Goals!
Reference: Arthroscopy. 2020 Jan;36(1):196-198. doi: 10.1016/j.arthro.2019.10.005.
Authors: Stein SM, Mandelbaum BR
Summary: Anterior cruciate ligament (ACL) injury affects a large number of athletes worldwide, and long-term rate of return to soccer is approximately 50% or less. ACL injury, which is noncontact in approximately 90% of cases, has a complex multifactorial etiology. Younger and higher-level players do better, and 10-year outcomes are superior to baseline. The role of genomics, hormonal status, neuromuscular deficiencies, anatomy, and the environment are all potential contributory risk factors that vary with respect to the individual, especially the female athlete. Furthermore, ACL injury results in a local and regional catabolic cascade and cytokine release, creating an intra-articular environment that is a homeostatic perfect storm and spectrum of scalable articular cartilage and meniscal injury. Once these complexities in the knee organ are defined and understood, the surgeon's early objectives are stabilization, repair, and restoration with full harmonization of biomechanics, neuromuscular control, and homeostasis. The goal is optimizing long-term outcomes, decreasing the rate of subsequent ACL injury, and preventing osteoarthritis.


#9 Positional Differences in Peak- and Accumulated- Training Load Relative to Match Load in Elite Football
Reference: Sports (Basel). 2019 Dec 23;8(1). pii: E1. doi: 10.3390/sports8010001.
Authors: Baptista I, Johansen D, Figueiredo P, Rebelo A, Pettersen SA
Download link: https://www.mdpi.com/2075-4663/8/1/1/pdf
Summary: Quantification of training and match load is an important method to personalize the training stimulus' prescription to players according to their match demands. The present study used time-motion analysis and triaxial-accelerometer to quantify and compare: a) The most demanding passages of play in training sessions and matches (5-min peaks); b) and the accumulated load of typical microcycles and official matches, by playing position. Players performance data in 15 official home matches and 11 in-season microcycles were collected for analysis. Players were divided into four different playing positions: Centre-backs, wing-backs, centre midfielders, and centre forwards. The results show that match demands were overperformed for acceleration counts (acccounts) (131%-166%) and deceleration counts (deccounts) (108%-134%), by all positions. However, relative to match values, training values for sprint distance (sprintdist) and high-intensity run distance (HIRdist) were considerably lower (36%-61% and 57%-71%) than for accelerations and decelerations. The most pronounced difference on the 5-min peaks was observed in sprints (sprintpeak), with wing-backs achieving during the microcycle only 64% of the sprintpeak in matches, while centre backs, centre midfielders, and centre forwards levelled and overperformed the match values (107%, 100%, and 107%, respectively). Differences observed across playing positions in matches and microcycles underline the lack of position specificity of common training drills/sessions adopted by coaches in elite football.


#10 Why do football clubs fail financially? A financial distress prediction model for European professional football industry
Reference: PLoS One. 2019 Dec 26;14(12):e0225989. doi: 10.1371/journal.pone.0225989. eCollection 2019.
Authors: Alaminos D, Fernández MÁ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0225989&type=printable
Summary: The study of financial distress has been the focus of financial research in recent decades and has led to the development of models for predicting financial distress that help assess the financial situation and the risks faced by companies. These models have focused exclusively on industrial and financial companies. However, a specific model that reflects the special characteristics of the football industry has not yet been created. Since recently the governing bodies of the football industry have increased the financial control of the clubs, as in the case of UEFA with the approval of the Financial Fair Play Regulation and demand a pronouncement on going concern in the annual financial statements of clubs as well as presenting a break-even deficit caused by losses, it seems necessary to have a model adapted to the characteristics of this industry. The present study provides a new model of prediction of financial distress for the football industry with an accuracy that exceeds 90%. It also offers a vision of the challenges facing the football industry in financial matters, helping the different interest groups to assess the financial solvency expectations of the clubs.


#11 A multilevel hypernetworks approach to capture meso-level synchronisation processes in football
Reference: J Sports Sci. 2019 Dec 26:1-9. doi: 10.1080/02640414.2019.1707399. [Epub ahead of print]
Authors: Ribeiro J, Lopes R, Silva P, Araújo D, Barreira D, Davids K, Ramos J, Maia J, Garganta J
Summary: Understanding team behaviours in sports performance requires understanding the interdependencies established between their levels of complexity (micro-meso-macro). Previously, most studies examined interactions emerging at micro- and macro-levels, thus neglecting those emerging at a meso-level (reveals connections between player and team levels, depicted by the emergence of coordination in specific sub-groups of players-simplices during performance). We addressed this issue using the multilevel hypernetworks approach, adopting a cluster-phase method, to record player-simplice synchronies in two performance conditions where the number, size and location of goals were manipulated (first-condition: 6 × 6 + 4 mini-goals; second-condition: Gk + 6 × 6 + Gk). We investigated meso-level coordination tendencies, as a function of ball-possession (attacking/defending), field-direction (longitudinal/lateral) and teams (Team A/Team B). Generally, large synergistic relations and more stable patterns were observed in the longitudinal direction of the field than the lateral direction for both teams, and for both game phases in the first condition. The second condition displayed higher synchronies and more stable patterns in the lateral direction than the longitudinal plane for both teams, and for both game phases. Results suggest: (i) usefulness of hypernetworks in assessing synchronisation of teams at a meso-level; (ii) coaches may consider manipulating these task constraints to develop levels of local synchronies within teams.


#12 Differences in Technical Performance of Players From 'The Big Five' European Football Leagues in the UEFA Champions League
Reference: Front Psychol. 2019 Dec 6;10:2738. doi: 10.3389/fpsyg.2019.02738. eCollection 2019.
Authors: Yi Q, Groom R, Dai C, Liu H, Gómez Ruano MÁ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6908525/pdf/fpsyg-10-02738.pdf
Summary: The current study aimed to identify the differences in technical performance between players from clubs of Bundesliga (Germany), La Liga (Spain), Ligue 1 (France), Premier League (England) and Serie A (Italy) when competing in the matches of the UEFA Champions League. Technical performance-related match data of 1,291 players from 1,125 matches (9,799 observations) of the UEFA Champions League (seasons 2009/2010-2017/2018) were collected and analysed. The generalised mixed linear modelling was employed taking the names of the league as the independent variable to predict the count number of 20 technical performance-related match actions and events performed by players belonging to different leagues. The non-clinical magnitude-based inference was used to evaluate the uncertainty in the true effects of the predictor. Results showed that differences in the technical performances between players from La Liga, Premier League and Ligue 1 were all trivial. Bundesliga players made higher numbers of shots than players from La Liga, Premier League and Serie A and achieved more long balls than players from Ligue 1. Serie A players achieved lower numbers of ball touches, passes and lower pass accuracy per match than players from any of the other four leagues. In addition, players from Serie A performed a higher number of long balls per match than Ligue 1 players and lower number of dribbles per match than Premier League players. Non-significant differences in other variables related to passing and organising and all variables related to defending were identified in players between the five leagues. The identified differences in technical performance among leagues could provide a more thorough understanding for practitioners working within the fields of talent identification, player development, player recruitment, coaching and match preparation.

Wed

04

Mar

2020

Latest research in football - week 53 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Attitudes and behavior related to performance-enhancing substance use among elite Saudi football players
Reference: BMC Sports Sci Med Rehabil. 2019 Dec 5;11:35. doi: 10.1186/s13102-019-0149-1. eCollection 2019.
Authors: Al Ghobain M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896591/pdf/13102_2019_Article_149.pdf
Summary: The purpose was to investigate the attitudes, beliefs and behavior related to performance enhancing substances (PES) use in elite Saudi football players. A cross-sectional survey was conducted. Using a systematic random sample of elite Saudi male football players, the standard World Anti-doping Agency (WADA) Social Science Research Package questionnaire was distributed to 408 players. The overall prevalence rate of PES use was 3.9%, with the overall prevalence rate of doping susceptibility 17.1%. PES use or doping susceptibility is strongly correlated but negatively associated with morality and cheating measures (p <  0.011, the estimate is - 0.139), threat or deterrence appraisal (p <  0.001, the estimate is - 0.301) and beliefs about the reference group's endorsement (p < 0.001, the estimate is - 0.213) but not with legitimacy perceptions (p = 0.513) and beliefs about the benefits of doping (p = 0.678). The strongest relationship was found between threat or deterrence appraisal (p < 0.001), and beliefs about the reference group's endorsement of PES use (p < 0.001). Morality and cheating measures, threat or deterrence appraisal and beliefs about the reference group's endorsement are the main predictors for PES use in Saudi Arabia.


#2 The Effect of 1600 μg Inhaled Salbutamol Administration on 30 m Sprint Performance Pre and Post a Yo-Yo Intermittent Running Test in Football Players
Reference: J Sports Sci Med. 2019 Nov 19;18(4):716-721. eCollection 2019 Dec.
Authors: Merlini M, Beato M, Marcora S, Dickinson J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6873132/pdf/jssm-18-716.pdf
Summary: The purpose of the study was to investigate the effect of inhaling 1600 μg of salbutamol (SAL) on 30 m sprint before and after the Yo-Yo Intermittent Recovery test. In a randomised cross over single blind study 13 male non-asthmatic, football players volunteered (mean ± SD; age 18.1 ± 0.9 years; weight 69.5 ± 8.3 kg; height 1.78 ± 0.07 m). Participants completed two visits and were randomly assigned to either (SAL) or (PLA) treatment and performed a set of three sprints of 30 m before and after the Yo-Yo Intermittent Recovery Test (Yo-Yo IRT). Best sprint and mean sprint were analysed in addition to the distance covered during the Yo-Yo IRT; rating of perceived exertion and heart rate were collected at the end of each level completed. Repeated measures ANOVA were performed to investigate changes in performance between groups. Following the inhalation of supra-therapeutic salbutamol dose (1600 μg) neither 30 m sprint time (PLA 4.43 ± 0.14 s; SAL 4.44 ± 0.15 s, p = 0.76) nor distance covered in the Yo-Yo IRT test reported significant variation between PLA conditions (1660 ± 217 m) and SAL (1610 ± 229 m, p = 0.16). Moreover, lactate values, heart rate and RPE did not differ significantly between groups. The inhalation of 1600 μg salbutamol does not enhance 30 m sprint performance in non-fatigued and fatigue conditions. Our findings suggest when football players acutely inhale double the permitted dose of salbutamol, as indicated in the World Anti-Doping Agency List of Prohibited Substances and Methods, they will not experience improvements in sprint or endurance performance.


#3 The Physiological, Physical, and Biomechanical Demands of Walking Football: Implications for Exercise Prescription and Future Research in Older Adults
Reference: J Aging Phys Act. 2019 Dec 10:1-11. doi: 10.1123/japa.2019-0330. [Epub ahead of print]
Authors: Harper LD, Field A, Corr LD, Naughton RJ.
Summary: The aim of this investigation was to profile the physiological, physical, and biomechanical responses during walking football. A total of 17 male participants (aged 66 ± 6 years) participated. Heart rate; blood lactate; accelerometer variables (biomechanical load [PlayerLoad™], changes of direction); and rating of perceived exertion were measured. Participants mean percentage of maximum heart rate was 76 ± 6% during the sessions, with rating of perceived exertion across all sessions at 13 ± 2. Blood lactate increased by ∼157% from presession (1.24 ± 0.4 mmol/L) to postsession (3.19 ± 1.7 mmol/L; p ≤ .0005). PlayerLoad™ values of 353 ± 67 arbitrary units were observed, as well as ∼100 changes of direction per session. In conclusion, walking football is a moderate- to vigorous-intensity activity. The longitudinal health benefits of walking football remain to be elucidated, particularly on bone health, cardiovascular fitness, and social and mental well-being.


#4 Experiences Influencing Walking Football Initiation in 55- to 75-Year-Old Adults: A Qualitative Study
Reference: J Aging Phys Act. 2019 Dec 10:1-13. doi: 10.1123/japa.2019-0123. [Epub ahead of print]
Authors: Cholerton R, Breckon J, Butt J, Quirk H.
Summary: Adults aged 55 and older are least likely to play sport. Despite research suggesting this population experiences physical and psychological benefits when doing so, limited research focuses on older adult sport initiation, especially in "adapted sports" such as walking football. The aim of this study was to explore initiation experiences of walking football players between 55 and 75 years old. Semistructured interviews took place with 17 older adults playing walking football for 6 months minimum (Mage = 64). Inductive analysis revealed six higher order themes representing preinitiation influences. Eight further higher order themes were found, relating to positive and negative experiences during initiation. Fundamental influences preinitiation included previous sporting experiences and values and perceptions. Emergent positive experiences during initiation included mental development and social connections. Findings highlight important individual and social influences when initiating walking football, which should be considered when encouraging 55- to 75-year-old adults to play adapted sport. Policy and practice recommendations are discussed.


#5 The 11+ Kids warm-up programme to prevent injuries in young Iranian male high-level football (soccer) players: A cluster-randomised controlled trial
Reference: J Sci Med Sport. 2019 Dec 9. pii: S1440-2440(19)30140-9. doi: 10.1016/j.jsams.2019.12.001. [Epub ahead of print]
Authors: Zarei M, Abbasi H, Namazi P, Asgari M, Rommers N, Rössler R
Download link: https://www.jsams.org/article/S1440-2440(19)30140-9/pdf
Summary: The purpose was to assess the effectiveness of the 11+ Kids warm-up programme regarding injury reduction in male high-level children's football players. Male youth football teams of Iran's high-level football schools were invited to participate. Inclusion criteria were: teams are competing in the highest league of their province; players are between 7 and 14 years old; regular training takes place at least twice per week. Teams were excluded if they used an injury prevention measure. Participating clubs were randomised to an intervention (INT, N = 20 teams) and a control group (CON, N = 22 teams), stratified by the number of teams and the age group. The groups were blinded against each other. The follow-up period was one season (9 months). INT replaced their warm-up by 11+ Kids. CON performed a standard warm-up programme. The primary outcome was the injury incidence density (injuries per 1000 h of football exposure), compared between groups by incidence rate ratios (RR). In total, 64,047 h of football exposure of 962 players (INT = 443 players, 31,934 h of football, CON = 519 players, 32,113 h of football) were recorded. During the study, 90 (INT = 30; CON = 60) injuries occurred. The overall injury incidence density in INT was reduced by 50% compared to CON (RR 0.50; 95%-CI 0.32, 0.78). No injuries occurred during the execution of the intervention exercises. The 11+ Kids reduces injuries in high-level children's football players, thus supporting player health and potentially performance and player development.


#6 Strategic rule breaking: Time wasting to win soccer games
Reference: PLoS One. 2019 Dec 18;14(12):e0224150. doi: 10.1371/journal.pone.0224150. eCollection 2019.
Authors: Greve HR, Rudi N, Walvekar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6919576/pdf/pone.0224150.pdf
Summary: Rules regulate behavior, but in competitive contexts they also create incentives for rule-breaking because enforcement is imperfect. Sports is a prime example of this, and one that lends itself well to investigation because strategic rule-breaking is often measurable. Professional soccer is a highly competitive team sport with economic rewards for winning given to teams and players. It has a set of rules to ensure fair play, but the enforcement is incomplete, and hence can lead to strategic behavior. Using newly available data, we examine strategic time-wasting, a behavior that help teams win games, or tie games against superior opponents, but is contrary to the objective of game play as entertainment for the spectators. We demonstrate that strategic time-wasting is widespread and is done through delayed restart of the game after goalie capture of the ball, goal kick, throw-in, free kick, corner kick, and substitution. The strategic time-wasting has substantial magnitude, and models of the value per minute predict time-wasting well. Because this time-wasting is a result of incentives created by not stopping the game clock, we predict that a change to rules with stopped game clock when the play is stopped would make game play more time efficient.


#7 Hidden dynamics of soccer leagues: The predictive 'power' of partial standings
Reference: PLoS One. 2019 Dec 18;14(12):e0225696. doi: 10.1371/journal.pone.0225696. eCollection 2019.
Authors: Beggs CB, Bond AJ, Emmonds S, Jones B
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0225696&type=printable
Summary: Soccer leagues reflect the partial standings of the teams involved after each round of competition. However, the ability of partial league standings to predict end-of-season position has largely been ignored. Here we analyze historical partial standings from English soccer to understand the mathematics underpinning league performance and evaluate the predictive 'power' of partial standings. Match data (1995-2017) from the four senior English leagues was analyzed, together with random match scores generated for hypothetical leagues of equivalent size. For each season the partial standings were computed and Kendall's normalized tau-distance and Spearman r-values determined. Best-fit power-law and logarithmic functions were applied to the respective tau-distance and Spearman curves, with the 'goodness-of-fit' assessed using the R2 value. The predictive ability of the partial standings was evaluated by computing the transition probabilities between the standings at rounds 10, 20 and 30 and the final end-of-season standings for the 22 seasons. The impact of reordering match fixtures was also evaluated. All four English leagues behaved similarly, irrespective of the teams involved, with the tau-distance conforming closely to a power law (R2>0.80) and the Spearman r-value obeying a logarithmic function (R2>0.87). The randomized leagues also conformed to a power-law, but had a different shape. In the English leagues, team position relative to end-of-season standing became 'fixed' much earlier in the season than was the case with the randomized leagues. In the Premier League, 76.9% of the variance in the final standings was explained by round-10, 87.0% by round-20, and 93.9% by round-30. Reordering of match fixtures appeared to alter the shape of the tau-distance curves. All soccer leagues appear to conform to mathematical laws, which constrain the league standings as the season progresses. This means that partial standings can be used to predict end-of-season league position with reasonable accuracy.


#8 Positive fantasies and negative emotions in soccer fans
Reference: Cogn Emot. 2019 Dec 17:1-12. doi: 10.1080/02699931.2019.1703649. [Epub ahead of print]
Authors: Sevincer AT, Wagner G, Oettingen G
Summary: Positive thinking is often assumed to foster effort and success. Research has shown, however, that positive thinking in the form of fantasies about achieving an idealised future predicts less (not more) effort and success and more (not less) depressive symptoms over time. This relationship was mediated by people having invested little effort and achieved little success. Here, we ask a different question. We investigate the emotional consequences of positive fantasies about futures that people cannot act on. Specifically, we analyse these consequences when the future fantasies fail to come true (one's favourite soccer team loses). Study 1 provided correlational evidence. The more positively soccer fans fantasised about their favourite team winning an upcoming match, the stronger were their negative emotions when their team lost. That is, the more sad, disappointed, and frustrated they felt. Study 2 provided experimental evidence. Soccer fans who were led to fantasise positively about their team winning an upcoming match reported feeling stronger negative emotions after their team lost than those who were led to fantasise negatively. Positive fantasies were not related to how positive participants felt after their team won (joy, happiness, relief). We discuss theoretical and applied implications for emotion regulation in everyday life.


#9 Half Soccer Season Induced Physical Conditioning Adaptations in Elite Youth Players
Reference: Int J Sports Med. 2019 Dec 16. doi: 10.1055/a-1014-2809. [Epub ahead of print]
Authors: Arregui-Martin MA, Garcia-Tabar I, Gorostiaga EM
Summary: This study aimed to investigate training-induced fitness changes and their relationship with training-competition load during half a soccer season (18 wks). Training load [heart rate (HR) and ratings of perceived exertion (RPE)] and match time were monitored, including 108 training (3 223 individuals) and 23 match sessions, in 38 youth elite male soccer players. Fitness variables were assessed before and after the study. Yo-Yo intermittent recovery test 1 (Yo-Yo IRT1) improved (P<0.001; 90%CI: 418-632 m; ES: 2.14). Anthropometrical, jump, sprint, and change-of-direction measures remained unchanged. Jump test correlated with sprint (r=0.74; P<0.001; SEE=3.38 m·s-1) and Yo-Yo IRT1 (r=-0.58; P=0.005; SEE=4.11 m) tests. Initial sum of 6 skinfolds was associated with changes in this same measure (r=-0.51; P<0.001; SEE=21%). Initial Yo-Yo IRT1 results were related to changes in Yo-Yo IRT1 (r=-0.84; P<0.001; SEE=10%) and match time played (r=0.44; P=0.033; SEE=445 m). Mean RPE records were related to training spent within 75-90% maximal HR (r=0.54; P<0.001; SEE=4%). The half-season was beneficial for endurance running performance but not for lower-limb strength-velocity production capacity. The more aerobically deconditioned players played fewer minutes of match, although they showed the greatest improvements in endurance performance. Non-soccer-specific, scientifically based, and individualized fitness programs in addition to soccer-specific training are recommended.


#10 Oculomotor Control in Amputee Soccer Players
Reference: Adapt Phys Activ Q. 2019 Dec 14:1-15. doi: 10.1123/apaq.2019-0028. [Epub ahead of print]
Authors: Jedziniak W, Lesiakowski P, Zwierko T
Summary: The authors investigated the dynamics of saccadic parameters during a stationary oculomotor target task in amputee soccer players (n = 16), able-bodied soccer players (n = 16), and nonathletic control subjects (n = 16). Eye movements during the visual-search tasks were recorded binocularly using a mobile eye-tracking system, and the gaze parameters were analyzed (fixation duration, saccade duration, saccade amplitude, saccade average acceleration, saccade peak deceleration, saccade average velocity, and ocular mobility index). The average saccade acceleration in the amputee soccer players was significantly lower than in the able-bodied players (p = .021). Other saccade characteristics in disabled athletes were comparable to those of the able-bodied groups. Moreover, the able-bodied soccer players presented faster saccadic parameters than nonathletes in terms of saccade acceleration (p = .002), deceleration (p = .015), and velocity (p = .009). The modification of oculomotor functions may result from extensive practice and participation in ball games. The authors' hypothesis that oculomotor functions in amputee soccer players may be impaired was not fully confirmed.


#11 Prevalence and severity of groin problems in Spanish football: A prospective study beyond the time-loss approach
Reference: Scand J Med Sci Sports. 2019 Dec 17. doi: 10.1111/sms.13615. [Epub ahead of print]
Authors: Esteve E, Clausen MB, Rathleff MS, Vicens-Bordas J, Casals M, Palahí-Alcàcer A, Hölmich P, Thorborg K
Summary: The time-loss definition of injury is commonly adopted in epidemiological groin-injury studies in football, with a significant risk of underestimating the impact of these injuries. This study investigated the extent of groin problems, beyond the time-loss approach, over a full Spanish football season. Players from 17 amateur male teams were followed over 39 consecutive weeks. Groin-injury time loss and self-reported groin pain, irrespective of time loss, were combined to calculate the average weekly prevalence of all groin problems with or without time loss. A subscale measuring hip- and groin-related sporting function from the Copenhagen Hip And Groin Outcome Score questionnaire (HAGOS, Sport/Rec) was registered every 4 weeks. In total, 407 players participated in the study. The average (range) weekly prevalence of all groin problems was 11.7% (7.2-20.8%); 1.3% with time loss (0.0-3.2%) and 10.4% without time loss (6.3-17.6%). Players with groin problems reported lower scores (mean difference) on the HAGOS, Sport/Rec subscale compared to players without (-19.5 (95% CI: -20.7 - -18.4), while there was no difference between players reporting groin problems with and without time loss (4.0 (95% CI: -1.1 - 9.1). The traditional time-loss measure only captured 10% of all groin problems. Hip- and groin-related sporting function was not different between players reporting groin problems with or without time loss, suggesting the reason for continuing to play is not only related to the severity of symptoms. These findings question the judicious use of the time-loss approach in overuse conditions, such as groin pain in footballers.


#12 Electrocardiographic and Echocardiographic Findings in Elite Ghanaian Male Soccer Players
Reference: Clin J Sport Med. 2019 Dec 24. doi: 10.1097/JSM.0000000000000801. [Epub ahead of print]
Authors: Pambo P, Adu-Adadey M, Agbodzakey H, Scharhag J
Summary: The purpose was to analyze the athlete's heart of adult and adolescent elite male soccer players by electrocardiography (ECG) and echocardiography (ECHO) and to describe typical ECG and ECHO findings in this cohort (West African elite soccer players). A cross-sectional study of ECGs and ECHOs conducted as part of precompetition medical assessment for national male soccer teams preparing for various Fédération Internationale de Football Association (FIFA) tournaments in 2016 and 2017. One hundred fifty-nine players playing for the National male soccer teams preparing for tournaments in 2016 and 2017 participated in this study. Number of athletes with abnormal ECGs and ECHO findings were used as main outcome measures. Twenty-three percent of the players had abnormal ECGs. Nine percent of the participants had T-wave inversions in lateral leads (V5-V6). Sokolow-Lyon criteria for left ventricular hypertrophy were present in 64% of participants. Thirty-six (23%) players had left ventricular wall thickness (LVWT) ≥13 mm, with no player exceeding 16 mm. Four percent of players had left ventricular cavity dimension greater than 60 mm. Relative wall thickness >0.42 was present in 44% of the players. Uncommon ECG changes seem to be more common in elite Ghanaian soccer players compared with previously reported results for Caucasians and even mixed populations of black athletes. Although ST elevation, T-wave inversions, and LVWT up to 15 mm are common, ST depression, deep T-waves in lateral leads, and LVWT ≥16 mm always warrant further clinical and scientific investigations.

Mon

02

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2020

Latest research in football - week 52 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Comparing the Aerobic Fitness of Professional Male Soccer Players and Soccer Referees
Reference: Curr Sports Med Rep. 2019 Dec;18(12):497-501. doi: 10.1249/JSR.0000000000000668.
Authors: Santos-Silva PR, D'Andrea Greve JM, Pedrinelli A, Almeida AM, Osorio BB, Ferreira M, Ferreira C
Summary: We looked to compare the aerobic performance between professional soccer referees and players. Fifty male soccer referees and 61 male soccer players were tested on a treadmill. The referees and players possessed 15 ± 7 years and 7 ± 3 years of experience in soccer, respectively. Significant differences were observed between the referees and players with regards to: age (34.8 ± 4.6 years vs 20.8 ± 2.7 years; P < 0.001, maximum oxygen uptake (54.7 ± 5.4 mL·kg·min vs 58.8 ± 4.4 mL·kg·min; P < 0.001), and maximal heart rate in peak exercise (184 ± 11 bpm vs 192 ± 9 bpm, P < 0.001). Less significant differences also were observed and included; running speed at the maximum oxygen uptake (16.6 ± 1 km·h vs 16.4 ± 1.1 km·h), running speed at the ventilatory threshold (213.5 ± 1.1 km·h vs 13.2 ± 0.9 km·h), and percentage of maximal oxygen uptake at the ventilatory threshold (285.1% ± 3.2% vs 84.1% ± 6.2%). The effect size of most comparative variables between the two groups was small (<0.6). Older elite-level soccer referees are able to reach and maintain aerobic physical fitness levels similar to professional soccer players. Aerobic physical fitness may be a measurable factor for maintaining elite-level soccer licensure rather than age alone.


#2 Scapula Fractures in Elite Soccer and Rugby Players
Reference: Orthop J Sports Med. 2019 Dec 2;7(12):2325967119887388. doi: 10.1177/2325967119887388. eCollection 2019 Dec.
Authors: McIntosh J, Akhbari P, Malhas A, Funk L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6887832/pdf/10.1177_2325967119887388.pdf
Summary: Scapula fractures are uncommon in sports and are poorly understood in this patient group. The purpose was to report on scapula fractures in contact and collision athletes and assess the injury patterns of different mechanisms of injury. A retrospective case series was performed of all sports-related scapula fractures treated at a single institution between 2007 and 2015. The mechanisms of injury were divided into direct lateral impact, fall onto an outstretched arm, or abduction/external rotation. A total of 11 patients were identified: 9 professional rugby players, 1 professional soccer player, and 1 amateur soccer player. The mean age was 28 years (range, 18-35 years). The mean return to play was 127 days in those treated nonoperatively and 163 days in those treated operatively. A direct impact mechanism occurred in 7 patients, all of whom sustained glenoid neck and body fractures and were treated nonoperatively. Two rugby players had a concomitant suprascapular nerve injury. An outstretched arm mechanism occurred in 2 cases, leading to posterior and inferior glenoid fractures. Both patients were treated operatively. An abduction/external rotation mechanism occurred in 2 cases, resulting in an anteroinferior and an anterior glenoid rim fracture. One case was treated operatively and the other was treated nonoperatively. Of those with glenoid fractures, 75% were not visible on plain radiographs and required further imaging. Scapula fractures acquired in sports are a serious injury with a prolonged recovery period. The mechanism of injury can help predict the injury pattern and highlight the need for further imaging. There is a high association with suprascapular nerve injuries.


#3 Infrared Low-Level Laser Therapy (Photobiomodulation Therapy) before Intense Progressive Running Test of High-Level Soccer Players: Effects on Functional, Muscle Damage, Inflammatory, and Oxidative Stress Markers-A Randomized Controlled Trial
Reference: Oxid Med Cell Longev. 2019 Nov 16;2019:6239058. doi: 10.1155/2019/6239058. eCollection 2019.
Authors: Tomazoni SS, Machado CDSM, De Marchi T, Casalechi HL, Bjordal JM, de Carvalho PTC, Leal-Junior ECP
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6885272/pdf/OMCL2019-6239058.pdf
Summary: The effects of preexercise photobiomodulation therapy (PBMT) to enhance performance, accelerate recovery, and attenuate exercise-induced oxidative stress were still not fully investigated, especially in high-level athletes. The aim of this study was to evaluate the effects of PBMT (using infrared low-level laser therapy) applied before a progressive running test on functional aspects, muscle damage, and inflammatory and oxidative stress markers in high-level soccer players. A randomized, triple-blind, placebo-controlled crossover trial was performed. Twenty-two high-level male soccer players from the same team were recruited and treated with active PBMT and placebo. The order of interventions was randomized. Immediately after the application of active PBMT or placebo, the volunteers performed a standardized high-intensity progressive running test (ergospirometry test) until exhaustion. We analyzed rates of oxygen uptake (VO2 max), time until exhaustion, and aerobic and anaerobic threshold during the intense progressive running test. Creatine kinase (CK) and lactate dehydrogenase (LDH) activities, levels of interleukin-1β (IL-1-β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α), levels of thiobarbituric acid (TBARS) and carbonylated proteins, and catalase (CAT) and superoxide dismutase (SOD) activities were measured before and five minutes after the end of the test. PBMT increased the VO2 max (both relative and absolute values-p < 0.0467 and p < 0.0013, respectively), time until exhaustion (p < 0.0043), time (p < 0.0007) and volume (p < 0.0355) in which anaerobic threshold happened, and volume in which aerobic threshold happened (p < 0.0068). Moreover, PBMT decreased CK (p < 0.0001) and LDH (p < 0.0001) activities. Regarding the cytokines, PBMT decreased only IL-6 (p < 0.0001). Finally, PBMT decreased TBARS (p < 0.0001) and carbonylated protein levels (p < 0.01) and increased SOD (p < 0.0001)and CAT (p < 0.0001) activities. The findings of this study demonstrate that preexercise PBMT acts on different functional aspects and biochemical markers. Moreover, preexercise PBMT seems to play an important antioxidant effect, decreasing exercise-induced oxidative stress and consequently enhancing athletic performance and improving postexercise recovery.


#4 Effects of a 6-Week Strength Training of the Neck Flexors and Extensors on the Head Acceleration during Headers in Soccer
Reference: J Sports Sci Med. 2019 Nov 19;18(4):729-737. eCollection 2019 Dec.
Authors: Becker S, Berger J, Backfisch M, Ludwig O, Kelm J, Fröhlich M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6873131/pdf/jssm-18-729.pdf
Summary: The importance of well trained and stable neck flexors and extensors as well as trunk muscles for intentional headers in soccer is increasingly discussed. The neck flexors and extensors should ensure a coupling of trunk and head at the time of ball contact to increase the physical mass hitting the ball and reduce head acceleration. The aim of the study was to analyze the influence of a 6-week strength training program (neck flexors, neck extensors) on the acceleration of the head during standing, jumping and running headers as well as after fatigue of the trunk muscles on a pendulum header. A total of 33 active male soccer players (20.3 ± 3.6 years, 1.81 ± 0.07 m, 75.5 ± 8.3 kg) participated and formed two training intervention groups (IG1: independent adult team, IG2: independent youth team) and one control group (CG: players from different teams). The training intervention consisted of three exercises for the neck flexors and extensors. The training effects were verified by means of the isometric maximum voluntary contraction (IMVC) measured by a telemetric Noraxon DTS force sensor. The head acceleration during ball contact was determined using a telemetric Noraxon DTS 3D accelerometer. There was no significant change of the IMVC over time between the groups (F=2.265, p=.121). Head acceleration was not reduced significantly for standing (IG1 0.4 ± 2.0, IG2 0.1 ± 1.4, CG -0.4 ± 1.2; F = 0.796, p = 0.460), jumping (IG1-0.7 ± 1.4, IG2-0.2 ± 0.9, CG 0.1 ± 1.2; F = 1.272, p = 0.295) and running (IG1-1.0 ± 1.9, IG2-0.2 ± 1.4, CG -0.1 ± 1.6; F = 1.050, p = 0.362) headers as well as after fatigue of the trunk musculature for post-jumping (IG1-0.2 ± 2.1, IG2-0.6 ± 1.4; CG -0.6 ± 1.3; F = 0.184, p = 0.833) and post-running (IG1-0.3 ± 1.6, IG2-0.7 ± 1.2, CG 0.0 ± 1.4; F = 0.695, p = 0.507) headers over time between IG1, IG2 and CG. A 6-week strength training of the neck flexors and neck extensors could not show the presumed preventive benefit. Both the effects of a training intervention and the consequences of an effective intervention for the acceleration of the head while heading seem to be more complex than previously assumed and presumably only come into effect in case of strong impacts.


#5 Monitoring the Athlete Match Response: Can External Load Variables Predict Post-match Acute and Residual Fatigue in Soccer? A Systematic Review with Meta-analysis
Reference: Sports Med Open. 2019 Dec 9;5(1):48. doi: 10.1186/s40798-019-0219-7.
Authors: Hader K, Rumpf MC, Hertzog M, Kilduff LP, Girard O, Silva JR
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-019-0219-7
Summary: Monitoring athletes' external load during a soccer match may be useful to predict post-match acute and residual fatigue. This estimation would allow individual adjustments to training programs to minimize injury risk, improve well-being, and restore players' physical performance and inform the recovery process. Using a systematic review and meta-analysis of the literature, the aim is to determine which monitoring variables would be the strongest predictors of acute (immediately) and residual (up to 72 h) fatigue states in soccer. PubMed, SPORTDiscus, and Web of Science databases were searched (until September 2018). Studies concurrently examining soccer match-related external load metrics and subjective and/or objective measures were selected to determine pooled correlations ([Formula: see text]) with confidence intervals (CI). The quality and strength of the findings of each study were evaluated to identify overall levels of evidence. Eleven studies were included (n = 165 athletes). Acute ([Formula: see text] = 0.67; 95% CI = [0.40, 0.94]) and residual (24 h post-match, [Formula: see text] = 0.54; 95% CI = [0.35, 0.65]) changes in muscle damage markers and countermovement jump peak power output (CMJPPO) were, with moderate to strong evidence, largely correlated with running distance above 5.5 m s-1. No other external load metric was largely correlated with both biochemical and neuromuscular markers. For every 100-m run above 5.5 m·s-1, CK activity measured 24 h post-match increased by 30% and CMJPPO decreased by 0.5%. Conversely, the total distance covered did not present any evidence of a clear relationship with any fatigue-related marker at any time-point. Running distance above 5.5 m·s-1 represents the most sensitive monitoring variable characterizing biochemical and neuromuscular responses, at least when assessed during the initial 24 h (not at 48 h/72 h) post-match recovery period. In addition, total distance covered is not sensitive enough to inform decision-making during the fatigue monitoring process.


#6 A bioecological perspective on talent identification in junior-elite soccer: A Pan-European perspective
Reference: J Sports Sci. 2019 Dec 9:1-10. doi: 10.1080/02640414.2019.1702282. [Epub ahead of print]
Authors: Reeves MJ, Roberts SJ
Summary: Elite soccer clubs across Europe spend ever-increasing sums of money on transfers and salaries for world-class players. Consequently, clubs' talent identification and development processes for junior players have become more professionalised. Based on a holistic ecological approach, this study presents an analysis of talent identification practices across some of the most productive soccer academies in Europe (N = 11). Data were collected via semi-structured interviews with 11 heads of academy recruitment from clubs in the "big five" European leagues. Clubs were purposively sampled based on their player productivity ranking. Interviews ranged from 52:26 minutes to 114:06 minutes in length (m = 87:53 ± 20.10 minutes). This study argues that holistic ecological approaches the environments were characterised through the interplay of factors that ranged from high-level internal to international level relationships. This resulted in the identification and recruitment of players from local and international environments. The purpose of recruitment was suggested to have a dual purpose: recruitment of players for the first team; recruitment of players for further development/monitoring and/or selling to another club.


#7 Endocrine Responses to Various 1 × 1 Small-Sided Games in Youth Soccer Players
Reference: Int J Environ Res Public Health. 2019 Dec 6;16(24). pii: E4974. doi: 10.3390/ijerph16244974.
Authors: Chmura P, Podgórski T, Konefał M, Rokita A, Chmura J, Andrzejewski M
Download link: https://www.mdpi.com/1660-4601/16/24/4974/pdf
Summary: The aim of this study was to determine relationships between repeated 1 × 1 small-sided games (SSGs) (variable duration, constant work-to-rest ratio) and the concentration of steroid hormones and characteristic fatigue markers in youth soccer players. Eighteen young male soccer players were assigned at random to two experimental groups: E1-undertaking a six 30 s one-on-one SSGs with a 2 min rest period; and E2-playing six 45 s SSGs with a 3 min rest interval. Capillary blood was collected from the players at rest, after the last game, and 15 and 30 min after the exercise protocol. The variables assessed included serum cortisol (C), free testosterone (FT) and total testosterone (TT). An effect was observed between the measurement times (TT (F = 15.26, p ≤ 0.0001), FT (F = 6.86, p = 0.0006)). In terms of cortisol (C) levels, no interactions or effect between the studied groups were revealed, but an interaction was found (F = 4.01, p = 0.0126) and the effect appeared between the measurement times (F = 11.16, p ≤ 0.0001). The study results show that in all likelihood, longer rest intervals in repeated 30 s 1 × 1 SSGs can reduce catabolic reactions and hence the risk of overtraining in youth soccer players.


#8 Interactive Improvements of Visual and Auditory Function for Enhancing Performance in Youth Soccer Players
Reference: Int J Environ Res Public Health. 2019 Dec 5;16(24). pii: E4909. doi: 10.3390/ijerph16244909.
Authors: Song YH, Ha SM, Yook JS, Ha MS
Download link: https://www.mdpi.com/1660-4601/16/24/4909/pdf
Summary: We analyzed the effects of a regular training program on the health- and skill-related physical fitness (PF) of talented soccer players aged < 12 years; visual reaction time (VRT) and auditory reaction time (ART) were also assessed. In this single-group interventional study, 78 talented male youth soccer players (mean age, 9.54 years) were critically selected by the Korean Educational Development Institute and underwent a 22-week training program consisting of 16 weeks of PF and basic skill training (90 min/week) and 6 weeks of intensive training (3, 150-min sessions/week). We assessed the pre- and post-training body composition, cardiovascular endurance, muscle strength and endurance, and flexibility. We also measured power, agility, coordination and speed, passing ability, VRT, and ART. All variables improved after training. Post-training VRT correlated with ART, muscle mass, power, cardiovascular endurance, 10-m dribble time, 10-m ball touch count, and 10-m successful pass count. ART only correlated with muscle mass. ART and 10-m ball-touch count influenced VRT, and VRT influenced ART. In conclusion, the training program enhanced the PF and visual- and auditory-related reactions in talented youth soccer players. This study suggests the importance of the assessed relationships, indicating that a training program that improves these parameters enhances the players' performance.


#9 Effect of Training Load on Post-Exercise Cardiac Troponin T Elevations in Young Soccer Players
Reference: Int J Environ Res Public Health. 2019 Dec 2;16(23). pii: E4853. doi: 10.3390/ijerph16234853.
Authors: Cirer-Sastre R, Legaz-Arrese A, Corbi F, López-Laval I, Puente-Lanzarote J, Hernández-González V, Reverter-Masià J
Download link: https://www.mdpi.com/1660-4601/16/23/4853/pdf
Summary: Training load (TL) metrics are usually assessed to estimate the individual, physiological and psychological, acute, and adaptive responses to training. Cardiac troponins (cTn) reflect myocardial damage and are routinely analyzed for the clinical diagnosis of myocardial injury. The association between TL and post-exercise cTn elevations is scarcely investigated in young athletes, especially after playing common team sports such as soccer. The objective of this study was to assess the relationship between TL measurements during a small-sided soccer game and the subsequent increase in cTn in young players. Twenty male soccer players (age 11.9 ± 2 years, height 151 ± 13 cm, weight 43 ± 13 kg) were monitored during a 5 × 5 small-sided game and had blood samples drawn before, immediately after, and 3 h after exercise for a posterior analysis of high-sensitivity cardiac troponin T (hs-cTnT). Internal, external, and mixed metrics of TL were obtained from the rating of perceived exertion (RPE), heart rate (HR), and GPS player tracking. The results show that the concentration of hs-cTnT peaked at 3 h post-exercise in all participants. The magnitude of hs-cTnT elevation was mainly explained by the exercise duration in the maximal heart rate zone (Maximum Probability of Effect (MPE) = 92.5%), time in the high-speed zone (MPE = 90.4 %), and distance in the high-speed zone (MPE = 90.45%). Our results support the idea that common metrics of TL in soccer, easily obtained using player tracking systems, are strongly associated with the release of hs-cTnT in children and adolescents.


#10 Recreational Football is Medicine against Non-Communicable Diseases: A systematic Review
Reference: Scand J Med Sci Sports. 2019 Dec 13. doi: 10.1111/sms.13611. [Epub ahead of print]
Authors: Sarmento H, Manuel Clemente F, Marques A, Milanovic Z, David Harper L, Figueiredo A
Summary: The purpose of this research was to conduct a systematic review of published articles related to the effect of recreational football on non-communicable diseases. A systematic review of Web of Science, SPORTdiscus, MEDLINE and PubMed databases was performed according PRISMA guidelines. Only empirical studies were included. There were no restrictions on the types of study design eligible for inclusion. The primary outcome measures result from the potential effects of recreational football on non-communicable diseases (e.g., blood pressure, bone density, LDL-Cholesterol, fat mass, etc.). A total of 44 articles met the inclusion criteria and were included. Recreational football is shown to: (1) decrease blood pressure and resting heart rate, improve cardiac structure and functioning, as well as increase maximal oxygen uptake in both sexes; (2) reduce cholesterol and triglycerides levels, increase insulin sensitivity, and have a positive impact on glycaemic control; (3) improve bone mineralization, increase both bone mineral density and content, as well as acting as a stimulus for osteogenesis; (4) be clearly beneficial for bone health, whilst slightly beneficial for body composition, muscle strength and maximal oxygen uptake in adults with prostate cancer. The present systematic review demonstrated the benefits of recreational football practice on non-communicable diseases related to cardiovascular and bone health, body composition, type 2 diabetes and prostate cancer. The effectiveness of recreational football on the aforementioned diseases may be related to age and gender; however, further research is required.

Tue

25

Feb

2020

Latest research in football - week 51 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Effects of Lower-Extremity Plyometric Training on Soccer-Specific Outcomes in Adult Male Soccer Players: A Systematic Review and Meta-Analysis
Reference: Int J Sports Physiol Perform. 2019 Dec 4:1-15. doi: 10.1123/ijspp.2019-0565. [Epub ahead of print]
Authors: van de Hoef PA, Brauers JJ, van Smeden M, Backx FJG, Brink MS.
Summary: Plyometric training is a specific form of strength training that is used to improve the physical performance of athletes. An overview of the effects of plyometric training on soccer-specific outcomes in adult male soccer players is not available yet. The purpose was to systematically review and meta-analyze the effects of plyometric training on soccer-specific outcome measures in adult male soccer players and to identify which programs are most effective. PubMed, Embase/Medline, Cochrane, PEDro, and Scopus were searched. Extensive quality and risk of bias assessments were performed using the Cochrane ROBINS 2.0 for randomized trials. A random effects meta-analysis was performed using Cochrane Review Manager 5.3. Seventeen randomized trials were included in the meta-analysis. The impact of plyometric training on strength, jump height, sprint speed, agility, and endurance was assessed. Only jump height, 20-m sprint speed, and endurance were significantly improved by plyometric training in soccer players. Results of the risk of bias assessment of the included studies resulted in overall scores of some concerns for risk of bias and high risk of bias. This review and meta-analysis showed that plyometric training improved jump height, 20-m sprint speed, and endurance, but not strength, sprint speed over other distances, or agility in male adult soccer players. However, the low quality of the included studies and substantial heterogeneity means that results need to be interpreted with caution. Future high-quality research should indicate whether or not plyometric training can be used to improve soccer-specific outcomes and thereby enhance performance.


#2 The influence of playing position in soccer on the recovery kinetics of cognitive and physical performance
Reference: J Sports Med Phys Fitness. 2019 Nov;59(11):1812-1819. doi: 10.23736/S0022-4707.19.09433-7.
Authors: Nedelec M, Dupont G
Summary: The physical activity and playing actions performed during a soccer match vary according to player position. The aim of the present study was to analyze the recovery kinetics of cognitive performance, physical performance and subjective ratings after a competitive soccer match. Eight goalkeepers and eight outfield players played in the match with data collected before, 45 min, 24 h and 48 h after the match. Subjective ratings, Vienna Reaction Test (reaction time, motor time), Vienna Determination Test (number of stimuli, number of correct responses), squat jump, countermovement jump and 6-s sprint were analyzed. No significant interaction between position and time was found for Vienna Reaction Test and Vienna Determination Test performance. No significant interaction between position and time was found for squat jump and countermovement jump but squat jump and countermovement jump significantly decreased (P<0.01) at 24 h. Countermovement jump performance was still significantly affected at 48h (P<0.05). A significant interaction between position and time (P<0.05) was found for 6-s sprint. Sprint performance was significantly reduced for outfield players only immediately after the match (P<0.01). There was no interaction effect of position and time on subjective ratings. A significant correlation was found between number of jumps and ball kicks performed during the match by goalkeepers and the change score in squat jump (r =-0.90; P<0.01) and countermovement jump (r =-0.90; P<0.01) observed at 48 h. Outfield players require a longer time than goalkeepers to recover sprint performance whilst cognitive function tested in the present study is not affected by the match whatever the position.


#3 Accuracy of the functional movement screen (FMS) active straight leg raise test to evaluate hamstring flexibility in soccer players
Reference: Int J Sports Phys Ther. 2019 Dec;14(6):877-884.
Authors: Medeiros DM, Miranda LLP, Marques VB, de Araujo Ribeiro-Alvares JB, Baroni BM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6878869/pdf/ijspt-14-877.pdf
Summary: Poor flexibility is considered a risk factor for the hamstring strain injury, and the active straight leg raise (ASLR) test proposed as a part of the Functional Movement Screen™ (FMS™) has been used to assess athletes hamstring flexibility. However, the accuracy of this screening test remains undescribed. The purpose was to examine the accuracy of the FMS™ ASLR test for assessment of hamstring flexibility in soccer players. One-hundred and one male soccer players (age, 21 ± 3 years; height, 179 ± 7 cm; weight, 75 ± 9 kg) were bilaterally evaluated. All players performed a gold standard test for hamstring flexibility evaluation: the passive straight leg raise (PSLR) test measured using a gravitational inclinometer. All players also performed the ASLR test and were scored using the criteria proposed by the FMS™. Of the 202 lower limbs evaluated, 17.82% scored a 1 on the ASLR [mean passive flexibility: 80.44 ± 14.69 ° (55 °-110 °)], 50.99% scored a 2 on the ASLR [mean passive flexibility = 84.60 ± 10.59 ° (56 °-115 °)], and 31.18% scored a 3 on the ASLR [mean passive flexibility = 92.32 ± 11.53 ° (70 °-120 °)]. Limbs with FMS™ score of 3 presented significantly higher values for passive flexibility than limbs with scores of 1 and 2 (p < 0.05), but there was no significant difference between limbs with scores of 1 and 2 (p > 0.05). The score obtained in the FMS™ ASLR test does not satisfactorily stratify the level of hamstring flexibility in soccer players.


#4 Workload and Injury in Professional Soccer Players: Role of Injury Tissue Type and Injury Severity
Reference: Int J Sports Med. 2019 Dec 4. doi: 10.1055/a-0997-6741. [Epub ahead of print]
Authors: Enright K, Green M, Hay G, Malone JJ
Summary: The purpose of the present study was to examine the influence of workload prior to injury on injury (tissue type and severity) in professional soccer players. Twenty-eight days of retrospective training data prior to non-contact injuries (n=264) were collated from 192 professional soccer players. Each injury tissue type (muscle, tendon and ligament) and severity (days missed) were categorised by medical staff. Training data were recorded using global positioning system (GPS) devices for total distance (TD), high speed distance (HSD,>5.5 m/s-1), and sprint distance (SPR,>7.0 m/s-1). Accumulated 1, 2, 3, 4-weekly loads and acute:chronic workload ratios (ACWR) (coupled, uncoupled and exponentially weighted moving average (EWMA) approaches) were calculated. Workload variables and injury tissue type were compared using a one-way ANOVA. The association between workload variables and injury severity were examined using a bivariate correlation. There were no differences in accumulated weekly loads and ACWR calculations between muscle, ligament, and tendon injuries (P>0.05). Correlations between each workload variable and injury severity highlighted no significant associations (P>0.05). The present findings suggest that the ability of accumulated weekly workload or ACWR methods to differentiate between injury type and injury severity are limited using the present variables.


#5 Variations of training load, monotony, and strain and dose-response relationships with maximal aerobic speed, maximal oxygen uptake, and isokinetic strength in professional soccer players
Reference: PLoS One. 2019 Dec 4;14(12):e0225522. doi: 10.1371/journal.pone.0225522. eCollection 2019.
Authors: Clemente FM, Clark C, Castillo D, Sarmento H, Nikolaidis PT, Rosemann T, Knechtle B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6892557/pdf/pone.0225522.pdf
Summary: This study aimed to identify variations in weekly training load, training monotony, and training strain across a 10-week period (during both, pre- and in-season phases); and to analyze the dose-response relationships between training markers and maximal aerobic speed (MAS), maximal oxygen uptake, and isokinetic strength. Twenty-seven professional soccer players (24.9±3.5 years old) were monitored across the 10-week period using global positioning system units. Players were also tested for maximal aerobic speed, maximal oxygen uptake, and isokinetic strength before and after 10 weeks of training. Large positive correlations were found between sum of training load and extension peak torque in the right lower limb (r = 0.57, 90%CI[0.15;0.82]) and the ratio agonist/antagonist in the right lower limb (r = 0.51, [0.06;0.78]). It was observed that loading measures fluctuated across the period of the study and that the load was meaningfully associated with changes in the fitness status of players. However, those magnitudes of correlations were small-to-large, suggesting that variations in fitness level cannot be exclusively explained by the accumulated load and loading profile.


#6 A Comparison of Training Modality and Total Genotype Scores to Enhance Sport-Specific Biomotor Abilities in Under 19 Male Soccer Players
Reference: J Strength Cond Res. 2019 Nov 27. doi: 10.1519/JSC.0000000000003299. [Epub ahead of print]
Authors: Suraci BR, Quigley C, Thelwell RC, Milligan GS
Summary: Soccer-specific training (SST) and small-sided games (SSGs) have been shown to develop physical proficiency in soccer. Research on genetics and epigenetics in the prescription of training is limited. The aims of this study were to compare the impact of 3 different SST/SSG methods and investigate if a total genotype score (TGS) influences training response. Subjects (n = 30 male soccer players, mean ± SD; age 17.2 ± 0.9 years, stature = 172.6 ± 6.2 cm; body mass = 71.7 ± 10.1 kg) were stratified into a "power" (PG) or "endurance" (EG) gene profile group, where a 15 single nucleotide polymorphism panel was used to produce an algorithmically weighted TGS. Training 1 (T1-SSGs only), training 2 (T2-SSGs/SST), and training 3 (T3-SST only) were completed (in that respective order), lasting 8 weeks each, interspersed by 4-week washouts. Acceleration (10-m sprint) was improved by T2 only (1.84 ± 0.09 seconds vs. 1.73 ± 0.05 seconds; Effect Size [ES] = 1.59, p < 0.001). Speed (30-m sprint) was improved by T2 (4.46 ± 0.22 seconds vs. 4.30 ± 0.19 seconds; ES = 0.81, p < 0.001) and T3 (4.48 ± 0.22 seconds vs. 4.35 ± 0.21 seconds; ES = 0.58, p < 0.001). Agility (T-test) was improved by T1 (10.14 ± 0.40 seconds vs. 9.84 ± 0.42 seconds; ES = 0.73, p < 0.05) and T3 (9.93 ± 0.38 seconds vs. 9.66 ± 0.45 seconds; ES = 0.66, p < 0.001). Endurance (Yo-Yo level 1) was improved by T1 (1,682.22 ± 497.23 m vs. 2,028.89 ± 604.74 m; ES = 0.63, p < 0.05), T2 (1,904.35 ± 526.77 m vs. 2,299.13 ± 606.97 m; ES = 0.69, p < 0.001), and T3 (1,851.76 ± 490.46 m vs. 2,024.35 ± 588.13 m; ES = 0.35, p < 0.05). Power (countermovement jump) was improved by T3 only (36.01 ± 5.73 cm vs. 37.14 ± 5.62 cm; ES = 0.20, p < 0.05). There were no differences in T1, T2, and T3 combined when comparing PG and EG. The PG reported significantly (χ(20) = 4.42, p = 0.035, ES = 0.48) better training responses to T3 for power than the EG. These results demonstrate the efficacy of SSGs and SSTs in developing biomotor abilities. Although these results refute talent identification through the use of a TGS, there may be use in aligning the training method to TGS to develop power-based qualities in soccer.


#7 To Measure Peak Velocity in Soccer, Let the Players Sprint
Reference: J Strength Cond Res. 2019 Nov 27. doi: 10.1519/JSC.0000000000003406. [Epub ahead of print]
Authors: Kyprianou E, Di Salvo V, Lolli L, Al Haddad H, Villanueva AM, Gregson W, Weston M
Summary: Expressing externals loads relative to a player's individual capacities has potential to enhance understanding of dose-response. Peak velocity is an important metric for the individualization process and is usually measured during a sprint test. Recently, however, peak velocity was reported to be faster during soccer matches when compared with a 40-m sprint test. With the aim of developing the practice of individualized training prescription and match evaluation, we examined whether the aforementioned finding replicates in a group of elite youth soccer players across a broader range of soccer activities. To do this, we compared the peak velocities of 12 full-time male youth soccer players (age 16.3 ± 0.8 years) recorded during a 40-m sprint test with peak velocity recorded during their routine activities (matches, sprints, and skill-based conditioning drills: small-sided games [SSG], medium-sided games [MSG], large-sided games [LSG]). All activities were monitored with 10-Hz global positioning systems (Catapult Optimeye S5, version 7.32) with the highest speed attained during each activity retained as the instantaneous peak velocity. Interpretation of clear between-activity differences in peak velocity was based on nonoverlap of the 95% confidence intervals for the mean difference between activities with sprint testing. Peak velocity was clearly faster for the sprint test (8.76 ± 0.39 m·s) when compared with matches (7.94 ± 0.49 m·s), LSG (6.94 ± 0.65 m·s), MSG (6.40 ± 0.75 m·s), and SSG (5.25 ± 0.92 m·s), but not sprints (8.50 ± 0.36 m·s). Our data show the necessity for 40-m sprint testing to determine peak velocity.


#8 Contribution of Eccentric Strength to Cutting Performance in Female Soccer Players
Reference: J Strength Cond Res. 2019 Nov 28. doi: 10.1519/JSC.0000000000003433. [Epub ahead of print]
Authors: Jones PA, Dos'Santos T, McMahon JJ, Graham-Smith P
Summary: The aim of this study was to examine the contribution of eccentric strength to performance of a 70-90° cutting task (CUT) (time to complete: 5 m approach, 70-90° cut, 3 m exit). Nineteen female soccer players (mean ± SD age, height, and mass; 21.7 ± 4.3 years, 1.67 ± 0.07 m, and 60.5 ± 6.1 kg) from the top 2 tiers of English women's soccer participated in the study. Each player performed 6 trials of the CUT task whereby three-dimensional motion data from 10 Qualisys proreflex cameras (240 Hz) and ground reaction forces from 2 Advanced Mechanical Technology, Inc. force platforms (1,200 Hz) were collected. Relative eccentric knee extensor (ECC-KE) and flexor peak moments (ECC-KF) were collected from both limbs at 60°·s using a Kin-Com isokinetic dynamometer. Hierarchical multiple regression revealed that minimum center of mass (CM) and approach velocities (CM velocity at touchdown of penultimate foot contact) could explain 82% (79% adjusted) of the variation in CUT completion time (F(1,16) = 36.086, p < 0.0001). ECC-KE was significantly (p < 0.05) moderately associated (R ≥ 0.610) with velocities at key instances during the CUT. High (upper 50th percentile) ECC-KE individuals (n = 9) had significantly (p ≤ 0.01; d ≥ 1.34) greater velocities at key instances during the CUT. The findings suggest that individuals with higher ECC-KE produce faster CUT performance, by approaching with greater velocity and maintaining a higher velocity during penultimate and final contact, as they are better able to tolerate the larger loads associated with a faster approach.


#9 Epidemiology of Anterior Cruciate Ligament Injury in Italian First Division Soccer Players
Reference: Sports Health. 2019 Dec 4:1941738119885642. doi: 10.1177/1941738119885642. [Epub ahead of print]
Authors: Grassi A, Macchiarola L, Filippini M, Lucidi GA, Della Villa F, Zaffagnini S
Summary: The burden of anterior cruciate ligament (ACL) injury in professional soccer players is particularly relevant as it represents a potentially career-threatening injury. Our hypotheses were that (1) injury incidence rate would be similar to that reported in the literature, (2) we would identify a uniform distribution of the injuries along the season, and (3) injury incidence rate would be similar in high-ranked and lower ranked teams, based on final placement in the league. Professional male soccer players participating in the Serie A championship league in 7 consecutive seasons (2011-2012 to 2017-2018) were screened to identify ACL injuries through the online football archive transfermarkt.com . Exposure in matches and training were calculated. There were 84 ACL injuries found (mean player age, 25.3 ± 4.2 years). Overall, 25% of ACL injuries were reruptures (15%) or contralateral injuries (10%). ACL incidence rate was 0.4215 per 1000 hours of play during Serie A matches, 0.0305 per 1000 hours of training (rate ratio [RR], 13.8; 95% CI, 8.4-22.7; P < 0.0001), and 0.0618 per 1000 hours of total play. Injury distribution had a bimodal peak, with the highest number of events in October and March. Alternatively, training injuries peaked in June and July. A significantly higher incidence rate was found for the teams ranked from 1st to the 4th place compared with those ranked 5th to 20th (0.1256 vs 0.0559 per 1000 hours of play; RR, 2.2; 95% CI, 1.4-3.6; P = 0.0003). A similar finding was found for injury incidence proportion (3.76% vs 1.64%; P = 0.0003). The overall incidence rate of ACL injuries in Italian Serie A was 0.062 per 1000 hours, with a 14-fold risk in matches compared with training. Relevantly, 25% were second injuries. Most injuries occurred in October and March, and an almost 2-fold incidence rate and incidence proportion were noted in those teams ranked in the first 4 positions of the championship league. Knowing the precise epidemiology of ACL injury in one of the most competitive professional football championship leagues could help delineate fields of research aimed to investigate its risk factors.


#10 Factors Associated With Knee Pain and Heel Pain in Youth Soccer Players Aged 8 to 12 Years
Reference: Orthop J Sports Med. 2019 Nov 20;7(11):2325967119883370. doi: 10.1177/2325967119883370. eCollection 2019 Nov.
Authors: Iwame T, Matsuura T, Suzue N, Iwase J, Uemura H, Sairyo K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6868579/pdf/10.1177_2325967119883370.pdf
Summary: Soccer is played by many children younger than 12 years. Despite its health benefits, soccer has also been linked to a high number of sport-related injuries. The purpose was to investigate the relationship between clinical factors and knee or heel pain in youth soccer players. Study participants included 602 soccer players aged 8 to 12 years who were asked whether they had experienced episodes of knee or heel pain. Data were collected on age, body mass index, years of playing soccer, playing position, and training hours per week. Associations of clinical factors with the prevalence of knee or heel pain were examined by univariate and multivariate logistic regression analyses. Episodes of knee and heel pain were reported by 29.4% and 31.1% of players, respectively. Multivariate analyses revealed that older age and more years of playing soccer were significantly and positively associated with the prevalence of knee pain (P = .037 and P = .015 for trend, respectively) but did not identify any significant associations for heel pain. In this study of youth soccer players, knee pain was associated with older age and more years of play, but heel pain was not significantly associated with any factor.


#11 Intra- and Post-match Time-Course of Indicators Related to Perceived and Performance Fatigability and Recovery in Elite Youth Soccer Players
Reference: Front Physiol. 2019 Nov 15;10:1383. doi: 10.3389/fphys.2019.01383. eCollection 2019.
Authors: Kunz P, Zinner C, Holmberg HC, Sperlich B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874152/pdf/fphys-10-01383.pdf
Summary: Our aims were to examine (i) the internal load during simulated soccer match-play by elite youth players; and (ii) the time-course of subsequent recovery from perceived and performance fatigability. Eleven male youth players (16 ± 1 years, 178 ± 7 cm, 67 ± 7 kg) participated in a 2 × 40-min simulated soccer match, completing 30 rounds (160 s each) with every round including multidirectional and linear sprinting (LS20m), jumping (CMJ) and running at different intensities. During each round, LS20m, CMJ, agility, heart rate (HR), oxygen uptake (VO2), energy expenditure (EE), substrate utilization and perceived exertion RPE were assessed. In addition, the blood level of lactate (Lac) was obtained after each of the five rounds. Creatine kinase (CK) concentration, maximal voluntary isometric knee extension and flexion, CMJ, number of skippings in 30 s, and subjective ratings on the Acute Recovery and Stress Scale (ARSS) were examined before and immediately, 24 and 48 h after the simulation. During the game %HRpeak (p < 0.05, d = 1.08), %VO2 peak (p < 0.05; d = 0.68), Lac (p < 0.05, d = 2.59), RPEtotal (p < 0.05, d = 4.59), and RPElegs (p < 0.05, d = 4.45) all increased with time during both halves (all p < 0.05). Agility improved (p < 0.05, d = 0.70) over the time-course of the game, with no changes in LS20m (p ≥ 0.05, d = 0.34) or CMJ (p ≥ 0.05, d = 0.27). EE was similar during both halves (528 ± 58 vs. 514 ± 61 kcal; p = 0.60; d = 0.23), with 62% (second half: 65%) carbohydrate, 9% (9%) protein and 26% (27%) fat utilization. With respect to recovery, maximal voluntary knee extension (p ≥ 0.05, d = 0.50) and flexion force (p ≥ 0.05, d = 0.19), CMJ (p ≥ 0.05, d = 0.13), number of ground contacts (p ≥ 0.05, d = 0.57) and average contact time (p ≥ 0.05, d = 0.39) during 30-s of skipping remained unaltered 24 and 48 h after the game. Most ARSS dimensions of load (p < 0.05, d = 3.79) and recovery (p < 0.05, d = 3.22) returned to baseline levels after 24 h of recovery. Relative to baseline values, CK was elevated immediately and 24 h after (p < 0.05, d = 2.03) and normalized 48 h later. In youth soccer players the simulated match evoked considerable circulatory, metabolic and perceptual load, with an EE of 1042 ± 118 kcal. Among the indicators of perceived and performance fatigability examined, the level of CK and certain subjective ratings differed considerably immediately following or 24-48 h after a 2 × 40-min simulated soccer match in comparison to baseline. Accordingly, monitoring these variables may assist coaches in assessing a U17 player's perceived and performance fatigability in connection with scheduling training following a soccer match.


#12 Injury Incidence and Workloads during congested Schedules in Football
Reference: Int J Sports Med. 2019 Dec 2. doi: 10.1055/a-1028-7600. [Epub ahead of print]
Authors: Howle K, Waterson A, Duffield R
Summary: This study compared injury incidence and training loads between single and multi-match weeks, and seasons with and without congested scheduling. Measures of internal (session-Rating of Perceived Exertion × duration for training/match and % maximal heart rate) and external load (total, low-, high-, and very high-intensity running distances) along with injury incidence rates were determined from 42 players over 3 seasons; including 1 without and 2 (season 2 and 3) with regular multi-match weeks. Within-player analyses compared 1 (n=214) vs. 2-match (n=86) weeks (>75min in matches), whilst team data was compared between seasons. Total injury rates were increased during multi-match weeks (p=0.001), resulting from increased match and training injuries (50.3, 16.9/1000h). Between-season total injury rates were highest when congested scheduling was greatest in season 3 (27.3/1000h) and season 2 (22.7/1000h) vs. season 1 (14.1/1000h; p=0.021). All external load measures were reduced in multi-match weeks (p<0.05). Furthermore, all internal and external training loads were lowest in seasons with congestion (p<0.05). In conclusion, increased injury rates in training and matches exist. Total loads remain comparable between single and multi-match weeks, though reduce in congested seasons. Whether injuries result from reduced recovery, increased match exposure or the discreet match external loads remain to be elucidated.

Mon

17

Feb

2020

Latest research in football - week 50 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Analysis of Physical Demands during Youth Soccer Match-play: Considerations of Sampling Method and Epoch Length
Reference: Res Q Exerc Sport. 2019 Nov 27:1-9. doi: 10.1080/02701367.2019.1669766. [Epub ahead of print]
Authors: Doncaster G, Page R, White P, Svenson R, Twist C
Summary: The purpose of this study was to examine the physical match profiles of professional soccer players using 3 and 5 min fixed and rolling averages as well as fixed 1 min averages, with considerations to training prescription. Twenty-nine professional U23 soccer outfield players competed across 17 competitive matches during the 2017/18 season, equating to a total of 130 separate physical match profiles. Match activities were recorded using global positioning system (GPS) devices with integrated micro-electrical mechanical systems (MEMS), recording total distance (TD), high-speed running (HSR), and metabolic power (MP). For each individual match profile and variable, 1, 3, and 5 min peak, post-peak, and average values were calculated using fixed-time epochs (FIXED) and rolling averages (ROLL). Linear mixed models were employed to examine the differences in the dependent variables as a function of the method of measurement. Results revealed significantly higher peak values, for relative TD, relative HSR and relative MP when employing the ROLL sampling method, in comparison to the FIXED method, for both 3 min and 5 min epoch lengths. Analysis of epoch length revealed significantly higher peak values, across all positions, for relative TD, relative HSR and MP for 1 min epochs, in comparison to 3 min and 5 min epochs. The data offers a novel insight into the appropriate identification of physical demands during youth soccer match-play. Researchers and practitioners should consider the sampling method and epoch length when assessing the physical demands of competitive match-play, as well as when designing and prescribing sport-specific conditioning drills.


#2 Maturity offset affects standing postural control in youth male soccer players
Reference: J Biomech. 2019 Nov 18:109523. doi: 10.1016/j.jbiomech.2019.109523. [Epub ahead of print]
Authors: Zago M, Moorhead AP, Bertozzi F, Sforza C, Tarabini M, Galli M
Summary: Quantifying the response of postural control in developmental athletes makes it possible to understand critical coordination and learning phases and to improve technical-physical interventions. However, the influence of maturation on postural control amongst young soccer players has neither been tested using quantitative methods, nor over a wide age range. In this study, we examined stabilometric parameters of 238 young male soccer players from 9 to 17 years old relative to maturity offset. Two 30-s tests (eyes open and eyes closed) were recorded on a baropodometric platform at 50 Hz. Participants were split into six groups according to their maturity offset, expressed as years from individual's peak height velocity. Dependent variables were: Sway Area, Center-of-Pressure velocity, standard deviation of the antero-posterior and medio-lateral Center-of-Pressure trajectory, Romberg Quotient. Sway Area was significantly higher in players with maturity offset <-1.5 than in groups with maturity offset > 0.5 years (p < 0.001, large effect). Center-of-Pressure velocity markedly dropped in players with maturity offset >-0.5 years (p < 0.001, very large effect). Antero-posterior standard deviation was higher before than after peak height velocity (p < 0.05, large effect) and significantly higher with closed eyes at some points. Medio-lateral standard deviation was higher in the youngest group of players (maturity offset <-2.5 years, large effect) than in those with maturity offset >-0.5 years. In sum, stabilometric parameters improved with age until zero maturity offset was achieved. Thereafter, variables describing postural control in developing soccer players were almost stable. No evidence of a changing role of vision in postural sway control during maturation was observed.


#3 Effect of pre-season training phase on anthropometric, hormonal and fitness parameters in young soccer players
Reference: PLoS One. 2019 Nov 25;14(11):e0225471. doi: 10.1371/journal.pone.0225471. eCollection 2019.
Authors: Perroni F, Fittipaldi S, Falcioni L, Ghizzoni L, Borrione P, Vetrano M, Del Vescovo R, Migliaccio S, Guidetti L, Baldari C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0225471&type=printable
Summary: The aims of the study were to investigate 1) the effect of 8 weeks of PSP training on anthropometrics, salivary hormones and fitness parameters in youth soccer players, 2) the correlations between fitness and hormonal parameters, and 3) the impact of the experience of the coach and his methodology of training on these parameters. Weight, height, BMI, pubertal development (PDS), salivary Cortisol (sC), salivary Testosterone (sT), salivary sDHEAS, intermittent tests (VO2max), and countermovement jump test (CMJ) modifications of 35 youth soccer players (age: 14±0 yrs; BMI: 20.8±1.8 k/m2) from two Italian clubs ("Lupa Frascati" -LF-; "Albalonga" -AL) were analysed. A significant (p<0.05) time by club effect was observed in sC (F(1,31) = 9.7, ES = 1.13), sT (F(1,31) = 4.2, ES = 0.74), CMJ (F(1,28) = 26.5, ES = 1.94), and VO2max (F(1,28) = 8.5, ES = 1.10). Statistical differences (p<0.05) in weight (F(1,32) = 25.5, ES = 0.11), sC (F(1,31) = 32.1, ES = 1.43), sT/sC ratio (F(1,31) = 10.1, ES = 0.97), sDHEAS/sC ratio (F(1,31) = 6.3, ES = 0.70), and VO2max (F(1,28) = 64.3, ES = 1.74) were found within time factor. Between clubs, differences (p<0.05) in sC (F(1,32) = 8.5, ES = 1.17), sT (F(1,31) = 4.2, ES = 0.74), CMJ (F(1,28) = 26.5, ES = 1.50), and VO2max (F(1,28) = 8.5, ES = 1.10) were found. CMJ was inversely correlated with sDHEAS (r = -0.38) before PSP, while Δ of CMJ showed significant correlations with Δ of sC (r = 0.43) and ΔVO2max was inversely correlated with ΔBMI (r = -0.54) and ΔsC (r = -0.37) in all subjects. Considering each single club, ΔVO2max showed correlations with ΔBMI (r = -0.45) in AL, while ΔCMJ showed correlations with ΔPDS (r = 0.72) in LF club. Since the PSP is often limited training time to simultaneously develop physical, technical and tactical qualities, an efficient method to distribute the training load is important in youth soccer players to increase the performance and to avoid injuries.


#4 Relationship Between Repeated Sprint Ability, Aerobic Capacity, Intermittent Endurance, and Heart Rate Recovery in Youth Soccer Players
Reference: J Strength Cond Res. 2019 Dec;33(12):3406-3413. doi: 10.1519/JSC.0000000000002193.
Authors: Rodríguez-Fernández A, Sanchez-Sanchez J, Ramirez-Campillo R, Nakamura FY, Rodríguez-Marroyo JA, Villa-Vicente JG
Summary: The purpose was to investigate the relationship between repeated sprint ability (RSA) and several aerobic and anaerobic-related soccer-performance indicators, 45 youth soccer players (age 16.8 ± 0.1 years) were classified into "high" (HAF) or "low" aerobic fitness (LAF) (VO2max ≥ or <60 ml·kg·min, respectively) and completed an RSA test measuring best (RSAbest), mean (RSAmean), total sprint time (RSAtotal), and percent sprint decrement (Sdec). A laboratory VO2max test (LabTest) together with anaerobic threshold (VT) and peak speed was measured (vLabTest). In addition, a 20-m multistage shuttle run test (MSRT) and a soccer-specific test (TIVRE-Soccer test-TST) were completed. Heart rate (HR) and HR recovery (HRR) were measured during all tests. High aerobic fitness presented greater (p ≤ 0.05) performance in LabTest, MSRT and TST, at maximal effort, at VT, as well as faster HRR. RSA was similar between HAF and LAF. Contrary to HAF, LAF showed negative correlation between vLabTest with RSAmean (r = -0.6, p = 0.000) and Sdec (r = -0.4, p = 0.044). Also, LAF showed negative correlation between TST end speed (vTST) and RSAmean (r = -0.5, p = 0.005) and Sdec (r = -0.5, p = 0.003). In LAF, RSA was strongly correlated with locomotor factors (e.g., vTST; VT) in both laboratory and field tests. Athletes with high total HRR (>12.5%) in TST presented better (p ≤ 0.05) Sdec in the RSA test. The multiple regression revealed that the LAF vLabTest explained 44.9, 40.0, and 13.5% of the variance in RSAbest, RSAmean, and Sdec, respectively. Practitioners may consider these findings to optimize youth athletes' assessment and preparation processes.


#5 Workload efficiency as a new tool to describe external and internal competitive match load of a professional soccer team: A descriptive study on the relationship between pre-game training loads and relative match load
Reference: Eur J Sport Sci. 2019 Nov 25:1-17. doi: 10.1080/17461391.2019.1697374. [Epub ahead of print]
Authors: Grünbichler J, Federolf P, Gatterer H
Summary: The current study introduces a new index for external and internal workload, "workload efficiency", and assesses in professional soccer the influence of pre-match training load on match workload efficiency. External and internal workloads were determined for 44 training sessions and 16 competitive matches using a 10-Hz global positioning system (GPS) and a 200-Hz accelerometer/heart rate monitor. Training loads were registered from day five (D-5) to day one (D-1) prior to each competitive match. Workload efficiency was calculated for each match as the ratio between overall external and internal load. A multiple stepwise regression analysis (including z-transformed variables) was used to determine training load variables that predict workload efficiency of the following matches. Training load variables of the previous days explained 26.6% of the variance in workload efficiency during the following matches. Long sprinting distance on D-3 and D-4 and total distance on D-1 positively influenced the players' workload efficiency, whereas long training durations and high training load on D-1 showed adverse effects. The present outcomes suggest that including sprint training (high sprinting distance) four and three days prior to a match, may provide a positive stimulus for the subsequent workload efficiency in matches. The negative impact of long training duration and high training load one day before the game highlights the importance of a diligent planning of the immediate competition preparation phase. This study shows that workload efficiency is a useful metric to assess match performance and that body-worn sensor technology can be useful for tailoring training loads.


#6 Contribution of lower body segment rotations in various height soccer volley kicking
Reference: Sports Biomech. 2019 Nov 25:1-16. doi: 10.1080/14763141.2019.1667422. [Epub ahead of print]
Authors: Sugi S, Nunome H, Tamura Y, Iga T, Lake M
Summary: We aimed to quantify the contribution of lower body segment rotations in producing foot velocity during the soccer volley kick. Fifteen male experienced university players kicked a soccer ball placed at four height conditions (0, 25, 50 and 75 cm). Their kicking motion was captured at 500 Hz. The effectiveness of lower body segment rotations in producing forward (Ffv) and upward (Fuv) foot velocity were computed and time integrated. Major contributors for Ffv were a) left hip linear velocity, b) knee extension and c) pelvis retroflexion (the pitch rotation). The contribution of a) become smaller as the ball height increased while those of b) and c) did not change significantly. Moreover, the pelvis clockwise rotation (the yaw rotation) showed apparent contribution only for volley kicking (except 0 cm height). Major contributors for Fuv were 1) knee flexion, 2) hip internal rotation, 3) pelvis clockwise rotation (the roll rotation) and 4) hip flexion. The contributions of 1) and 4) become consistently smaller as the ball height increased, while those of 2) and 3) become larger systematically. Soccer volley kicking was found to have unique adaptations of segmental contributions to achieve higher foot position while maintain foot forward velocity.


#8 Physical capacity, not skeletal maturity, distinguishes competitive levels in male Norwegian U14 soccer players
Reference: Scand J Med Sci Sports. 2019 Oct 12. doi: 10.1111/sms.13572. [Epub ahead of print]
Authors: Grendstad H, Nilsen AK, Rygh CB, Hafstad A, Kristoffersen M, Iversen VV, Nybakken T, Vestbøstad M, Algrøy EA, Sandbakk Ø, Gundersen H
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13572
Summary: The main aim of the present study was to compare skeletal maturity level and physical capacities between male Norwegian soccer players playing at elite, sub-elite and non-elite level. Secondary, we aimed to investigate the association between skeletal maturity level and physical capacities. One hundred and two U14 soccer players (12.8-14.5 years old) recruited from four local clubs, and a regional team were tested for bone age and physical capacities. Bone age was estimated with x-ray of their left hand and used to indicate maturation of the skeleton. Players went through a comprehensive test battery to assess their physical capacities. Between-groups analysis revealed no difference in chronological age, skeletal maturity level, leg strength, body weight, or stature. However, elite players were superior to sub-elite and non-elite players on important functional characteristics as intermittent-endurance capacity (running distance: 1664 m ± 367 vs 1197 m ± 338 vs 693 m ± 235) and running speed (fastest 10 m split time: 1.27 seconds ± 0.06 vs 1.33 seconds ± 0.10 vs 1.39 seconds ± 0.11), in addition to maximal oxygen uptake ( VO2max ), standing long jump, and upper body strength (P < .05 for all comparisons). Medium-to-large correlations were found between skeletal maturity level and peak force (r = 695, P < .01), power (r = 684, P < .01), sprint (r = -.471, P<.001), and jump performance (r = .359, P < .01), but no correlation with upper body strength, VO2max , or intermittent-endurance capacity. These findings imply that skeletal maturity level does not bias the selection of players, although well-developed physical capacity clearly distinguishes competitive levels. The superior physical performance of the highest-ranked players seems related to an appropriate training environment.


#9 Incidence of injuries among professional football players in Spain during three consecutive seasons: A longitudinal, retrospective study
Reference: Phys Ther Sport. 2019 Nov 19;41:87-93. doi: 10.1016/j.ptsp.2019.11.008. [Epub ahead of print]
Authors: Torrontegui-Duarte M, Gijon-Nogueron G, Perez-Frias JC, Morales-Asencio JM, Luque-Suarez A
Download link: https://reader.elsevier.com/reader/sd/pii/S1466853X19304250?token=A205FA12B1E4D0FE059F31870B57FF709CFC4E84B429CB4451FE37D08CEEABF1DDC17FE35DEA18E2C4EE9C25499FFCEA
Summary: The aim of the study was to determine risk factors that maybe be associated with a higher incidence of injuries in elite football players in the Spanish league during a three-year follow-up. Injury was defined as a musculoskeletal complaint (pain and/or discomfort) reported by players to the medical staff and receiving medical attention.  Seventy-one players from Malaga Football Club, who were in the first squad team for three consecutive seasons participated in this study. Incidence, location, severity of injuries were reported according to the Injury Consensus Group for football injuries. Three hundred and fifty six injuries were found, with the highest proportion (44%) being located in the thigh. We found 6.9 (SD 5.87) injuries per 1000 h of match time and 0.23 (SD 0.22) per 1000 h of training. Forwards presented the highest rates in both incidence and severity of injury. Exposure to training was inversely related to the total number of injuries, which means that the greater the exposure to training the lesser the number of injuries. This information can assist clinicians in the identification of risk factors and, thus, the elaboration of prevention programmes that reduce football injuries.


#10 An Extensive Comparative Analysis of Successful and Unsuccessful Football Teams in LaLiga
Reference: Front Psychol. 2019 Nov 8;10:2566. doi: 10.3389/fpsyg.2019.02566. eCollection 2019.
Authors: Brito de Souza D, López-Del Campo R, Blanco-Pita H, Resta R, Del Coso J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856952/pdf/fpsyg-10-02566.pdf
Summary: The characterization of the in-game actions with the strongest influence on victory in football might be useful for designing playing styles that enhance teams' performance. The aim of this study was to analyze in-game match statistics on the top-3 and bottom-3 teams ranked in LaLiga. Accumulated offensive and defensive match statistics when playing at home and away were obtained from LaLiga for 8 consecutive seasons. Data extraction was performed by computerized video-analysis. The top-3 and bottom-3 teams were compared using independent t-test analysis and the magnitude of the difference was cataloged with effect sizes. Overall, the offensive variable with the greatest magnitude of difference in the top-3 vs. bottom-3 comparison was shooting accuracy (ES ± 90% confidence interval = 4.15 ± 0.52) followed by the number of offsides (2.25 ± 0.60) and corners (2.14 ± 0.61). However, when playing away, the offensive variable with the greatest magnitude of difference in the top-3 vs bottom-3 comparison was the number of shots (3.30 ± 0.44). The defensive variables that best differentiated top 3 - bottom 3 teams were the number of corners (2.16 ± 0.43) and shots conceded (2.04 ± 0.39). In conclusion, the match statistics that best discriminated successful from unsuccessful football teams were shooting accuracy while attacking and the number of shots conceded while defending.


#11 Submaximal field testing validity for aerobic fitness assessment in recreational football
Reference: Scand J Med Sci Sports. 2019 Nov 27. doi: 10.1111/sms.13606. [Epub ahead of print]
Authors: Cristina Araújo Póvoas S, Krustrup P, Castagna C
Summary: Submaximal field tests are especially recommended when repeated testing is warranted. This study aimed at assessing the validity of the submaximal versions of the Yo-Yo intermittent tests in male recreational football players in untrained and trained status. The participants' (n=66; age 39.3±5.8 years, VO2max 41.2±6.2 ml·kg-1 ·min-1 , body mass 81.9±10.8 kg, height 173.2±6.4 cm) heart rate after 2 min (HR2min ) during the level 1 (YYIE1HR2min ) and 2 (YYIE2HR2min ) versions of the Yo-Yo intermittent endurance test and the level 1 version of the Yo-Yo intermittent recovery test (YYIRHR2min ) was plotted against individual VO2max values. Thirty-two participants performed all the tests after a 12-week recreational football intervention for test responsiveness. Associations between VO2max and YYIE1HR2min were large to small (P=0.0001). Large to trivial associations were found between YYIE2HR2min , YYIR1HR2min and VO2max (P<0.01). Maximal Yo-Yo performances were large, significant and inversely related to HR2min (-0.68 to -0.49, P<0.0001). Pre-to-post-intervention ICC values were good for YYIE1HR2min and YYIE2HR2min , and excellent for YYIR1HR2min . Post-intervention associations between HR2min and Yo-Yo maximal performances were large to very large (-0.55 to -0.72; P<0.002, n=32). Training-induced changes in VO2max moderately correlated with YYR1HR2min (-0.48; P=0.007; n=32). HR2min lower than 89%, 98% and 91%HRmax for YYIE1HR2min , YYIE2HR2min and YYIR1HR2min , respectively, may be considered as signs of good to excellent VO2max levels. Since in the YYIE1HR2min , the participants attained 84%HRmax and test specificity increased for HR2min values <89%, this test may be the preferred choice when repeated assessment of aerobic fitness, using submaximal intermittent Yo-Yo tests, is considered in recreational football.

Fri

14

Feb

2020

Latest research in football - week 49 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Football as a Health Promotion Strategy
Reference: Dtsch Arztebl Int. 2019 Oct 25;116(43):721-728. doi: 10.3238/arztebl.2019.0721.
Authors: Eberl M1, Tanaka LF, Klug SJ, Adamek HE.
Download links: https://www.aerzteblatt.de/pdf.asp?id=210459
Summary: Football training can be a primary prevention strategy to reach people who otherwise would not be physically active. This systematic review summarizes the evidence on the health effects of controlled recreational football training as an intervention in children, adolescents, adults and the elderly. A systematic review (PROSPERO record CRD42018083665) of the literature was carried out in MEDLINE, Cochrane, Scopus, and SPORTDiscus databases to identify randomized and non-randomized intervention studies in which healthy individuals of any age participated in controlled football training and were investigated for health outcomes related to prevention of obesity, hypertension, diabetes mellitus, and cardiovascular disease. The studies included-14 randomized and three non-randomized intervention studies-have sample sizes too small for reliable statistical analysis and bear a considerable risk of systematic bias. The evidence of positive effects of playing football is limited to short-term loss of body fat and improvement in aerobic fitness. For all other health outcomes, no conclusive results were found. A considerable number of intervention studies reporting on football-based intervention programs have been published, and there is a widespread assumption that such programs have positive health effects. However, this systematic review shows that the empirical evidence is insufficient to permit such a conclusion.


#2 Methods to collect and interpret external training load using microtechnology incorporating GPS in professional football: a systematic review
Reference: Res Sports Med. 2019 Nov 22:1-22. doi: 10.1080/15438627.2019.1686703. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Costa J, Barreira D, Krustrup P, Rebelo A
Summary: The aim of this article was to systematically review the methods adopted to collect and interpret external training load (ETL) using microtechnology incorporating global positioning system (GPS). The main deficiencies identified concerned the non-collection of match ETL, and the non-consideration of potential confounders (e.g. playing position, fitness level, starting status or session content). Also, complementary training (individual/reconditioning) and pre-match warm-up were rarely quantified. To provide a full picture of the training demands, ETL was commonly complemented by internal training load monitoring with the rating of perceived exertion predominantly adopted instead of heart rate recordings. Continuous data collection and interpretation of ETL data in professional football vary widely between observational studies, possibly reflecting the actual procedures adopted in practical settings. Evidence about continuous ETL monitoring in female players, and female as well as male goalkeepers is lacking.


#3 Psychological factors and future performance of football players: A systematic review with meta-analysis
Reference: J Sci Med Sport. 2019 Nov 1. pii: S1440-2440(19)30559-6. doi: 10.1016/j.jsams.2019.10.021. [Epub ahead of print]
Authors: Ivarsson A, Kilhage-Persson A, Martindale R, Priestley D, Huijgen B, Ardern C, McCall A
Summary: This systematic review had 3 key objectives: (1) to investigate whether psychological factors were associated with future football performance (e.g., progression to professional football, better game statistics during the next season); (2) to critically review the methodological approaches used in the included studies and summarize the evidence for the current research question; (3) to provide guidelines for future studies. Electronic databases (SPORTDiscus, PubMed and PsycINFO) and previously published systematic and scoping reviews were searched. Only prospective studies were considered for inclusion. Eleven published studies that reported 39 effect sizes were included. Psychological factors; task orientation, task-oriented coping strategies and perceptual-cognitive functions had small effects on future performance in football (ds=0.20-0.29). Due to high risk of bias there were low certainty of evidence for psychological factors relationship with future football performance. Psychological factors investigated showed small effects on future football performance, however, there was overall uncertainty in this evidence due to various sources of bias in the included studies. Therefore psychological factors cannot be used as a sole deciding factor in player recruitment, retention, release strategies, however it would appear appropriate to include these in the overall decision-making process. Future, studies with more appropriate and robust research designs are urgently needed to provide more certainty around their actual role.


#4 Physical preparation and return to sport of the football player with a tibia-fibula fracture: applying the 'control-chaos continuum'
Reference: BMJ Open Sport Exerc Med. 2019 Oct 30;5(1):e000639. doi: 10.1136/bmjsem-2019-000639. eCollection 2019.
Authors: Taberner M, van Dyk N, Allen T, Richter C, Howarth C, Scott S, Cohen DD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6830476/pdf/bmjsem-2019-000639.pdf
Summary: Contact in elite football can result in severe injury such as traumatic fracture. Limited information exists regarding the rehabilitation and return to sport (RTS) of these injuries especially in elite football. We outline the RTS of an elite English Premier League footballer following a tibia-fibula fracture including gym-based physical preparation and the use of 'control-chaos continuum' as a framework for on-pitch sport-specific conditioning, development of technical skills while returning the player to pre-injury chronic running loads considering the qualitative nature of movement in competition. Strength and power diagnostics were used to back up clinical reasoning and decision-making throughout rehabilitation and the RTS process. The player returned to full team training after 7.5 months, completed 90 min match-play after 9 months and remains injury-free 11 months post-RTS.


#5 The Attacking Process in Football: A Taxonomy for Classifying How Teams Create Goal Scoring Opportunities Using a Case Study of Crystal Palace FC
Reference: Front Psychol. 2019 Oct 16;10:2202. doi: 10.3389/fpsyg.2019.02202. eCollection 2019.
Authors: Kim J, James N, Parmar N, Ali B, Vučković G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6843076/pdf/fpsyg-10-02202.pdf
Summary: Whilst some studies have comprehensively described the different features associated with the attacking process in football they have not produced a methodology of practical use for performance enhancement. This study presents a framework of comprehensive and meaningful metrics to objectively describe the attacking process so that useful performance profiles can be produced. The attacking process was categorized into three independent situations, no advantage (stable), advantage, and unstable (potential goal scoring opportunity) situations. Operational definitions for each situation enhanced their reliability and validity. English Premier League football matches (n = 38) played by Crystal Palace Football Club in the 2017/2018 season were analyzed as an exemplar. Crystal Palace FC created a median of 53.5 advantage situations (IQR = 16.8) and 23 unstable situations (IQR = 8.8) per match. They frequently utilized wide areas (Median = 21.5, IQR = 9.8) to progress, but only 26.6% resulted in unstable situations (Median = 6.0, IQR = 3.8), the lowest rate compared to the other advantage situations. This classification framework, when used with contextual factors in a multi-factorial manner, including individual player contributions, will provide practically useful information for applied practice. This approach will help close the so called theory-practice gap and enable academic rigor to inform practical problems.


#6 Recovery Kinetics After Speed-Endurance Training in Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Nov 21:1-14. doi: 10.1123/ijspp.2018-0984. [Epub ahead of print]
Authors: Tzatzakis T, Papanikolaou K, Draganidis D, Tsimeas P, Kritikos S, Poulios A, Laschou VC, Deli CK, Chatzinikolaou A, Batrakoulis A, Basdekis G, Mohr M, Krustrup P, Jamurtas AZ, Fatouros IG.
Summary: The purpose was to determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72 h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3 h posttraining. Fatigue increased (P < .05) in SEPT/1:5 (∼4-30%) for 3 h and in SEPT/1:8 (∼8-17%) for 2 h. Strength performance declined (P < .05) in both SEPT trials (∼5-20%) for 48 h. Speed decreased (∼4-18%; P < .05) for 72 h in SEPT/1:5 and for 48 h in SEPT/1:8. Countermovement-jump performance decreased (∼7-12%; P < .05) in both SEPT trials for 24 h. DOMS increased (P < .05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48 h. Creatine kinase increased (∼1- to 2-fold, P < .05) in both SEPT trials for 72 h. SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48 h), speed (72 h), and jump performance (24 h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics.


#7 Effect of opposition quality and match location on the positional demands of the 4-2-3-1 formation in elite soccer
Reference: J Exerc Sci Fit. 2020 Jan;18(1):40-45. doi: 10.1016/j.jesf.2019.11.001. Epub 2019 Nov 3.
Authors: Paraskevas G, Smilios I, Hadjicharalambous M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849351/pdf/main.pdf
Summary: The present study examined the influence of match location, quality of opposition team, and playing position on physical performance indicators of the 4-2-3-1 formation. Twenty-six (n = 26) games (with 184 player-observations; n = 17 players, played full 90 min games) were recorded with a video system and the physical demands of the players were analyzed according to their specific playing position (classified into central and wide defenders, central and wide midfielders and forwards). Match performance variables analyzed included total distance (TD), high-intensity running (HIR), very-high-intensity running (VHIR) and sprinting (SPR). There was a main effect of position for TD (F = 37.84, p < 0.001), HIR (F = 41.19, p < 0.001), VHIR (F = 27.89, p < 0.001) and SPR (F = 22.25, p < 0.001). Wide defenders covered the most SPR and -along with the central midfielders-the most VHIR. Central midfielders covered the most TD and HIR. Match location and opposition quality had interactive effects on TD (F = 12.96, p < 0.001), HIR (F = 8.33 p = 0.004) and VHIR (F = 8.17 p = 0.005). Competing against "weak" opponents, more TD, HIR and VHIR covered during home games compared to away games (p < 0.05). However, more TD was covered during away games against "strong" opponents compared to away games against "weak" opponents (p < 0.05). The current study supports more intense-based drills (i.e. repeated sprint training) for wide defenders and more volume-based drills (i.e. long interval training) for central midfielders, whilst total weekly training load can be adjusted based on match location and quality of oppositions on the anticipated game-load.


#8 Effects of Two Competitive Soccer Matches on Landing Biomechanics in Female Division I Soccer Players
Reference: Sports (Basel). 2019 Nov 14;7(11). pii: E237. doi: 10.3390/sports7110237.
Authors: Snyder BJ, Hutchison RE, Mills CJ, Parsons SJ
Download link: https://www.mdpi.com/2075-4663/7/11/237/pdf
Summary: Fatigue has been proposed to increase the risk of knee injury. This study tracked countermovement jump, knee isometric strength, and kinetics and kinematics in 8 female soccer players (experimental group) during an anticipated sidestep maneuver before and after two matches played over a 43-h period. Time points were: Before and after match 1 (T0 and T1), 12 h after the first match (T2), and immediately after the second match (T3). A control group participated only in practice sessions. Isometric knee extension strength decreased by 14.8% at T2 (p = 0.003), but knee flexion was not affected until T3, declining by 12.6% (p = 0.018). During the sidestep maneuver, knee joint degrees of flexion at initial contact was increased by 17.1% at T3, but maximum knee and hip angle at initial contact were unchanged. Peak resultant ground reaction force (GRF) increased by 12.6% (p = 0.047) at T3 (3.03 xBW) from 2.69 xBW at T0, while posterior GRF was significantly higher than T0 at all three subsequent time points (T1 = 0.82 ± 0.23 xBW, T2 = 0.87 ± 0.22 xBW, T3 = 0.89 ± 0.22 xBW). Anterior tibial shear force increased significantly (p = 0.020) at T3 (1.24 ± 0.12 xBW) compared to T1 (1.15 ± 0.13 xBW), an 8.8% increase. Lateral tibial shear force was significantly higher at both T1 (0.95 ± 0.20 xBW) and T3 (1.15 ± 0.38 xBW) compared to T0 (0.67 ± 0.25 xBW). These findings suggest that participation in a soccer match has significant effects on both physical performance parameters and kinetics/kinematics during a sidestep cut, but these can be more pronounced after a second match with short rest.


#9 Higher neck strength is associated with lower head acceleration during purposeful heading in soccer: A systematic review
Reference: J Sci Med Sport. 2019 Nov 12. pii: S1440-2440(19)30660-7. doi: 10.1016/j.jsams.2019.11.004. [Epub ahead of print]
Authors: Peek K, Elliott JM, Orr R
Summary: The purpose was to systematically review the literature to investigate the potential relationship between neck strength and head acceleration during purposeful heading in soccer. Comprehensive search of five electronic databases: EMBASE, MEDLINE, CINAHL, SportsDiscus and Web of Science. Studies were included if they reported data on the relationship between neck strength and head impact and/or acceleration during purposeful soccer heading, published in English (or translation available). From an initial search of 1174 potentially eligible papers, five cross-sectional studies met the eligibility criteria for inclusion in this review. Data from cross-sectional studies indicate that higher neck strength is associated with lower head acceleration during purposeful heading in soccer (p=<0.05; r<-0.5). This review provides evidence that higher neck strength may lower head acceleration during purposeful heading in soccer. Further research is required to determine the most effective method to strengthen the neck musculature in soccer players.


#10 Superior cardiac mechanics without structural adaptations in pre-adolescent soccer players
Reference: Eur J Prev Cardiol. 2019 Nov 28:2047487319890177. doi: 10.1177/2047487319890177. [Epub ahead of print]
Authors: Beaumont A, Oxborough D, George K, Rowland TW, Sculthorpe N, Lord R, Unnithan VB
Summary: This study aimed to evaluate left ventricular structure, function and mechanics, in highly-trained, pre-adolescent soccer players compared with age- and sex-matched controls. The study design was a prospective, cross-sectional comparison of left ventricular structure, function and mechanics. Twenty-two male soccer players from two professional youth soccer academies (age: 12.0 ± 0.3 years) and 22 recreationally active controls (age: 11.7 ± 0.3 years) were recruited. Two-dimensional conventional and speckle tracking echocardiography were used to quantify left ventricular structure, function and peak/temporal values for left ventricular strain and twist, respectively. End-diastolic volume index was larger in soccer players (51 ± 8 mm/(m2)1.5 vs. 45 ± 6 mm/(m2)1.5; p = 0.007) and concentricity was lower in soccer players (4.3 ± 0.7 g/(mL)0.667 vs. 4.9 ± 1.0 g/(mL)0.667; p = 0.017), without differences in mean wall thickness between groups (6.0 ± 0.4 mm vs. 6.1 ± 0.5 mm; p = 0.754). Peak circumferential strain at the base (-22.2% ± 2.5% vs. -20.5% ± 2.5%; p = 0.029) and papillary muscle levels (-20.1% ± 1.5% vs. -18.3% ± 2.5%; p = 0.007) were greater in soccer players. Peak left ventricular twist was larger in soccer players (16.92° ± 7.55° vs. 12.34° ± 4.99°; p = 0.035) and longitudinal early diastolic strain rate was greater in soccer players (2.22 ± 0.40 s-1 vs. 2.02 ± 0.46 s-1; p = 0.025). Highly-trained soccer players demonstrated augmented cardiac mechanics with greater circumferential strains, twist and faster diastolic lengthening in the absence of differences in wall thickness between soccer players and controls.


#11 The Role of Somatic Maturation on Bioimpedance Patterns and Body Composition in Male Elite Youth Soccer Players
Reference: Int J Environ Res Public Health. 2019 Nov 26;16(23). pii: E4711. doi: 10.3390/ijerph16234711.
Authors: Campa F, Silva AM, Iannuzzi V, Mascherini G, Benedetti L, Toselli S
Download link: https://www.mdpi.com/1660-4601/16/23/4711/pdf
Summary: The purpose of this study was to examine the influence of chronological age (CA) and somatic maturation on body composition (BC) and bioimpedance parameters in male elite soccer players. BC and bioimpedance variables were measured in a sample of 249 players aged 9-18 years of age and registered in two professional Italian soccer teams. Results from segmental analysis showed transition time points where the influence of CA and somatic maturation on bioimpedance patterns and BC characteristics increased or subsided. The accelerated phases were assessed for fat free mass, total body water, and upper muscle area, with a starting time point at approximately -2.00 years from peak at velocity (YPHV), and for body cell mass, whose developmental tempo sped up around -1.00 YPHV. An increase in the rate of development was also observed close to -2.00 YPHV for phase angle (PA), although without accelerated phases. From a CA point of view, significant slope changes were found for all BC and bioimpendance variables, except for the calf muscle area. Although the starting points and the span of the accelerated phases were different, they subsided or disappeared at ~ 15 years, except for PA, whose growth waned at ~ 17 years.

Thu

16

Jan

2020

Latest research in football - week 48 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Observational Studies in Male Elite Football: A Systematic Mixed Study Review
Reference: Front Psychol. 2019 Oct 18;10:2077. doi: 10.3389/fpsyg.2019.02077. eCollection 2019.
Authors: Preciado M, Anguera MT, Olarte M, Lapresa D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6813914/pdf/fpsyg-10-02077.pdf
Summary: This systematic mixed study review, focuses on the use of observation methodology in elite men's football matches, which constitutes an innovative approach, that opens up a new panorama of useful and productive research. The methods used in this study follow the recommendations for systematic reviews and meta-analysis guidelines (PRISMA). The search was carried out in five databases. Ninety-four articles out of 3,195 were selected and analyzed. In order to achieve a quality assessment, the guide was used to inform evaluations based on observation methodology (GREOM) (Portell et al., 2015), recognized by the EQUATOR network. From the methodological review analysis, information obtained indicates that 97% of the researches used direct observation and 3% indirect observation. On the other hand, 56.5% of the articles explain the instrument used and 77% justify the applied observational design. A quantitative comparison of the proportions was made in several methodological aspects, which resulted in only 15.21% reviewing the quality of the data, and that 67.3% of the articles contributed to the mixed methods approach. The methodological review allowed us to establish procedural profiles. The results indicate that 67% of the articles have been published in English, and of these, 77% were published in journals that have an impact factor. The majority of the researchers, 53.26%, belong to Spanish entities. The most studied substantive aspects were goal (34%), possession of the ball (28%), and corner (27%). The most observed events were Leagues, World Cups, individual players and other events. The results obtained refer to both substantive and methodological aspects and allow us to configure a systematic review of mixed studies, in which we emphasize the aspects of a "systematic review" and a "mixed study," within an integrated perspective.


#2 Hamstring injury prevention in Belgian and English elite football teams
Reference: Acta Orthop Belg. 2019 Sep;85(3):373-380.
Authors: Van Crombrugge G, Duvivier BM, Van Crombrugge K, Bellemans J, Peers K.
Summary: Hamstring injury is the most common injury in European professional football. The purpose of this study was to provide insight into the content of hamstring injury prevention programmes in English and Belgian elite football teams. Fifteen premier league teams (10 from Belgium and 5 from England) completed a questionnaire on hamstring injury prevention. Most football teams (93%) screened for hamstring injury risk factors. Less than 60% screened for risk factors including gluteus muscle strength, neural tension and body posture during running. While 80% of the teams had a hamstring injury prevention programme during preseason and official season ; only 47% had a prevention programme during mid-season break. Hamstring muscle strength exercises were mainly performed before (77%) instead of after warming-up. In conclusion, while most investigated football teams perform hamstring injury prevention, the content and implementation of the prevention programmes is suboptimal in many Belgian and English elite football teams.


#3 The Functional Movement Screen total score and physical performance in elite male collegiate soccer players
Reference: J Exerc Rehabil. 2019 Oct 28;15(5):657-662. doi: 10.12965/jer.1938422.211. eCollection 2019 Oct.
Authors: Lee S, Kim H, Kim J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834696/pdf/jer-15-5-657.pdf
Summary: The objectives of this study were to compare the differences in physical performance of elite male collegiate soccer players according to the Functional Movement Screen (FMS) total scores and to investigate the association between the FMS total score and physical performance. A total of 20 elite male collegiate soccer players (mean age, 19.6±0.7 years; height, 173.4±4.4 cm; body weight, 66.9±7.3 kg; and body mass index, 22.0±2.0 kg/m2) participated in the present study. The subjects were divided into two groups: the high FMS (FMS total score ≥14 points, n=10) and low FMS (FMS total score <14 points, n=10). All participants completed 10-m and 30-m sprint tests, the arrowhead agility test (right and left), and a coordination test. The statistical methods used to verify the study results were the independent sample t-test and Kendall's Tau b correlation test. There were significant differences between the high and low FMS groups in the 10-m (P=0.014) and 30-m sprint (P=0.002) and arrowhead agility tests (right, P=0.039). Conversely, there were no significant differences in the arrowhead agility (left) and coordination tests between the two groups (P>0.05). Moreover, the FMS total score was found to have significant negative correlations with the 10-m sprint (r=-0.444, P=0.017), 30-m sprint (r=-0.425, P=0.016), and arrowhead agility tests (right, r=-0.389, P=0.023). These results suggest that higher FMS total scores could have a positive effect on the physical performance of the players.


#4 Comparison of three types of warm-up upon sprint ability in experienced soccer players
Reference: J Sport Health Sci. 2019 Nov;8(6):574-578. doi: 10.1016/j.jshs.2016.05.006. Epub 2016 May 24.
Authors: van den Tillaar R, Lerberg E, von Heimburg E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835031/pdf/main.pdf
Summary: The study aimed to compare the effects of a long general warm-up, a long specific warm-up, and a short specific warm-up upon sprint ability in soccer players. Twelve male soccer players (age: 18.3 ± 0.8 years, mean ± SD; body mass: 76.4 ± 7.2 kg; body height: 1.79 ± 0.05 m) conducted 3 types of warm-ups with 1 week in between: a long general warm-up, a long specific warm-up, and a short specific warm-up followed by 3 sprints of 40 m each. The best, average, and total sprinting times together with heart rate and ratings of perceived exertion were measured. The sprint times (best, average, and total time) were significantly better when performing a long specific or short specific warm-up compared with the long general warm-up (all p < 0.05). The received perception exertion was significantly lower during the specific short warm-up (4.92 ± 0.90) compared with the longer ones (6.00 ± 0.74 and 6.25 ± 0.87, respectively). Specificity is more important in a warm-up routine before sprint performance than the duration of the warm-up.


#5 The effect of fatigue and duration knowledge of exercise on kicking performance in soccer players
Reference: J Sport Health Sci. 2019 Nov;8(6):567-573. doi: 10.1016/j.jshs.2016.02.001. Epub 2016 Feb 2.
Authors: Ferraz RMP, van den Tillaar R, Pereira A, Marques MC
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834994/pdf/main.pdf
Summary: The purpose of this study was to investigate the influence of fatigue upon kicking maximal ball velocity and the target-hitting accuracy of soccer players; and also to examine the effect of the knowledge of the exercise duration upon these 2 parameters. Twenty-four semi-professional soccer players participated in this study and performed maximal instep kicks before and after the implementation of an exercise protocol, either with or without knowledge of the duration of this protocol. A mixed model of analysis of variance showed that kicking maximal ball velocity was significantly affected (F(5, 85) = 11.6, p < 0.001, η 2 = 0.39) but only after just 1 circuit of the fatigue protocol and then remained similar. Accuracy did not change during the protocol (F(5, 75) = 0.23, p = 0.76, η 2 = 0.03) and knowing the duration of exercitation did not affect accuracy and velocity development (F(1, 23) ≤ 1.04, p ≥ 0.32, η 2 ≤ 0.06). These findings demonstrated the potential negative effects of fatigue on kicking ball velocity in soccer but not in the kicking accuracy and that the effect of fatigue may not be progressive over time. Knowing or not knowing the duration of exercitation did not affect the results.


#6 Effect of contextual factors in body composition of professional soccer players. A retrospective study
Reference: Nutr Hosp. 2019 Nov 13. doi: 10.20960/nh.02783. [Epub ahead of print] [Article in Spanish]
Authors: López Cáceres PA, Chena M, Asín Izquierdo I, Moreno-Ortega A, Moreno Rojas R
Summary: The requirements of physical demands in soccer have evolved in recent years, determining the need to investigate those aspects that condition athletic performance. The objective of this study was to describe the incidence of individualized training, company at meals, race, and demarcation on the anthropometric variables of professional soccer players since these four factors affect body composition, which is considered a predictor of performance and an indicator of lifestyle in these individuals. For this purpose, a retrospective study was developed in 51 professional players of the Spanish Football League Second Division B during the 2015/2016, 2016/2017, and 2017/2018 seasons. The anthropometric assessment was carried out under the technical standards of measurement recommended by the International Working Group of Kinanthropometry, adopted by the International Society for the Advancement of Kinanthropometry (ISAK). The results revealed that individualized training and company during meals were the factors that most influence exerted on the anthropometric variables that were collected. The values of fat mass and muscle mass, and the sum of fold measurements are sensitive to the effect of the intervention with these factors. The highest levels of interaction occurred between company during the meals and individualized training, and between demarcation and company during the meals. Considering body composition as an aspect to be taken into account in the development of performance, it should be considered that the application of certain training contents according to the individual characteristics and lifestyle of players are factors that may have a significant influence on professional soccer players.


#7 A case study of the use of verbal reports for talent identification purposes in soccer: A Messi affair!
Reference: PLoS One. 2019 Nov 12;14(11):e0225033. doi: 10.1371/journal.pone.0225033. eCollection 2019.
Authors: Reeves MJ, McRobert AP, Lewis CJ, Roberts SJ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0225033&type=printable
Summary: Using a two-study approach, the main purpose of this case study was to explore the use of a verbal reporting methodology to better understand the thought processes of soccer talent scouts during an in-situ talent identification environment. Study 1 developed a standardized coding-scheme to examine verbal cognitions during a single soccer game. Study 2 then utilized this methodology to examine two full-time recruitment staff trained in the use of concurrent verbal reporting before undertaking a live, in-game task. Participants also participated in a debrief interview following the game. The findings of the two studies suggest that developing a verbal reporting protocol is viable, however when applied in a live-game environment it is problematic. Future research should therefore consider a modified version of this task to further explore the cognitions of scouts whilst observing and identifying potential talent.


#8 Late Activation of the Vastus Medialis in Determining the Risk of Anterior Cruciate Ligament Injury in Soccer Players
Reference: J Sport Rehabil. 2019 Nov 7:1-4. doi: 10.1123/jsr.2019-0026. [Epub ahead of print]
Authors: Marotta N, Demeco A, de Scorpio G, Indino A, Iona T, Ammendolia A.
Summary: Activation time of the quadriceps is important in determining injury risk in professional soccer players. The objective was to compare the activation time of the quadriceps and hamstrings muscles during a movement that puts stress on anterior cruciate ligament (ACL) to assess the risk of ACL injury. Twenty (10 males and 10 females) professional soccer players participated in this study. An inertial sensor and 4 electrodes positioned on the quadriceps and hamstrings muscles were used for the surface electromyography. The athlete resting on 1 leg dropped, from a 32-cm-high platform, on the suspended foot (testing leg), without jumping or lowering his center of gravity and maintaining single-leg landing for 5 seconds. Using a software, it is possible to calculate the activation time of the rectus femoris, vastus medialis (VM), biceps femoris, and semimembranosus muscles before ground contact. The main outcome was to evaluate the activation times of the rectus femoris, VM, biceps femoris, and semitendinosus muscles before ground contact in comparison with the range of normality calculated by the manufacturer. All male soccer players demonstrated a low risk related to the correct activation of all the examined muscles, while female soccer players demonstrated delayed activation of the VM. Delayed activation of the VM registered in females determines an increase in anterior shear force, which is an important risk factor for incurring an ACL injury. This testing protocol becomes adequate for the screening of high-risk athletes and for targeting interventions to specific imbalances that may increase injury risk.


#9 Poor Sleep Quality's Association With Soccer Injuries: Preliminary Data
Reference: Int J Sports Physiol Perform. 2019 Nov 10:1-6. doi: 10.1123/ijspp.2019-0185. [Epub ahead of print]
Authors: Silva A, Narciso FV, Soalheiro I, Viegas F, Freitas LSN, Lima A, Leite BA, Aleixo HC, Duffield R, de Mello MT.
Summary: The purpose was to investigate the relationship between sleep quality and quantity and injuries in elite soccer players and to compare sleep-wake variables and injury characteristics. The current investigation was a prospective cohort study of 23 elite male soccer players competing for 2 teams over 6 mo in the highest-level Brazilian competition. The players' sleep behavior was monitored for 10 d in the preseason using self-reporting sleep diaries and wrist activity monitors to determine sleep duration and quality. Furthermore, injuries were recorded by the respective club's medical teams into a specific database. Details of injuries recorded included the type, location, and severity of each injury. The results were expressed as descriptive statistics, and the significance level was set at 5%. The Mann-Whitney U test was performed to compare the sleep variables between groups. Spearman correlation coefficient and linear-regression analysis were used. The results indicated a moderate negative correlation between sleep efficiency and particular injury characteristics, including absence time, injury severity, and amount of injuries. The linear-regression analysis indicated that 44% of the total variance in the number of injuries can be explained by sleep efficiency, 24% of the total variance in the absence time after injury (days) can be explained by sleep efficiency, and 47% of the total variance in the injury severity can be explained by sleep efficiency. Soccer players who exhibit lower sleep quality or nonrestorative sleep show associations with increased number and severity of musculoskeletal injuries.


#10 Was Zika introduced to Brazil by participants at the 2013 Beach Soccer World Cup held in Tahiti: A phylogeographical analysis
Reference: Travel Med Infect Dis. 2019 Nov 5:101512. doi: 10.1016/j.tmaid.2019.101512. [Epub ahead of print]
Authors: Le Hingrat Q, Perrier M, Charpentier C, Jacquot A, Houhou-Fidouh N, Descamps D, Visseaux B
Summary: Zika virus (ZIKV) was initially responsible for a limited number of punctual epidemics throughout Africa and Asia. Recently, large epidemics occurred in French Polynesia, Brazil and Pan-America. These outbreaks were associated with severe outcomes such as Guillain-Barré Syndrome and microcephaly of in-utero infected newborns. Previous studies demonstrated that ZIKV was introduced in Brazil from French Polynesia but failed to identify a founding event. All publicly available ZIKV full-genome sequences (n = 182) were phylogenetically analyzed, using Bayesian method, to estimate the introduction date of ZIKV into Brazil. Introduction date into Brazil was estimated between 8th of July 2013 and 4th of November 2013, encompassing the Beach Soccer World Cup held in French Polynesia, in September 2013, which gathered Brazilian athletes and supporters. We also observed that ZIKV sequences from travelers infected in South-East Asia or in Pacific islands were closely related to viruses identified prior to the French Polynesian epidemic, underlining an endemic circulation of ZIKV in those countries since 2007, at least. This work provides a narrower estimation of ZIKV introduction into Brazil and illustrates the need for a better exploration of ZIKV circulation and endemicity in South-East Asia, while epidemiological and prevention efforts have been mainly focused on the Pan-American epidemic.


#11 Constructing Spaces and Times for Tactical Analysis in Football
Reference: IEEE Trans Vis Comput Graph. 2019 Nov 8. doi: 10.1109/TVCG.2019.2952129. [Epub ahead of print]
Authors: Andrienko G, Andrienko N, Anzer G, Bauer P, Budziak G, Fuchs G, Hecker D, Weber H, Wrobel S.
Summary: A possible objective in analyzing trajectories of multiple simultaneously moving objects, such as football players during a game, is to extract and understand the general patterns of coordinated movement in different classes of situations as they develop. For achieving this objective, we propose an approach that includes a combination of query techniques for flexible selection of episodes of situation development, a method for dynamic aggregation of data from selected groups of episodes, and a data structure for representing the aggregates that enables their exploration and use in further analysis. The aggregation, which is meant to abstract general movement patterns, involves construction of new time-homomorphic reference systems owing to iterative application of aggregation operators to a sequence of data selections. As similar patterns may occur at different spatial locations, we also propose constructing new spatial reference systems for aligning and matching movements irrespective of their absolute locations. The approach was tested in application to tracking data from two Bundesliga games of the 2018/2019 season. It enabled detection of interesting and meaningful general patterns of team behaviors in three classes of situations defined by football experts. The experts found the approach and the underlying concepts worth implementing in tools for football analysts.


#12 The real penalty: number of OMFS patients presenting to the emergency department at Sunderland Royal Hospital after England fixtures before and during the 2018 FIFA Football World Cup
Reference: Br J Oral Maxillofac Surg. 2019 Nov 9. pii: S0266-4356(19)30709-0. doi: 10.1016/j.bjoms.2019.10.313. [Epub ahead of print]
Authors: Miller N, Kearns A, Bartram A, Banks R
Summary: The aim of this study was to establish a link between a large televised sporting event and the incidence of patients presenting to the emergency department with oral and maxillofacial injuries. When compared with daily attendances throughout the year, the mean (SD) number rose from 2.53 (1.69) to 4.00 (1.53) (p=0.005) between 1 November 2017 and 31 July 2018 on the day after an England fixture, an increase of 58%. These data show the need for workforce planning during large-scale national sporting events because of the rise in the number of patients presenting. They show that the increase in workload is caused by a higher number of both traumatic and non-traumatic injuries.


#13 Yo-Yo intermittent tests are a valid tool for aerobic fitness assessment in recreational football
Reference: Eur J Appl Physiol. 2019 Nov 9. doi: 10.1007/s00421-019-04258-8. [Epub ahead of print]
Authors: Castagna C, Krustrup P, Póvoas S
Summary: The purpose was to examine the suitability of three versions and two levels of the Yo-Yo intermittent tests for assessing and tracking aerobic fitness status development in male recreational football players. Sixty-six untrained participants (age 39 ± 6 years, VO2max 41.2 ± 6.2 ml kg-1 min-1, body mass 81.9 ± 10.8 kg, height 173.2 ± 6.4 cm) partook in a 12-week recreational football training program. They were evaluated during the Yo-Yo intermittent endurance level 1 (YYIE1) and 2 (YYIE2) tests and the Yo-Yo intermittent recovery level 1 test (YYIR1), and during a treadmill test for VO2max assessment, at baseline. Thirty-two out of these 66 participants replicated all these tests at post-intervention. An additional group of 30 male age-matched recreational football players that afterwards started the 12-week recreational football program (age 39 ± 6 years, VO2max 45.3 ± 5.8 ml kg-1 min-1, body mass 82.5 ± 7.8 kg, height 172.8 ± 5.4 cm) was evaluated at baseline to test cross-validation. The Yo-Yo tests showed very large associations with VO2max at baseline (r = 0.75-0.77; P < 0.0001) and at post-intervention (r = 0.76-0.82; P < 0.0005). Post-training, very large associations were found between YYIE2 performance and VO2max (r = 0.65, P < 0.0001). Cross-validation revealed small to large differences between the observed and estimated VO2max values (1.5-2.96 ml kg-1 min-1) with moderate typical error of estimation (7.9-8.7%) across the tests. Performance in the YYIE1, YYIE2 and YYIR1 tests of ≥ 1760, 480 and 600 m, respectively, indicated good to excellent VO2max values. The Yo-Yo tests considered here showed robust and consistent criterion validity. The YYIE2 could be a more accurate option to track aerobic fitness development in recreational football players.

Thu

05

Dec

2019

Latest research in football - week 47 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 An Evaluation of Heart Rate Variability in Female Youth Soccer Players Following Soccer Heading: A Pilot Study
Reference: Sports (Basel). 2019 Nov 4;7(11). pii: E229. doi: 10.3390/sports7110229.
Authors: Harriss AB, Abbott K, Kimpinski K, Holmes JD, Johnson AM, Walton DM, Dickey JP
Download link: https://www.mdpi.com/2075-4663/7/11/229/pdf
Summary: Most head impacts in soccer occur from purposeful heading; however, the link between heading and neurological impairment is unknown. Previous work suggests concussion may result in an uncoupling between the autonomic nervous system and cardiovascular system. Accordingly, heart rate variability (HRV) may be a sensitive measure to provide meaningful information regarding repetitive heading in soccer. The purpose of this pilot study assesses the feasibility of measuring HRV to evaluate autonomic function following soccer heading. Sixteen youth female participants underwent heart rate monitoring during a heading and footing condition. Participants completed a five minute resting supine trial at the start and end of each testing session. Standard 450 g soccer balls were projected at 6 m/s towards participants. Participants performed five headers, for the header condition, and five footers for the footer condition. The HRV for resting supine trials, pre- and post-header and footer conditions were assessed for both time and frequency domains. HRV effect sizes were small when comparing conditions, except absolute low frequency (d = 0.61) and standard deviation of the normal-normal (NN) intervals (d = 0.63). Participant retention and adherence were high, without adverse events. Findings suggest HRV is a feasible measure for evaluating the effects of heading on autonomic function.


#2 Combined Anterolateral, Anterior, and Anteromedial Ankle Impingement in an Adolescent Soccer Player: A Case Report and Review of the Literature
Authors: Cosma DI, Vasilescu DE, Corbu A, Todor A, Valeanu M, Ulici A
Summary: A unique case of combined anterolateral, anterior, and anteromedial ankle impingement in an adolescent soccer player is presented in this article. To the best of our knowledge, this is the only report of circumferential, massive, anterior ankle impingement in children described in the literature. The importance of proper diagnosis and treatment of such a lesion is illustrated in this case report. We also emphasize that clinical examination combined with 3D computed tomography scan reconstruction is an excellent and cost-effective imaging modality that can help with the diagnosis of anterior ankle impingement. Finally, open surgical treatment showed excellent results in an elite athlete.


#3 Defining the Process of a Cardiovascular Risk Assessment Program: Lessons Learned From Cardiac Assessment of Elite Soccer Players in the United Kingdom
Reference: Clin J Sport Med. 2019 Nov;29(6):500-505. doi: 10.1097/JSM.0000000000000534.
Authors: Speers C, Seth AN, Patel KC, Rakhit DJ, Gillett MJ
Summary: Retrospectively analyze the cardiac assessment process for elite soccer players, and provide team physicians with a systematic guide to managing longitudinal cardiac risk. Cardiac assessments incorporating clinical examination, 12-lead ECG, echocardiography, and health questionnaire were utilized in this study.  Soccer players at 5 professional clubs in England, the United Kingdom participated. Data was retrospectively collected, inspected, and analyzed to determine their clinical management and subsequent follow-up. Over 2 years, 265 soccer players, aged 13 to 37 years with 66% of white European ethnicity, were included in the cohort. Eleven percent had "not-normal" assessments, of these assessments, 83% were considered gray screens, falling into three broad categories: structural cardiac features (including valvular abnormalities), functional cardiac features, and electrocardiogram changes. After cardiology consultation, all assessments were grouped into low, enhanced and high-risk categories for ongoing longitudinal risk management. Overall clear-cut pathology was identified in 2%. Cardiovascular assessment is a vital tool in identifying athletes at risk of sudden cardiac death to mitigate their risk through surveillance, intervention, or participation restriction. The decision whether a player is fit to play or not requires a robust risk assessment followed by input from a multidisciplinary team that includes both the team physician and cardiologist. This educational article proposes a clinical management pathway to aid clinicians with this process. Sudden cardiac death is the important medical cause of death during exercise. The team physician should assume responsibility for the management of the longitudinal risk of their players' cardiac assessments in conjunction with sports cardiologist.


#4 Effects of a Computerized Training on Attentional Capacity of Young Soccer Players
Reference: Front Psychol. 2019 Oct 21;10:2279. doi: 10.3389/fpsyg.2019.02279. eCollection 2019.
Authors: Reigal RE, González-Guirval F, Morillo-Baro JP, Morales-Sánchez V, Juárez-Ruiz de Mier R, Hernández-Mendo A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6816454/pdf/fpsyg-10-02279.pdf
Summary: The purpose of this work was to analyze the effects of a computerized training on attentional capacity in a group of young soccer players. Seventy-five male adolescents from two soccer clubs in the city of Malaga (Spain) and aged between 14 and 18 (15.45 ± 1.43 years) participated in the investigation. A quasi-experimental design was used, and the adolescents were divided into control (n = 38) and experimental (n = 37) groups. The experimental group underwent a computerized training (Rejilla 1.0) of their attention during 9 weeks and 27 sessions. In addition, the D2 attention test was used to analyze the evolution of participants after the intervention program. The results showed positive effects of the computerized intervention program on selective attention, observing changes both in the executions of the software used (p < 0.001, Cohen's d = 1.58, 95% CI [1.06, 2.11]) and in the main measures of the D2 test, total effectiveness (p < 0.001, Cohen's d = 0.62, 95% CI [0.15, 1.08]) and concentration (p < 0.01, Cohen's d = 0.48, 95% CI [0.02, 0.94]).


#5 Growth pattern of lumbar bone mineral content and trunk muscles in adolescent male soccer players
Reference: J Bone Miner Metab. 2019 Nov 7. doi: 10.1007/s00774-019-01060-6. [Epub ahead of print]
Authors: Takei S, Taketomi S, Tanaka S, Torii S
Summary: Previous studies have reported that the peak in lean body mass (LBM) precedes the peak in bone mineral content (BMC). However, it is unknown whether the trunk region growth is similar. We investigated the difference between pubertal peak age in the increase of LBM in the trunk (trunk LBM) and pubertal peak age in the increase of BMC in the lumbar spine (lumbar BMC) in a longitudinal study of 201 Japanese male adolescent soccer players. The age of peak height velocity (PHV) and the developmental age were calculated. The participants were followed over a 2-year period, with height and dual-energy X-ray absorptiometry scans taken every 6 months. The trunk LBM (ρ = 0.732, p < 0.0001) and the lumbar BMC (ρ = 0.621, p < 0.0001) significantly correlated with the developmental age. The increase of trunk LBM and lumbar BMC was significantly different according to the developmental stages (Kruskal-Wallis test; p < 0.0001 and p < 0.001, respectively). We used a cubic spline to estimate the developmental age, when the increase reached its peak: the peak age of the increase in trunk LBM was estimated to be - 0.08 years (approximately - 1 month) prior to PHV age, whereas the peak age of the increase in lumbar BMC was estimated to be 0.42 years (approximately 5 months) after the PHV age. The maximal increase in trunk LBM occurs just before PHV age and approximately 6 months before the maximal increase in lumbar BMC during the pubertal growth spurt in the Japanese adolescent male soccer players.


#6 The impact of endurance training and table soccer on brain metabolites in schizophrenia
Reference: Brain Imaging Behav. 2019 Nov 5. doi: 10.1007/s11682-019-00198-1. [Epub ahead of print]
Authors: Rauchmann BS, Ghaseminejad F, Keeser D, Keller-Varady K, Schneider-Axmann T, Takahashi S, Karali T, Helms G, Dechent P, Maurus I, Hasan A, Wobrock T, Ertl-Wagner B, Schmitt A, Malchow B, Falkai P
Summary: Higher glutamate and glutamine (together: Glx) and lower N-acetyl-aspartate (NAA) levels were reported in schizophrenia. Endurance training normalizes NAA in the hippocampus, but its effects on other metabolites in the brain and the relationship of metabolites to clinical symptoms remain unknown. For 12 weeks, 20 schizophrenia inpatients (14 men, 6 women) and 23 healthy controls (16 men, 7 women) performed endurance training and a control group of 21 schizophrenia inpatients (15 men, 6 women) played table soccer. A computer-assisted cognitive performance training program was introduced after 6 weeks. We assessed cognitive performance, psychopathological symptoms, and everyday functioning at baseline and after 6 and 12 weeks and performed single voxel magnetic resonance spectroscopy of the hippocampus, left dorsolateral prefrontal cortex (DLPFC), and thalamus. We quantified NAA, Glx, total creatine (tCr), calculated NAA/tCr and Glx/tCr and correlated these ratios with physical fitness, clinical and neurocognitive scores, and everyday functioning. At baseline, in both schizophrenia groups NAA/tCr was lower in the left DLPFC and left hippocampus and Glx/tCr was lower in the hippocampus than in the healthy controls. After 6 weeks, NAA/tCr increased in the left DLPFC in both schizophrenia groups. Brain metabolites did not change significantly in the hippocampus or thalamus, but the correlation between NAA/tCr and Glx/tCr normalized in the left DLPFC. Global Assessment of Functioning improvements correlated with NAA/tCr changes in the left DLPFC. In our study, endurance training and table soccer induced normalization of brain metabolite ratios in the brain circuitry associated with neuronal and synaptic elements, including metabolites of the glutamatergic system.


#7 Maximal oxygen consumption and oxygen muscle saturation recovery following repeated anaerobic sprint test in youth soccer players
Reference: J Sports Med Phys Fitness. 2019 Oct 28. doi: 10.23736/S0022-4707.19.10162-4. [Epub ahead of print]
Authors: Michailidis Y, Chatzimagioglou A, Mikikis D, Ispirlidis I, Metaxas T
Summary: The purpose of the study was to examine whether differences in aerobic capacity (VO2max) influence muscle reoxygenation following repeated anaerobic sprint test (RAST) in soccer players. We hypothesized that muscle reoxygenation is faster in players with higher aerobic capacity. Ten male, youth soccer players participated in the study and performed RAST on a synthetic grass field. Oxygen saturation in muscle (StO2) of the right vastus lateralis muscle was measured by near-infrared spectroscopy. Half the time that was required for StO2 recovery (T1/2 StO2) after RAST was used to evaluate the reoxygenation in the recovery period after testing. The T1/2 StO2 was defined as the time from the end of RAST testing to the time of reaching 50% of StO2. Aerobic capacity (VO2max) was estimated by the Yo-Yo intermittent recovery test level 1 (YYIR1). The T1/2 StO2 had a significant inverse correlation with VO2max (r=-0.71; P=0.021) and with the distance which was covered by players on YYIR1 test (r=-0.71; P=0.021). In contrast, StO2 recovery rate showed no significant correlations with the VO2max in subjects. These results indicate that aerobic capacity can influence vastus lateralis reoxygenation following RAST in youth soccer players.


#8 Match Performance of Soccer Teams in the Chinese Super League-Effects of Situational and Environmental Factors
Reference: Int J Environ Res Public Health. 2019 Nov 1;16(21). pii: E4238. doi: 10.3390/ijerph16214238.
Authors: Zhou C, Hopkins WG, Mao W, Calvo AL, Liu H
Download link: https://www.mdpi.com/1660-4601/16/21/4238/pdf
Summary: The purpose of the study was to investigate the effects of situational factors (match location, strength of team and opponent) and environmental factors (relative air humidity, temperature and air quality index) on the technical and physical match performance of Chinese Soccer Super League teams (CSL). The generalized mixed modelling was employed to determine the effects by using the data of all 240 matches in the season 2015 collected by Amisco Pro®. Increase in the rank difference would increase the number of goal-scoring related, passing and organizing related actions to a small-to-moderate extent (Effect size [ES]: 0.37-0.99). Match location had small positive effects on goal-scoring related, passing and organizing related variables (ES: 0.27-0.51), while a small negative effect on yellow card (ES = -0.35). Increment in relative air humidity and air quality index would only bring trivial or small effects on all the technical performance (ES: -0.06-0.23). Increase in humidity would decrease the physical performance at a small magnitude (ES: -0.55--0.38). Teams achieved the highest number in the physical performance-related parameters at the temperature between 11.6 and 15.1 °C. In the CSL, situational variables had major effects on the technical performance but trivial effects on the physical performance, on the contrary, environmental factors affected mainly the physical performance but had only trivial or small impact on the technical performance.


#9 Psychological Intervention Program to Control Stress in Youth Soccer Players
Reference: Front Psychol. 2019 Oct 16;10:2260. doi: 10.3389/fpsyg.2019.02260. eCollection 2019.
Authors: Olmedilla A, Moreno-Fernández IM, Gómez-Espejo V, Robles-Palazón FJ, Verdú I, Ortega E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805695/pdf/fpsyg-10-02260.pdf
Summary: The influence on the psychological well-being of the players and their sports performance seems to be one of the keys to the current sports practice. The purpose of this study was to determine the effectiveness of a psychological intervention program for stress control in youth soccer players. A total sample of 19 male youth soccer players (age: 16.3 ± 0.99 years; years playing soccer: 10.89 ± 1.56 years) completed the current research. The Psychological Characteristics Questionnaire related to Sports Performance (CPRD) was used to assess stress factors related to sports competition. A program based on Cognitive-Behavioral Therapy was implemented during eight sessions of approximately 50 min each. A pre-post design was used and statistical differences between pre- and post-measures were checked through dependent sample t-tests. The results indicated that the post-test scores were higher than the pre-tests in "Influence of the Evaluation of Performance" and "Mental Skills" factors, which supposes a significant improvement of the stress management related to performance evaluation, as well as the use of psychological resources and techniques. In addition, the post-test scores were also higher in the "Stress Control" factor, although in this case the differences were not statistically significant. Practical indications deriving from the findings of this study can help youth soccer players to manage the stress of competition using a psychological training program.


#10 The effectiveness of a practical half-time re-warm-up strategy on performance and the physical response to soccer-specific activity
Reference: J Sports Sci. 2019 Nov 2:1-10. doi: 10.1080/02640414.2019.1686941. [Epub ahead of print]
Authors: Fashioni E, Langley B, Page RM
Summary: The aim of this study was to assess the influence of a half-time (HT) re-warm up (RWU) strategy on measures of performance and the physical and perceptual response to soccer-specific activity. Ten male soccer players completed a control (CON) and RWU trial, in which participants completed 60 min (4 x 15-min periods with a 15-min HT interspersing the third and fourth periods) of a soccer-specific exercise protocol. The CON trial comprised a passive 15-min HT, whilst the RWU trial comprised a passive 12-min period, followed by a 3-min RWU. The RWU elicited an improvement in 20 m sprint times (d= 0.6; CON: 3.42 ± 0.20 s; RWU: 3.32 ± 0.12 s), and both squat (d= 0.6; CON: 26.96 ± 5.00 cm; RWU: 30.17 ± 5.13 cm) and countermovement jump height (d= 0.7; CON: 28.15 ± 4.72 cm; RWU: 31.53 ± 5.43 cm) following the RWU and during the initial stages of the second half. No significant changes were identified for 5 m or 10 m sprint performance, perceived muscle soreness, or PlayerLoadTM. Ratings of perceived exertion were however higher (~2 a.u) following the RWU. These data support the use of a HT RWU intervention to elicit acute changes in performance.


#11 The adolescent motor performance development of elite female soccer players: A study of prognostic relevance for future success in adulthood using multilevel modelling
Reference: J Sports Sci. 2019 Nov 2:1-10. doi: 10.1080/02640414.2019.1686940. [Epub ahead of print]
Authors: Leyhr D, Raabe J, Schultz F, Kelava A, Höner O
Summary: Considering the scarce empirical evidence regarding talent predictors in female youth soccer, the present study aimed to investigate the long-term prognostic validity of elite female soccer players' adolescent motor performance for future success in adulthood. Additionally, the three-year development of highly talented girls' motor performance and the predictive value of this motor development for reaching a professional adult performance level (APL) was analysed.Overall, N = 737 female players participated in nationwide motor diagnostics (sprinting, agility, dribbling, ball control, shooting) within the German Soccer Association's talent identification and development programme at least twice between the age groups Under-12 (U12) and U15. Based on their APL at least four years later, participants were assigned to a professional (first German division, 6.2%) or non-professional group (lower divisions, 93.8%).Multilevel regression analyses revealed a general prognostic relevance for the investigated parameters with respect to players' APL. In addition, there was a non-linear improvement in participants' motor performance across all variables from U12 to U15. However, non-significant interactions between APL and these improvements indicate motor performance development itself cannot adequately predict players' future success in adulthood. Findings provide insightful information that can help coaches foster optimal support for young female soccer players' development.

Thu

05

Dec

2019

Latest research in football - week 46 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 A public data set of spatio-temporal match events in soccer competitions
Reference: Sci Data. 2019 Oct 28;6(1):236. doi: 10.1038/s41597-019-0247-7.
Authors: Pappalardo L, Cintia P, Rossi A, Massucco E, Ferragina P, Pedreschi D, Giannotti F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6817871/pdf/41597_2019_Article_247.pdf
Summary: Soccer analytics is attracting increasing interest in academia and industry, thanks to the availability of sensing technologies that provide high-fidelity data streams for every match. Unfortunately, these detailed data are owned by specialized companies and hence are rarely publicly available for scientific research. To fill this gap, this paper describes the largest open collection of soccer-logs ever released, containing all the spatio-temporal events (passes, shots, fouls, etc.) that occured during each match for an entire season of seven prominent soccer competitions. Each match event contains information about its position, time, outcome, player and characteristics. The nature of team sports like soccer, halfway between the abstraction of a game and the reality of complex social systems, combined with the unique size and composition of this dataset, provide an ideal ground for tackling a wide range of data science problems, including the measurement and evaluation of performance, both at individual and at collective level, and the determinants of success and failure.


#2 Soccer Injuries in Children and Adolescents
Reference: Pediatrics. 2019 Nov;144(5). pii: e20192759. doi: 10.1542/peds.2019-2759.
Authors: Watson A, Mjaanes JM
Download links: https://pediatrics.aappublications.org/content/pediatrics/144/5/e20192759.full.pdf
Summary: Participation in youth soccer in the United States continues to increase steadily, with a greater percentage of preadolescent participants than perhaps any other youth sport. Despite the wide-ranging health benefits of participation in organized sports, injuries occur and represent a threat to the health and performance of young athletes. Youth soccer has a greater reported injury rate than many other contact sports, and recent studies suggest that injury rates are increasing. Large increases in the incidence of concussions in youth soccer have been reported, and anterior cruciate ligament injuries remain a significant problem in this sport, particularly among female athletes. Considerable new research has identified a number of modifiable risk factors for lower-extremity injuries and concussion, and several prevention programs have been identified to reduce the risk of injury. Rule enforcement and fair play also serve an important role in reducing the risk of injury among youth soccer participants. This report provides an updated review of the relevant literature as well as recommendations to promote the safe participation of children and adolescents in soccer.


#3 Arachnoid cyst in young soccer players complicated by chronic subdural hematoma: personal experience and review of the literature
Reference: Acta Neurol Belg. 2019 Oct 25. doi: 10.1007/s13760-019-01224-1. [Epub ahead of print]
Authors: Gregori F, Colistra D, Mancarella C, Chiarella V, Marotta N, Domenicucci M
Summary: Arachnoid cysts (ACs) are congenital intracranial benign cavities originating from the meninges during embryological development. Several studies have shown the existence of a relationship between AC and a higher risk to develop ipsilateral chronic subdural hematoma (CSH) especially in a young population. In the presence of an AC, the practice of sport activities may expose young patients to minor head trauma and to an increased risk of developing CSH. We describe three cases of young soccer players with AC associated with CSH. Then, we performed a literature review of all the reported cases in the literature of patients younger than 18 years with AC-associated CSH related to sport practice. A total of 33 cases, including the three cases reported by us, are analyzed. Soccer is the most represented sport activity in this association (39% of cases). The treatment of choice is surgical in all patients, with burr hole or craniotomy in similar proportions. In one-third of patients, the AC has been fenestrated. Outcome is good in all the reported cases. We reviewed the main pathogenic theories, the main surgical strategies described in literature, as well as recurrence rate of CSH, the association of AC and cranial deformities, and the clinical outcome. AC might be associated with skull deformities, but their real incidence remains unclear. The clinical detection of such anomalies should suggest performing further radiological investigations. If the presence of AC is confirmed, the practice of sport activities should not be avoided, as the real incidence of AC-associated CSH is not clear yet and the reported outcomes in literature are good. Surgical treatment of AC-associated CSH should be hematoma removal through burr hole, reserving AC fenestration only for cases with intracystic bleeding or recurrences. The surgeon should adequately advise and inform the young patients and their families that they could have an increased risk of developing CSH given by the presence of the AC, and that they should be referred to a neurosurgical center if they become symptomatic.


#4 Prevalence of Relative Age Effect in Russian Soccer: The Role of Chronological Age and Performance
Reference: Int J Environ Res Public Health. 2019 Oct 23;16(21). pii: E4055. doi: 10.3390/ijerph16214055.
Authors: Bezuglov EN, Nikolaidis PT, Khaitin V, Usmanova E, Luibushkina A, Repetiuk A, Waśkiewicz Z, Gerasimuk D, Rosemann T, Knechtle B
Download link: https://www.mdpi.com/1660-4601/16/21/4055/pdf
Summary: The relative age effect (RAE) has been well studied in adolescent and adult soccer players; however, less information has been available about children engaged in regular soccer training and the role of performance. Thus, the aim of the present study was to examine the prevalence of RAE in children and adolescent soccer players, as well as the role of age and performance. Russian soccer players (n = 10,446) of various ages, playing positions and performance levels were examined for their date of birth. It was observed that RAE was widespread in Russian soccer teams of all age groups. RAE was most pronounced in children teams of the top tier Russian soccer academies and junior Russia national teams, where the proportions of soccer players born in the first quarter were 43.9% and 39.8%, respectively, whereas those born in the fourth quarter of the year were 7.7% and 6.3%, respectively. In top tier soccer academies, RAE did not vary by age group. In the middle tier soccer academies, RAE was less pronounced. It was still prevalent in the junior teams of the top tier clubs of the Russian Premier League, where 14.3% of the soccer players were born in the fourth quarter of the year compared to 42.9% born in the first quarter of the year. RAE can be observed in the top tier Russian adult teams as well, although it is less pronounced there. In summary, RAE is highly prevalent in Russian children and junior soccer and is associated with the level of competitiveness. At the same time, the proportion of players born in the fourth quarter of the year is higher in adult teams than in junior and youth teams, which is most likely due to the wider selection of players, not limited by their age and place of residence. In junior teams, RAE results in a bias towards selection of players who are more physically mature, whereas children who may be more talented but are less developed due to their younger chronological age tend to be overlooked.


#5 Women Are at Higher Risk for Concussions Due to Ball or Equipment Contact in Soccer and Lacrosse
Reference: Clin Orthop Relat Res. 2019 Oct 17. doi: 10.1097/CORR.0000000000000995. [Epub ahead of print]
Authors: Ling DI, Cheng J, Santiago K, Ammerman B, Jivanelli B, Hannafin J, Casey E
Summary: There is ample evidence to suggest sex- and gender-based differences in the incidence of sports-related concussions. The mechanisms of concussion may vary between male and female athletes and contribute to this observed difference. Understanding the underlying etiology by pooling data from primary studies across different settings and sport types will inform interventions that can reduce concussion rates. Specifically, we asked: (1) In which sports are female athletes less likely to experience concussions from player contact? (2) In which sports are female athletes more likely to experience concussions because of ball or equipment contact? PubMed, EMBASE, and Cochrane Library databases were searched to identify articles published from January 2000 to December 2018. Ten studies met the inclusion criteria, which were studies that reported concussion incidence by mechanism for both male and female athletes. Exclusion criteria included non-English studies, conference abstracts, and studies on non-sports related concussions. The sports represented by the 10 studies included ice hockey (n = 4), soccer (n = 5), basketball (n = 4), baseball/softball (n = 4), and lacrosse (n = 5). The rate ratio was calculated as the incidence rate in female athletes/male athletes for each concussion mechanism or activity. Data were pooled using the DerSimonian-Laird random-effects model. Study quality was assessed with the Newcastle-Ottawa Scale. Female athletes were at lower risk of player-contact-induced concussions in lacrosse (pooled rate ratio 0.33 [95% CI 0.25 to 0.43]; p < 0.001), basketball (pooled rate ratio 0.86 [95% CI 0.76 to 0.97]; p = 0.01), ice hockey (pooled rate ratio 0.64 [95% CI 0.56 to 0.73]; p < 0.001), soccer (pooled rate ratio 0.70 [95% CI 0.66 to 0.75]; p < 0.001), and soccer heading (pooled rate ratio 0.80 [95% CI 0.72 to 0.90]; p < 0.001); in these sports, men were at higher risk of concussions from player contact. Female athletes were more likely to experience concussions because of ball or equipment contact in lacrosse (pooled rate ratio 3.24 [95% CI 2.10 to 4.99]; p < 0.001), soccer (pooled rate ratio 2.04 [95% CI 1.67 to 2.49]; p < 0.001), and soccer heading (pooled rate ratio 2.63 [95% CI 1.84 to 3.77]; p < 0.001). The mechanism or activity underlying concussions differs between male and female athletes across different sports. This finding remains the same regardless of whether there are rule differences between the men's and women's games. The implementation of other interventions are required to further ensure player safety, including protective head equipment, concussion prevention training, or rules limiting player contact in the men's game.


#6 Jump performance in male and female football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Oct 30. doi: 10.1007/s00167-019-05747-1. [Epub ahead of print]
Authors: Arundale AJH, Kvist J, Hägglund M, Fältström A
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-019-05747-1.pdf
Summary: The purpose was to examine differences between men and women football players in clinically feasible jumping measures. Female football players (N = 46, ages 16-25) were matched based on age, training frequency, and playing position with 46 male players. All players performed the tuck jump and drop vertical jump (DVJ). DVJ was assessed quantitatively for valgus knee motion and probability of a high peak knee abduction moment (pKAM), as well as sagittal plane hip, knee, and ankle angles, and qualitatively with visual assessment of the player's knees upon landing; graded as good, reduced, or poor control. Women had higher total tuck jump scores (5 ± 2) (more technique flaws), than men (3 ± 2, P < 0.01). The quantitative analysis of the DVJ found that men had greater asymmetries between limbs, but women landed bilaterally in more knee valgus (interaction P = 0.04, main effect of sex P = 0.02). There was no difference in pKAM (interaction n.s.). Women also landed in less hip flexion (P = 0.01) and ankle dorsiflexion (P = 0.01) than men. The qualitative DVJ analysis found that more women (48%) had poor knee control compared to men (11%, P < 0.01). The results indicate that women perform worse on the tuck jump assessment than men. The results support previous findings that women land in more knee valgus than men, but also found that men may have larger asymmetries in knee valgus. These results from clinically feasible measures provide some suggestions for clinicians to consider during ACL reconstruction rehabilitation to enhance performance.


#7 Game-specific abilities in elite youth football players: validity and sensitivity to change in subjective coach ratings compared to objectively assessed data
Reference: J Sports Med Phys Fitness. 2019 Oct 25. doi: 10.23736/S0022-4707.19.10084-9. [Epub ahead of print]
Authors: Niederer D, Damm M, Grigereit A, Banzer W, Vogt L
Summary: Little is known on the accuracy of coaches' ratings of game-specific physical abilities in elite youth football players. The present study on elite youth football players aims to assess whether 1) the coaches' subjective assessment of the level of performance of each athlete within the team is in accordance with objectively collected data and 2) the coaches rate changes in the athletes'' performance level accurately or not. Data on jumping ability, sprinting speed, change of direction and strength were collected in seven age groups at a football youth academy (n = 150). The diagnostic battery was repeated after seven months (n = 138). Before the second session, the head coaches completed Likert-scaled closed questions on 1) the importance of running speed and reactive strength components and their relevance to the individual game performance of each of their athletes, 2) level of performance of their athletes, and 3) the change between the first and second performance testing results. Validity and sensitivity of change of their ratings in comparison to the performance data were calculated using analyses of interrelationship. The data of the head coaches showed a low to medium effect size in the agreement with the performance data (Cohen's W = .33 - .71). The evaluation of the change in level of performance was poorer (Cohen's W =.04 - .2; n.s.). Our results underline that functional/physical testing twice during a season may be crucial for displaying performance levels of elite youth football players. Simple self-reported ratings by the coach may be valid in recent performance level assessment but not for performance changes.


#8 Internal training load monitoring in professional football: a systematic review of methods using rating of perceived exertion
Reference: J Sports Med Phys Fitness. 2019 Oct 24. doi: 10.23736/S0022-4707.19.10000-X. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Costa J, Krustrup P, Rebelo A
Summary: The rate of perceived exertion (RPE) is widely adopted to quantify internal training load (ITL) in professional football. The aim of this study was to systematically review the use RPE-based methods in professional football. Observational studies conducted during training routines of professional football players over a minimum of one- week were selected based on the preferred reporting items for systematic reviews and meta-analyses statement. Thirty-eight articles met the inclusion criteria (average qualitative score was 6.3 out of 10 [3 to 9]). The main deficiencies identified concerned the poor description of study design (~52% of the studies), and the non-quantification of match load (~44%). Ten studies complemented RPE-based ITL information with time-motion analysis (~26%) and seven studies added HR recordings (~18%). Nine studies collected RPE data after complementary training, separately to field sessions (~3%). Operational questions (e.g. How was your workout? ~71%) were preferred to instructions (e.g. Please rate the intensity of today's session; ~8%). Session-RPE (s-RPE; RPE multiplied by training duration) was more commonly adopted as measure of exercise intensity than isolated RPE (~76 vs. ~8%). RPE-derived variables calculated on weekly values included absolute week-to-week change, acute: chronic workload ratio, monotony and strain and were not frequently used (7 to 15%). Four studies (~11%) divided RPE in two components: respiratory and muscular. There is a lack of consensus for the use of RPE in professional football and "good practices" are warranted. This review might help practitioners regarding procedures to adopt in RPE data collection and interpretation.


#9 No association between perceived exertion and session duration with hamstring injury occurrence in professional football
Reference: Scand J Med Sci Sports. 2019 Oct 30. doi: 10.1111/sms.13591. [Epub ahead of print]
Authors: Lolli L, Bahr R, Weston M, Whiteley R, Tabben M, Bonanno D, Gregson W, Chamari K, Di Salvo V, van Dyk N
Download link: https://onlinelibrary.wiley.com/doi/pdf/10.1111/sms.13591
Summary: Training and competition loads have emerged as modifiable composite risk factors of non-contact injury. Hamstring strains are the most common injuries in football with substantial burden on the individual player and club. Nevertheless, robust evidence of a consistent load-hamstring injury relationship in professional football is lacking. Using available data from the Qatar Stars League over three competitive seasons, this study investigated the separate and combined effects of perceived exertion and session duration on hamstring injury occurrence in a sample of 30 outfield football players. Load variables were calculated into 7-day, 14-day, 21-day, 28-day periods of data, and week-to-week changes for average ratings of perceived exertion (RPE; au) score and session-RPE (s-RPE; session-duration X score), plus the cumulative training and match minutes and s-RPE, respectively. Conditional logistic regression models estimated load-injury relationships per 2-within-subject standard deviation increments in each candidate variable. Associations were declared practically important based on the location of the confidence interval in relation to thresholds of 0.90 and 1.11 defining small beneficial and harmful effects, respectively. The uncertainty for the corrected odds ratios show that typically high within-subject increments in each candidate variable were not practically important for training- and match-related hamstring injury (95% confidence intervals range: 0.85 to 1.16). We found limited exploratory evidence regarding the value of perceived exertion and session duration as aetiological factors of hamstring injury in Middle-East professional football. Monitoring remains valuable to inform player load management strategies, but our exploratory findings suggest its role for type-specific injury risk determination appears empirically unsupported.


#10 Risk of acute and overuse injuries in youth elite soccer players: Body size and growth matter
Reference: J Sci Med Sport. 2019 Oct 10. pii: S1440-2440(19)30355-X. doi: 10.1016/j.jsams.2019.10.001. [Epub ahead of print]
Authors: Rommers N, Rössler R, Goossens L, Vaeyens R, Lenoir M, Witvrouw E, D'Hondt E
Summary: This study investigated anthropometric measures and growth as risk factors for overuse and acute injuries in younger (U10-U12) and older (U13-U15) elite level soccer players. Height, weight, and sitting height were measured at the start and the end of the 2016-2017 competitive season and growth velocities were calculated. Throughout the season, injuries were registered continuously by the (para-)medical staff of the included clubs. We analyzed the injury risk using multilevel Poisson regression models, accounting for club and team clustering. Of the included 314 players (11.7±1.7 years of age), 160 players sustained 133 overuse and 163 acute injuries (i.e. 106 injuries in 69 players of the younger group, 190 in 91 players of the older group). In the younger group, risk of overuse injuries was associated with an increase in leg length over the season (incidence rate ratio (IRR) 1.620 [95% CI 1.230-2.117]) and risk of acute injuries with relatively younger age (IRR 1.003 [95% CI 1.000-1.006]). In the older group, a higher leg length was associated with an increased risk of overuse injuries (IRR 1.055 [95% CI 1.011-1.108]), and a higher weight and a lower growth rate with an increased risk of acute injuries (IRR 1.043 [95% CI 1.021-1.067] and 0.903 [95% CI 0.831-0.981], respectively). Injury risk factors differ by age group and type of injury. The age-specific anthropometric and growth-related risk factors should be monitored and these risk profiles should be considered to manage injury risk effectively.


#11 Effects of Ramadan fasting on physical performances in soccer players: a systematic review
Reference: Tunis Med. 2019 Oct;97(10):1114-1131.
Authors: Chtourou H, Trabelsi K, Boukhris O, Ammar A, Shephard RJ, Bragazzi NL.
Summary: The purpose was to evaluate the effects of Ramadan fasting on physical performance measures in soccer players through a systematic appraisal of the literature. Systematic review Data sources: The entire content of two databases, PubMed/MEDLINE and Web of Science. Eligibility criteria for selecting studies: Both singlegroup, pre-post and crossover design studies published in any language before March 15, 2019 were included. Assessments of physical performance were accepted for analysis. study appraisal: The methodological quality of the included studies was assessed using 'QualSyst'. Of 18 selected articles, 16 were generally of strong quality and the remaining studies (n=2) were rated as moderate, although most lacked significant details about the Ramadan fasting. Most studies showed that Ramadan fasting did not impair short-term maximal performances in soccer players (i.e., vertical jump, sprint performance, maximal voluntary contraction, hand grip, agility performance). During the 30-s Wingate test, the repeated sprint exercise (RSE) tasks, and the long-duration incremental and non-incremental exercises, most studies reported some negative effects of Ramadan fasting even when the training load was maintained. For the soccer specific skills and test with ball, most studies reported that there was no significant negative effects of the fasting month on performance when the training load was maintained or slightly reduced during the Ramadan. The continuance of training during Ramadan fasting, with maintained training load, has no negative effects on short-term maximal performances and soccer specific skills and test with ball. However, performances of the 30-s Wingate test, the RSE tasks, and the long-duration incremental and non-incremental exercises were significantly impaired during Ramadan fasting even when the training load was maintained.

Wed

20

Nov

2019

Latest research in football - week 45 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Improvements in strength and functional performance after Kinesio taping in semi-professional male soccer players with and without functional ankle instability
Reference: Foot (Edinb). 2019 Jun 27;41:12-18. doi: 10.1016/j.foot.2019.06.006. [Epub ahead of print]
Authors: Fereydounnia S, Shadmehr A, Attarbashi Moghadam B, Talebian Moghadam S, Mir SM, Salemi S, Pourkazemi F
Summary: The objectives of this study were to compare the immediate effects of two methods of Kinesio taping on muscle strength, functional performance, and balance in athletes with and without functional ankle instability (FAI). The present study investigated the effects of distal taping (muscle application over peroneus longus) and proximal- distal taping (muscle application over gluteus medius and peroneus longus) on the strength of evertor and hip abductor muscles, side hop test, figure of 8 hop test, and star excursion balance test in semi-professional male soccer players with and without FAI (n=15 in each group). A Multifactorial repeated measure ANOVA was used for comparison. There were significant differences for factor effect in all outcome measures (P<0.05), except for the figure of 8 hop test. No significant differences for group effects and group by factor interaction effects (P>0.05) was observed except for the side hop test. Kinesio taping had immediate effects on improving strength, performance and balance. However, there were no differences on the method of application. Clinicians can consider the application Kinesio taping during the rehabilitation process of athletes with FAI, to improve balance and strength. The long-term impacts of taping on the functional, balance and strength measures should be investigated in future studies.


#2 Hip Range of Motion: Which Plane of Motion Is More Predictive of Lower Extremity Injury in Elite Soccer Players? A Prospective Study
Reference: J Surg Orthop Adv. 2019 Fall;28(3):201-208.
Authors: Shah SS, Testa EJ, Gammal I, Sullivan J, Gerland RW, Goldstein J, Sheridan B, Mashura M, Shah AS, Goodwillie A, Cohn RM
Summary: The objective of this study was to determine which plane of hip motion (rotational or sagittal) is more predictive of lower extremity (LE) injury in elite soccer players. A total of 69 athletes (43 professional and 26 collegiate) were examined (mean age, 22.6 years). Bilateral hip internal rotation (IR), external rotation, extension, and flexion measurements were taken along with the modified Thomas test during preseason physicals. There were 42 LE injuries (injury rate 3.74/1000 athlete exposures). Mean IR was 25.2. and 29.9° for injured versus noninjured extremities, respectively (p = .009). There was a significant association between decreased IR (categorized as IR < 28°) and incidence of ipsilateral LE injury (p = .042). Extremities with IR < 28° were 2.81 times more likely to sustain a LE injury (95% CI, 1.15.6.84; p = .023). With a utilitarian focus, the current study has identified a measurement of decreased hip IR with potential for substantial clinical value in collegiate and professional soccer players. (Journal of Surgical Orthopaedic Advances 28(3):201-208, 2019).


#3 Italian consensus statement (2020) on return to play after lower limb muscle injury in football (soccer)
Reference: BMJ Open Sport Exerc Med. 2019 Oct 15;5(1):e000505. doi: 10.1136/bmjsem-2018-000505. eCollection 2019.
Authors: Bisciotti GN, Volpi P, Alberti G, Aprato A, Artina M, Auci A, Bait C, Belli A, Bellistri G, Bettinsoli P, Bisciotti A, Bisciotti A, Bona S, Bresciani M, Bruzzone A, Buda R, Buffoli M, Callini M, Canata G, Cardinali D, Cassaghi G, Castagnetti L, Clerici S, Corradini B, Corsini A, D'Agostino C, Dellasette E, Di Pietto F, Enrica D, Eirale C, Foglia A, Franceschi F, Frizziero A, Galbiati A, Giammatei C, Landreau P, Mazzola C, Moretti B, Muratore M, Nanni G, Niccolai R, Orizio C, Pantalone A, Parra F, Pasta G, Patroni P, Pelella D, Pulici L, Quaglia A, Respizzi S, Ricciotti L, Rispoli A, Rosa F, Rossato A, Sannicandro I, Sprenger C, Tarantola C, Tenconi FG, Tognini G, Tosi F, Trinchese GF, Vago P, Zappia M, Vuckovich Z, Zini R, Trainini M, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6797382/pdf/bmjsem-2018-000505.pdf
Summary: Return to play (RTP) decisions in football are currently based on expert opinion. No consensus guideline has been published to demonstrate an evidence-based decision-making process in football (soccer). Our aim was to provide a framework for evidence-based decision-making in RTP following lower limb muscle injuries sustained in football. A 1-day consensus meeting was held in Milan, on 31 August 2018, involving 66 national and international experts from various academic backgrounds. A narrative review of the current evidence for RTP decision-making in football was provided to delegates. Assembled experts came to a consensus on the best practice for managing RTP following lower limb muscle injuries via the Delphi process. Consensus was reached on (1) the definitions of 'return to training' and 'return to play' in football. We agreed on 'return to training' and RTP in football, the appropriate use of clinical and imaging assessments, and laboratory and field tests for return to training following lower limb muscle injury, and identified objective criteria for RTP based on global positioning system technology. Level of evidence IV, grade of recommendation D.


#4 Physical Performance Differences Between Starter and Non-Starter Players During Professional Soccer Friendly Matches
Reference: J Hum Kinet. 2019 Oct 18;69:283-291. doi: 10.2478/hukin-2019-0018. eCollection 2019 Oct.
Authors: Giménez JV, Leicht AS, Gomez MA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815094/pdf/hukin-69-283.pdf
Summary: The aim of this study was to investigate the physical performance differences between players that started (i.e. starters, ≥65 minutes played) and those that were substituted into (i.e. non-starter) soccer friendly matches. Fourteen professional players (age: 23.2 ± 2.7 years, body height: 178 ± 6 cm, body mass: 73.2 ± 6.9 kg) took part in this study. Twenty, physical performance-related match variables (e.g. distance covered at different intensities, accelerations and decelerations, player load, maximal running speed, exertion index, work-to-rest ratio and rating of perceived exertion) were collected during two matches. Results were analysed using effect sizes (ES) and magnitude based inferences. Compared to starters, non-starters covered greater match distance within the following intensity categories: >3.3≤4.2m/s (very likely), >4.2≤5 m/s (likely) and >5≤6.9 m/s (likely). In contrast, similar match average acceleration and deceleration values were identified for starters and non-starters (trivial). Indicators of workloads including player loads (very likely), the exertion index (very likely), and the work-to-rest ratio (very likely) were greater, while self- reported ratings of perceived exertion were lower (likely) for non-starters compared to starters. The current study demonstrates that substantial physical performance differences during friendly soccer matches exist between starters and non-starters. Identification of these differences enables coaches and analysts to potentially prescribe optimal training loads and microcycles based upon player's match starting status.


#5 Player Load and Metabolic Power Dynamics as Load Quantifiers in Soccer
Reference: J Hum Kinet. 2019 Oct 18;69:259-269. doi: 10.2478/hukin-2018-0072. eCollection 2019 Oct.
Authors: Reche-Soto P, Cardona-Nieto D, Diaz-Suarez A, Bastida-Castillo A, Gomez-Carmona C, Garcia-Rubio J, Pino-Ortega J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815086/pdf/hukin-69-259.pdf
Summary: There has recently been an increase in quantification and objective analysis of soccer performance due to improvements in technology using load indexes such as Player Load (PL) and Metabolic Power (MP). The objectives of this study were: (1) to describe the performance of PL and MP in competition according to the specific role, match-to- match variation, periods of play, game location and match status according to game periods, and (2) to analyze the relationship between both indexes. Twenty-one national-level soccer players were distributed in the following specific positional roles: external defenders (ED) (n = 4), central defenders (CD) (n = 4), midfielders (M) (n = 5), external midfielders (EM) (n = 4) and attackers (A) (n = 4). A total of 12 matches played by a Spanish Third Division team during the 2016/2017 season were analyzed. WIMU PROTM inertial devices (RealTrack System, Almeria, Spain) were used for recording the data. The main results were: (1) a performance reduction in both variables over the course of match time, (2) significant differences in both variables based on the specific position, (3) differences in physical demands during the season matches, (4) winning during a game period and the condition of being the visitor team provoked higher demands, and (5) a high correlation between both variables in soccer. In conclusion, different contextual variables influence the external load demands; both indexes are related so they could be used for external load quantification, and it is necessary to analyze physical demands of the competition for a specific and individualized load design in training sessions.


#6 Combined Small-Sided Game and High-Intensity Interval Training in Soccer Players: The Effect of Exercise Order
Reference: J Hum Kinet. 2019 Oct 18;69:249-257. doi: 10.2478/hukin-2018-0092. eCollection 2019 Oct.
Authors: Rabbani A, Clemente FM, Kargarfard M, Jahangiri S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815089/pdf/hukin-69-249.pdf
Summary: The aim of the present study was to compare combined small-sided game (SSG) and high-intensity interval training (HIT) with different order. Twenty-one semi-professional soccer players were divided into two groups: SSG+HIT (n = 10) and HIT+SSG (n = 11), and underwent similar four-week training programs. Players completed the 30-15 Intermittent Fitness Test (30-15IFT) before and after the experiment; maximum speed (VIFT) was recorded. During the experiment, seven sessions of SSG (3 vs 3) and HIT (15"-15" with 95-100% VIFT) were implemented. Weekly accumulated training loads for both groups during the experiment were similar. Moderate improvements in VIFT were observed in both SSG+HIT (+6.2%, 90% confidence limits, [CL] 4.6; 7.7 and Effect Size, [ES] +0.96) and HIT+SSG (+6.9%, 90% CL 4.6; 9.3 and ES +0.97) groups. Between-group difference in changes of VIFT was trivial (+0.7%, 90% CL -1.8; 3.3 and ES +0.11). Combining SSG and HIT in different order elicited the same enhancement in high-intensity intermittent performance in soccer players.


#7 Trends of Goal Scoring Patterns in Soccer: A Retrospective Analysis of Five Successive FIFA World Cup Tournaments
Reference: J Hum Kinet. 2019 Oct 18;69:231-238. doi: 10.2478/hukin-2019-0015. eCollection 2019 Oct.
Authors: Kubayi A, Toriola A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815073/pdf/hukin-69-231.pdf
Summary: This study analysed the 795 goals scored during a total of 320 matches played in five successive FIFA World Cup tournaments (1998-2014). Data were obtained through YouTube videos and analysed by means of Longomatch software. The variables analysed included the number of goals scored per half (45-min period), per 15-min period, and per 30-min period of extra time, goal scoring zones, goals scored by substitutes, types of goals scored, and goals scored according to the playing position. With regard to 15-min period analysis, most goals were scored between the 76th and 90th minutes (24.7%) of the game in all five World Cup competitions. Chi-square analyses showed no significant (p > 0.05) differences in the frequency of goal scoring patterns per 45-min and 15-min periods in the five World Cup tournaments. Most goals were scored from inside the goal (23.8%) and penalty (14.6%) areas. The greatest number of goals was scored by strikers (54.2%), followed by midfielders (33.3%) and defenders (2.3%). These findings provide practical implications for improving goal-scoring performance in soccer.


#8 Variability of Technical Actions During Small-Sided Games in Young Soccer Players
Reference: J Hum Kinet. 2019 Oct 18;69:201-212. doi: 10.2478/hukin-2019-0013. eCollection 2019 Oct.
Authors: Clemente FM, Sarmento H, Costa IT, Enes AR, Lima R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815080/pdf/hukin-69-201.pdf
Summary: The purpose of this study was three-fold: (i) to test the between-sessions variability of 3 vs. 3 and 6 vs. 6 formats in under-11 players, (ii) to assess the within-session variability of 3 vs. 3 and 6 vs. 6 formats, and (iii) to investigate the variations of technical actions between formats. Sixteen soccer players (10.1 ± 0.3 years old) participated in this study. Both formats of play were played twice within an interval of one week to test the between-session variability and the variables of conquered balls (CBs), received balls (RBs), lost balls (LBs), attacking balls/passes (ABs) and shots (Ss) were analyzed using the Performance Assessment in Team Sports instrument in all matches. Moderate variations on the sum of sets during the 3 vs. 3 and 6 vs. 6 formats were observed in all variables. Considering the variations of technical actions made between sets in the 3 vs. 3 format, likely moderate increases were found in set 2 vs. 1 in terms of RB (37.5%, [-2.7;94.2]), and likely small decreases were found in set 3 vs. 2 for the same variable (-18.3%, [-37.8;7.3]). In the 6 vs. 6 format, only possibly small increases were found for set 3 vs. 1 in S (22.5%, [-7.0;61.3]). Generally (sum of sets), the variables standardized per minute revealed almost certain very large decreases in the 6 vs. 6 vs. the 3 vs. 3 format in the variables of CB (-67.9%, [-75.3;-55.9]), LB (-66.0%, [-73.9;-55.7]), RB (-65.6%, [-74.8;- 53.1]) and S (-87.6%, [-93.1;-77.7]). The results of this study suggest that both formats of play are too noisy to be reproducible. The 3 vs. 3 format largely increased the number of individual technical actions.


#9 Analysis of Successful Offensive Play Patterns by the Spanish Soccer Team
Authors: Amatria M, Maneiro R, Anguera MT
Reference: J Hum Kinet. 2019 Oct 18;69:191-200. doi: 10.2478/hukin-2019-0011. eCollection 2019 Oct.
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815082/pdf/hukin-69-191.pdf
Summary: Victory is the ultimate aim in soccer and therefore when a team wins an elite European or world championship, attempts will invariably be made to emulate the winning team's style of play. In this study, we performed an in-depth analysis of play by the Spanish soccer team during the 2012 UEFA European Championship, where it was crowned champion. Using observational methodology and T-pattern analysis, we identified hidden patterns of play that ended in a goal for the Spanish team. A generalizability coefficient (e2) of 0.986 demonstrated that the offensive patterns detected are robust and highly generalizable. These patterns were formed by technical actions consisting of ball control and pass, with alternations between short and long passes, in the central area of the rival pitch, with use of both wings to achieve width of play and prioritization of width over depth of play. We also found patterns showing that goals and shots at goal were made on a ball delivered from the opposite direction to the shot and were not preceded by a technical action.


#10 Practical Use of the Navigate Pain Application for the Assessment of the Area, Location, and Frequency of the Pain Location in Young Soccer Goalkeepers
Reference: J Hum Kinet. 2019 Oct 18;69:125-135. doi: 10.2478/hukin-2019-0091. eCollection 2019 Oct.
Authors: Muracki J, Kumorek M, Kisilewicz A, Pożarowszczyk B, Larsen DB, Kawczyński A, Boudreau S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815074/pdf/hukin-69-125.pdf
Summary: Next to winning, minimizing injuries during training and matches is one of the primary goals of professional team sports games. Soreness and pain can be early indicators and risk factors for acute or long-term injuries. Monitoring pain intensity and duration, as well as potential sources, are useful for planning practices and can be effective means for preventing injury. The aim of this study was to assess the areas and locations of pain in young soccer goalkeepers during a training camp, and to differentiate the area and frequency between pain arising from the muscles (MP), joints (JP), or as a result of an impact (IP). Recordings of the MP, JP, and IP location along with the area were performed using digital body mapping software (Navigate Pain Android app, Aalborg University, Denmark) installed on a tablet personal computer at the end of each training day across a 5-day training camp. There was a significant difference in the area between the three types of pain (p < 0.001). The post hoc analysis revealed statistically significant differences between the pixel areas of IP versus JP (p < 0.001), IP versus MP (p < 0.001), and JP versus MP (p < 0.001). There was no significant time-effect for the IP area between 1-5 days of training (p = 0.610), neither for MP (p = 0.118) or JP (p = 0.797) and no significant difference for all three pain areas between the front and the back side of the body. The body regions most often reported for MP were thighs, while for JP they were groin and hips, and for IP the hips, shoulders, and forearms were most frequently indicated. This is the first study to map and report the pain distribution associated with training across a 5-day training camp in soccer goalkeepers, and these findings emphasize the value of using digital pain drawings clinically as well as for monitoring the health status of soccer players.


#11 Relationships between the Expression of the ACTN3 Gene and Explosive Power of Soccer Players
Reference: J Hum Kinet. 2019 Oct 18;69:79-87. doi: 10.2478/hukin-2019-0020. eCollection 2019 Oct.
Authors: Domańska-Senderowska D, Szmigielska P, Snochowska A, Jastrzębski Z, Jegier A, Kiszałkiewicz J, Jastrzębska J, Pastuszak-Lewandoska D, Cięszczyk P, Suchanecka A, Wilk M, Brzeziański M, Brzeziańska-Lasota E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815091/pdf/hukin-69-079.pdf
Summary: Muscle strength and maximal speed are factors determining athlete's results during competition. Their association with ACTN3 gene activity has been documented. The purpose of this study was the analysis of ACTN3 gene expression during a 2 month training cycle of soccer players and its correlation with the countermovement jump (CMJ) and squat jump (SJ). The study group consisted of 22 soccer players (aged 17-18). The study material included peripheral blood lymphocytes. The relative expression (RQ) of the ACTN3 gene was analyzed by qPCR and performed before and after the two-month training cycle. Before the training cycle low expression levels of ACTN3 (median RQ = 0.95) were observed, yet after the training cycle they were elevated (median RQ = 1.98) ( p = 0.003). There was an increase in performance of both jumps: SJ (p = 0.020) and CMJ (p = 0.012) at the end of the training cycle. A simultaneous increase in the ACTN3 gene expression level and height in both jump tests was observed in 73% of athletes (p > 0.05). There were no significant relationships between the ACTN3 gene expression level and the results of the CMJ and SJ. However, explosive strength is a complex feature shaped by many different factors and it could be the reason why we did not observe correlations between these variables.


#12 Correlations between body composition, aerobic capacity, speed and distance covered among professional soccer players during official matches
Reference: J Sports Med Phys Fitness. 2019 Oct 24. doi: 10.23736/S0022-4707.19.09979-1. [Epub ahead of print]
Authors: Radzimiński Ł, Szwarc A, Padrón-Cabo A, Jastrzębski Z
Summary: The importance of sprinting and high-speed running activities during a soccer match is indisputable. The main purpose of this study was to investigate the relations between the players' speed, aerobic capacity, body composition and distance covered in different speed zones during official soccer matches and to compare the match performance variables according to playing position. Twenty-three professional soccer players (age: 27.9 ± 4.58 y, body mass: 78.8 ± 7.35 kg, height: 181.7 ± 6.53 cm) participated in this study. During 13 weeks of the competitive season, players participated in 16 official matches and completed body composition analyses, sprint tests, multistage shuttle run tests (MST), and incremental running tests (IRTs). Significant negative correlations were found between sprint distance and percent of fat mass (FM; r = -0.57, p < 0.0001), MST (r = 0.45, p < 0.001), maximal speed (r = 0.44, p < 0.001). High-speed running (HSR) distance covered by the players during the matches was significantly correlated with FM (r = -0.38, p < 0.001) and MST distance (r = 0.30, p < 0.01). These data indicate that professional soccer players with lower fat content and higher levels of aerobic capacity are able to cover longer distances in sprinting and HSR during official matches.


#13 Knee muscle and tendon stiffness in professional soccer players: a shear-wave elastography study
Reference: J Sports Med Phys Fitness. 2019 Oct 24. doi: 10.23736/S0022-4707.19.09938-9. [Epub ahead of print]
Authors: Taş S, Özkan Ö, Karaçoban L, Dönmez G, Çetin A, Korkusuz F
Summary: It is well known that several risk factors such as fatigue, previous injury, muscle strength deficit or imbalance are related to a higher incidence of knee injuries in professional soccer players. Knee muscle and tendon stiffness may be another factor that is related to knee injuries in professional soccer players. Therefore, the aim of the present study was to investigate the differences between professional soccer players and healthy sedentary males in terms of the stiffness of patellar tendon (PT), quadriceps tendon (QT), and rectus femoris muscle (RF) and vastus medialis muscle (VM). The study group was comprised of 17 professional male soccer players in age range of 24-37 years. The control group was comprised of 22 healthy sedentary males in an age range of 21-36 years. Shear-Wave Velocity (SWV) measurements of the selected muscles and tendons were performed using an ultrasonography device with a lineal probe. The professional soccer players had lower SWV of PT (p=0.024) and QT (p<0.001) in the dominant leg compared to the control group; however, SWV of PT (p=0.455) and QT (p=0.827) in the non-dominant leg were similar in both groups. SWV of RF was higher in both dominant and non-dominant legs in professional soccer players compared to the control group (p<0.05); however, SWV of VM was similar in both groups (p>0.05). Professional soccer players had lower PT and QT stiffness. On the other hand, they had higher RF stiffness compared to sedentary individuals. Furthermore, VM stiffness was similar in both groups.

Wed

20

Nov

2019

Latest research in football - week 44 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effect of the FIFA 11+ on Landing Patterns and Baseline Movement Errors in Elite Male Youth Soccer Players
Reference: J Sport Rehabil. 2019 Oct 18:1-8. doi: 10.1123/jsr.2018-0374. [Epub ahead of print]
Authors: Akbari H, Sahebozamani M, Daneshjoo A, Amiri-Khorasani M, Shimokochi Y.
Summary: There is no evidence regarding the effect of the FIFA 11+ on landing kinematics in male soccer players, and few studies exist regarding the evaluating progress of interventions based on the initial biomechanical profile. The aim was to investigate the effect of the FIFA 11+ program on landing patterns in soccer players classified as at low or high risk for noncontact anterior cruciate ligament injuries. Field-based functional movement screening performed at the soccer field was measured in a total of 24 elite male youth soccer players participated in this study. The intervention group performed the FIFA 11+ program 3 times per week for 8 weeks, whereas the control group performed their regular warm-up.Before and after the intervention, all participants were assessed for landing mechanics using the Landing Error Scoring System. Pretraining Landing Error Scoring System scores were used to determine risk groups. The FIFA 11+ group had greater improvement than the control group in terms of improving the landing pattern; there was a significant intergroup difference (F1,20 = 28.86, P < .001, ηp2=.591). Soccer players categorized as being at high risk displayed greater improvement from the FIFA 11+ program than those at low risk (P = .03). However, there was no significant difference in the proportion of risk category following the routine warm-up program (P = 1.000). The present study provides evidence of the usefulness of the FIFA 11+ program for reducing risk factors associated with noncontact anterior cruciate ligament injuries. The authors' results also suggest that soccer players with the higher risk profile would benefit more than those with lower risk profiles and that targeting them may improve the efficacy of the FIFA 11+ program.


#2 Neurodegenerative Disease Mortality among Former Professional Soccer Players
Reference: N Engl J Med. 2019 Oct 21. doi: 10.1056/NEJMoa1908483. [Epub ahead of print]
Authors: Mackay DF, Russell ER, Stewart K, MacLean JA, Pell JP, Stewart W
Summary: Neurodegenerative disorders have been reported in elite athletes who participated in contact sports. The incidence of neurodegenerative disease among former professional soccer players has not been well characterized. We conducted a retrospective cohort study to compare mortality from neurodegenerative disease among 7676 former professional soccer players (identified from databases of Scottish players) with that among 23,028 controls from the general population who were matched to the players on the basis of sex, age, and degree of social deprivation. Causes of death were determined from death certificates. Data on medications dispensed for the treatment of dementia in the two cohorts were also compared. Prescription information was obtained from the national Prescribing Information System. Over a median of 18 years, 1180 former soccer players (15.4%) and 3807 controls (16.5%) died. All-cause mortality was lower among former players than among controls up to the age of 70 years and was higher thereafter. Mortality from ischemic heart disease was lower among former players than among controls (hazard ratio, 0.80; 95% confidence interval [CI], 0.66 to 0.97; P = 0.02), as was mortality from lung cancer (hazard ratio, 0.53; 95% CI, 0.40 to 0.70; P<0.001). Mortality with neurodegenerative disease listed as the primary cause was 1.7% among former soccer players and 0.5% among controls (subhazard ratio [the hazard ratio adjusted for competing risks of death from ischemic heart disease and death from any cancer], 3.45; 95% CI, 2.11 to 5.62; P<0.001). Among former players, mortality with neurodegenerative disease listed as the primary or a contributory cause on the death certificate varied according to disease subtype and was highest among those with Alzheimer's disease (hazard ratio [former players vs. controls], 5.07; 95% CI, 2.92 to 8.82; P<0.001) and lowest among those with Parkinson's disease (hazard ratio, 2.15; 95% CI, 1.17 to 3.96; P = 0.01). Dementia-related medications were prescribed more frequently to former players than to controls (odds ratio, 4.90; 95% CI, 3.81 to 6.31; P<0.001). Mortality with neurodegenerative disease listed as the primary or a contributory cause did not differ significantly between goalkeepers and outfield players (hazard ratio, 0.73; 95% CI, 0.43 to 1.24; P = 0.24), but dementia-related medications were prescribed less frequently to goalkeepers (odds ratio, 0.41; 95% CI, 0.19 to 0.89; P = 0.02). In this retrospective epidemiologic analysis, mortality from neurodegenerative disease was higher and mortality from other common diseases lower among former Scottish professional soccer players than among matched controls. Dementia-related medications were prescribed more frequently to former players than to controls. These observations need to be confirmed in prospective matched-cohort studies. (Funded by the Football Association and Professional Footballers' Association.).


#3 Sport Specialization and Coordination Differences in Multisport Adolescent Female Basketball, Soccer, and Volleyball Athletes
Reference: J Athl Train. 2019 Oct;54(10):1105-1114. doi: 10.4085/1062-6050-407-18.
Authors: DiCesare CA, Montalvo A, Foss KDB, Thomas SM, Hewett TE, Jayanthi NA, Myer GD
Summary: Early sport specialization, or the participation in 1 sport year-round to the exclusion of all others, is a growing concern in youth athletics because of its possible association with musculoskeletal injury. The underlying injury risk may be the result of coordination differences that sport-specialized athletes have been speculated to exhibit relative to multisport athletes; however, little evidence exists to support or refute this notion. The aim was to examine relative hip- and knee-joint angular-motion variability among adolescent sport-specialized and multisport female adolescent athletes to determine how sport specialization may affect coordination. A total of 366 sport-specialized and 366 multisport adolescent female basketball, soccer, and volleyball players participated in this study with an drop-vertical-jump (DVJ) assessment. Average coupling-angle variability (CAV) for hip flexion and knee flexion, knee flexion and ankle flexion, hip flexion and knee abduction, knee flexion and knee abduction, knee flexion and knee internal rotation, and knee abduction and knee internal rotation. The sport-specialized group exhibited increased coupling variability in dominant-limb hip flexion and knee flexion (P = .015), knee flexion and knee abduction (P = .014), and knee flexion and knee internal rotation (P = .048) while landing during the DVJ, although they had small effect sizes (η2 = 0.010, 0.010, and 0.007, respectively). No differences were present between groups for any of the other CAV measures of the dominant limb, and no differences were found for any CAV measures of the nondominant limb (all P values > .05). Sport specialization was associated with increased variability of critical hip- and knee-joint couplings responsible for effective landing during the DVJ. Altered coordination strategies that involve the hip and knee joints may underlie unstable landings, inefficient force-absorption strategies, or greater contact forces that can place the lower extremities at risk for injury (or a combination of these).


#4 Evaluation for the effects of nutritional education on Chinese elite male young soccer players: The application of adjusted dietary balance index (DBI)
Reference: J Exerc Sci Fit. 2020 Jan;18(1):1-6. doi: 10.1016/j.jesf.2019.08.004. Epub 2019 Aug 20.
Authors: Zeng D, Fang ZL, Qin L, Yu AQ, Ren YB, Xue BY, Zhou X, Gao ZY, Ding M, An N, Wang QR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6796798/pdf/main.pdf
Summary: The aim of this study was to evaluate the effect of nutrition education on Chinese elite male young soccer players through the knowledge, attitude, behavior (KAP) survey and an adjusted dietary balance index (DBI). 30 Chinese elite male young soccer players were randomly divided into two groups: lecture group (N = 15, Age: 16.7 ± 1.8 years, Height: 173.9 ± 9.0 cm; Weight: 62.4 ± 13.0 kg; Training years: 5.6 ± 2.7 years) and non-lecture group (N = 15, Age: 16.8 ± 1.7 years, Height: 175.5 ± 7.9 cm; Weight: 62.5 ± 12.3 kg; Training years: 6.2 ± 3.3). The comics book was given to the non-lecture group, while the a four-week nutritional quality education along with comic books were given to the lecture group. Before and after 4 weeks nutritional education, dietary nutritional status of both groups was assessed. The main outcome measurements included the scores for each part of the KAP survey, diet status (food-weighing method) and the dietary index in the adjusted DBI-07 system (DBI-low bound score, LBS; DBI-high bound score, HBS; and DBI-diet quality distance, DQD). In the lecture group, significant differences were found in the scores of general nutrition knowledge, sports nutrition knowledge and total scores of KAP dietary questionnaire after 4 weeks nutritional education (P < 0.01). However, there is no significant difference in dietary attitude and dietary behavior (P > 0.05) on both two groups. There is no significant change in the DBI-low bound score (LBS), DBI-high bound score (HBS) and DBI-diet quality distance (DQD) of dietary quality index (P > 0.05) in both two groups. Four weeks nutritional quality education improved the understanding of dietary nutrition among Chinese elite male young soccer players.


#5 Analysis of the Association between Running Performance and Game Performance Indicators in Professional Soccer Players
Reference: Int J Environ Res Public Health. 2019 Oct 21;16(20). pii: E4032. doi: 10.3390/ijerph16204032.
Authors: Modric T, Versic S, Sekulic D, Liposek S
Download link: https://www.mdpi.com/1660-4601/16/20/4032/pdf
Summary: Running performance (RP) and game performance indicators (GPI) are important determinants of success in soccer (football), but there is an evident lack of knowledge about the possible associations between RP and GPI. This study aimed to identify associations between RP and GPI in professional soccer players and to compare RP and GPI among soccer playing positions. One hundred one match performances were observed over the course of half of a season at the highest level of national competition in Croatia. Players (mean ± SD, age: 23.85 ± 2.88 years; body height: 183.05 ± 8.88 cm; body mass: 78.69 ± 7.17 kg) were classified into five playing positions (central defenders (n = 26), full-backs (n = 24), central midfielders (n = 33), wide midfielders (n = 10), and forwards (n = 8). RP, as measured by global positioning system, included the total distance covered, distance covered in five speed categories (walking, jogging, running, high-speed running, and maximal sprinting), total number of accelerations, number of high-intensity accelerations, total number of decelerations, and number of high-intensity decelerations. The GPI were collected by the position-specific performance statistics index (InStat index). The average total distance was 10,298.4 ± 928.7 m, with central defenders having the shortest and central midfielders having the greatest covered distances. The running (r = 0.419, p = 0.03) and high-intensity accelerations (r = 0.493, p = 0.01) were correlated with the InStat index for central defenders. The number of decelerations of full-backs (r = -0.43, p = 0.04) and the distance covered during sprinting of forwards (r = 0.80, p = 0.02) were associated with their GPI obtained by InStat index. The specific correlations between RP and GPI should be considered during the conditioning process in soccer. The soccer training should follow the specific requirements of the playing positions established herein, which will allow players to meet the game demands and to perform successfully.


#6 Working memory capacity does not always promote dual-task motor performance: The case of juggling in soccer
Reference: Scand J Psychol. 2019 Oct 21. doi: 10.1111/sjop.12589. [Epub ahead of print]
Authors: Laurin R, Finez L
Download link: https://onlinelibrary.wiley.com/doi/abs/10.1111/sjop.12589
Summary: The aim of this research was to refine our understanding of the role of working memory capacity (WMC) on motor performances that require attentional control in dual-task situations. Three studies were carried out on soccer players. Each participant had to perform a juggling task in both normal and dual-task conditions. In Study 1, the interfering task was a mental calculation test performed under time pressure (strong cognitive load). In Study 2, the interfering task was a count-down test (low cognitive load). In Study 3 an intra-individual design in which participants perform dual-tasks increasingly complex has been proposed. Results showed a positive relationship between participants' WMC and their dual-task motor performance when the cognitive load was low and a negative relationship when the cognitive load was high. This paper highlights the role of the WMC in the activation of different modes of processing and its importance on the performance in dual-task.


#7 Injury Profile of Elite Male Young Soccer Players in a Spanish Professional Soccer Club: A Prospective Study During 4 Consecutive Seasons
Reference: J Sport Rehabil. 2019 Oct 18:1-7. doi: 10.1123/jsr.2019-0113. [Epub ahead of print]
Authors: Raya-González J, Suárez-Arrones L, Navandar A, Balsalobre-Fernández C, Sáez de Villarreal E.
Summary: As the number of injuries in young soccer players increases, an epidemiological study is the first step in improving preventive strategies. The aim was to analyze the injury profile of a Spanish professional soccer club's academy during 4 consecutive seasons and to examine the injury incidence across different chronological age groups. Aggregate injury and exposure data collected during 4 consecutive seasons were collected of three hundred nine elite male young soccer players. Injuries that led to participation time missed from training and match play prospectively reported by medical or coaching staff of the club were used as outcome measures. A total of 464 time-loss injuries were observed during this study period. The overall injury incidence was 2.93 injuries per 1000 hours, with higher incidence during matches than during training (10.16 vs 2.10 injuries/1000 h; rate ratio [RR] = 0.21; 95% confidence interval [CI], 0.17-0.25; P < .05), with the U14 age group presenting the lowest injury rate (2.39 injuries/1000 h; RR = 1.15-1.57; P < .05). In terms of injury severity, moderate injuries were the most frequent (1.42 injuries/1000 h). Muscle injuries were the most common type of injuries (57.7%; 2.75 injuries/1000 h; RR = 1.84-13.4; P < .05), and hamstrings (93/268) were the most affected muscle group (0.58 injuries/1000 h; RR = 1.58-2.91; P < .05). Injury incidence showed a seasonal variation as indicated by peaks in August and October. In matches, specifically, the match period between 75 and 90 minutes showed the highest injury incidence (10.29 injuries/1000 h; RR = 1.89-6.38; P < .01). The findings of this study suggest that specific preventive strategies must be implemented to try to reduce the injury incidence in Spanish elite young soccer players attending to the characteristics of each age group.


#8 Elite Players' Perceptions of Football Playing Surfaces: A Qualitative Study
Reference: Res Q Exerc Sport. 2019 Oct 24:1-13. doi: 10.1080/02701367.2019.1660757. [Epub ahead of print]
Authors: Roberts JR, Osei-Owusu P, Mears AC, Harland AR
Summary: The decision by the International Football Association Board in 2004 to approve the use of artificial surfaces in elite football (soccer) competitions remains controversial amongst many players, managers and coaching staff. The aim of this study was to conduct a comprehensive assessment of players' opinions to better understand the influence of playing surfaces on the game of football and identify factors that may contribute to differences of opinion. Qualitative data were collected from 103 elite footballers and 21 coaching staff during a series of interviews and focus groups. A thematic analysis was conducted to identify patterns in the data. Players considered that the type and condition of a playing surface influenced ball-surface interactions, game play, tactics/strategy, footwear selection, movement, risk of injury and fatigue. Together these influence a player's perception of the suitability of a surface and also their mindset, which could ultimately affect their performance. The majority of participants in this study expressed a higher preference for natural grass over artificial turf pitches. A perceived increased risk of injury on artificial turf remains a primary concern despite a lack of supporting evidence in research studies. To address this discrepancy, the reporting of muscle soreness and the effect of constant surface switching merit further consideration. Not all participants shared the same views and player characteristics such as age, surface experience, injury history and playing style/position were found to be potential factors that could account for differences in elite players' opinions regarding the surfaces used in football.


#9 Acute effects of differential learning on football kicking performance and in countermovement jump
Reference: PLoS One. 2019 Oct 23;14(10):e0224280. doi: 10.1371/journal.pone.0224280. eCollection 2019.
Authors: Gaspar A, Santos S, Coutinho D, Gonçalves B, Sampaio J, Leite N
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0224280&type=printable
Summary: The aim of this study was to identify the acute effects of a differential-learning training program on football kicking performance and countermovement jump. Twenty youth Portuguese under-15 football players participated in this study. All players were exposed to two training approaches: i) traditional, in which the players performed a total of 36 kicks in a blocked and repetitive approach; and ii) differential learning, which consisted in the 36 kicks using differential variations in each kick. Football kicking impact and velocity were assessed using a Stalker radar gun, while the kicking accuracy was assessed by aggregating the total number of points achieved during 12 kicks into a goal, which was divided into quantifiable scoring zones. Lastly, leg power was measured using a countermovement jump. Measurements were performed at baseline, post-intervention, and following a 35-minute training match. The comparisons between the baseline and post-test revealed that the differential learning approach promoted a possibly ~5% increase in the countermovement jump (small effects) and a likely ~3% increase in the average velocity (small effects) when compared with the traditional training approach. From the accuracy perspective, there was a moderate decrease from the baseline to the post-test and post-match in accurate kicks into zone 1 (centre of the goal) and a moderate decrease from the baseline to the post-match in accurate kicks into zone 5 (lateral zones at short height) in the differential intervention. In turn, a small increase in the accurate kicks into zones 4 and 6 (lateral zones of the goal and nearest to the bar, respectively) was found from the baseline to the post-match in the differential intervention. Overall, the differential learning intervention was more beneficial than a traditional training protocol with respect to acute improvements in countermovement jump performance, football kicking velocity and higher scoring zones kicking accuracy.
 

#10 Testing the functionality of peripheral vision in a mixed-methods football field study
Reference: J Sports Sci. 2019 Dec;37(24):2789-2797. doi: 10.1080/02640414.2019.1664100. Epub 2019 Sep 6.
Authors: Vater C, Luginbühl S, Magnaguagno L
Summary: In team sports, peripheral vision might be useful to simultaneously monitor movements of opponents and teammates. Until now, however, little is known about the perceptual-cognitive processes underlying peripheral vision in a sporting task. Therefore, we used a mixed-methods approach with in-situ decision making (3 vs. 3 situations) and retrospective verbal reports to identify perceptual strategies used for optimal information pick-up in high- and low-skilled football players. Our results show that the use of peripheral vision by central defenders depends on the position of the ball and the position of the direct opponent. Players were shown to either use a pivot strategy, whereby they frequently look at the direct opponent if he is not in the possession of the ball in addition to making saccades to monitor other players, or they employ a more direct strategy, in which gaze is anchored on this location, avoiding saccades and monitoring the other players with peripheral vision. Based on our findings we make recommendations about how these gaze strategies can be further tested in future research and how sports practice can benefit from these results.


#11 The Relationship Between Personality Traits and Muscle Injuries in Swedish Elite Male Football Players
Reference: J Sport Rehabil. 2019 Oct 18:1-6. doi: 10.1123/jsr.2018-0473. [Epub ahead of print]
Authors: Eckerman M, Svensson K, Edman G, Alricsson M.
Summary: The physical and mental demands of an elite football player are complex, which may explain why injuries are common in football. At elite level, muscle injuries of the lower-extremity are the most common among male football players, and the research hitherto is limited. The aim was to investigate whether personality traits affect the incidence of muscle injuries among male football players from the first league in Sweden. A male football team from the first league in Sweden was prospectively followed, in terms of muscle injuries of the lower-extremity during 8 seasons, between 2007 and 2015. All muscle injuries included in this study were evaluated and diagnosed with ultrasonography. Players from the team filled out the Swedish Universities Scales of Personality questionnaire. Swedish Universities Scales of Personality questionnaire consists of 91 items and is divided into 13 categories. The raw values of each scale were linearly transformed to T scores, having a mean (SD) of 50 (10). All variables were summarized with standard descriptive statistics, such as frequency, mean, and SD. As data were of interval scale and no variable distribution was severely skewed, differences between noninjured players, rarely injured players, and frequently injured players were analyzed with 1-way analysis of variance with post hoc tests by Tukey honestly significant difference test. No significant difference in personality traits were observed between noninjured players, rarely injured players, and frequently injured players regarding number of muscle injuries (P > .05). However, a trend (P = .07) was seen, where frequently injured players scored higher on stress susceptibility than rarely injured players. A player's stress susceptibility should be taken into consideration by the player, coaches, and medical staff when assessing the risk of a muscle injury. Also, preventive measures available for these players may need to be considered.

Tue

05

Nov

2019

Latest research in football - week 43 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Acute sleep hygiene strategy improves objective sleep latency following a late-evening soccer-specific training session: A randomized controlled trial
Reference: J Sports Sci. 2019 Dec;37(23):2711-2719. doi: 10.1080/02640414.2019.1661938. Epub 2019 Sep 6.
Authors: Vitale JA, La Torre A, Banfi G, Bonato M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6768094/pdf/fphys-10-01187.pdf
Summary: The aim of this study was to evaluate the effects of sleep hygiene (SH) education on sleep quality in soccer players after a late-evening small-sided-game (SSG) training session. Twenty-nine non-professional players were recruited and allocated to either an experimental group (EG, n = 17) that received SH education, or a control group (CG, n = 12). SSG consisted of 3 × 4 min in a 4vs4, with 3 min of recovery and was performed at 8.00 p.m. Sleep quality was monitored via actigraphy and sleep diary entries before (PRE) and two nights after (POST1, POST2) the SSG. Sleep latency (SL) differed between the two groups at POST1 (4.9 ± 5.4 vs. 15.5 ± 16.1 for EG and CG, respectively; p = 0.017, effect size [ES] = 2.0); SL values were lower at POST1 compared to PRE for the EG (-47%; p = 0.021, ES = 0.6). Subjective sleep quality was better in the EG than the CG at POST1 (8.6 ± 1.0 vs. 7.1 ± 2.0 for EG and CG, respectively; p = 0.016, ES = 0.9) with a significant improvement over PRE-values (+11.0%, p = 0.004, ES = 0.8). Although SL and subjective sleep quality did not decrease significantly from POST1 to POST2 values at POST2 no longer differed significantly form baseline and, hence, indicate that observed effects may be short-lasting. No other objective sleep indices were influenced by late-evening training or SH practices implemented by the EG. Soccer players may benefit from acute SH strategies to reduce the time to sleep onset after late-evening training sessions.


#2 New curve sprint test for soccer players: Reliability and relationship with linear sprint
Reference: J Sports Sci. 2019 Oct 13:1-6. doi: 10.1080/02640414.2019.1677391. [Epub ahead of print]
Authors: Fílter A, Olivares J, Santalla A, Nakamura FY, Loturco I, Requena B
Summary: The speed performance is involved not only in linear sprints, but also in a wide spectrum of multi-directional movements, such as curve sprinting. Curved sprint can be defined as sprint with gradual and continuous change of direction (COD). Although ~85% of the actions performed at maximum velocity in a professional soccer league are curvilinear sprints, there is not any specific test to assess this ability. This study aimed to analyse the reliability of a new curve sprint test, and compare its results with those obtained by soccer players in linear sprint. Forty experienced soccer players performed 3 attempts of curve sprint (using the penalty arc) to right and left side (17 m), and 3 linear sprints (17 m) in two different days. The ICCs (inter-session reliability) were 0.93 for sprint curve right side (CSRS) and 0.89 for sprint curve left side (CSLS), considered "acceptable". The CVs (intra-session reliability) were 0.87% in CSRS and 1.15% in CSLS. The coefficient of determination (R2) between linear and curve sprinting was ~35%. The association between curve sides was "very large" (r = 0.878; p < 0.01). In summary, we showed that "curve sprint test" is highly reliable, and that curvilinear and linear sprints are different and independent actions.


#3 The most demanding passages of play in football competition: a comparison between halves
Reference: Biol Sport. 2019 Sep;36(3):233-240. doi: 10.5114/biolsport.2019.86005. Epub 2019 Jun 14.
Authors: Casamichana D, Castellano J, Diaz AG, Gabbett TJ, Martin-Garcia A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786330/pdf/JBS-36-86005.pdf
Summary: The purpose of this investigation was to determine the differences between halves in the most demanding passages of play in football players according to playing position and duration-specific activity. Global positioning system data were collected from twenty-three football players from a reserve squad of the Spanish La Liga. A total of 265 individual match half data were analysed across the competitive season. Players were categorised based on positional groups: full-back (FB), central defender (CD), midfielder (MF), offensive midfielder (OMF) and forwards (FW). The most demanding passage of match play was analysed using a rolling average method, where maximal values were calculated for five different time durations (1, 3, 5, 10 min and half completed) using distance (m·min-1), high metabolic load distance (HMLD; m·min-1) and average metabolic power (AMP; W·kg-1) as variables of interest. The differences between the first and second half increased as the rolling duration increased, reaching the greatest difference between halves in the complete half (45 min) in all the variables studied (ES = 0.54 ± 0.15, 0.75 ± 0.15 and 0.76 ± 0.15 in distance, HMLD and AMP). The CDs were the players that presented the greatest differences, and it was in the AMP variable where the greatest differences between the first and second half were found. Large decreases in AMP were found for CD (ES = -1.30 ± 0.36) and moderate decreases were found in AMP for FB (ES = -0.84 ± 0.30) and OMF (ES = -0.78 ± 0.37). These results provide insight into the most demanding passages of play to inform training practices for specific football playing positions.


#4 A method for predicting background advertisement exposure parameters in sporting events: Televised football game approach
Reference: PLoS One. 2019 Oct 17;14(10):e0223662. doi: 10.1371/journal.pone.0223662. eCollection 2019.
Authors: Xiao Y, John C, Ren X, Zhang P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6797103/pdf/pone.0223662.pdf
Summary: The background advertisement exposure parameters (BAEP) forms a premise for sponsorship negotiation and the basis for estimating the sponsorship value of background advertising. Prediction of the BAEP has a great contribution to the sporting events organizers and sponsors in terms of negotiating, decision-making for bidding, and income-generating. Virtual Reality (VR), technology was utilized to construct a virtual three-dimensional model of the sports venue and simulate the telecast of the event. Based on VR technology and computer graphics theory, a pre-event prediction method for estimating the background advertisement exposure parameters of sporting events was put forward. The pre and post measures of the thirty BAEP of televised football games were compared to verify the effectiveness of the prediction method. There was no significant difference between the pre- and post-measurement results for the same football game. The pre- and post-measurement results of the thirty BAEP of televised football games were tightly matched. Using the prediction method can predict the BAEP of televised football games effectively and overcomes the shortcomings of current prediction methods that inhibits the effectiveness of the prediction of exposure parameters due to changes such as the type of the sporting events, the size of the sports venue, the layout of the background advertisements, and the placement of the television cameras, etc.


#5 Trait Self-Control Discriminates Between Youth Football Players Selected and Not Selected for the German Talent Program: A Bayesian Analysis
Reference: Front Psychol. 2019 Sep 26;10:2203. doi: 10.3389/fpsyg.2019.02203. eCollection 2019.
Authors: Wolff W, Bertrams A, Schüler J
Download link:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6775196/pdf/fpsyg-10-02203.pdf
Summary: Trait self-control predicts success in various walks of life. Sports is a prototypical domain, where self-control is required, and there is evidence that successful athletes display superior self-control. Here, we assess if self-control already differs between athletes that were selected for a talent development program and non-selected athletes. Self-reported trait self-control was assessed in n = 25 (7 = female, 13.2 ± 1.7 years) youth football players who were part of the German talent development program and in n = 27 (6 = female, 13.6 ± 1.8 years) age and sex matched youth football players, who trained at the same clubs but had not been selected for the program. A one-sided Bayesian two-sample t-test yielded a Bayes factor of 54.99, indicating very strong evidence for the hypothesis that elite youth football players have higher trait self-control than non-elite youth football players. The 95% credibility interval indicates that the true value of δ lies between 0.28 and 1.42, indicating some uncertainty regarding the effects' magnitude. We show that already at young age, elite athletes display higher levels of self-control than their less successful peers. This underlines the importance of self-control as an important personality factor for success. These findings might have implications for talent selection and for sport psychological training.


#6 Clinical Features and isokinetic Parameters in Assessing Injury Risk in elite Football Players
Reference: Int J Sports Med. 2019 Oct 15. doi: 10.1055/a-1014-2911. [Epub ahead of print]
Authors: Liporaci RF, Saad M, Grossi DB, Riberto M
Summary: Football players frequently face the occurrence of non-contact injuries. Although there are likely multiple factors that contribute to increased risk of non-contact injury, it remains a challenge to correlate all these factors. However, it is not clear how much of individual training abilities may interfere in these events. As such, the primary aim of the present study was to determine whether the reduction of functional performance of the thigh in the isokinetic knee tests, anthropometric and morbid history can establish risk factors for lower-limb musculoskeletal injuries throughout the season. The incidence of injuries and odds ratios were calculated for suspected risk factors. Hamstring/Quadriceps conventional ratio outside of the safety range (55-64%) may be involved in the occurrence of non-contact muscle injuries and the risk for any musculoskeletal injuries in the lower extremities is 16 times higher when extensor peak of torque exceeds 10% and 12 times higher when flexor peak of torque difference was greater than 10%. This kind of evaluation can result in intervention programs that may decrease the risk of lower-limb musculoskeletal injuries. Based on these results we can establish a specific and individualized exercise program for each athlete and thus protect them during the season.


#7 Psychological characteristics of developing excellence in elite youth football players in English professional academies
Reference: J Sports Sci. 2019 Oct 13:1-7. doi: 10.1080/02640414.2019.1676526. [Epub ahead of print]
Authors: Saward C, Morris JG, Nevill ME, Minniti AM, Sunderland C
Summary: This mixed-longitudinal prospective study examined the development of psychological characteristics of developing excellence in relation to the career progression of elite youth football players. In a 20-month period, 111 academy football players aged 11-16 completed the Psychological Characteristics of Developing Excellence Questionnaire (PCDEQ) on 1-5 occasions. This combination of single and repeated assessments resulted in a mixed-longitudinal sample of 226 completed PCDEQs. Players were then prospectively tracked, and their scholarship status assessed at follow-up, at age U17. Multilevel modelling revealed that coping with performance and developmental pressures scores increased with age, and that Category 1-2 academy scholars (4.35 ± 0.61) scored higher than Category 3-4 academy scholars (3.99 ± 0.67) and non-scholars (4.02 ± 0.78) (p < .05). Evaluating performances and working on weaknesses scores increased with age for Category 1-2 academy scholars (U12-U14 vs. U15-U16 = 5.16 ± 0.48 vs. 5.38 ± 0.45), compared to non-scholars (U12-U14 vs. U15-U16 = 5.11 ± 0.59 vs. 5.03 ± 0.71) (p < .05). Imagery use during practice and competition scores decreased with age (U12-U14 vs. U15-U16 = 4.45 ± 0.66 vs. 4.29 ± 0.70) (p < .05). A blend of PCDEs may facilitate optimal career progression. Football academies should develop players' PCDEs, with a particular focus on developing their coping skills and their ability to realistically evaluate performances and work on weaknesses.


#8 How does the modern football goalkeeper train? - An exploration of expert goalkeeper coaches' skill training approaches
Reference: J Sports Sci. 2019 Jul 16:1-9. doi: 10.1080/02640414.2019.1643202. [Epub ahead of print]
Authors: Otte FW, Millar SK, Klatt S
Summary: The football goalkeeper position arguably represents a unique role within the team sport. Despite its highly complex skill demands, research on football goalkeeping has only sporadically examined the position within isolated and limited parameters. In particular, there is limited literature on "modern" skill acquisition training methods and approaches within the field of goalkeeper training. In a cross-cultural study with fifteen expert goalkeeper coaches, researchers here examined the overarching research question of "how does the modern football goalkeeper train?". Semi-structured interviews explored expert coaches' views on critical skills for performance in goalkeeping and the training approaches used to develop these critical skills. Results indicate that four skill sets are considered essential by goalkeeper coaches, these are: decision-making skills, athleticism, mentality, and technical skills. In terms of developing these skills in goalkeeper-specific training, the majority of expert coaches apply a similar microstructure to training sessions. This structure involves a steady progression from simple to complex training tasks, where for large parts, isolated technical training appears to be prioritised over a holistic training approach that integrates technical skills and perceptual-cognitive components (e.g., decision making). Scientific and practical recommendations for researchers and practitioners in the field of football goalkeeper coaching are provided.


#9 The effect of age on between-match physical performance variability in professional soccer players
Reference: Res Sports Med. 2019 Oct 20:1-9. doi: 10.1080/15438627.2019.1680985. [Epub ahead of print]
Authors: Lorenzo-Martínez M, Rey E, Padrón-Cabo A
Summary: This study aimed to analyse the effect of age on between-match variability of physical performance in professional soccer players. For this purpose, observations on entire match performance were collected on 787 professional soccer players competing in the first or second division of Spanish league during the 2017-2018 season. Players were classified into six groups according to their age: G1 (≤22.5 years), G2 (22.6-25.1 years), G3 (25.2-27.5 years), G4 (27.6-30.1 years), G5 (30.2-33.1 years) and G6 (≥33.2 years). Coefficients of variation (CVs) were calculated individually for each player and performance variable: total distance, low- intensity, medium-intensity, high-intensity running (HIR), sprinting, number of HIR, number of sprints, average speed and maximal speed. The main finding of this study was that players under 25.2 years (G1 and G2) showed lower CVs for high-intensity activities (HIR and sprinting) in comparison with players over 33.1 years (G6). These findings provide useful information for soccer coaches, who could put extra attention on physical performance of the oldest players when they have to play an entire match, because their performance is more variable and uncertain in comparison with the youngest.


#10 Basal Serum Cortisol and Testosterone/Cortisol Ratio Are Related to Rate of Na+ Lost During Exercise in Elite Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2019 Oct 17:1-6. doi: 10.1123/ijsnem.2019-0129. [Epub ahead of print]
Authors: Castro-Sepulveda M, Cancino J, Fernández-Verdejo R, Pérez-Luco C, Jannas-Vela S, Ramirez-Campillo R, Del Coso J, Zbinden-Foncea H
Summary: During exercise, the human body maintains optimal body temperature through thermoregulatory sweating, which implies the loss of water, sodium (Na+), and other electrolytes. Sweat rate and sweat Na+ concentration show high interindividual variability, even in individuals exercising under similar conditions. Testosterone and cortisol may regulate sweat Na+ loss by modifying the expression/activity of the cystic fibrosis transmembrane conductance regulator. This has not been tested. As a first approximation, the authors aimed to determine whether basal serum concentrations of testosterone or cortisol, or the testosterone/cortisol ratio relate to sweat Na+ loss during exercise. A total of 22 male elite soccer players participated in the study. Testosterone and cortisol were measured in blood samples before exercise (basal). Sweat samples were collected during a training session, and sweat Na+ concentration was determined. The basal serum concentrations of testosterone and cortisol and their ratio were (mean [SD]) 13.6 (3.3) pg/ml, 228.9 (41.4) ng/ml, and 0.06 (0.02), respectively. During exercise, the rate of Na+ loss was related to cortisol (r = .43; p < .05) and to the testosterone/cortisol ratio (r = -.46; p < .01), independently of the sweating rate. The results suggest that cortisol and the testosterone/cortisol ratio may influence Na+ loss during exercise. It is unknown whether this regulation depends on the cystic fibrosis transmembrane conductance regulator.


#11 Comparison of Drop Jump and Tuck Jump Knee Joint Kinematics in Elite Male Youth Soccer Players: Implications for Injury Risk Screening
Reference: J Sport Rehabil. 2019 Oct 18:1-6. doi: 10.1123/jsr.2019-0077. [Epub ahead of print]
Authors: Lloyd RS, Oliver JL, Myer GD, De Ste Croix MB, Wass J, Read PJ.
Summary: Despite the popularity of jump-landing tasks being used to identify injury risk factors, minimal data currently exist examining differences in knee kinematics during commonly used bilateral jumping tasks. This is especially the case for rebounding-based protocols involving young athletes. The aim was to compare the frontal plane projection angles (FPPAs) during the drop vertical jump (DVJ) and tuck jump assessment (TJA) in a cohort of elite male youth soccer players of varying maturity status. A total of 57 male youth soccer players from an English championship soccer club participated in this study. Participants performed 3 trials of the DVJ and TJA, during which movement was recorded with 2-dimensional video cameras. FPPA for both right (FPPA-r) and left (FPPA-l) legs, with values <180° indicative of medial knee displacement. On a whole-group level, FPPA-r (172.7° [7.4°] vs 177.2° [11.7°]; P < .05; effect size [ES] = 0.46) and FPPA-l (173.4° [7.3°] vs 179.2° [11.0°]; P < .05; ES = 0.62) were significantly greater for both limbs in the TJA compared with the DVJ; however, these differences were less consistent when grouped by maturity status. FPPA-r during the TJA was significantly and moderately greater in the circa-peak height velocity (PHV) group compared with the post-PHV cohorts (169.4° [6.4°] vs 175.3° [7.8°]; P < .05; ES = 0.49). Whole-group data showed moderate relationships for FPPA-r and FPPA-l between the TJA and DVJ; however, stronger relationships were shown in circa- and post-PHV players compared with the pre-PHV cohort. Considering that the TJA exposed players to a larger FPPA and was sensitive to between-group differences in FPPA-r, the TJA could be viewed as a more suitable screen for identifying FPPA in young male soccer players.

Fri

25

Oct

2019

Latest research in football - week 42 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Return-to-Play Practices Following Hamstring Injury: A Worldwide Survey of 131 Premier League Football Teams
Reference: Sports Med. 2019 Oct 8. doi: 10.1007/s40279-019-01199-2. [Epub ahead of print]
Authors: Dunlop G, Ardern CL, Andersen TE, Lewin C, Dupont G, Ashworth B, O'Driscoll G, Rolls A, Brown S, McCall A
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-019-01199-2.pdf
Summary: Return-to-play (RTP) is an on-going challenge in professional football. Return-to-play related research is increasing. However, it is unknown to what extent the recommendations presented within research are being implemented by professional football teams, and where there are gaps between research and practice. The purposes of this study were (1) to determine if premier-league football teams worldwide follow a RTP continuum, (2) to identify RTP criteria used and (3) to understand how RTP decision-making occurs in applied practice. We sent a structured online survey to practitioners responsible for the RTP programme in 310 professional teams from 34 premier-leagues worldwide. The survey comprised four sections, based on hamstring muscle injury: (1) criteria used throughout RTP phases, (2) the frequency with which progression criteria were achieved, (3) RTP decision-making process and (4) challenges to decision-making. One-hundred and thirty-one teams responded with a completed survey (42%). One-hundred and twenty-four teams (95%) used a continuum to guide RTP, assessing a combination of clinical, functional and psychological criteria to inform decisions to progress. One-hundred and five (80%) teams reported using a shared decision-making approach considering the input of multiple stakeholders. Team hierarchy, match- and player-related factors were common challenges perceived to influence decision-making. General research recommendations for RTP and the beliefs and practices of practitioners appear to match with, the majority of teams assessing functional, clinical and psychological criteria throughout a RTP continuum to inform decision-making which is also shared among key stakeholders. However, specific criteria, metrics and thresholds used, and the specific involvement, dynamics and interactions of staff during decision-making are not clear.


#2 Match Running Performance on Three Different Competitive Standards in Norwegian Soccer
Reference: Sports Med Int Open. 2019 Oct 16;3(3):E82-E88. doi: 10.1055/a-0943-3682. eCollection 2019 Dec.
Authors: Sæterbakken A, Haug V, Fransson D, Grendstad HN, Gundersen HS, Moe VF, Ylvisaker E, Shaw M, Riiser A, Andersen V
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6795532/pdf/10-1055-a-0943-3682.pdf
Summary: The aim of the study was to compare running performance of three competitive standards and to examine the effects of being promoted to a higher league in Norwegian football. One club's first and second team were included. The first team consisted of professional soccer players playing at Level 2 (2015 season) and Level 1 (2016 season). The second team consisted of amateurs playing at Level 4. A fully automatic tracking system was used to examine running performance, divided into different running-speed categories and playing position. Forty-one matches were included containing 278 observations. Level 1 performed 61 and 51% sprinting compared to Level 2 and Level 4 but similar high-speed running. Similar high-speed running distances were observed only for the different playing positions at Level 1 compared to Level 2 and 4. The sprinting distance was greater for the central defender and attacker, and the number of accelerations was greater for central midfielders and wide midfielders' playing at Level 1 compared to lower competitive standards. In conclusion, better competitive standards resulted in greater high-intensity actions than lower leagues in Norwegian soccer. Furthermore, only central defenders and attackers increased their high-intensity locomotions when the team was promoted.


#3 Effects of different repeated sprint-training frequencies in youth soccer players
Reference: Biol Sport. 2019 Sep;36(3):257-264. doi: 10.5114/biolsport.2019.87047. Epub 2019 Jul 31.
Authors: Rey E, Padrón-Cabo A, Costa PB, Lago-Fuentes C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786322/pdf/JBS-36-87047.pdf
Summary: The aim of this study was to determine the effects of 2 different repeated-sprint ability (RSA) training frequencies (2 RSA sessions per week [RSA2D] or 1 RSA session [RSA1D]) under volume-equated conditions on sprint and RSA performance in under-15 (U15) soccer players. Twenty-seven youth male soccer players (age: 12.29±0.47 years; height: 158.35±10.86 cm; weight: 45.08±8.05 kg) were randomly assigned to RSA2D (n=14) or RSA1D (n=13) groups. The players performed the same RSA training for 6 weeks, and only the training frequency differed between the groups. Before and after the training period, 5 m sprint, 10 m sprint, 20 m sprint and the RSA test were assessed. No significant time × group interactions were observed (p>0.05). Within-group analysis showed significant improvements in 20 m sprint (p=0.046, partial eta squared [η p 2 ] = 0.150, large) and RSA average time (p=0.001, η p 2 =0.438, large), fastest time (p=0.012, η p 2 =0.229, large), and total time (p=0.001, η p 2 =0.438, large) from pre-test to post-test in RSA1D and RSA2D groups. However, no significant pre-post changes (p>0.05) were found in 5 m and 10 m sprint tests. In the between-group analysis, there were no significant differences between RSA1D and RSA2D groups in any variable. In conclusion, the current findings suggest that 6 weeks of RSA training 1 or 2 times per week in addition to typical soccer training produced significant and similar improvements in sprint and RSA performances. This information could be useful for coaches when planning training sessions during congested fixtures of soccer competitions or in periods when the emphasis should be placed on other physical qualities.


#4 Running technique is more effective than soccer-specific training for improving the sprint and agility performances with ball possession of prepubescent soccer players
Reference: Biol Sport. 2019 Sep;36(3):249-255. doi: 10.5114/biolsport.2019.87046. Epub 2019 Jul 31.
Authors: Lupo C, Ungureanu AN, Varalda M, Brustio PR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786321/pdf/JBS-36-87046.pdf
Summary: Soccer-specific training is easily associable to players' sprint abilities demonstrated during a match. However, no clear evidence has been provided to show whether this approach is more effective than training focused on running techniques for sprints in prepubescent soccer players. Thus, the present study aimed at comparing the effects of these two training approaches on prepubescent soccer players' sprint performances. Ninety-five players (10±2 years) competing in local (Piedmont, Italy) Under-9 (N=21), -10 (N=24), -11 (N=25) and -13 (N=25) championships were recruited for the study. Sixty-three and 32 players were included in the running training group (RTG) and soccer-specific group (SSG), respectively. Before (PRE) and after (POST) the training period (2 weekly sessions for 12 weeks), sprint abilities were evaluated by means of four 20-m sprint tests: linear sprint (20-mL), linear sprint with ball possession (20-mLB), sprint with change of direction (20-mCoD), sprint with change of direction and with ball possession (20-mCoDB). A linear mixed model was applied to evaluate differences (P≤0.05) between the RTG and SSG in the four tests and categories, comparing PRE and POST performances. A main effect emerged for the interaction between groups, sessions (p=0.014; Between PRE ES range=0.03, 0.85; Within PRE-POST ES range=-0.45, 0.09), highlighting a POST improvement of RTG for the 20-mLB (Δ=-7.9%; ES=0.85) and 20-mCoDB (Δ=-5.9%; ES=0.33). In contrast, no improvements emerged for the SSG. The present findings indicate that the training approach of the RTG is more able to improve prepubescent soccer players' sprint performances than that of the SSG, with the emphasis on ball possession executions, which are particularly game-related.


#5 Effects of in-season enhanced negative work-based vs traditional weight training on change of direction and hamstrings-to-quadriceps ratio in soccer players
Reference: Biol Sport. 2019 Sep;36(3):241-248. doi: 10.5114/biolsport.2019.87045. Epub 2019 Jul 31.
Authors: Coratella G, Beato M, Cè E, Scurati R, Milanese C, Schena F, Esposito F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786325/pdf/JBS-36-87045.pdf
Summary: The present study investigated the effects of in-season enhanced negative work-based training (ENT) vs weight training in the change of direction (COD), sprinting and jumping ability, muscle mass and strength in semi-professional soccer players. Forty male soccer players participated in the eight-week, 1 d/w intervention consisting of 48 squat repetitions for ENT using a flywheel device (inertia=0.11 kg·m -2 ) or weight training (80%1 RM) as a control group (CON). Agility T-test, 20+20 m shuttle, 10 m and 30 m sprint, squat jump (SJ) and countermovement jump (CMJ), lean mass, quadriceps and hamstrings strength and the hamstrings-to-quadriceps ratio were measured. Time on agility T-test and 20+20 m shuttle decreased in ENT (effect-size =-1.44, 95% CI -2.24/-0.68 and -0.75, -1.09/-0.42 respectively) but not in CON (-0.33, -0.87/0.19 and -0.13, -0.58/0.32). SJ and CMJ height increased in both ENT (0.71, 0.45/0.97 and 0.65, 0.38/0.93) and CON (0.41, 0.23/0.60 and 0.36, 0.12/0.70). Overall, quadriceps and hamstrings strength increased in both ENT and CON (0.38/0.79), but the hamstrings-to-quadriceps ratio increased in ENT (0.31, 0.22/0.40) but not in CON (0.03, -0.18/0.24). Lean mass increased in both ENT (0.41, 0.26/0.57) and CON (0.29, 0.14/0.44). The repeated negative actions performed in ENT may have led to improvements in braking ability, a key point in COD performance. Semi-professional soccer players may benefit from in-season ENT to enhance COD and the negative-specific adaptations in muscle strength and hamstrings-to-quadriceps ratio.


#6 Do asymmetry scores influence speed and power performance in elite female soccer players?
Reference: Biol Sport. 2019 Sep;36(3):209-216. doi: 10.5114/biolsport.2019.85454. Epub 2019 May 30.
Authors: Loturco I, Pereira LA, Kobal R, Abad CCC, Rosseti M, Carpes FP, Bishop C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786326/pdf/JBS-36-85454.pdf
Summary: This study examined the relationships between vertical jump asymmetries and speed and power performance in elite female soccer athletes. Sixteen professional female soccer players (age: 23.0 ± 3.8 years; body mass: 60.2 ± 7.3 kg; height: 165.1 ± 5.5 cm) from the same professional club participated in this study. Athletes performed unilateral and bilateral squat jumps (SJ) and countermovement jumps (CMJ) on a portable force plate; 30-m sprinting test; Zigzag change-of-direction (COD) test; and muscle power testing using the jump squat (JS) exercise. Asymmetry scores were obtained from the results of the unilateral SJ and CMJ by the percentage difference between the dominant and non-dominant legs. The Pearson product-moment coefficient of correlation was used to analyse the correlations between the bilateral and unilateral vertical jump variables and the physical tests. The bilateral vertical jump performance (in both SJ and CMJ) was closely related to sprinting and JS power performances (r values ranging from 0.50 to 0.73; P< 0.05). In contrast, no significant associations were found between jump asymmetries and performance measures. Our data suggest that asymmetry scores derived from unilateral vertical jumps are not capable of influencing the speed-power performance of professional female soccer players.


#7 Adolescent female soccer players' soccer-specific warm-up effects on performance and inter-limb asymmetries
Reference: Biol Sport. 2019 Sep;36(3):199-207. doi: 10.5114/biolsport.2019.85453. Epub 2019 May 28.
Authors: Pardos-Mainer E, Casajús JA, Gonzalo-Skok O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6786331/pdf/JBS-36-85453.pdf
Summary: No studies have assessed whether changes in physical performance and inter-limb asymmetries (ILA) can be achieved with the FIFA 11+ prevention programme in adolescent female soccer players. The aim of this study was to assess the effect of the FIFA 11+ programme compared with a standard warm-up on physical performance and ILA in adolescent female soccer players. Thirty-six adolescent female soccer players were randomly assigned to an experimental (EG; n = 19) or a control group (CG; n = 17). Unilateral/bilateral countermovement jump (CMJ), drop jump (DJ) and horizontal jump tests, two different change of direction tests, an ankle dorsiflexion test, the Y-Balance test (YBT) and inter-limb asymmetries were measured before and after 10 weeks of training. The results revealed no significant group-by-time interactions in the vast majority of variables (p>0.05). Paired t-test revealed significant improvements of the right [effect size (ES):0.56] and left (ES:0.49) CMJ, right (ES:0.74) and left (ES:0.54) DJ (ES:0.74), right (ES:1.27) and left (ES:1.26) posteromedial direction and right (ES:0.89) and left (ES:0.84) posterolateral direction in the YBT in the EG (p < 0.05). Right anterior direction in the YBT and V-cut test were significantly improved in both groups (p<0.05). For inter-limb asymmetry variables, no significant group-by-time interactions (ES:0 to 0.93) and an improvement between pre- and post-tests (ES:-0.76 to 0.49) were observed. Therefore, the FIFA 11+ programme led to improved unilateral jumping, dynamic balance and reduced lower extremity symmetries of several tests in adolescent female soccer players.


#8 Retraction Note: Assessing cardiorespiratory fitness of soccer players: is test specificity the issue?-a review
Reference: Sports Med Open. 2019 Oct 17;5(1):42. doi: 10.1186/s40798-019-0217-9.
Authors: Jemni M, Prince MS, Baker JS
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-019-0217-9


#9 Effect of Kinesio Taping and balance exercises on postural control in amateur soccer players: A randomised control trial
Reference: J Sports Sci. 2019 Dec;37(24):2853-2862. doi: 10.1080/02640414.2019.1677016. Epub 2019 Oct 15.
Authors: Inglés M, Serra-Añó P, Méndez ÀG, Zarzoso M, Aguilar-Rodríguez M, Suso-Martí L, Cuenca-Martínez F, Espí-López GV
Summary: The objective of this study was to determine the effect of Kinesio Taping (KT), alone or together with balance exercises (BE), on parameters related to postural control, such as dynamic balance, static balance and flexibility. Forty-four male amateur soccer players (mean age 24.45 (4.79) years) were randomly allocated to 3 groups: KT+BE that received KT and BE (n = 16); KTp+BE, in which the KT was used as a placebo (n = 15) and KT alone (n = 13). The intervention period lasted 4 weeks. Star Excursion Balance Test (SEBT), Unipedal Stance Test (UST) and the Toe Touch Test (TTT) were assessed at baseline (pre), two weeks after beginning the treatment (mid) and after the intervention (post). We observed a significant improvement on the SEBT (mid and post-treatment) and the UST (post-treatment), but not on the TTT in either KT+BE or KTp+BE groups post treatment. No differences were found either in KT group at any time point or between groups in any variable studied. In conclusion, KT functional correction technique does not improve static and dynamic balance when applied alone, whereas BE alone or combined with KT significantly improves these variables. None of these techniques has any effect on flexibility.


#10 Pediatric retinal damage due to soccer-ball-related injury: Results from the last decade
Reference: Eur J Ophthalmol. 2019 Oct 15:1120672119882332. doi: 10.1177/1120672119882332. [Epub ahead of print]
Authors: Leshno A, Alhalel A, Fogel-Levin M, Zloto O, Moisseiev J, Vidne-Hay O
Summary: The aim was to outline the incidence of posterior segment injuries related to soccer-ball blunt trauma in children. Retrospective search of the computerized hospital medical database between the years 2007 and 2017. All pediatric trauma cases were reviewed and cases with blunt trauma related to direct orbital/ocular hit from a soccer-ball were included. Cases were divided into two groups (non-severe and severe) based on the presence of sight-threatening findings on presentation (e.g. retinal tear, vitreous hemorrhage, retinal detachment, and macular edema). Out of 343 pediatric patients with relevant diagnoses, 14 (4.1%) were treated for injuries related to soccer-ball trauma. All patients were males at their early-to-mid teens (14.3 ± 2.1 years). The most common funduscopic finding was peripheral commotio retina (13, 93%). There was equal distribution between the two groups (seven each). Retinal injury in the severe group included retinal tear (3), vitreous hemorrhage (4), retinal detachment (1), and macular hole (1). Five patients in this group presented with visual acuity of 20/25 or better. Rate of external signs of injury were similar in both groups. Soccer-ball blunt trauma in children can cause significant posterior segment injuries regardless of the presence of external injury or ocular complaints. A thorough ocular exam is mandatory in all cases for the detection of vision-threatening retinal injuries.


#11 Acute sleep hygiene strategy improves objective sleep latency following a late-evening soccer-specific training session: A randomized controlled trial
Reference: J Sports Sci. 2019 Dec;37(23):2711-2719. doi: 10.1080/02640414.2019.1661938. Epub 2019 Sep 6.
Authors: Vitale JA, La Torre A, Banfi G, Bonato M
Summary: The aim of this study was to evaluate the effects of sleep hygiene (SH) education on sleep quality in soccer players after a late-evening small-sided-game (SSG) training session. Twenty-nine non-professional players were recruited and allocated to either an experimental group (EG, n = 17) that received SH education, or a control group (CG, n = 12). SSG consisted of 3 × 4 min in a 4vs4, with 3 min of recovery and was performed at 8.00 p.m. Sleep quality was monitored via actigraphy and sleep diary entries before (PRE) and two nights after (POST1, POST2) the SSG. Sleep latency (SL) differed between the two groups at POST1 (4.9 ± 5.4 vs. 15.5 ± 16.1 for EG and CG, respectively; p = 0.017, effect size [ES] = 2.0); SL values were lower at POST1 compared to PRE for the EG (-47%; p = 0.021, ES = 0.6). Subjective sleep quality was better in the EG than the CG at POST1 (8.6 ± 1.0 vs. 7.1 ± 2.0 for EG and CG, respectively; p = 0.016, ES = 0.9) with a significant improvement over PRE-values (+11.0%, p = 0.004, ES = 0.8). Although SL and subjective sleep quality did not decrease significantly from POST1 to POST2 values at POST2 no longer differed significantly form baseline and, hence, indicate that observed effects may be short-lasting. No other objective sleep indices were influenced by late-evening training or SH practices implemented by the EG. Soccer players may benefit from acute SH strategies to reduce the time to sleep onset after late-evening training sessions.

Sun

20

Oct

2019

Latest research in football - week 41 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Isometric Posterior Chain Peak Force Recovery Response Following Match-Play in Elite Youth Soccer Players: Associations with Relative Posterior Chain Strength
Reference: Sports (Basel). 2019 Oct 1;7(10). pii: E218. doi: 10.3390/sports7100218.
Authors: Constantine E, Taberner M, Richter C, Willett M, Cohen DD
Download link: https://www.mdpi.com/2075-4663/7/10/218/pdf
Summary: The purpose of this study was to determine changes in two tests of lower limb isometric posterior chain force (IPC-F) following 90 min of match-play in elite youth soccer players and the interaction between relative strength and recovery profile. 14 players (age: 16 ± 2 years) performed 3 × 3 second IPC-F tests unilaterally at 30° and 90° of knee and hip flexion pre- and post-match, +24 h, +48 h, and +72 h post-match. Peak force was recorded for both limbs, combined and expressed relative to bodyweight (N/kg). A two-way repeated measures analysis of variance was performed to determine differences in force output between joint angles, time intervals and subjects. As there was no interaction between angle and time (p = 0.260), we report the change between timepoints as mean Δ in 90° + 30° IPC-F. Relative to pre-match IPC-F, there were significant decreases post (Δ = -18%; p > 0.001) and at +24 h (Δ = -8%; p = 0.040), no significant difference at +48 h (Δ = 0%; p = 0.992) and a significant increase at +72 h (Δ = +12%; p = 0.005). There was a large inter-individual variability in recovery profile at both angles and substantial differences between post-match deficits at 90° (-10.8%) compared to 30° (-20.7%). Higher pre-match IPC-F was correlated with the magnitude of IPC-F deficits at both angles and all time points (r = 0.56 to 0.70, p = < 0.01) except for post-match 90°. Regular IPC-F monitoring to determine the magnitude of match-induced fatigue and track recovery may help inform decision-making regarding modifications to individual players training load, particularly as there is a large inter-individual variability in response to competition. Further research is warranted to better understand and address the finding that stronger players showed larger force deficits and slower recovery following match-play.


#2 Investigating the Clinical Effect of Kinesio Tape on Muscle Performance in Healthy Young Soccer Players - A Prospective Cohort Study
Reference: Clinics (Sao Paulo). 2019 Sep 26;74:e1158. doi: 10.6061/clinics/2019/e1158. eCollection 2019.
Authors: Alrawaili SM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751367/pdf/cln-74-1158.pdf1
Summary: Kinesio tape (KT) is a visible adhesive restorative tape that has typically been utilized for injury prevention, recovery, and even performance improvement, but limited studies have assessed the effect of KT on muscle performance. The purpose of this study was to investigate the clinical impact of KT on muscle performance in healthy young soccer players. Between 25 March and 21 April 2017, sixteen healthy soccer players with a mean age of 20±2.17 were enrolled in this prospective cohort study. All participants were selected from the college football team of Prince Sattam Bin Abdulaziz University. The muscle performance of the players was evaluated with an isokinetic dynamometer for the following three conditions: without tape, immediately after applying KT, and 8 hrs post-KT application while the tape remained on the same site. The differences in peak torque and total work among the three conditions were nonsignificant (p>0.05). Additionally, applying KT to the thigh muscles did not decrease or increase the performance of non injured healthy soccer players (p>0.05). KT does not lead to beneficial outcomes of muscle performance in healthy young soccer players.


#3 Biomechanical mechanisms of jumping performance in youth elite female soccer players
Reference: J Sports Sci. 2019 Oct 1:1-7. doi: 10.1080/02640414.2019.1674526. [Epub ahead of print]
Authors: Jeras NMJ, Bovend'Eerdt TJH, McCrum C
Summary: We aimed to determine key biomechanical parameters explaining age-related jumping performance differences in youth elite female soccer players. Multiple biomechanical parameters from countermovement (CMJ) squat (SJ) and drop (DJ) jump testing of elite female soccer players (n = 60) within the same national training centre were analysed across ages 9-11y, 12-14y and 15-19y. Effects of age group and jump type on jump height were found, with the older jumping higher than the younger groups in all jumps (P < 0.05). For DJ, higher reactive strength index was found for older, compared to each younger group (P < 0.001). For CMJ and SJ, peak power was the most decisive characteristic, with significant differences between each group for absolute peak power (P < 0.0001) and body-weight-normalised peak power in CMJ (57 ± 7W/kg, 50 ± 7W/kg, 44.7 ± 5.5W/kg; P < 0.05) and between the older and each younger group in SJ (56.7 ± 7.1W/kg, 48.9 ± 7.1W/kg, 44.6 ± 6W/kg; P < 0.01). Age-related differences in jumping performance in youth elite female soccer players appear to be due to power production during standing jumps and by the ability to jump with shorter ground contact times during reactive jumps.


#4 Effect of Match Location, Team Ranking, Match Status and Tactical Dimensions on the Offensive Performance in Spanish 'La Liga' Soccer Matches
Reference: Front Psychol. 2019 Sep 12;10:2089. doi: 10.3389/fpsyg.2019.02089. eCollection 2019.
Authors: González-Rodenas J, Aranda-Malavés R, Tudela-Desantes A, Calabuig Moreno F, Casal CA, Aranda R
K

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751314/pdf/fpsyg-10-02089.pdf
Summary: The aim of this paper was to study the combined effects of tactical and contextual dimensions on achieving offensive performance in open play possessions from Spanish "La Liga" soccer matches. 1860 team possessions from 20 random matches were evaluated by means of multidimensional observation. Multilevel regression models were constructed to predict the probability to achieve offensive performance according to the tactical and contextual dimensions registered in each possession. Performing penetrative actions after recovering the ball (OR = 1.497; 95% CI: 1.022-2.192; P < 0.05), and progressing by fast attacks (OR = 3.588; 95% CI: 2.045-6.294; p < 0.001) or counterattacks (OR = 7.097; 95% CI: 3.530-14.269; P < 0.001) was more effective to create scoring opportunities than performing a non-penetrative action and progressing by combinative attack, respectively. Also, progressing by long possessions (OR = 5.057; 95% CI: 2.406-10.627; p < 0.001) was more effective than progressing by short possessions to create scoring opportunities. As for contextual dimensions, multivariate analyses showed how playing at home and against high-ranked opponents registered more likelihood of achieving offensive penetration, although no associations were found in the production of scoring opportunities. Tactical dimensions as initial penetration, type of attack and possession length played an important role on achieving offensive penetration and goal scoring opportunities in Spanish Soccer "La Liga".


#5 Transformational Leadership, Task-Involving Climate, and Their Implications in Male Junior Soccer Players: A Multilevel Approach
Reference: Int J Environ Res Public Health. 2019 Sep 28;16(19). pii: E3649. doi: 10.3390/ijerph16193649.
Authors: Álvarez O, Castillo I, Molina-García V, Tomás I
Download link: https://www.mdpi.com/1660-4601/16/19/3649/pdf
Summary: Despite the well-known positive consequences of transformational coaches in sport, there is still little research exploring the mechanisms through which coaches' transformational leadership exerts its impact on athletes. Multilevel SEM was used to examine the relationship between coaches' transformational leadership style, a task-involving climate, and leadership effectiveness outcome criteria (i.e., players' extra effort, coach effectiveness, and satisfaction with their coach), separately estimating between and within effects. A representative sample of 625 Spanish male soccer players ranging from 16 to 18 years old and nested in 50 teams completed a questionnaire package tapping the variables of interest. Results confirmed that at the team level, team perceptions of transformational leadership positively predicted teams' perceptions of task climate, which in turn positively predicted the three outcome criteria. At the individual level, players' perceptions of transformational leadership positively predicted teams' perceptions of task climate, which in turn positively predicted teams' extra effort and coach effectiveness. Mediation effects appeared at the team level for all the outcome criteria, and at the individual only for extra effort. Transformational leadership is recommended to enhance task climate, in order to increase players' extra effort, their perceptions of the effectiveness of their coach, and their satisfaction with his/her leadership style.


#6 Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players
Reference: J Bodyw Mov Ther. 2019 Jul;23(3):452-455. doi: 10.1016/j.jbmt.2019.01.016. Epub 2019 Jan 30.
Authors: Cavalcante Silva RL, Hall E, Maior AS
Summary: The aim of this study was to investigate the effects of IMT on exercise tolerance, repeated sprint ability (RSA) performance, maximal inspiratory pressure (MIP), and peak inspiratory flow (PIF) in a cohort of professional male soccer players. Twenty-two healthy male professional soccer players (18.3 ± 1.4 years; 174.5 ± 6.1 cm; 70.5 kg ± 4.6 kg; body fat 10.1 ± 4.2%) from a club in the Brazilian first division soccer league participated in this study. IMT consisted of 15 and 30 self-paced inspiratory breaths (each to 50% maximal static inspiratory pressure [P0]) in the 1-and 2-week intervention period, respectively. IMT was performed prior to soccer training (1 sets.d-1; 6 d.wk-1) with repeated sprint ability (RSA) assessed pre- and post- the 2-week period of IMT. Statistical analyses identified a significant (p < 0.001) decrease in sprint time post-IMT. Additionally, RSAbest, RSAmean, total sprint time and percentage of RSA performance decrement (RSA % dec) also showed significant decreases (p < 0.0001) post-IMT. Additional measures including MIP and PIF were also significantly elevated (p < 0.0002) following the 2-week period of IMT. In conclusion, our results raise two important issues. Firstly, IMT demonstrated enhanced inspiratory muscle strength in professional soccer players. Secondly, this increase in inspiratory muscle efficiency led to a decrease in sprint time and improved exercise tolerance. We recommend that a standard training protocol be developed and tested in an experimental and control group with a large representative sample.


#7 Regarding: "Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players"
Reference: J Bodyw Mov Ther. 2019 Jul;23(3):443-444. doi: 10.1016/j.jbmt.2019.03.012. Epub 2019 Apr 2.
Authors: Matte DL, Ribeiro GS, Esquivel MS, Karsten M
Summary: The Journal of Bodywork & Movement Therapies recently published an article by Silva et al., entitled "Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players" (Silva et al., 2019). After close reading we find that the new findings of Silva et al., (2019) are relevant and provide a promising indication that IMT can improve the performance of young male soccer players. However, some additional important points must be considered when interpreting these positive findings.


#8 Session-To-Session Variations of External Load Measures of Youth Soccer Players in Medium-Sided Games
Reference: Int J Environ Res Public Health. 2019 Sep 26;16(19). pii: E3612. doi: 10.3390/ijerph16193612.
Authors: Clemente FM, Rabbani A, Kargarfard M, Nikolaidis PT, Rosemann T, Knechtle B
Download link: https://www.mdpi.com/1660-4601/16/19/3612/pdf
Summary: The aim of this study was to analyze the variability of time-motion variables during five vs. five games when completed within the same session as, and between, two different sessions. Ten under-19 male soccer players (18.27 ± 0.47 years old) participated in this study. The five vs. five matches (3 × 5 min) were played twice with a 3-day interval of rest in the same week. Moderate between-session variations were observed for TD (total distance) (range coefficient of variation (CV), 6.9; 8.3%, confidence interval (CI), (5.0; 14.0), standardized typical error (STE), 0.68; 1.06, (0.64; 1.75)) and RD (running distance) (range CV, 53.3; 145.7%, (36.6; 338.9), STE, 0.83; 1.09, (0.60; 1.76)). PL (player load) showed small variations (range CV, 4.9; 6.0%, [3.6; 10.1], STE, 0.37; 0.43, (0.27; 0.71)). In within-session analyses for examining the differences between sets, a small decrease was observed in RD in set 3 versus set 2 (-14.8%, 90% CI (-32.1; 6.9%); standardized difference (ES): -0.39 (0.95; 0.16)). TD decreased with moderate (-3.5%, (-6.8; -0.1%); ES: -0.65(-1.30; -0.01)) and large (-8.2%, (-11.4; -4.9%); ES: -1.58(-2.24; -0.92)) effects in sets 2 and 3, respectively, versus set 1. Our results suggest that PL is the most stable performance variable. It was also verified that measures had a progressive decreasing tendency within a session.


#9 Head impact exposure in youth football - are current interventions hitting the target?
Reference: Scand J Med Sci Sports. 2019 Oct 4. doi: 10.1111/sms.13562. [Epub ahead of print]
Authors: Sandmo SB, Andersen TE, Koerte IK, Bahr R
Summary: Restrictions on heading in youth football have been implemented in some countries to limit head-impact exposure. However, current interventions remain poorly guided by evidence. Our objective was to quantify heading exposure in youth football, assessing the effects of sex and age. Football matches played during an international youth football tournament with no heading restrictions were directly observed, including players from both sexes (11-19 years). The elite senior level was included for comparison, using video analysis. All heading events were registered, classified and assigned to individual players. Heading rates were calculated for each sex and age group. We observed a total of 267 matches, corresponding to 4011 player hours (1927 player hours for females, 2083 player hours for males). Males headed more frequently than females (2.7 vs. 1.8 headers/player hour; p<0.001). Heading rates increased with age (ANOVA, p<0.001), approaching the elite senior level for players 16 years and older. There was substantial variation within teams for all age and sex groups, with the widest range (1-18 headers) observed for girls aged 19. Girls younger than 12 years had the lowest exposure, with an average of less than two players per team heading the ball, each with 1-2 headers. In conclusion, age and sex influence head-impact exposure in youth football, and warrants careful consideration when introducing injury prevention measures. Males are more frequently exposed than females, heading rates increase with age, and there is substantial variation between players. Heading is a rare event in the youngest age groups, especially among females.


#10 Trapezoid Fracture Associated with Scaphoid Fracture in a Football Goalkeeper
Reference: Case Rep Orthop. 2019 Sep 5;2019:7949754. doi: 10.1155/2019/7949754. eCollection 2019.
Authors: Yamamoto T, Matsushita T, Ito K, Matsushima S, Yoshida K, Kuroda R
Download link: http://downloads.hindawi.com/journals/crior/2019/7949754.pdf
Summary: A 19-year-old male who played as a football goalkeeper visited our hospital with complaints of sustained pain from the right wrist to the hand after punching a ball. Scaphoid fracture was diagnosed on plain radiographs, whereas trapezoid fracture was overlooked. Computed tomography revealed a displaced trapezoid fracture associated with a scaphoid fracture. Both fractures were successfully treated by open reduction and internal fixation using cannulated screws. Almost complete bone union was achieved at 5 months after surgery. The patient returned to play as a football goalkeeper. The simultaneous occurrence of trapezoid and scaphoid fractures has never been reported. Trapezoid fractures are rare and can be overlooked on plain radiographs, as what happened in the present case, because the trapezoid is small and overlaps with other carpal bones on plain radiographs. If there is sustained pain in the wrist and hand after punching, combined trapezoid and scaphoid fractures should be considered as the possible injury.


#11 Is Physical Performance a Differentiating Element between More or Less Successful Football Teams?
Reference: Sports (Basel). 2019 Sep 30;7(10). pii: E216. doi: 10.3390/sports7100216.
Authors: Asian Clemente JA, Requena B, Jukic I, Nayler J, Hernández AS, Carling C
Download link: https://www.mdpi.com/2075-4663/7/10/216/pdf
Summary: This study investigated the time-motion characteristics of football teams in the Spanish first division, in relation to their final competitive level as defined by league position (Champions League, Europa League, Upper mid-table, lower mid-table and relegation). Match observations (n = 9641) were collected using a multiple-camera computerized tracking system during the 2013-2014 competitive season. The following match parameters were analyzed: total distance, relative distance (m·min-1), distance < 14 km·h-1, >14 km·h-1, between 14-21 km·h-1, >21 km·h-1, and >24 km·h-1. Total distance and distance at different velocities (>14, 21, and 24 km·h-1) in and out of ball possession were also analyzed. A repeated analysis of variance and a comparison of effect sizes were carried out to compare the performance of the teams. The analysis of the data showed differences in physical performance characteristics between competitive levels. The volume of distance covered in the variables analyzed did not relate to success in soccer. Both successful and unsuccessful teams presented the same running requirements at higher velocities. These findings provide valuable information about the physical demands of the running requirements according to their final position in the league table.


#12 Community-based football in men with prostate cancer: 1-year follow-up on a pragmatic, multicentre randomised controlled trial
Reference: PLoS Med. 2019 Oct 1;16(10):e1002936. doi: 10.1371/journal.pmed.1002936. eCollection 2019 Oct.
Authors: Bjerre ED, Petersen TH, Jørgensen AB, Johansen C, Krustrup P, Langdahl B, Poulsen MH, Madsen SS, Østergren PB, Borre M, Rørth M, Brasso K, Midtgaard J
Download link: https://journals.plos.org/plosmedicine/article/file?id=10.1371/journal.pmed.1002936&type=printable
Summary: Physical exercise has been shown to be effective in relation to fatigue, aerobic fitness, and lower body strength in men with prostate cancer. However, research into the clinically relevant effects of interventions conducted in heterogeneous patient populations and in real-life clinical practice settings is warranted. We conducted a pragmatic, multicentre, parallel randomised controlled trial in 5 Danish urological departments. Recruitment began in May 2015, the first participant was randomised in June 2015, and the last participant was included in February 2017. In total, 214 men with prostate cancer were randomly assigned to either 6 months of free-of-charge football training twice weekly at a local club (football group [FG]) (n = 109) or usual care (usual care group [UG]) (n = 105), including brief information on physical activity recommendations at randomisation. Participants were on average 68.4 (SD 6.2) years old, 157 (73%) were retired, 87 (41%) were on castration-based treatment, 19 (9%) had received chemotherapy, and 41 (19%) had skeletal metastases at baseline. In this 1-year follow-up study, we evaluated the effects of community-based football training on the following outcomes: primary outcome, quality of life; secondary outcomes: continuation of football after 6 months, hip and lumbar spine bone mineral density (BMD), mental health score, fat and lean body mass, and safety outcomes, i.e., fractures, falls, and hospital admissions. Intention to treat (ITT) and per protocol (PP) analyses were conducted. No statistically significant between-group difference was observed in change in prostate-cancer-specific quality of life (ITT: 1.9 points [95% CI -1.9 to 5.8], p = 0.325; PP: 3.6 points [95% CI -0.9 to 8.2], p = 0.119). A statistically significant between-group difference was observed in change in total hip BMD, in favour of FG (0.007 g/cm2 [95% CI 0.004 to 0.013], p = 0.037). No differences were observed in change in lumbar spine BMD or lean body mass. Among patients allocated to football, 59% chose to continue playing football after the end of the 6-month intervention period. At 1-year follow-up in the PP population, FG participants had more improvement on the Mental Component Summary (2.9 [95% CI 0.0 to 5.7], p = 0.048 points higher) than UG participants, as well as a greater loss of fat mass (-0.9 kg [95% CI -1.7 to -0.1], p = 0.029). There were no differences between groups in relation to fractures or falls. Hospital admissions were more frequent in UG compared to FG (33 versus 20; the odds ratio based on PP analysis was 0.34 for FG compared to UG). There were 3 deaths in FG and 4 in UG. Main limitations of the study were the physically active control group and assessment of physical activity by means of self-report. In this trial, participants allocated to football appeared to have improved hip BMD and fewer hospital admissions. Men who played football more than once a week for 1 year lost fat mass and reported improved mental health. Community-based football proved to be acceptable, even when club membership was not subsidised.

Sun

20

Oct

2019

Latest research in football - week 40 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Is Playing Soccer More Osteogenic for Females Before the Pubertal Spurt?
Reference: J Hum Kinet. 2019 Jul 5;67:153-161. doi: 10.2478/hukin-2018-0074. eCollection 2019 Jun.
Authors: Lozano-Berges G, Matute-Llorente Á, Gómez-Bruton A, González-Agüero A, Vicente-Rodríguez G, Casajús JA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6714372/pdf/hukin-67-153.pdf
Summary: The aims of this study were to assess bone mass in children and adolescent soccer players and to evaluate the influence of both gender and pubertal status on bone mass. A total of 110 soccer players (75 males / 35 females; 12.73 ± 0.65 / 12.76 ± 0.59 years) participated in this cross-sectional study. They were divided into two groups according to their pubertal status. Bone and lean masses were measured with Dual-energy X-ray Absorptiometry. An independent t-test and an adjusted by subtotal lean and training experience multivariate analysis of covariance were used to analyse the differences in bone mass values between genders and maturity status. Female soccer players presented higher bone mass values than their male counterparts in most of the measured weight-bearing sites. Moreover, when stratifying by pubertal status, peripubertal and postpubertal females had higher subtotal body and lumbar spine bone mass than males. Comparing between pubertal status groups before adjustment, both male and female postpubertal players showed higher bone mass than their pubertal counterparts. After adjusting, these differences disappeared and, in fact results were inverted as bone mass at the femoral neck was higher in both male and female peripubertal soccer players than in postpubertal players. Bone mass seems to be more intensely stimulated by playing soccer in female than male players, particularly in the lumbar spine. The results of peripubertal players showing higher bone mass at the femoral neck after adjusting suggest that playing soccer during the peripubertal stage could


#2 Decrease in Attentional Performance After Repeated Bouts of High Intensity Exercise in Association-Football Referees and Assistant Referees
Reference: Front Psychol. 2019 Sep 6;10:2014. doi: 10.3389/fpsyg.2019.02014. eCollection 2019.
Authors: Schmidt SL, Schmidt GJ, Padilla CS, Simões EN, Tolentino JC, Barroso PR, Narciso JH, Godoy ES, Costa Filho RL
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2019.02014/pdf
Summary: Referees and assistant referees are submitted to high physical stress during matches. Pressure to make decisions in front of large crowds is another potential stressor. These two stressors can impair attention executive control, depending on physical fitness and individual vulnerability or resilience to situational pressure. Error percentage for referees and assistants may reach around 14% during a soccer match. Although previous studies have suggested that soccer referees and assistants should take cognitive assessments, they are only required by Fédération Internationale de Football Association (FIFA) to demonstrate knowledge of the rules and pass annually in a fitness test (FIFA-Test). This study aimed to assess attention performance in referees and assistants before and after the mandatory FIFA-Test. It is hypothesized that the high physical demands associated with the pressure to pass the FIFA-Test would interfere with attention performance. The sample included 33 referees and 20 assistants. The Continuous Visual Attention Test (CVAT) consisted of a 15-min Go/No-go task. Performance in the CVAT is based on four variables: omission and commission errors, reaction time, and variability of reaction time (VRT). Failure in the CVAT was defined by a performance below the 5th percentile of the age- and sex-matched normative data in at least one variable of the CVAT. Before the FIFA-Test all participants performed the CVAT. The second CVAT began 3-7 min directly following completion of the FIFA-test. Considering only the officials who passed both the FIFA-Test and the first CVAT (19 referees and 15 assistants), 44% (9 referees and 6 assistants) exhibited a performance decline in the second CVAT. A significant increase in VRT was found after the high intensity exercise. As increase in VRT is thought to reflect executive dysfunctions and lapses of attention, we concluded that physical fitness alone may not be enough to help officials cope with the physical and contextual stresses associated with the FIFA-Test. These data suggest that over 35% of soccer referees and their assistants who were considered physically able to referee matches may not be mentally prepared for the attentional demands of refereeing soccer matches.


#3 You Don't Bend It Like Beckham if You're Female and Reminded of It: Stereotype Threat Among Female Football Players
Reference: Front Psychol. 2019 Aug 28;10:1963. doi: 10.3389/fpsyg.2019.01963. eCollection 2019.
Authors: Grabow H, Kühl M
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01963/pdf
Summary: Originally, the stereotype threat effect - poorer performance due to a fear of fulfilling a negative stereotype about one's group - was demonstrated for cognitive tasks (e.g. Steele and Aronson, 1995, or Steele, 1997). Drawing on the widespread stereotype of women being unable to play football we experimentally tested (N = 80) whether a respective threat affected female football players' goal scoring precision, i.e. a complex and demanding motor task. Those participants who were reminded of the stereotype scored significantly less hits than those not reminded. Additionally, deviations from the instruction during task execution (e.g. shooting from another distance than demanded or using the wrong foot) were recorded. Stereotype threat did not affect this comparatively more cognitive task of following instructions correctly. In order to explore underlying mechanisms of the observed stereotype effect, several potential mediators, e.g. measures of cognitive interference, or collective identification, were tested. None emerged as an unquestionable link between threat and motor performance. We discuss, however, why collective identification - in comparison to cognitive demand - appears to be the more promising explanatory concept.


#4 Corrigendum: Football Players Do Not Show "Neural Efficiency" in Cortical Activity Related to Visuospatial Information Processing During Football Scenes: An EEG Mapping Study
Reference: Front Psychol. 2019 Aug 27;10:1877. doi: 10.3389/fpsyg.2019.01877. eCollection 2019.
Authors: Del Percio C, Franzetti M, De Matti AJ, Noce G, Lizio R, Lopez S, Soricelli A, Ferri R, Pascarelli MT, Rizzo M, Triggiani AI, Stocchi F, Limatola C, Babiloni C
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01877/pdf


#5 Strategies for Maintaining the Coach-Analyst Relationship Within Professional Football Utilizing the COMPASS Model: The Performance Analyst's Perspective
Reference: Front Psychol. 2019 Sep 10;10:2064. doi: 10.3389/fpsyg.2019.02064. eCollection 2019.
Authors: Bateman M, Jones G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6748348/pdf/fpsyg-10-02064.pdf
Summary: There is a considerable body of research by that has investigated the coach-athlete relationship in sport. However, given the multi-disciplinary nature of modern elite coaching, there is a scarcity of research focusing on the relationship between coaches and other members of the coaching and support team. This study examined the perceptions of six elite professional football analyst's relationships with their respective coaches. Semi structured interviews utilizing the COMPASS Framework were conducted focusing on Conflict, Openness, Motivation, Preventative Strategies, Assurance, Support, and Social Networks. The results verified that the COMPASS Model of relationship maintenance was applicable to this dyad. Content analysis indicated that there was 215 raw data units comprising of 16 higher order themes across the model which was further broken down into 29 lower order themes. All aspects of the model were found to contribute toward a positively maintained relationship. Having an open relationship underpinned by honesty and being able to provide an opinion was seen as the highest rated attribute that was closely followed by supporting the coach by understanding their requirements for successful coaching practice. Not meeting the coach's expectations was found to cause conflict and was further highlighted by an inductive analysis that revealed the existence of a relationship that is fundamentally dictated by the coach. Implications of this investigation are that professionals which support elite performers need to set out clear expectations of working practice and hierarchies in order to minimize the chance of internal conflict that can impact on the service levels received by the performer.


#6 A study protocol for the development and internal validation of a multivariable prognostic model to determine lower extremity muscle injury risk in elite football (soccer) players, with further exploration of prognostic factors
Reference: Diagn Progn Res. 2019 Sep 19;3:19. doi: 10.1186/s41512-019-0063-8. eCollection 2019.
Authors: Hughes T, Riley R, Sergeant JC, Callaghan MJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751574/pdf/41512_2019_Article_63.pdf
Summary: Indirect muscle injuries (IMIs) are a considerable burden to elite football (soccer) teams, and prevention of these injuries offers many benefits. Preseason medical, musculoskeletal and performance screening (termed periodic health examination (PHE)) can be used to help determine players at risk of injuries such as IMIs, where identification of PHE-derived prognostic factors (PF) may inform IMI prevention strategies. Furthermore, using several PFs in combination within a multivariable prognostic model may allow individualised IMI risk estimation and specific targeting of prevention strategies, based upon an individual's PF profile. No such models have been developed in elite football and the current IMI prognostic factor evidence is limited. This study aims to (1) develop and internally validate a prognostic model for individualised IMI risk prediction within a season in elite footballers, using the extent of the prognostic evidence and clinical reasoning; and (2) explore potential PHE-derived PFs associated with IMI outcomes in elite footballers, using available PHE data from a professional team. This is a protocol for a retrospective cohort study. PHE and injury data were routinely collected over 5 seasons (1 July 2013 to 19 May 2018), from a population of elite male players aged 16-40 years old. Of 60 candidate PFs, 15 were excluded. Twelve variables (derived from 10 PFs) will be included in model development that were identified from a systematic review, missing data assessment, measurement reliability evaluation and clinical reasoning. A full multivariable logistic regression model will be fitted, to ensure adjustment before backward elimination. The performance and internal validation of the model will be assessed. The remaining 35 candidate PFs are eligible for further exploration, using univariable logistic regression to obtain unadjusted risk estimates. Exploratory PFs will also be incorporated into multivariable logistic regression models to determine risk estimates whilst adjusting for age, height and body weight. This study will offer insights into clinical usefulness of a model to predict IMI risk in elite football and highlight the practicalities of model development in this setting. Further exploration may identify other relevant PFs for future confirmatory studies and model updating, or influence future injury prevention research.


#7 Limited positive effects on jump-landing technique in girls but not in boys after 8 weeks of injury prevention exercise training in youth football
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Sep 20. doi: 10.1007/s00167-019-05721-x. [Epub ahead of print]
Authors: Lindblom H, Waldén M, Carlfjord S, Hägglund M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-019-05721-x.pdf
Summary: The aim was to evaluate changes in jump-landing technique in football-playing boys and girls after 8 weeks of injury prevention training. Four boys' and four girls' teams (mean age 14.1 ± 0.8 years) were instructed to use either the original Knee Control injury prevention exercise programme (IPEP) or a further developed IPEP, Knee Control + , at every training session for 8 weeks. Baseline and follow-up testing of jump-landing technique included drop vertical jumps (DVJ), assessed subjectively and with two-dimensional movement analysis, and tuck jump assessment (TJA). Only minor differences in intervention effects were seen between the two IPEPs, and results are therefore presented for both intervention groups combined. At baseline 30% of the boys showed good knee control during the DVJ, normalised knee separation distances of 77-96% (versus hip) and a median of 3 flaws during the TJA. Among girls, 22% showed good knee control, normalised knee separation distances of 67-86% and a median of 4 flaws during the TJA. At follow-up, boys and girls performed significantly more jumps during TJA. No changes in jump-landing technique were seen in boys, whereas girls improved their knee flexion angle at initial contact in the DVJ (mean change + 4.7°, p < 0.001, 95% CI 2.36-6.99, d = 0.7) and their TJA total score (- 1 point, p = 0.045, r = - 0.4). The study showed small positive effects on jump-landing technique in girls, but not in boys, after 8 weeks of injury prevention training.


#8 Prevention of severe knee injuries in men's elite football by implementing specific training modules
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Sep 20. doi: 10.1007/s00167-019-05706-w. [Epub ahead of print]
Authors: Krutsch W, Lehmann J, Jansen P, Angele P, Fellner B, Achenbach L, Krutsch V, Nerlich M, Alt V, Loose O
Summary: Injury prevention of knee injuries by means of training and warm-up exercises has been investigated in several studies in amateur football. However, the number of investigations in elite football is limited despite the currently higher injury incidence of severe knee injuries. Therefore, the purpose of this study was to investigate whether specifically adapted preventive training modules may reduce severe knee injuries in elite football. In a prospective controlled cohort study of elite football players in Germany, an injury prevention programme with 5 modules was implemented in the season of 2015-2016. The training modules were specifically adapted to this skill level and based on scientific evidence, team coach preferences, and the specific environment of this playing level. Of the 62 teams taking part in this study, 26 used the new trainings modules and 36 continued their standard programme as a control group. Success of the programme was documented by means of an injury report over one season. The primary outcome was reduction in severe knee injuries. A pre-seasonal investigation had identified five modules to be implemented in the training routine. Postural stability, mobilisation of lower extremity joints, leg and trunk stabilisation, jumping, and landing exercises as well as agility movements were incorporated into the programme to prevent severe knee injuries in elite football. Over the season, the study group (529 players) with the adapted training modules had sustained 52 severe knee injuries (incidence: 0.38 per 1000 h football exposure; prevalence: 9.8%) compared to 108 severe knee injuries in the control group (601 players) using the standard programme (incidence: 0.68 per 1000 h football exposure; prevalence: 18.0%; p < 0.05). The overall injury incidence for any other type of injury was comparable between the two groups (3.3 vs. 3.4 in h 1000 football, n.s.). Appropriate preventive training modules reduce severe knee injuries in elite football significantly. The key for the sustainability of preventive training measures are programmes specifically adapted to the demands of the playing level and to the preferences of the coaches