Blog archive

Wed

25

Nov

2020

Website update

I have updated the special topic - Performance analysis - CLICK HERE to get to the page or follow the navigation

Tue

24

Nov

2020

Allometric modelling of peak oxygen uptake in male soccer players of 8–18 years of age

The aim was to examine the contribution of maturity status and body size descriptors to age-associated inter-individual variability in VO2peak and to present static allometric models to normalize in male youth soccer players.

Mon

23

Nov

2020

Optimal recovery time for post activation potentiation in professional soccer players

The aim of this study was to determine the optimal recovery time to elicit PAP after a bout of high-intensity resistance exercise in professional soccer players.

Sat

21

Nov

2020

Latest research in football - week 34 - 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 Performance changes during the off-season period in football players - Effects of age and previous hamstring injury
Reference: J Sports Sci. 2020 Jul 13;1-11. doi: 10.1080/02640414.2020.1792160. Online ahead of print.
Authors: Jordi Vicens-Bordas, Ernest Esteve, Azahara Fort-Vanmeerhaeghe, Martí Casals, Thomas Bandholm, Lasse Ishøi, David Opar, Anthony Shield, Kristian Thorborg
Summary: The aims of this study were to investigate changes in selected performance measures during an off-season period, their association, and the potential role of age and previous hamstring injury in semi-professional and amateur football players. Seventy-four male players (age: 25 ± 4 years, stature: 178.0 ± 6.6 cm, body mass: 74.9 ± 8.1 kg) were assessed at the beginning and end of the off-season summer-period for sprint, change-of-direction performance and eccentric hamstring strength. Small to medium increases in sprint times were observed at 5 (d = 0.26, p = 0.057), 10 (d = 0.42, p < 0.001) and 30 m (d = 0.64, p < 0.001). Small (d = -0.23, p = 0.033) improvements were observed for COD performance, and no changes in eccentric hamstring strength (d = 0.10, p = 0.317). The changes in the outcomes were not affected by age (p = 0.449 to 0.928) or previous hamstring injury (p = 0.109 to 0.995). The impaired sprint performance was not related to changes in eccentric hamstring strength (r = -0.21 to 0.03, p = 0.213 to 0.856), instead, changes in COD performance were associated with changes in eccentric hamstring strength (r = -0.42, p = 0.008).


#2 Tattoos among professional football players in the 2018-2019 Spanish La Liga season
Reference: Ann Dermatol Venereol. 2020 Jul 9;S0151-9638(20)30249-0.
doi: 10.1016/j.annder.2020.03.008. Online ahead of print.
Authors: N Kluger , R Ahava
Summary: Data regarding tattoos among football players are limited. We investigated the prevalence and characteristics of tattoos among elite players over a full season in the Spanish La Liga. We assessed whether tattoos had any impact on the performance and behavior of players and teams on the pitch. Demographic (age, geographic origin, position), performance (goal-scoring) and disciplinary data (yellow/red cards received) for 476 players and overall team statistics over the 2018-2019 season were analyzed according to the presence of visible tattoos (head and neck, upper arms, lower limbs) for each player. Of the 472 players analyzed, 160 (36%) had visible tattoos (upper limbs, 99%; lower limbs, 18.5%; head and neck, 12%), most of which were in black ink (83%). Players from South and Central America had the highest prevalence of visible tattoos (50%) and significantly more head and neck tattoos than Europeans (19% vs. 10% P=0.02). Tattoos were not significantly related to players' age or position. The mean number of goals scored was higher in the tattooed player group (2.7±4.6 goals vs. 1.9±3.3; P=0.013). There was a correlation between having tattoos and number of goals (Spearman rho 0.103, P=0.034). Tattooed players were more likely to have received≥1 yellow card (91% vs. 83.5%, P=0.03). There was no difference regarding red cards received (15 vs. 14%, P>0.05). The mean number of yellow cards was higher among players with tattoos than those without (4.4±3.2 vs. 3.6±3.2; P=0.01). However, the proportion of tattooed players in a team did not influence the overall team outcomes. The results were no longer significant when we included only players taking part in at least in 22 matches. Among footballers in La Liga, 36% had visible tattoos, with individual variations attributable to differences in geographic, social, cultural and religious background. Having tattoos was associated with certain aspects of individual performance and discipline. The question whether this factor should be taken into consideration by players' agents and team managers remains open.


#3 Systematic Reductions in Differential Ratings of Perceived Exertion Across a 2-Week Repeated-Sprint-Training Intervention That Improved Soccer Players' High-Speed-Running Abilities
Reference: Int J Sports Physiol Perform. 2020 May 6;1-8. doi: 10.1123/ijspp.2019-0568. Online ahead of print.
Authors: Shaun J McLaren, Jonathan M Taylor, Tom W Macpherson, Iain R Spears, Matthew Weston
Summary: The purpose was to quantify changes in differential ratings of perceived exertion (dRPE) across a 2-wk repeated-sprint-training intervention that improved high-intensity intermittent-running ability and linear speed of semiprofessional soccer players.  Thirteen players completed 3 (sessions 1-3) or 4 (sessions 4-6) sets of 7 sprints (group 1 [n = 7]: 30-m straight; group 2 [n = 6]: 2 × 10-m shuttle), with 20 s and 4 min of recovery between sprints and sets, respectively. Postset perceptions of breathlessness (RPE-B) and leg-muscle exertion (RPE-L) were rated using the CR100 scale. Overall, RPE-B (mean [SD]: 46 [13] arbitrary units [AU], "hard") was most likely higher than RPE-L (39 [13] AU, "somewhat hard," mean difference: 8 AU; 90% confidence limits [CLs]: ±2). Set-to-set increases in dRPE (in AU; 90% CL: approximately ±2) were large in session 1 (RPE-B: 15; RPE-L: 14), moderate in sessions 2-5 (RPE-B: 7-10; RPE-L: 7-8), and small (RPE-B: 6) to moderate (RPE-L: 7) in session 6. Across the intervention, RPE-B reduced moderately in sets 3 (-13; 90% CL: ±4) and 4 (-12; 90% CL: ±12) and RPE-L reduced by a small magnitude in set 3 (-5; 90% CL: ±6). The set 4 change in RPE-L was unclear (-11; 90% CL: ±13). The authors observed systematic intrasession and intersession changes in dRPE across a 2-wk repeated-sprint-training intervention, with a fixed prescription of external load that improved semiprofessional soccer players' high-speed-running abilities. These findings could support dRPE as a measure of internal load and highlight its usefulness in evaluating repeated-sprint-training dose-response.


#4 The influence of thermal stress on the physical and technical activities of soccer players: lessons from the 2018 FIFA World Cup in Russia
Reference: Int J Biometeorol. 2020 Jul 16. doi: 10.1007/s00484-020-01964-3. Online ahead of print.
Authors: Marek Konefał, Paweł Chmura, Michał Zacharko, Jarosław Baranowski, Marcin Andrzejewski, Krzysztof Błażejczyk, Jan Chmura
Download link: https://link.springer.com/content/pdf/10.1007/s00484-020-01964-3.pdf
Summary: The present study attempts to assess changes in soccer players' physical and technical activity profiles due to thermal stress, measured with the Universal Thermal Climate Index (UTCI), in training centres and during matches of the 2018 FIFA World Cup in Russia. The study also verifies the theoretical models of soccer players' physiological parameters. The study sample consisted of 945 observations of 340 players of national teams taking part in the World Cup in Russia. The measured variables included physical activities: total distance covered, distances covered with an intensity of 20-25 km/h, number of sprints; technical activities: number of shots, number of passes, pass accuracy and physiological indicators: evaporative water loss and heart rate. In addition, the final ranking places of each national team were also used in the study. The UTCI was calculated based on meteorological data recorded at training centres and during matches. The UTCI records were then classified into two ranges: NTS-no thermal stress (UTCI 9-26 °C) and TS-thermal stress (UTCI > 26 °C). Climatic conditions at soccer training centres assessed as involving "no thermal stress" are found to be more beneficial for increasing the total distance covered and the number of sprints performed by players during a match. The theoretical models for determining soccer players' physiological parameters used in the study reduce the players' heart rate effort and evaporative water loss, which is in line with findings in studies by other authors. The climatic conditions at soccer training centres and during tournament matches should be taken into account in planning preparations for future World Cup tournaments, especially those in hotter countries.


#5 Multidirectional sprints in soccer: are there connections between linear, curved, and change-of-direction speed performances?
Reference: J Sports Med Phys Fitness. 2020 Jun 16. doi: 10.23736/S0022-4707.20.11155-1. Online ahead of print.
Authors: Tomás T Freitas, Ian Jeffreys , Valter P Reis , Victor Fernandes, Pedro E Alcaraz, Lucas A Pereira, Irineu Loturco
Summary: The aim of this study was to investigate the relationships between linear sprint, curve sprint (CS), and change of direction (COD) abilities and vertical jump performance in elite young soccer players. Twenty-nine players from the same soccer club participated in this study. On the same day, athletes performed countermovement jump (CMJ), 17-m linear sprint (with a 10- m split time), CS (for both sides), and COD tests. A Pearson product moment correlation was performed to determine the associations between the assessed variables. Significance level was set at P< 0.05. Linear sprint was significantly related to CS (r ranging from 0.67 and 0.76; P< 0.05) but not to COD performance (r = 0.23 and 0.33 for 10- and 17-m, respectively; P> 0.05). CS ability (for both good and weak sides) was significantly associated with COD performance (r = 0.60 and 0.54, respectively; P< 0.05). CMJ height was significantly correlated with both linear and CS velocities (r varying between 0.50 and 0.68; P< 0.05), but not with COD velocity (r =0.37; P> 0.05). Based on these findings, it is possible to suggest that training strategies designed to improve vertical jumping capacity may potentially improve both linear and curvilinear sprint abilities. Moreover, increases in COD velocity may also produce positive changes in CS performance.


#6 The effects of soccer training in aerobic capacity between trained and untrained adolescent boys of the same biological age
Reference: J Sports Med Phys Fitness. 2020 Jul 16. doi: 10.23736/S0022-4707.20.11117-4. Online ahead of print.
Authors: Athanasios Mandroukas, Thomas I Metaxas, Yiannis Michailidis, Kosmas Christoulas, Jan Heller
Summary: The purpose of this study was to examine the effects of soccer training on maximal oxygen uptake and anthropometric characteristics in different ages of soccer players and untrained adolescents of the same biological age. A total of one hundred and twenty six (n=126) young soccer players and untrained boys throughout the developmental ages of 12 (soccer players n=22; untrained boys=22) 14 (soccer players n=20; untrained boys= 18) and 16 (soccer players n=22; untrained boys=22) volunteered to participate in the study. Sexual maturation was classified according to Tanner's stages. Soccer players participated both in their school's physical education program and in a soccer training program, while the untrained participated only in their school's physical education program. All participants underwent anthropometric measurements and performed a maximal exercise test on a motor driven treadmill to determine maximal oxygen uptake (V̇O2max) and cardiorespiratory indices. Blood lactate (BL) concentration was determined in the 5th minute of recovery using a lactate photometer. The trained group showed significantly higher VO2max, in absolute and relative values (P<0.001), BLmax (P<0.05) and maximal respiratory exchange ratio (RERmax) (P<0.05) compared to the untrained group. Resting heart rate (HR) and systolic blood pressure were significantly lower (P<0.05) for the trained compared to untrained. The results of this study showed that systematic soccer training has a positive effect in the central cardiovascular system expressed as VO2max, HR and blood pressure.


#7 Peak torque angle, acceleration time and time to peak torque as additional parameters extracted from isokinetic test in professional soccer players: a cross-sectional study
Reference: Sports Biomech. 2020 Jul 16;1-12. doi: 10.1080/14763141.2020.1784260. Online ahead of print.
Authors: Daniel Germano Maciel, Glauko André Figueiredo Dantas, Mikhail Santos Cerqueira, Jean Artur Mendonça Barboza, Vinícius Vieira De Alencar Caldas, Alef Cavalcanti Matias de Barros, Ronan Romeno Varela, Diego Helps Magalhães, Wouber Hérickson de Brito Vieira
Summary: This study investigated additional and traditional variables from isokinetic test of thigh muscles in soccer players across different field positions. One hundred and eighty-nine athletes performed maximal concentric isokinetic knee contractions on dominant (DL) and non-dominant limb (NDL) at 60º/s and 240º/s. The additional outcomes peak torque angle (AngPT), acceleration time (AcT) and time to peak torque (TPT) and traditional outcomes Peak torque (PT), total work (TW) and power (Pw) were extracted from the exam. Goalkeepers (GK), side backs (SB), central backs (CB), central defender midfielders (CDM), central attacking midfielders (CAM) and forwards (FW) were considered. Comparisons between limbs and positions demonstrated that SB extensors of the DL presented TPT lower (p = 0.006) and AngPT higher (p = 0.011) than NDL at 60°/s. CDM extensors of the DL showed lower TPT at 60°/s (p = 0.003) and 240°/s (p = 0.024). CAM flexors of the DL showed lower TPT (p = 0.026) and AcT (p = 0.021) at 240°/s than NDL. CB, CDM and CAM extensors of the NDL showed higher PT, TW and Pw than DL (p < 0.05). In conclusion, there are muscle imbalances between limbs in SB, CDM and CAM and across different field positions.


#8 Walking Soccer: A Systematic Review of a Modified Sport
Reference: Scand J Med Sci Sports. 2020 Jul 15. doi: 10.1111/sms.13772. Online ahead of print.
Authors: Rekesh Corepal, Jia Yu Zhang, Sanya Grover, Harry Hubball, Maureen C Ashe
Summary: Walking soccer (football) is an emerging modified sport gaining recognition globally. The aim was to synthesize current evidence for walking soccer, and provide a summary of global walking soccer organizations. We searched for studies published across all years and all languages within multiple databases for studies focused on walking soccer (football) in adults (18+ years). Two authors independently screened citations at Level 1 and 2. We also conducted a forward citation search and reviewed the reference lists for included studies. We searched the grey literature to identify walking soccer organizations. We conducted the last database search in December 2019. We conducted a standard systematic review following established guidelines. We also summarized findings from a limited search for walking soccer organizations. For peer-reviewed literature, we used the Mixed Methods Appraisal Tool (MMAT) to assess methodological quality, and conducted a narrative synthesis of the evidence. We identified nine peer-reviewed studies (with 117 participants). Most studies included small sample sizes and interventions with short duration. Walking soccer is an emerging modified sport that is popular across the United Kingdom (UK), with its reach extending to other countries. Limited published evidence exists for walking soccer, despite is global popularity. For the studies identified, generalizability was limited to predominately older men from the UK. Based on preliminary findings, walking soccer has the potential to confer health benefits and build social connections.



#9 Individual versus team heart rate variability responsiveness analyses in a national soccer team during training camps
Reference: Sci Rep. 2020 Jul 16;10(1):11726. doi: 10.1038/s41598-020-68698-5.
Authors: Alejandro Muñoz-López , José Naranjo-Orellana
Download link: https://www.nature.com/articles/s41598-020-68698-5.pdf
Summary: Heart rate variability (HRV) analyses can be performed using group or individual changes. Individual changes could be of potential interest during training camps for national soccer teams. The purpose of this study was to compare whether analysis of individual daily HRV could detect changes in cardiac autonomic responses during training camps for national soccer teams. During two different training camps, 34 professional soccer players were monitored daily over 9 days, using heart rate monitors. Players were divided into First Eleven (those who participated in the main squad) or Reserves. Daily HRV was individually analyzed using a day-to-day method or a baseline (days prior to first match) method, using the smallest worthwhile change and the typical error in the estimate to establish a trivial (random change) zone. Group changes were also analyzed using an ANOVA one-way repeated measures test. Players' responsiveness was classified as High-, Low- or Non-response depending on individual changes. Both analyses showed substantial daily individual changes after playing a soccer match, regardless of the group. However, group changes showed that only First Eleven players had significant changes after playing a soccer match. In conclusion, individual daily HRV analyses are useful in detecting individual changes in professional soccer players.


#10 Prevalence and Incidence of Microhemorrhages in Adolescent Football Players
Reference: AJNR Am J Neuroradiol. 2020 Jul;41(7):1263-1268.
doi: 10.3174/ajnr.A6618.
Authors: B R Shah, J M Holcomb, E M Davenport, C M Lack, J M McDaniel, D M Imphean, Y Xi, D A Rosenbaum, J E Urban, B C Wagner, A K Powers, C T Whitlow, J D Stitzel, J A Maldjian
Summary: SWI is an advanced imaging modality that is especially useful in cerebral microhemorrhage detection. Such microhemorrhages have been identified in adult contact sport athletes, and the sequelae of these focal bleeds are thought to contribute to neurodegeneration. The purpose of this study was to utilize SWI to determine whether the prevalence and incidence of microhemorrhages in adolescent football players are significantly greater than those of adolescent noncontact athletes. Preseason and postseason SWI was performed and evaluated on 78 adolescent football players. SWI was also performed on 27 adolescent athletes who reported no contact sport history. Two separate one-tailed Fisher exact tests were performed to determine whether the prevalence and incidence of microhemorrhages in adolescent football players are greater than those of noncontact athlete controls. Microhemorrhages were observed in 12 football players. No microhemorrhages were observed in any controls. Adolescent football players demonstrated a significantly greater prevalence of microhemorrhages than adolescent noncontact controls (P = .02). Although 2 football players developed new microhemorrhages during the season, microhemorrhage incidence during 1 football season was not statistically greater in the football population than in noncontact control athletes (P = .55). Adolescent football players have a greater prevalence of microhemorrhages compared with adolescent athletes who have never engaged in contact sports. While microhemorrhage incidence during 1 season is not significantly greater in adolescent football players compared to adolescent controls, there is a temporal association between playing football and the appearance of new microhemorrhages.


#11 Soccer Heading and Subclinical Neuropsychiatric Symptomatology in Professional Soccer Players
Reference: Neurology. 2020 Jul 10;10.1212/WNL.0000000000010244. doi: 10.1212/WNL.0000000000010244. Online ahead of print.
Authors: Nadav Amitay, Yair Zlotnik, Tara Coreanu, Lior Zeller, Ibrahim Abu-Salameh, Victor Novack, Gal Ifergane
Summary: The aim was to evaluate the association between post-concussive symptomatology and heading in professional soccer players, overcoming the bias of self-reported exposure, we evaluated several clinical neuropsychiatric symptoms using questionnaires after a thorough objective follow-up of players heading-exposure throughout an entire season We collected heading data for all Israeli Premier League players for an entire season using a web-based platform for performance analysis, which enabled us to quantify the exact number of headers per player. Players filled questionnaires regarding post-concussion symptoms, depression, anxiety and sleep disorders. We tested the association between the number of headers and each outcome using a negative binomial regression corrected for the hours played. 159 players were included, of which 79 considered in the high heading exposure group (49%) defined as more than median number of headings (1.34 per game hour). Among players without any past head injury, those with higher heading exposure were less likely to suffer post-concussion symptoms compared to players with low heading exposure (RR per heading per hour=0.94, 95%CI [0.912;0.963]). Players with high heading exposure suffered less from depression symptoms (RR=0.98, 95%CI [0.961;0.997]), anxiety (RR=0.98, 95%CI [0.958;0.997]) and sleep disorders (RR=0.98, 95%CI [0.961;0.996]). Professional soccer players with high heading rate do not display higher post-concussive symptomatology severity. Symptoms among players with low heading exposure might be explained by low resilience, possibly associated with an inferior heading technique. Alternatively, it can reflect heading avoidant behavior.


#12 Reliability of a musculoskeletal profiling test battery in elite academy soccer players
Reference: PLoS One. 2020 Jul 23;15(7):e0236341. doi: 10.1371/journal.pone.0236341. eCollection 2020.
Authors: Neval Grazette, Scot McAllister, Chin Wei Ong, Caroline Sunderland, Mary E Nevill, John G Morris
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0236341&type=printable
Summary: The study aimed to quantify the measurement error / reliability of a musculoskeletal profiling test battery administered in young, elite academy soccer players, and to examine if the order in which the test battery was administered, and who it was administered by, influenced reliability. Players (n = 75; age 12-20 years; stature 1.47-1.95 m; body mass 36-89 kg) from U-12 to U-23 age groups were assigned to either: 1) intra-rater-fixed order; 2) intra-rater-non-fixed order; 3) inter-rater-fixed order; or, 4) inter-rater-non-fixed order groups. On two separate occasions separated by 3 to 7 days, 12 raters conducted a musculoskeletal profiling test battery comprising 10 tests (Supine Medial Hip Rotation, Supine Lateral Hip Rotation, Hamstring 90/90, Prone Medial Hip Rotation [degrees]; Combined Elevation, Thoracic Rotation, Weight-Bearing Dorsiflexion, Y-Balance [centimetres]; Beighton, Lumbar Quadrant [categorical]). The measurement error / reliability for tests measured in degrees and centimetres was evaluated using the intraclass correlation (relative reliability), coefficient of variation and ratio limits of agreement (absolute reliability). Intraclass correlations varied from 0.04 ("poor") to 0.95 ("excellent"), coefficient of variation from 2.9 to 43.4%, and the ratio limits of agreement from 1.058 (*/÷ 1.020) to 2.026 (*/÷ 1.319) for the tests measured in degrees and centimetres. The intraclass correlation, coefficient of variation and ratio limits of agreement were smallest for five out of eight tests measured in degrees and centimetres when the tests were administered in an intra-rater-fixed test order. These findings emphasise that different testing methods, and the administration of a musculoskeletal profiling test battery using a less than optimal design, will influence measurement error and hence test reliability. These observations need to be considered when investigating musculoskeletal function and age, injury, training or asymmetry in young, elite academy soccer players.

Sat

21

Nov

2020

Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor

The aim was to assess the utility of an inertial sensor for assessing recovery in professional soccer players.

Fri

20

Nov

2020

Effects of horizontal plyometric training volume on soccer players’ performance

The aim was to examine the dose reponse effect of plyometric training on soccer performance variables.

Wed

18

Nov

2020

Latest research in football - week 33 - 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 Nighttime Hypoglycemia in Children With Type 1 Diabetes After One Day of Football Tournament
Reference: Int J Sports Med. 2020 Jul 7. doi: 10.1055/a-1192-5992. Online ahead of print.
Authors: Mikołaj Kamiński, Andrzej Gawrecki, Aleksandra Araszkiewicz, Agnieszka Szadkowska, Bogda Skowrońska, Witold Stankiewicz, Arkadiusz Michalak, Aleksandra Cieluch, Katarzyna Dżygało, Sebastian Seget, Grzegorz Biegański, Anna Adamska, Katarzyna Ksiądz, Elektra Szymańska-Garbacz, Justyna Flotyńska, Dorota Zozulinska-Ziolkiewicz
Summary: The aim of the study was to investigate factors related to the occurrence of nighttime hypoglycemia after a football tournament in children with type 1 diabetes mellitus. The multicenter study (GoalDiab study) included 189 children and adolescents with type 1 diabetes mellitus, from 11 diabetes care centers in Poland. Hypoglycemia was defined according to the International Hypoglycemia Study Group Statement. We analyzed the data of 95 participants with completed protocols with regards to nighttime hypoglycemia (82% male), aged 11.6 (9.8-14.2) years, diabetes duration 5.0 (2.0-8.0) years. There were 47 episodes of nighttime Level 1 hypoglycemia (≤3.9 mmol/L). Occurrence of clinically important Level 2 hypoglycemia (<3.0 mmol/L) during a game period was positively associated with nighttime hypoglycemia (≤3.9 mmol/L) incident (Odds Ratio=10.7; 95% Confidence Interval: 1.1-100.2; p=0.04). Using Continuous Glucose Monitoring was negatively associated with the occurrence of nighttime hypoglycemia (≤3.9 mmol/L) compared with using glucose meters or Flash Glucose Monitoring (Odds Ratio=0.31; 95% Confidence Interval: 0.12-0.83; p=0.02). The occurrence of clinically important hypoglycemia related to physical activity is associated with the occurrence of hypoglycemia during the night. Continuous Glucose Monitoring is negatively associated with nighttime hypoglycemia after a day of competition.


#2 Feasibility and Safety of a Walking Football Program in Middle-Aged and Older Men With Type 2 Diabetes
Reference: Prog Cardiovasc Dis. 2020 Jul 4;S0033-0620(20)30137-7. doi: 10.1016/j.pcad.2020.06.014. Online ahead of print.
Authors: Ana Barbosa, João Brito, Júlio Costa, Pedro Figueiredo, André Seabra, Romeu Mendes
Summary: This study aimed to analyze the feasibility and safety of a community-based walking football program in middle-aged and older men with type 2 diabetes (T2D).  Thirty-one male (age, 64.4 ± 4.5 years old; glycated hemoglobin, 6.7 ± 1.0%; body mass index: 28.8 ± 3.3 kg/m2) patients with T2D were recruited from primary health care units in Porto, Portugal. The participants engaged in a 12-wk walking football program (three sessions per week of 60 min; consisting of strength and conditioning exercises, technical skills drills, and small-sided walking football games). Exercise intensity was planned to be gradual throughout the program in three 4-wk phases (phase I, light-intensity; phase II, moderate-intensity; phase III, vigorous-intensity) through the manipulation of game constraints, and monitored by OMNI scale and heart rate reserve (HRR). Sessions' enjoyment level, and exercise-related injuries and adverse events were recorded in all sessions.  The median (P25-P75) adherence to the program was 86.1% (77.8-97.2%). The median enjoyment levels reported by participants was 5 (4-5) points in phase I, 5 (5-5) points in phase II and 5 (5-5) points in phase III. Sessions' average subjective exercise intensity was 3.0 ± 0.6 points in OMNI scale in phase I, 3.5 ± 0.4 points in phase II, and 3.8 ± 0.4 points in phase III. Sessions' average HRR was 35.8 ± 6.7% in phase I, 41.6 ± 4.2% in phase II, and 37.3 ± 4.3% in phase III. Most participants attained vigorous-intensity peaks in all phases. Falls (n = 25) and musculoskeletal injuries (n = 8) were the most frequent adverse events. 31% of these events interfered with exercise participation, but no harm has resulted from it.  A community-based walking football program for T2D patients revealed high levels of adherence and enjoyment, and light-to-vigorous exercise intensity. The adverse events were according to the expected for the population and activity. Therefore, walking football seems to be feasible and safe exercise strategy, and therefore has the potential for large scale implementation for T2D control.


#3 A Teaching Games for Understanding Program to Deal With Reasons for Dropout in Under-11 Football
Reference: Res Q Exerc Sport. 2020 Jul 7;1-12. doi: 10.1080/02701367.2020.1759767. Online ahead of print.
Authors: Carmen Barquero-Ruiz, María T Morales-Belando, José L Arias-Estero
Summary: Young players report that they dropout of organized football due to excessive emphasis on technical execution, low success, and the lack of autonomy and motivation experienced by players during training sessions.  The purpose was to determine whether a TGfU intervention during a youth football program led players to improve in variables related to dropout. That means tactical-technical competence (decision-making, skill execution), success (successful game performance), autonomy (number of decisions made, player autonomy, number of game involvements, player participation), and motivation (enjoyment, intention to be physically active). Twenty under-11-players and two coaches were recruited from 17 clubs. A pretest-posttest design with a multi-method approach was used. Coaches were trained and mentored in TGfU. Data were collected using Game Performance Assessment Instrument, enjoyment and intention to be physically active scales, and two focus groups with the players and the coaches. Players improved in decision-making, skill execution, successful game performance, number of decisions made, number of game involvements, and intention to be physically active (p < .05). Participants attributed the results to the TGfU pedagogical features emphasized during the coaches' training and mentoring. Considering the reasons for dropout in football, in terms of excessive emphasis on technical execution, low success, and the lack of autonomy and motivation experienced by players, TGfU could be a useful pedagogical approach for teaching-learning organized youth football. The TGfU pedagogical features emphasized during coaches' training and mentoring could be crucial to obtain these results due to the fact that they were the sub-themes highlighted during the focus groups.


#4 Composite Indices of Femoral Neck Strength in Middle-Aged Inactive Subjects Vs Former Football Players
Reference: J Clin Densitom. 2020 Jun 12;S1094-6950(20)30093-7. doi: 10.1016/j.jocd.2020.06.002. Online ahead of print.
Authors: Boutros Finianos, Gautier Zunquin, El Hage Rawad
Summary: The purpose of this study was to compare composite indices of femoral neck strength ((compression strength index [CSI], bending strength index [BSI], and impact strength index [ISI]) in inactive middle-aged men (n = 20) and middle-aged former football players (n = 15). 35 middle-aged men participated in this study. Body composition and bone variables were evaluated by dual-energy X-ray absorptiometry. Composite indices of femoral neck strength (CSI, BSI, and ISI) were calculated. Handgrip strength, vertical jump, maximum power of the lower limbs (watts), horizontal jump, maximal half-squat strength, maximal bench-press strength, sprint performance (10 meters), and maximum oxygen consumption (VO2 max, ml/min/kg) were evaluated using validated tests. CSI, BSI, and ISI were significantly higher in football players compared to inactive men. Vertical jump, horizontal jump, maximal half-squat strength, VO2 max and sprint performance were significantly different between the 2 groups. CSI, BSI, and ISI remained significantly higher in football players compared to inactive men after adjusting for physical activity level. The current study suggests that former football practice is associated with higher composite indices of femoral neck strength in middle-aged men.


#5 Association Between the Acute to Chronic Workload Ratio and Injury Occurrence in Young Male Team Soccer Players: A Preliminary Study
Reference: Front Physiol. 2020 Jun 24;11:608. doi: 10.3389/fphys.2020.00608. eCollection 2020.
Authors: Hamid Arazi, Abbas Asadi, Farhood Khalkhali, Daniel Boullosa, Anthony C Hackney, Urs Granacher, Hassane Zouhal
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7327085/pdf/fphys-11-00608.pdf
Summary: This study aimed to investigate the relationship between the acute to chronic workload ratio (ACWR), based upon participant session rating of perceived exertion (sRPE), using two models [(1) rolling averages (ACWRRA); and (2) exponentially weighted moving averages (ACWREWMA)] and the injury rate in young male team soccer players aged 17.1 ± 0.7 years during a competitive mesocycle. Twenty-two players were enrolled in this study and performed four training sessions per week with 2 days of recovery and 1 match day per week. During each training session and each weekly match, training time and sRPE were recorded. In addition, training impulse (TRIMP), monotony, and strain were subsequently calculated. The rate of injury was recorded for each soccer player over a period of 4 weeks (i.e., 28 days) using a daily questionnaire. The results showed that over the course of the study, the number of non-contact injuries was significantly higher than that for contact injuries (2.5 vs. 0.5, p = 0.01). There were also significant positive correlations between sRPE and training time (r = 0.411, p = 0.039), ACWRRA (r = 0.47, p = 0.049), and ACWREWMA (r = 0.51, p = 0.038). In addition, small-to-medium correlations were detected between ACWR and non-contact injury occurrence (ACWRRA, r = 0.31, p = 0.05; ACWREWMA, r = 0.53, p = 0.03). Explained variance (r 2) for non-contact injury was significantly greater using the ACWREWMA model (ranging between 21 and 52%) compared with ACWRRA (ranging between 17 and 39%). In conclusion, the results of this study showed that the ACWREWMA model is more sensitive than ACWRRA to identify non-contact injury occurrence in male team soccer players during a short period in the competitive season.


#6 Comment on: "Changes in Skeletal Muscle Glycogen Content in Professional Soccer Players before and after a Match by a NonInvasive MuscleSound ® Technology. A Cross Sectional Pilot Study
Reference: Nutrients 2020, 12(4), 971"
Authors: Niels Ørtenblad, Joachim Nielsen, Kasper D Gejl, Harry E Routledge, James P Morton, Graeme L Close, David C Niemann, Julia L Bone, Louise M Burke
Download link: https://www.mdpi.com/2072-6643/12/7/2070/pdf


#7 Reply to Comment on: "Changes in Skeletal Muscle Glycogen Content in Professional Soccer Players before and after a Match by a Non-Invasive MuscleSound ® Technology. A Cross Sectional Pilot Study
Reference: Nutrients. 2020 Jul 12;12(7):E2066. doi: 10.3390/nu12072066.
Authors: Iñigo San-Millán, John C Hill, Julio Calleja-González
Download link: https://www.mdpi.com/2072-6643/12/7/2066/pdf



#8 Sodium Bicarbonate Supplementation Does Not Improve Running Anaerobic Sprint Test Performance in Semiprofessional Adolescent Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2020 Jul 15;1-8. doi: 10.1123/ijsnem.2020-0031. Online ahead of print.
Authors: Rodrigo Dos Santos Guimarães, Alcides Correa de Morais Junior, Raquel Machado Schincaglia, Bryan Saunders, Gustavo Duarte Pimentel, João Felipe Mota
Summary: Ergogenic strategies have been studied to alleviate muscle fatigue and improve sports performance. Sodium bicarbonate (NaHCO3) has improved repeated sprint performance in adult team-sports players, but the effect for adolescents is unknown. The aim of the present study was to evaluate the effect of NaHCO3 supplementation on repeated sprint performance in semiprofessional adolescent soccer players. In a double-blind, placebo-controlled, crossover trial, 15 male semiprofessional adolescent soccer players (15 ± 1 years; body fat 10.7 ± 1.3%) ingested NaHCO3 or a placebo (sodium chloride) 90 min before performing the running anaerobic sprint test (RAST). A countermovement jump was performed before and after the RAST, and ratings of perceived exertion, blood parameters (potential hydrogen and bicarbonate concentration), and fatigue index were also evaluated. Supplementation with NaHCO3 promoted alkalosis, as demonstrated by the increase from the baseline to preexercise, compared with the placebo (potential hydrogen: +0.07 ± 0.01 vs. -0.00 ± 0.01, p < .001 and bicarbonate: +3.44 ± 0.38 vs. -1.45 ± 0.31 mmol/L, p < .001); however, this change did not translate into an improvement in RAST total time (32.12 ± 0.30 vs. 33.31 ± 0.41 s, p = .553); fatigue index (5.44 ± 0.64 vs. 6.28 ± 0.64 W/s, p = .263); ratings of perceived exertion (7.60 ± 0.33 vs. 7.80 ± 0.10 units, p = .525); countermovement jump pre-RAST (32.21 ± 3.35 vs. 32.05 ± 3.51 cm, p = .383); or countermovement jump post-RAST (31.70 ± 0.78 vs. 32.74 ± 1.11 cm, p = .696). Acute NaHCO3 supplementation did not reduce muscle fatigue or improve RAST performance in semiprofessional adolescent soccer players. More work assessing supplementation in this age group is required to increase understanding in the area.


#9 Effects of 6 Weeks Direct Instruction and Teaching Games for Understanding Programs on Physical Activity and Tactical Behaviour in U-12 Soccer Players
Reference: Int J Environ Res Public Health. 2020 Jul 12;17(14):E5008. doi: 10.3390/ijerph17145008.
Authors: Juan Vicente Sierra-Ríos, Filipe Manuel Clemente, Ezequiel Rey, Sixto González-Víllora
Download link: https://www.mdpi.com/1660-4601/17/14/5008/pdf
Summary: The purpose of this study was to compare the effects of 6 weeks direct instruction and teaching games for understanding (TGfU) programs on the decision-making and execution (post-interventions), as well, as on the physical activity (PA) levels during sessions. Thirty under-12 football players participated in this study (age: 10.3 ± 0.45 years) and were randomly assigned to TGfU (n = 15) or direct instruction (n = 15) group. Two sessions/week were implemented. Results revealed that TGfU promoted higher levels (p = 0.043; d = 2.99) of light PA (28.96%) compared with direct instruction (27.55%). Non-significant higher sedentary PA levels (p = 0.073; d = 2.62) were found in the control group (35.48%). In terms of tactical principles, conservation of the ball increased the percentage of moderate to vigorous physical activity in TGfU (43.60%) compared with direct instruction (38.05%). According to the Game Performance Evaluation Tool (GPET), significant improvements (p = 0.018, d = 3.78) of the attacking player with the ball in the percentage of change between groups in the unsuccessful execution in TGfU (% = -62.2) were observed compared with direct instruction (% = 14.2). TGfU seems to be more appropriate than direct instruction to increase the light PA levels during sessions while no significant differences were found between programs in moderate and vigorous intensities. Regarding the effects of programs in decisions, greater improvements in decisions with the ball were found in TGFU compared to DI.


#10 Adductor Muscles Strength and Strength Asymmetry as Risk Factors for Groin Injuries among Professional Soccer Players: A Prospective Study
Reference: Int J Environ Res Public Health. 2020 Jul 9;17(14):E4946. doi: 10.3390/ijerph17144946.
Authors: Goran Markovic, Nejc Šarabon, Jelena Pausic , Vedran Hadžić
Download link: https://www.mdpi.com/1660-4601/17/14/4946/pdf
Summary: The aim of this study was to prospectively examine the association between isometric hip adductor strength and between-limb strength asymmetry to groin injuries in male professional soccer players. Isometric hip adductor strength and between-limb strength asymmetry of 45 professional outfield soccer players from three First Division teams were tested during the 2017/2018 preseason. Players were then monitored throughout the 2017/2018 season for groin injuries. Ten groin injuries were recorded. When compared with uninjured players, players who sustained groin injury had significantly lower strength of respective muscle groups and significantly higher between-limb strength asymmetries (all p < 0.05; ES = 1.16 and 0.88; mean % difference = 26% and 51%). Isometric hip adductor strength had a significant inverse relationship with the incidence of occurring groin injuries (p = 0.016). No significant relationship between hip adductor strength asymmetry and the incidence of future groin injury was observed (p = 0.09). Finally, players' age and previous groin injury were not significantly associated with the incidence of future groin injuries (all p > 0.05). These results generally suggest that isometric adductor strength is a significant predictor of future groin injuries in men's professional football; however, due to the relatively low sample size, further studies are required.


#11 Injuries on the Youth Soccer (Football) Field: Do Additional Referees Reduce Risk? Randomized Crossover Trial
Reference: J Pediatr Psychol. 2020 Jul 11;jsaa050. doi: 10.1093/jpepsy/jsaa050. Online ahead of print.
Authors: David C Schwebel, D Leann Long, Leslie A McClure
Summary: Youth soccer injury can be prevented through various means, but few studies consider the role of referees. Following previous research suggesting children take fewer risks when supervised intensely, this randomized crossover trial evaluated whether risky play and injuries decrease under supervision from three referees instead of one referee. Youth soccer clubs serving a metropolitan U.S. area participated. Boys' and girls' clubs at under age 10 (U10) and under age 11 (U11) levels were randomly assigned such that when the same clubs played each other twice in the same season, they played once with one referee and once with three referees. A total of 98 games were videotaped and subsequently coded to obtain four outcomes: collisions between players, aggressive fouls (involving physical player-to-player contact) called by the referee(s) on the field, aggressive fouls judged by trained coders, and injuries requiring adult attention or play stoppage. Poisson mixed model results suggest players in the 98 games committed fewer aggressive fouls, as identified independently by referees (rate ratio [RR] 0.58; 95% confidence interval [CI] 0.35-0.96) and by researchers (RR 0.67; 95% CI 0.50-0.90), when there were three referees versus one referee. Collisions (RR 0.98; 95% CI 0.86-1.12) and injury rates (RR 1.15; 95% CI 0.60-2.19) were similar across conditions. When the same youth soccer clubs played with three referees rather than one, they committed fewer aggressive fouls. More intense supervision created better rule adherence. Injury rates were unchanged with increased supervision. Results raise questions concerning whether financial investment in additional referees on youth soccer fields yields safety benefits.


#12 'When you have the adrenalin pumping, it kind of flushes out any negative emotions': a qualitative exploration of the benefits of playing football for people with mental health difficulties
Reference: J Ment Health. 2020 Jul 17;1-8. doi: 10.1080/09638237.2020.1793119. Online ahead of print.
Authors: Mark Llewellyn, Alecia L Cousins, Philip John Tyson
Summary: Physical activity is a factor by which mental health can be improved. However, the association between mental health and physical exercise, in a "team-based sport" setting within the community, remains unclear. The current paper aims to provide an evaluation of a football programme, implemented by Time to Change Wales, funded by the Welsh Government, to improve mental health. Participants attended weekly 90-120 minute football sessions, held in local community venues across Wales, UK, with no requirement on the number of sessions that participants had to attend. A qualitative method was employed to explore the experiences of those who took part. Individuals who participated in the programme reported psychosocial and physical benefits, such as improved physical and mental health, improved social confidence and having a sense of purpose added to their day-to-day living. Factors affecting participation were also identified within the data, such as environmental barriers. The findings provide both support and contextual extension to previous research in this area; demonstrating the positive effects of sport-based therapy for those with mental health difficulties. Implications and conclusions should be used to inform future research into developing community sport-based programmes to improve mental health.

Wed

18

Nov

2020

Running Performance and Game performance Indicators in Professional Soccer Play

The study aimed to identify associations between running performance and game performance indicators in professional footballers compared to their playing position.

Tue

17

Nov

2020

Planning training workload in football using small-sided games density

The purpose was to assess the relation between training workload and SSGs' density.

Thu

12

Nov

2020

Latest research in football - week 32 - 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 Short and Long-Term Effects of a Simple-Strength-Training Program on Injuries Among Elite U-19 Soccer Players
Reference: Res Q Exerc Sport. 2020 Jul 7;1-9. doi: 10.1080/02701367.2020.1741498. Online ahead of print.
Authors: Javier Raya-González, Luis Suarez-Arrones, Javier Sanchez-Sanchez, Rodrigo Ramirez-Campillo, Fabio Y Nakamura, Eduardo Sáez De Villarreal
Summary: The aim of this study was to examine the short and long-term effects of a simple strength training program on muscle injury prevention in soccer players. Twenty-seven U-19 elite male soccer players participated in the study. The investigation was conducted over two consecutive and similar seasons (e.g., the same staff, players, weekly training schedule), the first being the control and the second the experimental season. The strength program was carried out 2 times per week, for 10 weeks, during part of the preseason and in-season. Injury incidence and absence days were compared between both seasons, according to the injury rate ratio (IRR), with 95% CI and the Z test. A lower number of total and hamstring injuries were recorded during the experimental (9 and 2, respectively) compared to the control (15 and 7, respectively) period. During the 10 weeks intervention period, the injury rate ratio (IRR) was lower in the experimental season than in the control season (IRR = 8.12; 95% CI: 1.00-66.03; effect size (ES) = 3.30, large). In addition, there was a decline in absence days per injury and in the number of absence days/1000 h (IRR = 2.44; 95% CI: 1.90-3.14; ES = 1.12) during the experimental season. The results of this study suggest that this simple strength-training program could reduce the muscle injury incidence during its application period in young soccer players.


#2 Role of Sports Psychology and Sports Nutrition in Return to Play From Musculoskeletal Injuries in Professional Soccer: An Interdisciplinary Approach
Reference: Eur J Sport Sci. 2020 Jul 7;1-19. doi: 10.1080/17461391.2020.1792558. Online ahead of print.
Authors: Ian Rollo, James M Carter, Graeme L Close, Javier Yanguas Leyes, Antonio Gomez, Daniel Medina Leal, Joan L Duda, Donough Holohan, Sam J Erith, Leslie Podlog
Summary: Musculoskeletal injuries are prevalent in professional soccer and can result in lost training time or match play. It is intuitive that the "return to play" (RTP) pathway will depend, in large part, on the expertise of sports medicine practitioners (e.g., surgeons, physicians, physiotherapists) responsible for player's recovery. Consensus statements on returning athletes to sport following injury acknowledge the contributions of sport psychology and sports nutrition. However, specific consideration on how to integrate these two recognized - but often overlooked components of injury rehabilitation - into existing sport medicine approaches has yet to be examined. Using a framework of milestones directed by the medical physician and physical trainer, evidence is summarised and suggestions provided on the integration of sports psychology and sports nutrition into an interdisciplinary RTP approach. We examine recovery from a phase approach (acute injury and functional recovery) to highlight interdisciplinary opportunities in the management of musculoskeletal soccer injuries. An interdisciplinary approach is understood to achieve outcomes that could not be achieved within the framework of a single discipline. The incorporation of sports psychology and nutrition theoretically compliment milestones used in current medically-based RTP models. Our hope is that this article serves as a catalyst for interdisciplinary practice and research - not only in sports nutrition and sports psychology - but across all sport and exercise disciplines.


#3 Assessment of Energy Availability and Associated Risk Factors in Professional Female Soccer Players
Reference: Eur J Sport Sci. 2020 Jul 7;1-27. doi: 10.1080/17461391.2020.1788647. Online ahead of print.
Authors: Samantha L Moss, Rebecca K Randell, Darren Burgess, Stephanie Ridley, Caibre ÓCairealláin, Richard Allison, Ian Rollo
Summary: This study aimed to assess energy availability (EA), alongside possible risk factors of reduced or low EA of professional female soccer players during a competitive season. Thirteen players (age: 23.7 ± 3.4 y, stature: 1.69 ± 0.08 m, body mass: 63.7 ± 7.0 kg) engaged in a 5-day (two rest days, one light training, heavy training and match day) monitoring period. Energy intake (EI) and expenditure during exercise (EEE) were measured. EA was calculated and categorised as optimal, reduced or low (≥45, 31-44, ≤30 kcal·kg FFM-1·day-1, respectively). Relationships between EA and bone mineral density, resting metabolic rate (RMR), plasma micronutrient status, biochemical markers and survey data were assessed. EA was optimal for 15%, reduced for 62% and low for 23% of players. Higher EA was observed on rest days compared to others (P<0.05). EA was higher for the light compared to the heavy training day (P<0.001). EEE differed significantly between days (P<0.05). EI (2124 ± 444 kcal), carbohydrate (3.31 ± 0.64 g·kg·day-1) and protein (1.83 ± 0.41 g·kg·day-1) intake remained similar (P>0.05). Survey data revealed 23% scored ≥ 8 on the Low Energy Availability in Females Questionnaire and met criteria for low RMR (ratio <0.90). Relationships between EA and risk factors were inconclusive. Most players displayed reduced EA and did not alter EI or carbohydrate intake to training or match demands. Although cases of low EA were identified, further work is needed to investigate possible long-term effects and risk factors of low and reduced EA separately to inform player recommendations.


#4 The Influence of a Soccer Season on Non-Contact Injury and Isokinetic Peak Torque of the Quadriceps and Hamstrings in Professional Youth Soccer Players
Reference: Res Sports Med. 2020 Jul 6;1-14. doi: 10.1080/15438627.2020.1771336. Online ahead of print.
Authors: Colin Charles Brow, Andisheh Bakhshi, Russ Wrigely, Viswanath B Unnithan
Summary: Isokinetic strength screening is utilized in professional soccer. However, there has been little research on the interaction between seasonal changes in players' peak torque (PT) and injury incidence. Twenty-five (age 16.5[Formula: see text]0.68 years) professional youth soccer players participated in the study. Bilateral isokinetic concentric (CON) and eccentric (ECC) testing of Quadriceps (Q) and Hamstrings (H) were conducted at three time-points across the season. Absolute CON and ECC PT were measured at 60 degree/sec and in a supine 170-degree position. Testing data was normalized to body mass. A mixed design (2 by 3) repeated measures ANOVA with injury as a co-variate was conducted to evaluate the effect of season and/or limb dominance on PT and injury incidence. With regard to the seasonal variation and injury incidence, an interaction was identified with respect to non-dominant limb (NDL) QCON (p = 0.01) and to a lesser extent the dominant limb (DL) QCON (p = 0.05). The seasonal variation of the PT of the NDL QCON was different between the injured and non-injured individuals. Non-injured individuals, QCON strength increased over the course of the season. While for the Injured players, QCON declined from pre-season to mid-season then increased but never recovered to starting pre-season values.


#5 Muscular Strength Imbalances Are Not Associated With Skin Temperature Asymmetries in Soccer Players
Reference: Life (Basel). 2020 Jul 2;10(7):E102. doi: 10.3390/life10070102.
Authors: Rodrigo Mendonça Teixeira, Rodolfo A Dellagrana, Jose I Priego-Quesada, João Claudio B P Machado, Juliano Fernandes da Silva, Tallyne Mayara Pacheco Dos Reis, Mateus Rossato
Download link: https://www.mdpi.com/2075-1729/10/7/102/pdf
Summary: Although strength imbalances using isokinetic dynamometer have been examined for injury risk screening in soccer players, it is very expensive and time-consuming, making the evaluation of new methods appealing. The aim of the study was to analyze the agreement between muscular strength imbalances and skin temperature bilateral asymmetries as well as skin temperature differences in the hamstrings and quadriceps. The skin temperature of the anterior and posterior thigh of 59 healthy male soccer athletes was assessed at baseline using infrared thermography for the identification of hamstrings-quadriceps skin temperature differences and thermal asymmetries (>0.5 °C). Subsequently, concentric and eccentric peak torque of the quadriceps and hamstrings were considered in the determination of the ratios, as well as muscular asymmetries (>15%). When considering the torque parameters, 37.3% (n = 22) of the players would be classified as high risk for injuries. The percentage of those presenting skin temperature imbalances superior to 0.5 °C was 52.5% (n = 31). The skin temperature assessment showed sensitivity (22%) and specificity (32.2%) to identify torque asymmetries, demonstrating the inability to identify false negatives (15.3%) and false positives (30.5%) from all soccer athletes. In conclusion, skin temperature differences between hamstrings and quadriceps could be more related to thermoregulatory factors than strength imbalances.


#6 Effects of a 20-min Nap After Sleep Deprivation on Brain Activity and Soccer Performance
Reference: Int J Sports Med. 2020 Jul 6. doi: 10.1055/a-1192-6187. Online ahead of print.
Authors: Amornpan Ajjimaporn, Papatsorn Ramyarangsi, Vorasith Siripornpanich
Summary: We examined effects of a 20-min nap following 3 h of sleep deprivation on brain wave activity, auditory reaction time, the running-based anaerobic sprint test, leg muscle strength and the rating of perceived exertion in male college soccer players. Eleven players underwent three sleep conditions; normal sleep, sleep deprivation and 20-min nap after sleep deprivation. The sleep deprivation demonstrated an increase in the mean power of delta waves over the frontal area and a decrease in the mean power of alpha waves over the parietal area compared to the normal sleep. The nap and the sleep deprivation showed an increase in auditory reaction time compared with those in the normal sleep. The sleep deprivation demonstrated a decrease in the running-based anaerobic sprint test compared to the normal sleep, whereas the nap has partially reversed only minimal power and average power of the running-based anaerobic sprint test. The nap showed a recovery effect on leg muscle strength, but not on the rating of perceived exertion compared with the sleep deprivation. Thus, a 20-min nap after sleep deprivation did not completely return brain activity back to active state and did not entirely reverse the negative impact of sleep deprivation on soccer performance in soccer players.


#7 Physical Match Performance in Sub-elite Soccer Players - Introduction of a New Index
Reference: Int J Sports Med. 2020 Jul 6. doi: 10.1055/a-1165-1950. Online ahead of print.
Authors: Lars Reinhardt, Stephan Schulze, Rene Schwesig, Eduard Kurz
Summary: This investigation examined the position-specific physical performance in different locomotor categories and physiological demands concurrently in official games of sub-elite players and to present a new performance index (PI). Time-motion (distance, velocity, acceleration) and heart rate data of 55 soccer players were simultaneously captured via a GPS tracking system. The relationship between external and internal match-load (PI) was determined on the basis of heart rate, average velocity and acceleration. In contrast to the mean heart rate (85.2±3.2%, P=0.806, ηp²=0.03), the average total distance covered (9946±715 m) was largely affected by players' position (P<0.001, ηp²=0.63). Furthermore, a mixed design ANOVA showed a large interaction effect between position and locomotor category (P<0.001, ηp²=0.44). On average, PI was 1.57±0.37 m/min²/%, with notably lower values in the 2nd half. The position-specific profiles already reported for higher leagues were also present in sub-elite soccer players. Despite lower values for total distance and smaller distances in the high-intensity zones (>14.4 km/h), internal loads were comparable to those observed in European top leagues. In comparison to a performance measure that ignores accelerations, PI was shown to be less dependent on the playing position and had higher variability. Consequently, PI is better suited to distinguish between players' performance


#8 The Developmental and Professional Activities of Female International Soccer Players From Five High-Performing Nations
Reference: J Sports Sci. 2020 Jul 4;1-9. doi: 10.1080/02640414.2020.1789384. Online ahead of print.
Authors: Paul R Ford, Nicola J Hodges, David Broadbent, Donna O'Connor , Dawn Scott, Naomi Datson, Helena A Andersson, A Mark Williams
Summary: We study the developmental and professional activities engaged in by 86 female adult soccer players from the senior national teams of Australia, Canada, England, Sweden, and the United States of America. Players completed the Participation History Questionnaire (PHQ) to elicit the amount and type of activities engaged in across their developmental and professional years, including milestones, soccer-specific activity and engagement in other sport activity. Greater specialisation than diversification characterised their childhood developmental activities, including all players starting in soccer in childhood and accumulating more hours in soccer activity than other sports during this period. However, interindividual variation further characterised these childhood activities, with a proportion of players diversifying into other sports and/or soccer play to a greater or lesser degree during childhood when compared to the other players. The amount of coach-led soccer practice increased for all players across their development culminating in an average of 15-16 h/wk across a 40-week season in early adulthood. In contrast, the amount of engagement in other sports and soccer peer-led play varied between players but generally decreased across adolescence to negligible amounts in late adolescence. Findings are commensurate with the deliberate practice framework and early engagement.


#9 Effects of Acute Inspiratory Loading During Treadmill Running on Cerebral, Locomotor and Respiratory Muscle Oxygenation in Women Soccer Players
Reference: Respir Physiol Neurobiol. 2020 Jul 2;103488. doi: 10.1016/j.resp.2020.103488. Online ahead of print.
Authors: Flavia Rossi Caruso, Bruno Archiza, Daniela Kuguimoto Andaku, Renata Trimer, José Carlos Bonjorno-Junior, Claudio Ricardo de Oliveira, Cleiton A Libardi, Shane A Phillips, Ross Arena, Renata Gonçalves Mendes, Audrey Borghi-Silva
Summary: Respiratory limitation can be a primary mechanism for exercise cessation in female athletes. This study aimed to assess the effects of IL on intercostal (IM), vastus lateralis (VL) and cerebral (Cox) oxygenation in women soccer players during high-intensity dynamic exercise. Ten female soccer players were randomized to perform in order two constant-load tests on a treadmill until the exhaustion time (Tlim) (100% of maximal oxygen uptake- V̇O2). They breathed freely or against a fixed inspiratory loading (IL) of 41 cm H2O (∼30% of maximal inspiratory pressure). Oxygenated (Δ[OxyHb]), deoxygenated (Δ[DeoxyHb]), total hemoglobin (Δ[tHb]) and tissue saturation index (ΔTSI) were obtained by NIRs. Also, blood lactate [La-] was obtained. IL significantly reduced Tlim (224 ± 54 vs 78 ± 20 sec; P < 0.05) and increased [La-], V̇O2, respiratory cycles and dyspnea when corrected to Tlim (P < 0.05). IL also resulted in decrease of Δ[OxyHb] of Cox and IM during exercise compared with rest condition. In addition, decrease of Δ[OxyHb] was observed on IM during exercise when contrasted with Sham (P < 0.05). Furthermore, significant higher Δ[DeoxyHb] of IM and significant lower Δ[DeoxyHb] of Cox were observed when IL was applied during exercise in contrast with Sham (P < 0.05). These results were accompanied with significant reduction of Δ[tHb] and ΔTSI of IM and VL when IL was applied (P < 0.05). High-intensity exercise with IL decreased respiratory and peripheral muscle oxygenation with negative impact on exercise performance. However, the increase in ventilatory work did not impact cerebral oxygenation in soccer players.


#10 Body Composition of National Collegiate Athletic Association (NCAA) Division I Female Soccer Athletes Through Competitive Seasons
Reference: Int J Sports Med. 2020 Jul 10. doi: 10.1055/a-1177-0716. Online ahead of print.
Authors: Erica Roelofs, April Bockin, Tyler Bosch, Jonathan Oliver, Christopher W Bach, Aaron Carbuhn, Philip R Stanforth, Donald R Dengel
Summary: The purpose of this study was to examine body composition of National Collegiate Athletic Association Division I female soccer players by position and season. One hundred seventy-five female athletes were categorized by positions of forward (n=47), midfielder (n=51), defender (n=57), and goalkeeper (n=20). A dual X-ray absorptiometry scan assessed percent body fat, total lean mass, total fat mass, arm and leg lean mass and fat mass, and visceral adipose tissue. Goalkeepers had significantly higher total, arm, and leg lean mass and fat mass compared to all other positions (p<0.05). For seasonal changes, body fat percentage was significantly higher in winter off-season (26.7%) compared to summer off-season (25.7%) and pre-season (25.8%; p<0.01) for all positions. Total and leg lean mass was significantly lower in winter off-season compared to all other seasons, and total lean mass was significantly higher in summer off-season than pre-season (p<0.01). Overall, goalkeepers were significantly different than all other positions. Body fat percentage increased and lean mass decreased in winter off-season indicating potential undesired changes in training and/or nutrition over the break whereas lean mass was the highest in summer off-season potentially reflecting the emphasis on resistance training and increased volume of training.


#11 Developing a Two-Dimensional Landscape Model of Opportunities for Penetrative Passing in Association Football - Stage I
Reference: J Sports Sci. 2020 Jul 10;1-8. doi: 10.1080/02640414.2020.1786991. Online ahead of print.
Authors: Pedro Passos, Rodrigo Amaro E Silva, Luís Gomez-Jordana, Keith Davids
Summary: This study investigated a method for modelling a landscape of opportunities for penetrative passing completed on the ground by ball carriers in association football. Analysis of video footage of competitive, professional football performance was undertaken, identifying a sample (n = 20) of attacking sub-phases of gameplay which ended in a penetrative pass being made between defenders to a receiver. Players' relative co-positioning during performance was modelled using bi-dimensional x and y coordinates of each player recorded at 25 fps. Data on player movements during competitive interactions were captured using an automatic video tracking system, recording player co-locations emerging over time, as well as current and estimated running velocities. Results revealed that the half spaces between the midfield and both sidelines were the key locations on field providing most affordances for penetrating passes in the competitive performance sample analysed. Due to the dynamics of players' co-adaptive performance behaviours, it was expected that opportunities for penetrative passing by ball carriers would not display a homogeneous space-time spread across the entire field. Results agreed with these expectations, showing how a landscape of opportunities for penetrative passing might be specified by information emerging from continuous player interactions in competitive performance.


#12 Influence of Training Schedules on Objective Measures of Sleep in Adolescent Academy Football Players
Reference: J Strength Cond Res. 2020 Jul 7. doi: 10.1519/JSC.0000000000003724. Online ahead of print.
Authors: Georgia A Brown, Stella Veith, John A Sampson, Matthew Whalan, Hugh H K Fullagar
Summary: Football academy settings may pose risks to adolescent athletes achieving sufficient sleep because of the contextual challenges these players face (e.g., psychosocial pressure, changes in training, competition, and academic stress). Given the importance of sleep to overall health as well as physical athletic development and injury risk, this study aimed to investigate whether differences in training schedules (morning vs. evening training sessions) affected objective measures of sleep in adolescent academy football (soccer) players. Twelve academy players (mean age 14.18 ± 1.36 years) wore an ActiGraph accelerometer on nights before, and nights of, training days in 2 separate weeks where morning (09:00-11:00 hours) and evening (18:00-20:00 hours) training occurred. Objective sleep parameters and training load data were collected. Night-time sleep periods were categorized as sleep preceding morning training, preceding evening training, or after evening training. One-way univariate and multivariate analyses of variance for repeated measures were performed to determine the impact of the training schedule on sleep. Significance levels were set at p < 0.05. The total sleep time was below the recommended guidelines (<8 hours) across conditions. A large significant effect of the training schedule on time attempted to fall asleep (p = 0.004, effect size [ES] = 0.40) and time of sleep (p = 0.003, ES = 0.41) was present, with post-evening sessions resulting in the latest times. Overall, the players' sleep behavior was resilient to changes in training schedules. However, the low sleep durations (and potential risks to physical performance/injury) suggest that sleep education coupled with practical interventions are required in this cohort.

Wed

11

Nov

2020

In-season internal and external training load quantification of an elite European soccer team with regards to match-day

The aim was to provide in-season training load for different days within a mesocycle in elite soccer players.

Tue

10

Nov

2020

Effects of velocity loss during resistance training on performance in professional soccer players

The aim was to analyze the effects of 2 resistance programs using the same relative load but different repetition volume.

Fri

23

Oct

2020

Latest research in football - week 31- 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 Ball Passing and Space Detection Skill in Soccer: Implementation of Two New Soccer Tests
Reference: Res Sports Med. 2020 Jul 1;1-11. doi: 10.1080/15438627.2020.1789133. Online ahead of print.
Authors: Evangelos Bekris, Stylianos Kounalakis, Ioannis Ispirlidis, Athanasios Katis
Summary: The present study examined the validity and reliability of two new soccer tests: the Passing Accuracy Test (PAT), which assesses ball passing accuracy in combination with visual stimulus recognition and the Passing and Visual Recognition test (PVR), which assesses player's space detection skill in a 360 degrees range along with the frequency and the accuracy of ball passing technique. Participants were allocated in four (4) groups based on their age: the Under 11 (U11) group consisted of 101 players, the Under 14 (U14) group consisted of 100 players, the Under 17 (U17) group consisted of 118 players and the Adults (AD) group consisted of 43 players. The typical error, the limits of agreement and the ICC of PAT and PVR test were examined. The results of the study showed high validity and reliability for both tests with the exception in PAT for adult group (ICC = 0.33-0.83; P < 0.05). Therefore, both tests could be valuable tools to assess the accuracy of ball passing technique and the space detection skill in players of different ages.


#2 Talipes Equinus Deformity Caused by Fibrous Gastrocnemius Muscle Contracture After Direct Contusion in Football Players: Report of Two Cases
Reference: J Foot Ankle Surg. Jul-Aug 2020;59(4):816-820. doi: 10.1053/j.jfas.2019.10.004.
Authors: Yoichi Kaneuchi, Ken-Ichi Otoshi, Michiyuki Hakozaki, Kazuo Watanabe, Shin-Ichi Konno
Summary: Two main causes of gastrocnemius contracture have been considered: 1) congenital deformities in pediatric patients, such as limb-length discrepancy, cerebral palsy, flatfoot, and clubfoot; and 2) secondary conditions such as immobilization for trauma or a nonfunctional limb. Talipes equinus deformity caused by fibrous gastrocnemius contracture after a direct muscle contusion is extremely rare. We describe 2 cases of talipes equinus deformity caused by fibrous gastrocnemius muscle contracture after a direct contusion in football players. Both of the players had a talipes equinus deformity with a severe restriction of ankle dorsiflexion, and a cord-like structure was observed at the proximal part of the lateral gastrocnemius head. Both patients' histological examinations revealed fibrous tendon-like tissue within the structure. After discission of the cord-like structures, the restriction of ankle dorsiflexion was completely resolved, and the patients were able to fully return to playing football without any discomfort in their calves.
 

#3 Training Soccer Skills to Adolescents With Autism Spectrum Disorder via Peer-Mediated Behavioral Skills Training
Reference: Behav Anal Pract. 2019 Aug 19;13(2):454-461. doi: 10.1007/s40617-019-00381-2.
Authors: Caitlyn Chambers, Keith C Radley
Summary: Peer-mediated interventions have been identified as efficient means of promoting the acquisition of skills of students with autism spectrum disorder (ASD). Limited research, however, has evaluated the utility of such procedures for promoting recreational skills that may allow for greater interaction with peers. The purpose of the current study was to evaluate the effectiveness of peer-mediated behavioral skills training on the acquisition of discrete soccer skills of 3 students with ASD. Following the implementation of the intervention, all participants demonstrated substantial improvements in the accuracy of the target soccer skills.


#4 Relationships Between Controlling Interpersonal Coaching Style, Basic Psychological Need Thwarting, and Burnout, in Adolescent Soccer Players
Reference: Int J Environ Res Public Health. 2020 Jul 7;17(13):E4909. doi: 10.3390/ijerph17134909.
Authors: Verónica Morales-Sánchez, Miriam Crespillo-Jurado, David Jiménez-López, Juan P Morillo-Baro, Antonio Hernández-Mendo, Rafael E Reigal 
Download link: https://www.mdpi.com/1660-4601/17/13/4909/pdf
Summary: The aim of this paper is to analyze the relationships between a controlling interpersonal style, psychological need thwarting and burnout in adolescent soccer players and to test a structural equation model to analyze whether (a) a controlling interpersonal style is a predictor of psychological need thwarting and whether (b) psychological need thwarting is a predictor of burnout. A total of 103 male soccer players between the ages of 12 and 17 participated in the research (M = 14.91; SD = 5.56). The Controlling Coach Behaviors Scale, the Psychological Need Thwarting Scale, and the Athlete Burnout Questionnaire were used to evaluate the variables under study. The analyses revealed significant relationships between a controlling interpersonal style, psychological need thwarting and burnout. Furthermore, the proposed structural equations model, using the partial least squares (PLS) method, showed that a controlling style is a positive predictor of basic psychological need thwarting and that the latter is a predictor of burnout, as well as revealing an indirect relationship between a controlling style and burnout. This indirect effect of the controlling style variable on burnout can be enhanced (or attenuated) by the basic psychological need thwarting variable, which acts as a modulator.


#5 The Effects of Physical Fitness on Postactivation Potentiation in Professional Soccer Athletes
Reference: J Strength Cond Res. 2020 Jul 7. doi: 10.1519/JSC.0000000000003711. Online ahead of print.
Authors: Mauro A Guerra Jr, Leonardo C Caldas, Helder L Souza, Jason Tallis, Michael J Duncan, Lucas Guimarães-Ferreira 
Reference: The effects of physical fitness on postactivation potentiation in professional soccer athletes.
Summary: The purpose was to investigate the relationship of the response to postactivation potentiation (PAP) with scores of physical fitness. Twenty-four professional male soccer players undertook tests of agility, muscular power, aerobic capacity, and body composition. Conditioning activities (CAs) were performed consisting of plyometrics exercises and sprints with sled towing. In the first and second sessions, body composition, agility, power, and aerobic capacity were assessed. At the third session, countermovement jumps (CMJ) were performed with 1, 3, and 5 minutes after the execution of the CA. Significant differences were found for CMJ height 1, 3, and 5 minutes after the CA compared with baseline values (3.58, 5.10, 5.48%, respectively). There was a significant positive correlation between the level of general physical fitness and PAP (CMJ height increase) 5 minutes after (r = 0.73). When the athletes were divided into groups with higher and lower physical fitness, the CA caused a significant increase in CMJ height in both groups, but a significant difference (p < 0.05) was observed at all times after PAP induction, with better performance in higher versus lower fitness level. The results suggest that plyometrics exercises associated with sled towing sprints as a CA result in an increase in CMJ performance in athletes and that physical fitness directly influences the PAP occurrence, with higher fit players demonstrating an enhanced PAP response.


#6 High Coenzyme Q10 Plasma Levels Improve Stress and Damage Markers in Professional Soccer Players During Competition
Reference: Int J Vitam Nutr Res. 2020 Jul 8;1-12. doi: 10.1024/0300-9831/a000659. Online ahead of print.
Authors: Ana Sánchez-Cuesta, Ana Belén Cortés-Rodríguez, Ignacio Navas-Enamorado, José Antonio Lekue, Toscana Viar, Martín Axpe, Plácido Navas, Guillermo López-Lluch
Summary: Ubiquinol, the reduced form of Coenzyme Q10 (CoQ10), is a key factor in bioenergetics and antioxidant protection. During competition, professional soccer players suffer from considerable physical stress causing high risk of muscle damage. For athletes, supplementation with several antioxidants, including CoQ10, is widely recommended to avoid oxidative stress and muscle damage. We performed an observational study of plasma parameters associated with CoQ10 levels in professional soccer players of the Spanish First League team Athletic Club de Bilbao over two consecutive seasons (n = 24-25) in order determine their relationship with damage, stress and performance during competition. We analyzed three different moments of the competition: preterm, initial phase and mid phase. Metabolites and factors related with stress (testosterone/cortisol) and muscle damage (creatine kinase) were determined. Physical activity during matches was analyzed over the 2015/16 season in those players participating in complete matches. In the mid phase of competition, CoQ10 levels were higher in 2015/16 (906.8 ± 307.9 vs. 584.3 ± 196.3 pmol/mL, p = 0.0006) High levels of CoQ10 in the hardest phase of competition were associated with a reduction in the levels of the muscle-damage marker creatine kinase (Pearsons' correlation coefficient (r) = - 0.460, p = 0.00168) and a trend for the stress marker cortisol (r = -0.252, p = 0.150). Plasma ubiquinol was also associated with better kidney function (r = -0.287, p = 0.0443 for uric acid). Furthermore, high CoQ10 levels were associated with higher muscle performance during matches. Our results suggest that high levels of plasma CoQ10 can prevent muscle damage, improve kidney function and are associated with higher performance in professional soccer players during competition.


#7 Identification of Ankle Injury Risk Factors in Professional Soccer Players Through a Preseason Functional Assessment
Reference: Orthop J Sports Med. 2020 Jun 24;8(6):2325967120928434. doi: 10.1177/2325967120928434.
Authors: Lucas Sartori Manoel, Marcela Godoy Xixirry, Thabata Pasquini Soeira, Marcelo Camargo Saad, Marcelo Riberto
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7315686/pdf/10.1177_2325967120928434.pdf
Summary: Etiologically, the risk of an ankle injury depends on extrinsic and intrinsic factors, such as muscle strength asymmetry, decreased flexibility, and decreased proprioception, as well as patient age and history of injuries. The purpose of this study was to identify risk factors present in the preseason assessment that may predispose professional soccer players to ankle injuries. We hypothesized that analysis of these parameters could relate the incidence of injuries to the deficits found during the preseason period, enabling the identification of risk factors to predict the occurrence of injuries. A total of 89 professional soccer athletes were evaluated in the preseason period; the evaluation included athlete history and anthropometric data collection, an isokinetic ankle evaluation, and functional tests: the Dorsiflexion Lunge Test and Y-Balance Test (YBT). The athletes were monitored during the competitive period, and the incidence of injuries was surveyed. The association of quantitative variables and injury outcomes was analyzed using the Student t test for independent samples, with P < .05. For the association of categorical variables and injury outcomes, the chi-square test was performed, with P < .05. A higher incidence of ankle injuries was associated with lower YBT scores in the dominant (P = .04) and nondominant (P = .01) limbs. A higher body mass index was also associated with a higher injury occurrence (P = .01).
Functional tests, such as the YBT, are indicated tools for assessing the physical capacities and possible risks of ankle sprains, as they can evaluate the ankle functional capacity in a complex way, identifying athletes more prone to ankle injuries. Athletes' body mass index should also be taken into account to prevent such injuries.


#8 Effects of Different Solutions Consumed During Exercise on Cognitive Function of Male College Soccer Players
Reference: J Exerc Sci Fit. 2020 Sep;18(3):155-161. doi: 10.1016/j.jesf.2020.06.003. Epub 2020 Jun 20.
Authors: Feng-Hua Sun, Simon B Cooper, Frank Chak-Fung Tse
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7330616/pdf/main.pdf
Summary: The present study aimed to investigate the effects of three solutions, i.e. carbohydrate-electrolyte-solution (CES), carbohydrate-electrolyte-protein-solution (CEPS), and placebo (PLA), on cognitive function of college soccer players. Sixteen male college soccer players completed three main trials in a randomized cross-over study design. In each main trial, participants completed 90 min Loughborough Intermittent Shuttle Test (LIST) protocol and consumed one of three solutions. The cognitive function tests were performed; blood glucose and lactate concentrations, and several subjective measurements were also recorded in each trial. Compared with pre-exercise level, the accuracy of Rapid Visual Information Processing test (RVIPT) and the response time in Visual Search Test (VST, complex level) after LIST improved in CES and CEPS trials, but not in PLA trial. However, the accuracy of VST (complex level) decreased in both CES and CEPS trials, compared with PLA trial. CEPS consumption improved accuracy in VST (simple level), compared with CES consumption. Blood glucose concentrations were well maintained in CEPS trial, but not in CES and PLA trials. It seems that both CES and CEPS consumption show certain benefits on some aspects of cognitive function in male college soccer players in Hong Kong. However, these effects may be specific to the cognitive domain tested.


#9 Youth Soccer Parents' Attitudes and Perceptions About Concussions
Reference: J Adolesc Health. 2020 Jul 4;S1054-139X(20)30218-4. doi: 10.1016/j.jadohealth.2020.04.029. Online ahead of print.
Authors: Sungwon Kim, Daniel P Connaughton
Download link: https://www.jahonline.org/article/S1054-139X(20)30218-4/pdf
Summary: Parents are important figures in properly managing youth sport concussions. Although media attention has predominantly centered on concussions in contact/collision sports, evidence suggests that the concussion rate in soccer is comparable to those found in contact/collision sports. Given the high rate of concussions in youth soccer, this study aimed to examine parents of youth soccer athletes' attitudes and perceptions about concussions and associated factors. A cross-sectional study was conducted by surveying parents of youth soccer athletesfrom the five largest organized youth soccer programs across the U.S. The researchers developed a questionnaire after an extensive literature review and by modifying previously used instruments. Overall, 419 parents completed the survey. The vast majority (85%) agreed that a concussion is a serious injury, but only 27.9% believed that their child could suffer a concussion during the next season. Parents were most concerned about permanent brain damage when their child suffers a concussion. The vast majority (4.37 ± .89) perceived concussion reporting as an important injury prevention strategy. Greater appreciation and perceived risk about concussions was found particularly among parents who received concussion education and those who had witnessed or heard about a concussive incidence(s). Findings suggest that youth soccer parents have high appreciation and perceived risk about concussions. However, the need for more targeted education was noted, as improvements to better manage and reduce concussions can be made. Future research should continue examining youth sport parents' belief and understanding about concussions as well as factors affecting them.


#10 Fatigue Increases in Resting Muscle Oxygen Consumption After a Women's Soccer Match
Reference: Int J Sports Med. 2020 Jul 7. doi: 10.1055/a-1177-0849. Online ahead of print.
Authors: Aldo Alfonso Vasquez Bonilla, Rafael Timon, Alba Camacho-Cardeñosa, Marta Camacho-Cardeñosa, Samantha Guerrero, Guillermo Olcina
Summary: Currently, near infrared spectroscopy has a clear potential to explain the mechanisms of fatigue by assessing muscle oxygenation. The objective of the study was to observe the changes in muscle oxygen consumption after an official women's soccer match. The sample was 14 players who competing in the second division of Spain of women's soccer. They were evaluated before, immediately after and 24 h after the official match. Biochemical parameters were measured in blood plasma (BUN, GOT, LDH, CPK). The jumping in countermovement, perceived exertion and perceived muscle pain were also assessed. The muscle oxygen consumption and muscle oxygen saturation were evaluated in the gastrocnemius muscle with an arterial occlusion test. ANOVA of repeated measures, Pearson's correlation and Hopkins' statistics were applied to measure the magnitudes of change and effect size. There was observed an increase in kinetics of SmO2 at 24 h after the official match, using arterial occlusion. In addition, it was found that the increase in muscle oxygenation correlated with fatigue indicators, such as the increases in LDH, perceived muscle pain and the decrease in countermovement. It is confirmed that a women's soccer match produced an increase of resting muscle oxygenation in 24 h after the official match.

Thu

22

Oct

2020

Elite Players’ Perceptions of Football Playing Surfaces: A Qualitative Study

A comprehensive assessment of players' opinions to better understand the influence of playing surfaces (artificial and natural turf) on the game of football.

Wed

21

Oct

2020

In-season internal and external training load quantification of an elite European soccer team

The aim of the study was to provide seasonal internal and external training load includig the Hooper Index in elite soccer players during an in-season period.

Mon

19

Oct

2020

Latest research in football - week 30 - 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 Three Different Stretching Protocols on Hamstring Muscle Flexibility in Professional Soccer Players: A Randomized Study 

Reference: J Sports Med Phys Fitness. 2020 Jul;60(7):999-1004. doi: 10.23736/S0022-4707.20.10562-0. 

Authors: Vincenzo Manzi, Ferdinando Iellamo, Anas R Alashram, Rosario D'onofrio, Elvira Padua, Maurizio Casasco, Giuseppe Annino

Summary: The current study aimed to investigate and compare the influences of global postural rieducation techniques (GPR), stretching exercises on a whole-body vibration platform (WBV), and static stretching exercises on hamstrings flexibility in elite soccer players. 24 professional soccer players were randomly assigned to either global postural re-education (N.=8), stretching on whole-body vibration group (N.=8) or static stretching (N.=8), during the first 4 weeks of the precompetitive season. Assessment of hamstring muscle flexibility was performed using a straight leg raise test. All participants were assessed three times: at baseline, at the end of the study protocol and 14 days after the end of the study protocol. The short-term increase in hamstring muscle flexibility was observed in all 3 groups, without significant differences among groups. However, after 14 days from the end of the interventions only the WBV group maintained the flexibility level achieved just at the end of the protocol with no significant changes in both legs whereas a significant decrease in the SLRT in GPR and SS groups, in right and left legs (GPR, P=0.002; P=0.015; SS, P=0.0001; P=0.0001), was observed. These results would suggest that GPR, static stretching on whole-body vibration and static stretching techniques all improve hamstring muscle flexibility, but only stretching on WBV maintains the effect over time in professional soccer players. 

 

 

#2 Soccer Player With Unusual Right Shoulder and Arm Pain and Swelling 

Reference: J Prim Health Care. 2020 Jun;12(2):181-183. doi: 10.1071/HC19101. 

Authors: Alan Zakaria , Jasper Gill, Livia Maruoka Nishi, Jeff Nadwodny, George G A Pujalte

Summary: Paget-Schroetter syndrome, or effort thrombosis, refers to a deep venous thrombosis in an upper extremity. It is most commonly located in the axillary or subclavian veins and is associated with vigorous repetitive movements and anatomic abnormalities. This case study describes an 18-year-old Division 1 soccer player who presented with worsening axillary swelling and pain. He was found to have subclavian stenosis at the level of the thoracic inlet between the clavicle and first rib, with deep venous thrombosis in his right axillary, subclavian, proximal brachial, and basilic veins. It was diagnosed with ultrasound and confirmed with venography. He was treated initially with enoxaparin and warfarin before having mechanical thrombolysis, balloon venoplasty, infusion of tissue plasminogen activator, and a right first rib resection. CONCLUSION As Paget-Schroetter syndrome is rare, early recognition and management leads to fewer long-lasting sequelae and less morbidity. Left untreated, it can result in pulmonary embolism and residual upper extremity obstruction. 

 

 

#3 Variations of Estimated Maximal Aerobic Speed in Children Soccer Players and Its Associations With the Accumulated Training Load: Comparisons Between Non, Low and High Responders 

Reference: Physiol Behav. 2020 Jun 25;224:113030. doi: 10.1016/j.physbeh.2020.113030. Online ahead of print. 

Authors: Filipe Manuel Clemente, Ana Filipa Silva, Ana Ruivo Alves, Pantelis Theodoros Nikolaidis, Rodrigo Ramirez-Campillo, Ricardo Lima, Mustafa Sö?üt, Thomas Rosemann, Beat Knechtle

Summary: The aim of this study was twofold: (i) to examine the variations of estimated maximal aerobic speed between non, low and high responders and (ii) to analyze the relationships between accumulated training load parameters and variations of maximal aerobic speed in children soccer players. Forty-four male soccer players were assessed three times during the early and mid-season (second to fifth month of the season) and were monitored daily over the period of analysis using the rating of perceived exertion (RPE), recording the training duration (in min) and calculating the session-RPE (sRPE). Pairwise comparisons revealed that maximal aerobic speed (MAS) was greater for the third assessment than the first (p-value [p] = 0.003; standardized effect of Cohen [d] = 0.355) and second (p = 0.013; d = 0.193) assessments. Large correlations were found between MAS and accumulated RPE, accumulated time, and accumulated sRPE. Moreover, non, low and high responders differed in ?MAS (p<0.001) with the last group presenting the largest improvement in MAS. Results suggest that children with lower MAS baseline levels will improve more this capacity over the early and mid-season period compared to children with better baseline levels. Moreover, associations between accumulated training load and MAS were found, suggesting that the training effort can be related with aerobic capacity changes. 

 

 

#4 Association Between the ACE I/D Polymorphism and Muscle Injuries in Italian and Japanese Elite Football Players 

Reference: J Sports Sci. 2020 Jul 2;1-7. doi: 10.1080/02640414.2020.1787683. Online ahead of print. 

Authors: Myosotis Massidda, Eri Myamoto-Mikami, Hiroshi Kumagai, Hayato Ikeda, Yu Shimasaki, Masafumi Yoshimura, Paolo Cugia, Francesco Piras, Marco Scorcu, Naoki Kikuchi , Carla Maria Calò, Noriyuki Fuku 

Summary: ACE I/D polymorphism has been recently associated with the susceptibility to inflammation and muscle damage after exercise. The aim of this study was to understand the association between the ACE I/D polymorphism and muscle injuries in a large cohort of elite football players from two different countries. Seven hundred and ten male elite football players from Italy (n = 341) and Japan (n = 369) were recruited for the study. Genomic DNA was extracted from either the buccal epithelium or saliva using a standard protocol. Structural-mechanical injuries and functional muscle disorders were recorded from 2009 to 2018. A meta-analysis was performed using Review Manager 5.3.5. In the Japanese cohort, the ACE I/D polymorphism was significantly associated with muscle injury using the D-dominant model (OR: 0.48, 95% CI: 0.24-0.97, P = 0.040). The meta-analysis showed that in the pooled model (Italian and Japanese populations), the frequencies of the DD+ID genotypes were significantly lower in the injured groups than in non-injured groups (OR: 0.61, 95% CI: 0.38-0.98, P = 0.04) with a low degree of heterogeneity (I2 = 0%). Our findings suggest that the ACE I/D polymorphism could influence the susceptibility to developing muscle injuries among football players. 

 

 

#5 Effects of Daily Probiotics Supplementation on Anxiety Induced Physiological Parameters among competetive Football Players

Reference: Nutrients. 2020 Jun 29;12(7):E1920. doi: 10.3390/nu12071920.  

Authors: A M G C P Adikari, Mahenderan Appukutty, Garry Kuan

Download link: https://www.mdpi.com/2072-6643/12/7/1920

Summary: Competitive football players who undergo strenuous training and frequent competitions are more vulnerable to psychological disorders. Probiotics are capable of reducing these psychological disorders. The present study aimed to determine the effect of daily probiotics supplementation on anxiety induced physiological parameters among competitive football players. The randomized, double-blinded, placebo-controlled trial was conducted on 20 male footballers who received either probiotics (Lactobacillus Casei Shirota strain 3 × 1010 colony forming units (CFU) or a placebo drink over eight weeks. Portable biofeedback devices were used to measure the electroencephalography, heart rate, and electrodermal responses along with cognitive tests at the baseline, week 4, and week 8. Data were statistically analyzed using mixed factorial ANOVA and results revealed that there is no significant difference between the probiotic and placebo groups for heart rate (61.90 bpm ± 5.84 vs. 67.67 bpm ± 8.42, p = 0.09) and electrodermal responses (0.27 µS ± 0.19 vs. 0.41 µS ± 0.12, p = 0.07) after eight weeks. Similarly, brain waves showed no significant changes during the study period except for the theta wave and delta wave at week 4 (p < 0.05). The cognitive test reaction time (digit vigilance test) showed significant improvement in the probiotic group compared to the placebo (p < 0.05). In conclusion, these findings suggest that daily probiotics supplementation may have the potential to modulate the brain waves namely, theta (relaxation) and delta (attention) for better training, brain function, and psychological improvement to exercise. Further research is needed to elucidate the mechanism of current findings. 

 

 

#6 Injuries and Functional Performance Status in Young Elite Football Players: A Prospective 2-year Monitoring 

Reference: J Sports Med Phys Fitness. 2020 Jun 30. doi: 10.23736/S0022-4707.20.10886-7. Online ahead of print. 

Authors: Johanna Sieland, Frieder Krause, Kristin Kalo, Jan Wilke, Lutz Vogt, Winfried Banzer, Daniel Niederer

Summary: Motor function, such as strength asymmetries of the lower extremities and impaired dynamic stability, have a predictive value for the risk of injury. The present study aimed to reveal potential associations between injury and motor performance. Two hundred five (205) male youth elite (association) football (soccer) players (mean ± standard deviation: 13.5 ± 4.5 years, 57.2 ± 30.2 kg, 168 ± 35 cm) were included. A test battery was conducted twice per season, over two consecutive seasons (four times). Mobility (Sit and Reach Test, SnR), dynamic stability (Single Leg Hop for Distance, SLHD), linear sprinting speed (10 m, 30 m [s]), agility (Zig-Zag test with and without dribbling a ball [s]), jump performance (Counter Movement Jump (CMJ) and Drop Jump (DJ) [cm]) and Maximal Isometric Voluntary Force (MIVF [N]) of the knee extensors and flexors were assessed. All injuries occurring over the two-year period, as well as training and competition exposure time, were collected and used as grouping variables for statistical difference testing. One hundred twenty five (125) injuries in 93 players occurred (an injury incidence of 2.7/1000 hours of exposure). Age was associated with injury incidence (r=.191; p=.006). Neither DJ, CMJ, SnR nor agility performance were statistically different between injured and non-injured participants (p>.05). Group differences did occur for sprint and strength (p=.011; p=.016), but these lapsed after the inclusion of age as a covariate. Only for SLHD symmetry was a non-significant trend evident after the correction for age (p=.08). The occurrence of musculoskeletal injuries in junior football players are, probably, not related to baseline motor function. Group differences between injured and non-injured youth elite football players are mostly explained by age. Only the symmetry in SLHD could be a potential risk factor for injuries and merits further investigation. 

 

 

#7 Cross-Cultural Exploration of Baseline ImPACT Quick Test Performance Among Football Athletes in Zambia 

Reference: Phys Sportsmed. 2020 Jun 30. doi: 10.1080/00913847.2020.1790983. Online ahead of print. 

Authors: Jessica Wallace, Philip Schatz, Davie Mulenga, Mark Lovell, Gabriel Muyinda, Kachinga Agrippa Sichizya, Joseph Mulenga, Tracey Covassin

Summary: Concussion is a global sport injury; however, this public health issue has yet to be studied across Africa. It is unknown if tests such as the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) Quick Test (QT) are culturally appropriate for implementation as part of a concussion screening protocol in Zambia or other African nations. Study objectives included: 1) establish that Zambian athletes are able to complete the iPad-based ImPACT QT with respect to language or cultural barriers that may exist, and 2) document baseline neurocognitive percentile ranks among Zambian football athletes on the ImPACT QT. This study was completed with adult premiere league football athletes in Zambia (n=125) aged 24.48±5.41. Participants completed the ImPACT QT neurocognitive assessment prior to a preseason practice. Outcome measures were average performance on 3 factor scores: Motor Speed, Memory, and Attention Tracker, presented as percentile ranks using normative data built-into the ImPACT QT. Zambian athletes scored nearly two standard deviations below the mean on Motor Speed (7th percentile), using North American normative data. However, performance on Attention Tracker (44th percentile) and Memory (56th percentile) was within the average range. Results of the current study show that Zambian athletes are able to complete the ImPACT QT, despite any language or cultural differences that may exist. In addition, preliminary percentile ranks suggest Zambian football athletes have average scores on Attention and Memory and below average scores on Motor Speed. These data are the first to explore Zambian athletes' performance on a cognitive concussion measure. 

 

 

#8 Age-related and Training-Induced Changes in Morphological Characteristics of Young Elite Male Soccer Players 

Reference: J Sports Med Phys Fitness. 2020 Jun 30. doi: 10.23736/S0022-4707.20.11119-8. Online ahead of print. 

Authors: Nikolaos Androulakis, Nikolaos Koundourakis, Christos Tsiakiris, George Notas 

Summary: In soccer, morphological characteristics of young players are particularly important as they have a significant impact on the performance of many technical-tactical elements. Our aim in this study was to investigate whether soccer specific training on its own or combined with strength training can influence the morphological characteristics, of young soccer players and if so, to establish which age is more appropriate for interventions through individualized training. The study sample consisted of 61 young male soccer players, members of two under 17 (U171 and U172) and two under 19 (U191 andU192) teams. U171 (n= 17, consists of ages: 15.1±0.6) and U191 (n=14, consists of ages 17.3±0.5 years) teams performed only soccer specific training whilst U172 (n= 18, consists of ages 15.0±0.4 years) and U192 (n=12 consists of ages 17.1±0.7 years) teams had two extra strength trainings per week. Anthropometric measurements were performed at the beginning and at the end of the 10-months session. Lean body mass was increased whilst body fat decreased at the end of the study in all teams (p<0.001). No significant changes were found regarding endomorphic and ectomorphic outcome. Mesomorphic outcome was significantly increased only in U172 team (p<0.001). Our data supports that earlier interventions (between ages 15-17 years) in the training routine may be more effective in order to achieve anatomical and morphological characteristics most favorable for soccer. 

 

 

#9 Design and Validation of the Instrument for the Measurement of Learning and Performance in Football

Reference: Int J Environ Res Public Health. 2020 Jun 27;17(13):E4629. doi: 10.3390/ijerph17134629. 

Authors: Juan M García-Ceberino, Antonio Antúnez, Sergio J Ibáñez, Sebastián Feu

Download link: https://www.mdpi.com/1660-4601/17/13/4629/pdf

Summary: The assessment of tactical-technical knowledge of football is essential to develop optimal and integral teaching processes for students. Therefore, the aim of this study was to design and validate an instrument so that teachers, coaches, and researchers can observe and codify both the tactical behaviors and technical skills performed by the students in the game of football. The design and validation of the instrument were carried out in four phases: a) review of the literature and previous instruments; b) design of the Instrument for the Measurement of Learning and Performance in Football (IMLPFoot). It assesses all the offensive and defensive play actions, with and without the ball, as well as their three components (decision-making, technical execution, and final result); c) sample selection of experts (N = 12); and d) quantitative (Likert-type scale from 1 to 10) and qualitative assessment of degree the pertinence, unambiguity, and importance of each of the 33 items included in the IMLPFoot. Aiken's V coefficient was used to determine content validity. Likewise, internal consistency was calculated using Cronbach's ? coefficient. The results showed demanding levels of validity (V ? 0.77), internal consistency (? = 0.983), inter-rater, and intra-rater reliability. Therefore, it is a valid and reliable instrument that makes possible a complete assessment of football in physical education classes and/or in the sports context (out-of-school football). 

 

Fri

16

Oct

2020

External training loads and smartphone-derived heart rate variability indicate readiness to train in elite soccer

 

Player readiness can affect the ability to perform and tolerate prescribed training load. Consequently, practitioners need objective evidence to inform readiness to train.

Thu

15

Oct

2020

Monitoring Fatigue During the In-Season Competitive Phase in Elite Soccer Players

 

The purpose was to quantify the relationship between daily training load and a range of potential measures of fatigue.

Wed

14

Oct

2020

Latest research in football - week 29 - 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 A Case Study Comparison of Objective and Subjective Evaluation Methods of Physical Qualities in Youth Soccer Players
Reference: J Sports Sci. 2020 Jun 13;1-9. doi: 10.1080/02640414.2020.1766177. Online ahead of print.
Authors: James H Dugdale, Dajo Sanders, Tony Myers, A Mark Williams, Angus M Hunter
Summary: Subjective and objective assessments may be used congruently when making decisions regarding player recruitment in soccer, yet there have been few attempts to examine the level of agreement between these methods. Therefore, we compare levels of agreement between subjective and objective assessments of physical qualities associated with youth soccer performance. In total, 80 male youth soccer players (13.2 ± 1.9 years), and 12 professional coaches volunteered to participate. Players were objectively assessed using five fitness measures: Yo-Yo Intermittent Recovery Test Level 1; Countermovement vertical jump; Functional Movement Screen™; 5/20 m sprint; alongside anthropometric measures. Additionally, coaches subjectively rated each player on the same five physical qualities using 5-point Likert scales. Inter-rater agreement between ratings from lead and assistant coaches was established for each age group. Moreover, Bayesian regression models were fitted to determine how well coach ratings were able to predict fitness test performance. Although inter-rater agreement between lead and assistant coaches was moderate-to-substantial (ω = 0.48-0.68), relationships between coaches subjective rating's and corresponding fitness test performance were only highly related for the highest and lowest performing players. We suggest that while ratings derived from objective and subjective assessment methods may be related when attempting to differentiate between distinct populations, concerns exist when evaluating homogeneous samples using these methods. Our data highlight the benefits of using both types of measures in the talent identification process.


#2 Recommendations for Initial Examination, Differential Diagnosis and Management of Concussion and Other Head Injuries in High-Level Football
Reference: Scand J Med Sci Sports. 2020 Jun 17. doi: 10.1111/sms.13750. Online ahead of print.
Authors: Nina Feddermann-Demont, Georges Chiampas, Charlotte M Cowie, Tim Meyer, Anna Nordström, Margot Putukian, Dominik Straumann, Efraim Kramer
Summary: Head injuries can result in substantially different outcomes, ranging from no detectable effect to transient functional impairments to life-threatening structural lesions. In high-level international football (soccer) tournaments, on average, one head injury occurs in every third match. Making the diagnosis and determining the severity of a head injury immediately on-pitch or off-field is a major challenge for team physicians, especially because clinical signs of a brain injury can develop over several minutes, hours or even days after the injury. A standardised approach is useful to support team physicians in their decision whether the player should be allowed to continue to play or should be removed from play after head injury. A systematic, football-specific procedure for examination and management during the first 72 hours after head injuries and a graduated Return-to-Football programme for high-level players has been developed by an international group of experts based on current national and international guidelines for the management of acute head injuries. The procedure includes seven stages from the initial on-pitch examination to the graduated Return-to-Football programme. Details of the assessments and the consequences of different outcomes are described for each stage. Criteria for emergency management (red flags), removal from play (orange flags), and referral to specialists for further diagnosis and treatment (persistent orange flags) are provided. The guidelines for Return-to-Sport after concussion-type head injury are specified for football. Thus, the present paper presents a comprehensive procedure for team physicians after a head injury in high-level football.


#3 Position Statement of the Royal Spanish Football Federation for the Resumption of Football Activities After the COVID-19 Pandemic (June 2020)
Reference: Br J Sports Med 2020 Jun 16;bjsports-2020-102640. doi: 10.1136/bjsports-2020-102640. Online ahead of print.
Authors: Helena Herrero-Gonzalez, Rafael Martín-Acero, Juan Del Coso, Carlos Lalín-Novoa, Rafel Pol, Pilar Martín-Escudero, Ana Isabel De la Torre, Christopher Hughes, Magni Mohr, Francisco Biosca, Rafael Ramos
Download link: https://bjsm.bmj.com/content/bjsports/early/2020/06/15/bjsports-2020-102640.full.pdf


#4 The Effects of High-Intensity Interval Training (HIIT) in Improving VO2 Max
Reference: Enferm Clin. 2020 Jun;30 Suppl 4:507-511. doi: 10.1016/j.enfcli.2019.10.130.
Authors: Dilli Dwi Kuswoyo, Jori Lahinda, Syamsudin
Summary: This study aims to determine the effect of High-Intensity Interval Training (HIIT) in improving VO2 Max in Football Students Activity Unit, University of Musamus. This research is an experimental study with one group pretest and posttest design research. The population in this study was Football Students Activity Unit, the University of Musamus, which numbered 22 students who were the subjects of the study. Data retrieval technique is by tests and measurements. The instrument used is a multi-stage fitness test (bleep test). The students were given HIIT; it carried out twice a week for four weeks. Analysis of the data used is using t-test at 0.05% as the significance level. Based on the results, the number of pretests showed on 39.6773. While at the posttest after there was an improvement, the number showed on 48.5863. Based on the results of data analysis on the hypothesis in the study, it was found that there was a significant effect of HIIT in improving VO2 Max football student activity unit, University of Musamus, it was indicated by the score of t-count that higher than t-table (13.015>2.080). There was a significant effect of the HIIT in improving football students' VO2 of Max at University of Musamus.


#5 Prior Workload Has Moderate Effects on High-Intensity Match Performance in Elite-Level Professional Football Players When Controlling for Situational and Contextual Variables
Reference: J Sports Sci. 2020 Jun 16;1-12. doi: 10.1080/02640414.2020.1778355. Online ahead of print.
Authors: Matthew Springham, Sean Williams, Mark Waldron, Anthony J Strudwick, Chris Mclellan, Robert U Newton
Summary: This investigation examined the effect of prior workload on high-intensity football match performance. Player load variables were recorded using a global positioning system and converted into composite variables: rolling season accumulated load (AL), exponentially weighted moving average acute, chronic and acute:chronic workload ratio (A:C). Match-play high-intensity performance-per-minute: accelerations (ACC), sprints, high-speed running (HSR) and high metabolic load (HMLd) distances; and situational and contextual variables were recorded for all games. Partial least squares modelling, and backward stepwise selection determined the most parsimonious model for each performance variable. Quadratic relationships of small to moderate effect sizes were identified for sprint AL and sprint performance, HSR AL and HSR performance, acute HMLd and HMLd performance, acute sprint load and ACC performance and A:C sprint load and ACC performance. Match performance was typically greatest between the mean and +1SD. High chronic HMLd, and combined acceleration and deceleration (ACC+DEC) load exerted small beneficial effects on HMLd and HSR performance, whereas high acute load exerted trivial to moderate negative effects. High sprint A:C exerted a small beneficial effect on sprint performance and playing position exerted small effects on HSR and HMLd performance. Prior workload has trivial to moderate effects on high-intensity match performance in professional players.


#6 Adapted Recreational Football Small Sided Games Improves Cardiac Capacity, Body Composition and Muscular Fitness in Patients With Type 2 Diabetes: Results From a Pilot Study
Reference: J Sports Med Phys Fitness. 2020 Jun 12. doi: 10.23736/S0022-4707.20.10498-5. Online ahead of print.
Authors: Annamaria Mancini, Anna A Turco, Carlo G Tocchetti, Georgios Ermidis, Francesca Cozzolino, Giacomo Campi, Paolo Parrella, Valentina Mercurio, Ciro G Mainolfi, Teresa Mannarino, Adriana D'antonio, Maurizio Marra, Rita Polito, Luca Russomando, Domenico Martone, Stefania Orrù, Aurora Daniele, Brunella Capaldo, Francesco Salvatore, Pasqualina Buono
Summary: The usefulness of adapted small-side games (SSGs) in improving cardiac function in subjects with T2DM is still debated. Here we evaluated the effects of 18weeks Indoor Muscular Activation training (6 wks; IMA) followed by adapted SSGs football training (12wks) on cardiac function, muscular fitness, Body Composition and adiponectin expression in sedentary T2DM volunteers. 6 T2DM patients underwent IMA protocol of 6 wks, 2/wk followed by 12 wks SSGs (5vs5; once a wk) training. Glucose, lipid profile and serum homocysteine concentration, Body Composition (BC), bone mineral density (DEXA), were determined at baseline and after 18wks (IMA+SSGs). VO2max and muscular fitness were recorded at baseline and after IMA (6wks) and SSGs (12 wks), respectively. No significant differences were found for VO2max and muscular fitness after 6wks of IMA. After 18wks (6 wks IMA+ 12 wks SSGs) of training, significant improvements were found in the following parameters: work capacity, VO2peack, Ventilation (VEpeack), breathing reserve consumption and oxygen uptake efficiency (OUES) (p<0.05); leg fitness (p<0.05), BC (p<0.05), vertebral column T-score (p<0.01) and adiponectin (total and High Molecular Weight, HMW; p<0.05). Compared to baseline, a reduction in serum homocystein (Hcy) occurred after 18 wks of training (p<0.05). We evidenced that weekly adapted SSGs friendly football matches for 12 weeks improve cardiorespiratory capacity and the expression of independent markers associated with cardiovascular risk in T2DM patients, suggesting an overall reduced CVD-risk in these patients. These preliminary data encourage us to test the efficacy of this type of exercise in a larger population.


#7 Physical Fitness and Activity Changes After a 24-week Soccer-Based Adaptation of the U.S Diabetes Prevention Program Intervention in Hispanic Men
Reference: Prog Cardiovasc Dis. 2020 Jun 27;S0033-0620(20)30135-3. doi: 10.1016/j.pcad.2020.06.012. Online ahead of print.
Authors: Jennifer K Frediani, Alan F Bienvenida, Jianheng Li, Melinda K Higgins, Felipe Lobelo
Summary: One third of the U.S. adult population is estimated to have prediabetes. Hispanics have a 50% higher type 2 diabetes (T2DM) death rate compared to non-Hispanic whites, yet low participation in lifestyle change programs, making this subgroup an important target for prevention efforts. The purpose of this study was to determine the effects of an exercise intervention implementing the Center for Disease Control and Prevention National Diabetes Prevention Program (NDPP) plus recreational soccer (RS) in Hispanic men. Overweight and obese Hispanic men, aged 30-57 years with prediabetes at screening were recruited from the community. Trained soccer coaches led 30-min facilitated discussion of the NDPP modules after each RS session, with two weekly sessions delivered over 12 wks, then once a wk until 24 wks. The 1-h RS sessions followed the Football Fitness curriculum structure. Standardized study assessments included objectively measured physical activity via fitness tracker, physical fitness via validated field tests, global positional system soccer specific metrics and behavior change questionnaires. Mixed models assessed the outcomes as a function of time and cohort and incorporated an unstructured covariance structure to examine the difference between baseline, 12 and 24 wks. All analyses were conducted as intent-to-treat and generated using SAS v 9.4. Hispanic males (n = 41; mean age 41.9 [6.2 SD] years) were obese at baseline (mean BMI 32.7, standard error [0.7]). After 24 wks of the NDPP+RS intervention, there were significant beneficial changes in vertical jump (2.8 [1.3] cm; p = 0.048), agility and lower extremity muscular power (figure 8-run) at 12 wks (-4.7% change; p = 0.001) and 24 wks (-7.2% change; p < 0.0001), predicted VO2 max (12 wks: 1.9%; p = 0.007; 24 wks 1.0%; p = 0.036), modified push-ups increased 22% (p < 0.0001) at 12 wks and 31% (p < 0.0001) at 24 wks, dynamic sit-ups increased 10% (p = 0.005) at 12 wks and 15% (p < 0.0001) at 24 wks. Among middle-aged Latino men, broad-ranging significant improvements in physical fitness were observed after 24 wks participating in lifestyle education plus RS in a single arm feasibility trial.


#8 Analysis of Physical and Technical Performance of Substitute Players in Professional Soccer
Reference: Res Q Exerc Sport. 2020 Jun 30;1-8. doi: 10.1080/02701367.2020.1755414. Online ahead of print.
Authors: Miguel Lorenzo-Martínez, Alexis Padrón-Cabo, Ezequiel Rey, Daniel Memmert
Summary: Current soccer scientific literature is scarce with regard to examining the technical performance of substitute players. This study aimed to analyze the physical and technical performance of substitute players versus those who completed the entire match or were replaced and also examine the performance of substitutes across different playing positions. The sample was composed of 6,631 match observations from 431 professional soccer players competing in the German Bundesliga during the season 2018-2019. These observations were divided into three groups: entire match (n = 3,807), replaced (n = 1,412), and substitutes (n = 1,412). Linear mixed models were adjusted to compare the performance of the three groups independently of playing position and separately for each position (central defenders, fullbacks, central midfielders, wide midfielders, and attackers). Substitute players showed higher total distance covered (effect sizes [ES]: 0.99-1.06), number of sprints (ES: 0.60-0.64), and number of fast runs (ES: 0.83-0.91) relative to playing time than replaced and entire match players. The differences in technical performance between groups varied according to playing position. Substitute central defenders showed less possession (ES: 0.39-0.41), touches (ES: 0.47-0.57), and passes (ES: 0.54-0.59) but higher defensive performance (ES: 0.51-0.54) than replaced and entire match players. Substitutes in midfield and attack positions displayed more possession (ES: 0.22-0.47), touches (ES: 0.27-0.37), and shots (ES: 0.22-0.28) than replaced and entire match players. This study has shown that substitutes are able to improve the performance of the players who completed the entire match or were replaced in both physical and some technical variables depending on playing position.


#9 Changes in Perceptions of Mental Fatigue During a Season in Professional under-23 English Premier League Soccer Players
Reference: Res Sports Med. 2020 Jun 30;1-11. doi: 10.1080/15438627.2020.1784176. Online ahead of print.
Authors: William Abbott, Thomas E Brownlee, Robert J Naughton, Tom Clifford, Richard Page, Liam D Harper
Summary: The present study assessed changes in academy soccer players' perception of mental fatigue (MF) across a competitive season, investigating the relationship between MF and other subjective measures of wellness. Ten players completed a modified Brief Assessment of Mood (BAM+) questionnaire that included the question: "How mentally fatigued do you feel"? on match-day (MD) and one (MD+1), two (MD+2) and three (MD+3) days post-match (35 matches). Players reported their MF, along with other subjective measures (sleep, muscle soreness, fatigue and motivation). Results found MF was elevated on MD+1 (43±1 mm) compared to all other days (all P≤0.001). Players reported lower MF on MD+1 in the late-season phase (34±2 mm) compared to both early- (50±2 mm, P≤0.001) and mid-season (46±2 mm, P≤0.001). This coincided with an 80%-win rate in the late-season phase versus the early- (33%) and mid-season (50%). There were very strong repeated-measures correlations between changes in MF and sleep (r=-0.77), muscle soreness (r=0.94), fatigue (r=0.92) and motivation (r=-0.89; all P ≤ 0.0005). In conclusion, MF was closely aligned to match success and other wellness variables. This data suggests a potential lack of sensitivity for identifying MF using a subjective questionnaire. Therefore, researchers and practitioners could work together to identify other ways of practically assessing MF.


#10 Evolution of Soccer as a Research Topic
Reference: Prog Cardiovasc Dis . 2020 Jun 26;S0033-0620(20)30134-1. doi: 10.1016/j.pcad.2020.06.011. Online ahead of print.
Authors: Donald T Kirkendall, James R Urbaniak
Summary: Soccer has not only the largest number of worldwide participants, it is also the most studied sport, with nearly 14,000 citations listed on Pubmed and nearly 60% more articles than the next most studied sport. Research about soccer was limited until the late 1970s when exponential growth began; approximately 98% of all soccer-related research publications have occurred since 1980. This vast repository of soccer research shows trends in various major (e.g., 'sex' or 'age group' or 'performance' or 'injury') and specialty (e.g., agility, deceleration, elbow-head impact injuries, behavior) topics. Examining trends of the various topics provides insights into which subjects have come in and out of favor as well as what topics or demographics have been neglected and worthy of inquiry. A further examination can be used by students to learn the most productive researchers, which programs have a strong history of inquiry, and what journals have demonstrated a commitment to publishing research on soccer.

Tue

13

Oct

2020

Effects of mental fatigue on passing decision making performance in professional soccer athletes

The aim of this study was to analyse the effect of mental fatigue on passing decision-making in professional soccer athletes.

Mon

12

Oct

2020

Effects of Warm‑Up, Post‑Warm‑Up, and Re‑Warm‑Up Strategies on Explosive Efforts in Football

The results of a systematic review.

Sat

10

Oct

2020

Latest research in football - week 28 - 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 Financial Awards and Their Effect on Football Players' Anxiety and Coping Skills
Reference: Front Psychol. 2020 Jun 10;11:1148. doi: 10.3389/fpsyg.2020.01148. eCollection 2020.
Authors: Adriana Kaplánová
Summary: Financial awards can be an important factor affecting athletes' mental preparation and various skills to manage stress. Since such a link has not yet been studied, the study has been designed to evaluate the moderation effect of financial awards in relation to football players' anxiety and coping skills. The study consists of 110 male football players aged 18-32 years old (mean ± SD: 23.98 ± 3.01 years) who were divided into two groups: financial awarded (n = 48) and financial unawarded for sports performance (n = 62). The anxiety of football players was measured by the Sport Anxiety Scale SAS-2. Coping strategies to manage stress were assessed by the Athletic Coping Skills Inventory ACSI-28. The effect of financial awards in relation to football players' anxiety and coping skills was evaluated by the mediators' model using the PROCESS software (Hayes, 2018). The results suggest that financial awards are important factors that influence football players' anxiety and coping skills. The financial awards increase the motivation of football players to better prepare for sports performance, which has been proven, through better setting of performance goals and more careful mental preparation. Financially awarded football players seem to respect the coach and follow his instructions to a greater extent than unawarded football players, which may be due to the financial benefits and the commitment they have confirmed by signing to the football club. In another aspect, the financial awards are likely to increase the cognitive trait of the anxiety of football players. It seems that financial players are more concerned about the failure of the match, which increases their anxiety, especially since it is a cognitive part and affects their sports performance. For this reason, we encourage sports organizations to focus more on the mental preparation of football players. It is important to provide football players the opportunity to graduate from short- or long-term mental training conducted by a trained sports psychologist not only at the time of the athlete's failure but also as a preventive measure against increasing cognitive anxiety. We recommend sports organizations to train coaches in the field of mental training, preferably through annual short training sessions with a sports psychologist, to influence the development of desirable athletes' coping skills.


#2 Effect of Weekly Training Frequency With the Nordic Hamstring Exercise on Muscle-Strain Risk Factors in Football Players: A Randomized Trial
Reference: Int J Sports Physiol Perform. 2020 Jun 24;1-8. doi: 10.1123/ijspp.2018-0780. Online ahead of print.
Authors: Thales M Medeiros, João B Ribeiro-Alvares, Carolina G Fritsch, Gabriel S Oliveira, Lucas Severo-Silveira, Evangelos Pappas, Bruno M Baroni
Summary: The purpose was to examine the differences between performing Nordic hamstring exercises once or twice a week on hamstring eccentric strength and other muscle-strain risk factors in high-level football players. In this randomized trial, 32 football players (18-23 y old) completed an 8-week Nordic hamstring exercise training program in 1 of 2 experimental groups: group 1 (once a week; n = 15) and group 2 (twice a week; n = 17). Knee-flexor/extensor peak torques and biceps femoris long-head muscle architecture were assessed through isokinetic dynamometry and ultrasonography, respectively, before and after the training programs. Analysis of covariance, effect sizes (ESs), and t tests for percentage change were used to assess the effect of the 2 interventions on the outcome measures. Group 2 demonstrated higher hamstring concentric peak torque than group 1 posttraining (155-164 vs 149-158 N·m; P = .043; ES = 0.27), although there was also a statistical trend for higher hamstring eccentric peak torque (212-234 vs 198-221 N·m; P = .098; ES = 0.37), hamstring-to-quadriceps conventional ratio (0.56-0.59 vs 0.54-0.57; P = .089; ES = 0.31), and hamstring-to-quadriceps functional ratio (0.76-0.84 vs 0.71-0.79; P = .076; ES = 0.50). No between-groups differences were found for muscle thickness (P = .864; ES = 0.12), pennation angle (P = .289; ES = 0.18), fascicle length (P = .406; ES = 0.03), and quadriceps concentric peak torque (P = .340; ES = 0.02). Only the Nordic hamstring exercise training program performed twice a week strengthened the hamstrings of high-level football players, while similar changes in muscle architecture occurred with both once- and twice-weekly sessions.


#3 Football Can Tackle Type 2 Diabetes: A Systematic Review of the Health Effects of Recreational Football Practice in Individuals With Prediabetes and Type 2 Diabetes
Reference: Res Sports Med. 2020 Jun 22;1-19. doi: 10.1080/15438627.2020.1777417. Online ahead of print.
Authors: Ana Barbosa, João Brito , Pedro Figueiredo, André Seabra, Romeu Mendes
Summary: This work aimed to summarize the health effects of recreational football practice in individuals with prediabetes and type 2 diabetes (T2D), through a systematic review. An electronic search was performed in PubMed, Scopus, Web of Science, LILACS and list of references of the available reviews, until July 2019. Studies were eligible if they included any form of football practice, in patients diagnosed with prediabetes or T2D. After recreational football practice, participants with prediabetes or T2D improved fasting glucose, total and LDL cholesterol, triglycerides, body mass, body fat percentage, waist circumference, blood pressure, and maximal oxygen uptake. Further benefits were found in fat-free mass and resting heart rate for participants with prediabetes, and in glycated haemoglobin, body mass index and fat mass in individuals with T2D. This systematic review showed promising benefits of recreational football practice on both the prevention and control of T2D and related cardiovascular risk.


#4 Ankle Osteoarthritis and Its Association With Severe Ankle Injuries, Ankle Surgeries and Health-Related Quality of Life in Recently Retired Professional Male Football and Rugby Players: A Cross-Sectional Observational Study
Reference: BMJ Open. 2020 Jun 21;10(6):e036775. doi: 10.1136/bmjopen-2020-036775.
Authors: Liam D A Paget, Haruhito Aoki, Simon Kemp, Mike Lambert, Clint Readhead, Keith A Stokes, Wayne Viljoen, Gustaaf Reurink, Johannes L Tol, Gino M M J Kerkhoffs, Vincent Gouttebarge
Download link: https://bmjopen.bmj.com/content/bmjopen/10/6/e036775.full.pdf
Summary: The objective was to determine (1) the prevalence of ankle osteoarthritis (OA) among former professional football and rugby players, (2) assess the association between ankle injuries or ankle surgeries with ankle OA, and (3) compare the mental and physical quality of life (QoL) between former professional football and rugby players with and without OA. We conducted a questionnaire-based observational study with a cross-sectional design. Former professional football and rugby players were recruited by the Football Players Worldwide and the International Rugby Players. Information concerning ankle OA, sustained ankle injuries and ankle surgeries was gathered (medical record or most recent medical professional). Health-related QoL was assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) physical and mental health scores. Overall, 553 former professional football (n=401) and rugby (n=152) players were enrolled in the study (response rate of 56%). Ankle OA prevalence among former professional football and rugby players was 9.2% and 4.6%, respectively. Football players were more likely to suffer from ankle OA following every ankle injury and/or surgery. Football and rugby players with ankle OA had similar PROMIS physical and mental health scores to the norm for the general population. Former professional football and rugby players had higher ankle OA prevalence than the general population (3.4%). Football players are more likely to suffer from ankle OA following every ankle injury and/or surgery. No clinically relevant difference was seen for physical or mental health-related QoL among football and rugby players. Preventive measures for ankle injuries are recommended.


#5 Medial Epicondyle Avulsion After Elbow Dislocation in an Adolescent Non-Professional Soccer Player Treated With a Cannulated Screw: A Case Report
Reference: Acta Biomed. 2020 May 30;91(4-S):271-275. doi: 10.23750/abm.v91i4-S.9578.
Authors: Alessio Pedrazzini, Alberto Visigalli, Piergiulio Valenti, Nicola Bertoni, Henry Yewo Simo, Roberto Bisaschi, Vanni Medina, Bianca Pedrabissi, Francesco Ceccarelli, Francesco Pogliacomi
Summary: Medial epicondyle fractures of the humerus account for 11-20% of all elbow injuries in children and in 30-55% of cases they are associated with an elbow dislocation. Undisplaced fractures are usually treated conservatively but literature is controversial regarding the treatment of displaced fractures (≥5mm) in paediatric fractures. In recent years, there is an emerging consensus that such patients may benefit more from open reduction and internal fixation. Authors report a case of a 15 years old nonprofessional soccer player who suffered of an elbow dislocation with an intra-articular fragment derived from avulsion of the medial epicondyle. Clinical and instrumental evaluation confirmed elbow dislocation with an intra-articular fragment derived of the medial epicondyle. After the reduction an open reduction and internal fixation with cannulated screw was performed. Clinical evaluation after 90 days showed resolution of pain and almost complete ROM and complete recovery of strength and of functionality of the operated limb. Furthermore, x-rays demonstrated consolidation of the fracture. this case confirms that a precise evaluation of the fracture and its displacement is at the base of satisfactory outcomes. If fracture is displaced≥5mm and patient is near skeletal maturity open reduction and fixation is indicated.


#6 Long-term Test-Retest Evaluation of the King-Devick Test in Youth Soccer Athletes
Reference: J Neurol Sci. 2020 Jun 6;416:116951. doi: 10.1016/j.jns.2020.116951. Online ahead of print.
Authors: Abigail C Bretzin, Morgan Anderson, Ryan N Moran, Tracey Covassin
Summary: Despite the clinical utility of baseline comparisons during concussion assessments, little evidence exists on long-term test-retest reliability of baseline tests in youth athletes. In addition, sex differences in baseline performance are inconsistent in youth athletes, warranting further research. The purpose was to examine sex differences, prevalence of false-positive scores, and long-term test-retest reliability of the King-Devick (KD) test. Healthy youth athletes (23 males, 28 females) completed the KD test prior to the Spring 2016 and Fall 2017 seasons. Two-way random-effects intraclass correlation coefficients (ICCs) were utilized to determine test-retest reliability. A mixed between-within ANOVA with post-hoc t-tests were used to identify the interaction between sex and season, and frequencies were used to determine abnormal test score prevalence. The KD test demonstrated good test-retest reliability (0.77[95% CI, 0.43-0.89]), with 11.8% of youth athletes having clinically meaningful improvements between Season 1 to Season 2. There was a significant sex*season interaction (F(1,49) = 4.67, p = .04), with significantly greater improvements between seasons in male youth athletes compared to female youth athletes. However, 33-35% of youth athletes displayed abnormal test scores in Season 2 relative to Season 1. The KD test demonstrated good reliability and only a small percentage had clinically meaningful changes, however a high prevalence of false-positive scores were observed in this sample.


#7 Match Demands of Women's Collegiate Soccer
Reference: Sports (Basel). 2020 Jun 12;8(6):E87. doi: 10.3390/sports8060087.
Authors: Andrew R Jagim, Jason Murphy, Alexis Q Schaefer, Andrew T Askow, Joel A Luedke, Jacob L Erickson, Margaret T Jones
Download link: https://www.mdpi.com/2075-4663/8/6/87/pdf
Summary: Research describing the match and specific positional demands during match play in women's collegiate soccer is limited. The purpose of the study was to quantify the match demands of National Collegiate Athletic Association (NCAA) Division III soccer and assess position differences in movement kinematics, heart rate (HR), and energy expenditure. Twenty-five Division III women soccer players (height: 1.61 ± 0.3 m; body mass: 66.7 ± 7.5 kg; fat-free mass: 50.3 ± 6.5 kg; body fat%: 25.6 ± 5.1%) were equipped with a wearable global positioning system to assess the demands of 22 matches throughout a season. Players were categorized by position (goal keepers (GK), center defenders (CB), flank players (FP), forwards (F), and center midfielders (CM)). Players covered 9807 ± 2588 m and 1019 ± 552 m at high speeds (>249.6 m·m-1), with an overall average speed of 62.85 ± 14.7 m·m-1. This resulted in a mean HR of 74.2 ± 6% HR max and energy expenditure of 1259 ± 309 kcal. Significant and meaningful differences in movement kinematics were observed across position groups. CM covered the most distance resulting in the highest training load. FP covered the most distance at high speeds and mean HR values were highest in CM, CB, and FP positions.


#8 Predicting the Timing of the Peak of the Pubertal Growth Spurt in Elite Youth Soccer Players: Evaluation of Methods
Reference: Ann Hum Biol. 2020 Jun 16;1-23. doi: 10.1080/03014460.2020.1782989. Online ahead of print.
Authors: James Parr, Keith Winwood, Emma Hodson-Tole, Frederik J A Deconinck, Les Parry, James P Hill , Robert M Malina, Sean P Cumming
Summary: Three commonly used non-invasive protocols are implemented to estimate the timing at which PHV most likely occurs. Accurate estimation of circumpubertal years can aid in managing training load of adolescent athletes. Three protocols were compared against observed age at PHV: an estimate of 13.8 ± 1.0 years - generic age at PHV (from longitudinal measures); an estimate based on the maturity offset equation, predicted age at PHV ±1.0 year; a window of PHV based on 85 - 96% of predicted adult height at time of observation. A final sample of 23 (from 28) adolescent participants who were selected from the academy of an English Premier League club. Anthropometric measures were collected across five playing seasons; age at PHV was estimated with Super-Imposition by Translation and Rotation (SITAR). The three protocols were compared based on measures at 13.0 years. An age window based on predicted maturity offset did not improve estimation of PHV compared to generic age method; however, the percentage of predicted adult height window showed improvement in performance shown by the following results. Predicted age at PHV correctly assigned 15 participants (65%) as experiencing PHV, while the percentage height correctly assigned 17 participants (74%). Generic age and predicted age at PHV correctly predicted observed age at PHV for 14 participants (61%), percentage of adult height window correctly predicted 22 participants (96%).


#9 Psychosocial Outcomes Associated With Soccer Academy Involvement: Longitudinal Comparisons Against Aged Matched School Pupils
Reference: J Sports Sci. 2020 Jun 16;1-12. doi: 10.1080/02640414.2020.1778354. Online ahead of print.
Authors: Fieke Rongen, Jim McKenna, Stephen Cobley, Jason Cameron Tee, Kevin Till
Summary: Despite literature highlighting numerous risks to the healthy psychosocial development of youth elite academy soccer players, little of this research is based on high-quality research designs. This study employed a prospective longitudinal cohort design to track psychosocial outcomes of academy involvement within male youth elite soccer players (n = 33, U12-U16 age groups) compared to age-matched soccer-active school pupils (n = 44) over 12 months. Participants completed questionnaires assessing the most commonly raised psychosocial concerns at four equally spaced data collection periods (T1-T4). Repeated measures multivariate analysis of variance (MANOVAs) indicated that, over the year, both groups reported a healthy and improving stress and recovery balance, as well as positive and stable needs satisfaction and physical, psychological and social well-being. Academy players reported stable positive school-related quality of life, whereas school pupils reported increases from T3 to T4. Academy players reported consistent significantly higher total athletic identity and exclusivity of identity. Findings suggest that many concerns around negative psychosocial impacts of soccer academy involvement did not materialise in this context. However, heightened athletic identities remained a concern


#10 A Comparison of Bilateral vs. Unilateral-Biased Strength and Power Training Interventions on Measures of Physical Performance in Elite Youth Soccer Players
Reference: J Strength Cond Res. 2020 Jun 10. doi: 10.1519/JSC.0000000000003659. Online ahead of print.
Authors: Darren Stern, Oliver Gonzalo-Skok, Irineu Loturco, Anthony Turner, Chris Bishop
Summary: The aim of the present study was to compare the effects of bilateral and unilateral-biased strength and power training programs on measures of physical performance in male youth soccer players. Twenty-three elite youth players (age: 17.6 ± 1.2 years) were randomly assigned to either a unilateral (n = 11) or a bilateral (n = 12) group, who completed a strength and power intervention, twice per week for 6 weeks. The unilateral group completed rear foot elevated split squats (RFESS), single-leg countermovement jumps (SLCMJs), single-leg drop jumps (SLDJs), and single-leg broad jumps (SLBJs). The bilateral group intervention performed back squats, CMJs, drop jumps (DJ), and broad jumps (BJ). A 2 × 2 repeated measures analysis of variance showed no between-group differences. However, within-group differences were evident. The bilateral training group showed significant (p < 0.05) improvements in back squat strength (d = 1.27; %Δ = 26.01), RFESS strength (d = 1.64; %Δ = 23.34), BJ (d = 0.76; %Δ = 5.12), 10-m (d = -1.17; %Δ = 4.29), and 30-m (d = -0.88; %Δ = 2.10) performance. The unilateral group showed significant (p < 0.05) improvements in RFESS strength (d = 1.40; %Δ = 33.29), SLCMJ on the left leg (d = 0.76; %Δ = 9.84), SLBJ on the left leg (d = 0.97; %Δ = 6.50), 10 m (d = -1.50; %Δ = 5.20), and 505 on the right leg (d = -0.78; %Δ = 2.80). Standardized mean differences showed that bilateral training favored improvements in back squat strength and unilateral training favored improvements in RFESS strength, SLDJ on the right leg and 505 on the right leg. These results show that although both training interventions demonstrated trivial-to-large improvements in physical performance, the notion of training specificity was evident with unilateral training showing greater improvements in unilateral test measures.

Sat

10

Oct

2020

A match-day analysis of the movement profiles of substitutes from a professional soccer club before and after pitch-entry

The study profiled the match-day physical activities performed by substitutes focusing on the pre- and post-pitch-entry periods.

Thu

08

Oct

2020

Hamstring injury prevention in soccer: Before or after training?

The effects of a Nordic hamstring exercise before vs. after football training was examined.

Tue

06

Oct

2020

Latest research in football - week 27 - 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 Female Soccer Players' Psychological Profile: Differences Between Professional and Amateur Players
Reference: Int J Environ Res Public Health 2020 Jun 18;17(12):E4357. doi: 10.3390/ijerph17124357.
Authors: Cecilia Ruiz-Esteban , Aurelio Olmedilla, Inmaculada Méndez, Juan Jesús Tobal
Download link: https://www.mdpi.com/1660-4601/17/12/4357/pdf
Summary: The psychological variables that affect competitive performance are called the psychological profile of athletes. In recent years, the interest in female soccer players and the psychological characteristics that affect their performance has increased. The aim of the present study is to analyze the psychological characteristics of female professional soccer players and female amateur soccer players, as well as to determine the differences in the psychological profile of both groups. The participants were 134 federated female soccer players, with an average age of 18.28 years (SD = 4.05). To assess the psychological profile, the questionnaire on Psychological Characteristics related to Sports Performance (CPRD) by Gimeno, Buceta, and Pérez-Llantada (2001) was used. The results showed that female professional players presented higher values for motivation, while the female amateur players presented higher values for stress control and the influence of performance evaluation. These results can have a great impact on coaches' work, since they can help them to establish tasks and training methods consistent with the characteristics of their players.


#2 Directions of Single-Leg Landing Affect Multi-Segment Foot Kinematics and Dynamic Postural Stability in Male Collegiate Soccer Athletes
Reference: Gait Posture. 2020 Jun 13;80:285-291. doi: 10.1016/j.gaitpost.2020.06.007. Online ahead of print.
Authors: Shun Kunugi, Takashi Koumura, Ryota Myotsuzono, Akihiko Masunari, Naruto Yoshida, Shumpei Miyakawa, Naoki Mukai
Summary: Understanding lower limb kinematics and postural control in different directions of single-leg landings is critical to evaluate postural control and prevent lower limb injuries. However, foot and ankle kinematics and postural control during single-leg landings in different directions are less known. Therefore we questioned wheter the difference in the direction of single-leg landing affect the foot kinematics on the frontal plane and dynamic postural stability? A cross-sectional study was conducted. Forty-nine male collegiate soccer players performed single-leg forward (FL), 45° lateral (LL), and medial (ML) direction landings. The lower limb, foot (rearfoot, midfoot, forefoot), and ankle kinematics during an impact phase were evaluated, and a curve analysis was performed using a statistical parametric mapping method to compare the three landings. The three landings were compared in terms of postural control parameters, including time to stabilization (TTS), peak of ground reaction forces (GRFs), root-mean-square of the mediolateral GRFs for 0-0.4 s (GRFML0.4), loading rate, and magnitude of horizontal GRFs from 0-0.4 s (HGRF-0.4), 0.4-2.4 s (HGRF-2.4), and 3.0-5.0 s. Ankle and rearfoot kinematics in LL exhibited smaller eversion and pronation positions than FL and ML (p < 0.01). The TTS-mediolateral (TTS-ML) was longer in the LL than in FL and ML (p < 0.001). The GRFML0.4, HGRF-0.4, and -2.4 in the LL and ML were greater than those in the FL (p < 0.001). Directions of single-leg landing affect foot and ankle kinematics and postural stability. Specifically, the LL exhibits more inverted ankle and supinated rearfoot positions, and longer TTS-ML. Thus, the LL may induce stretching of the lateral ankle ligament. These findings can help understand foot kinematics and assess dynamic postural control.


#3 The Genetic Profile of Elite Youth Soccer Players and Its Association With Power and Speed Depends on Maturity Status

Reference: PLoS One. 2020 Jun 22;15(6):e0234458. doi: 10.1371/journal.pone.0234458. eCollection 2020.
Authors: Conall F Murtagh, Thomas E Brownlee, Edgardo Rienzi, Sebastian Roquero, Sacha Moreno, Gustavo Huertas, Giovani Lugioratto, Philipp Baumert, Daniel C Turner, Dongsun Lee, Peter Dickinson, K Amber Lyon, Bahare Sheikhsaraf, Betül Biyik, Andrew O'Boyle, Ryland Morgans, Andrew Massey, Barry Drust, Robert M Erskine
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307776/pdf/pone.0234458.pdf
Summary: We investigated the association of multiple single nucleotide polymorphisms (SNPs) with athlete status and power/speed performance in elite male youth soccer players (ESP) and control participants (CON) at different stages of maturity. ESP (n = 535; aged 8-23 years) and CON (n = 151; aged 9-26 years) were genotyped for 10 SNPs and grouped according to years from predicted peak-height-velocity (PHV), i.e. pre- or post-PHV, to determine maturity status. Participants performed bilateral vertical countermovement jumps, bilateral horizontal-forward countermovement jumps, 20m sprints and modified 505-agility tests. Compared to CON, pre-PHV ESP demonstrated a higher ACTN3 (rs1815739) XX ('endurance') genotype frequency distribution, while post-PHV ESP revealed a higher frequency distribution of the PPARA (rs4253778) C-allele, AGT (rs699) GG genotype and NOS3 (rs2070744) T-allele ('power' genotypes/alleles). BDNF (rs6265) CC, COL5A1 (rs12722) CC and NOS3 TT homozygotes sprinted quicker than A-allele carriers, CT heterozygotes and CC homozygotes, respectively. COL2A1 (rs2070739) CC and AMPD1 (rs17602729) GG homozygotes sprinted faster than their respective minor allele carrier counterparts in CON and pre-PHV ESP, respectively. BDNF CC homozygotes jumped further than T-allele carriers, while ESP COL5A1 CC homozygotes jumped higher than TT homozygotes. To conclude, we have shown for the first time that pre- and post-PHV ESP have distinct genetic profiles, with pre-PHV ESP more suited for endurance, and post-PHV ESP for power and speed (the latter phenotypes being crucial attributes for post-PHV ESP). We have also demonstrated that power, acceleration and sprint performance were associated with five SNPs, both individually and in combination, possibly by influencing muscle size and neuromuscular activation.


#4 Talent Identification and Development in Soccer Since the Millennium
Reference: J Sports Sci. 2020 Jun 22;1-12. doi: 10.1080/02640414.2020.1766647. Online ahead of print.
Authors: A Mark Williams, Paul R Ford, Barry Drust
Summary: At the turn of the millennium, a review paper was published in this journal on talent identification and development in soccer (Williams & Reilly, 2000). In the current paper, we assess progress made in this field over the last twenty years relative to the areas for future research highlighted in the original review. We evaluate developments in light of the calls made by Williams and Reilly to: a) undertake more multidisciplinary rather than mono-disciplinary research; b) embrace longitudinal rather than cross-sectional research designs; c) expand the research base on female football; and, d) better identify the subjective criteria used by scouts when selecting one player over another for entry into a formalised training environment. The body of mono-disciplinary research on this topic continues to expand, and progress has been made in publishing multidisciplinary, prospective, longitudinal data sets, along with advanced statistical modelling procedures, as well as in identifying the experiential criteria used by scouts. We found some variables in these studies have predictive value from adolescence to adult performance level in soccer. We present suggestions for future research to enhance knowledge and understanding of the best practices underpinning the identification and development of future generations of professional players.


#5 Brief Cycles of Lower Limb Occlusion Accelerates Recovery Kinetics In Soccer Players
Reference: Phys Sportsmed. 2020 Jun 22. doi: 10.1080/00913847.2020.1785260. Online ahead of print.
Authors: Wael Daab, Mohamed Amine Bouzid, Mehdi Lajri, Mustapha Bouchiba, Haithem Rebai
Summary: The aim of this study was to assess the effect of intermittent vascular occlusion (IVO) on recovery following simulated soccer physical demand test in soccer players. Twelve soccer players completed the Loughborough Intermittent Shuttle Test (LIST) in two conditions placebo (PLA) and IVO followed by intermittent lower limb occlusion. Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 meters sprint: SP), muscle damage parameters (creatine kinase: CK, Lactate dehydrogenase: LDH), inflammatory parameter (C-reactive protein: CRP) and perceived muscle soreness (DOMS) were assessed before, immediately after (0h), and 24h, 48h and 72h following the exercise. Following the LIST, a decrease was observed in all Physical performance within 48h in PLA condition (p<0.05),compared to PLA treatment, IVO treatment attenuated the decrease of SJ and CMJ at 24h and at 48hand for MVC and SP within 48h after the LIST (p<0.05). CK and LDH levels increased within 24h post exercise in both conditions (p<0.05), but with a lower level in IVO compared to PLA condition (p<0.05). Likewise, DOMS values were significantly lower with IVO condition compared to PLA condition immediately and at 24hafter exercise. The results of the present study suggest that the application of IVO after simulated soccer physical demand test accelerated recovery kinetics in soccer players.


#6 Femur, Tibia, and Fibula Fractures Secondary to Youth Soccer: A Descriptive Study and Review of the Literature
Reference: Cureus. 2020 May 18;12(5):e8185. doi: 10.7759/cureus.8185.
Authors: Peter Zaki, Sayyar Khakimov, Joseph Hess, William Hennrikus 
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301417/pdf/cureus-0012-00000008185.pdf
Summary: Objectives Soccer is the most popular sport in the world and is one of the top sports with increased participation. Despite the vast and increasing numbers of soccer players, limited data are available on pediatric lower extremity injuries. In particular, the purpose of the study is to describe the epidemiology of femur, tibia, and fibula fractures secondary to youth soccer. Methods A retrospective review concerning soccer-related femur, tibia, and fibula fractures was conducted in children under the age of 18 years from January 1, 2000 to December 31, 2015 with statewide data from the Pennsylvania Trauma Systems Foundation (PTSF), Mechanicsburg, PA. Results A total of 258 youth soccer players were admitted for femur, tibia, and fibula fractures from 2000 to 2015. These fractures constituted 33% of soccer-related injuries in youth admitted at trauma centers. Sixty-five percent of the fractures involved the tibia and 34% involved the femur. Body contact injury resulted in 54% of the fractures and non-body contact injury resulted in 46% of the fractures. Athletes the age of 13 and older sustained 67% of the fractures and were more likely to incur contact injuries (p-value=0.000041) than those less than 13. Males sustained 67% of the fractures, and gender was not associated with the mechanism of injury (p-value=0.43). Open fractures included 10% of tibia fractures and did not occur in femur fractures. The growth plate was involved in 24% of the femur fractures and 17% of the tibia fractures. Conclusion Youth soccer has the potential for serious femur, tibia, and fibula fractures. Intervention programs should aim at reducing non-body contact mechanism in children < 13 years of age and body contact mechanism in children ≥ 13 years of age. Further research should investigate injury prevention methods such as potentially reducing body contact mechanism by improving the effectiveness of shin guards.


#7 Tuck jump score is not related to hopping performance or patient-reported outcome measures in female soccer players
Reference: Int J Sports Phys Ther. 2020 May;15(3):395-406.
Authors: Amelia J H Arundale, Joanna Kvist, Martin Hägglund, Anne Fältström
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297000/pdf/ijspt-15-395.pdf
Summary: The tuck jump assessment was developed to identify players at risk for anterior cruciate ligament (ACL) injuries or gauge a player's progress through rehabilitation after ACL reconstruction. A tuck jump score of ≥ 6 out of 10 has been labeled poor and thought to identify players with high risk landing patterns. The purpose of this exploratory study was to examine if there was a relationship between tuck jump score, particularly tuck jump scores ≥ 6, hopping performance, and patient-reported outcome measures in female soccer players with ACL reconstruction (ACLR) and knee-healthy controls. Female soccer players (117 after ACLR, 117 knee-healthy) performed the single hop for distance, tuck jump assessment, and drop vertical jump (DVJ). All players were categorized based on as having a total tuck jump score ≥ 6 or < 6. Analyzing all players together, Spearman's rank correlations assessed if there were relationships between total tuck jump score or tuck jump scores ≥ 6 and single-legged hop limb symmetry or DVJ measures. Players with an ACLR also filled out the International Knee Documentation Committee 2000 Subjective Knee Form and the Knee injury Osteoarthritis Outcome Score. Spearman's rank correlations assessed if there were relationships between total tuck jump score or tuck jump scores ≥ 6 and patient-reported outcome measures. The mean tuck jump scores was 4.8 ± 1.8 (tuck jump score ≥ 6, 6.7 ± 0.9, tuck jump score < 6, 3.7 ± 1.1) with 87 (37%) athletes having tuck jump score ≥ 6. There were no significant relationships between tuck jump score or tuck jump score ≥ 6 and hopping performance or patient-reported outcome measures. The results of this current study indicate that tuck jump scores, including tuck jump scores ≥ 6, may not be related to functional or patient-reported outcome measures. Further work is needed to examine the clinical utility of the tuck jump assessment.


#8 Plantar Loading in the Youth Soccer Player During Common Soccer Movements and Risk for Foot Injury
Reference: Injury. 2020 Jun 12;S0020-1383(20)30515-5. doi: 10.1016/j.injury.2020.06.009. Online ahead of print.
Authors: Renato R Azevedo, Suellen B Nery, Darren J Stefanyshyn, Felipe P Carpes
Summary: Soccer players are at high risk of stress injuries in the foot. While most research addresses this issue in professional athletes, there is little information concerning young athletes. As soccer is practiced around the world since early infancy, we set out to determine whether young soccer athletes are susceptible to increased foot loading that increase risk factors for foot injuries in a similar manner as reported by the literature to the adult athlete. Twenty-six male adolescents (mean age 16 years old) were organized into two groups: soccer players (n = 13) and controls (n = 13). Groups were compared regarding foot sensitivity, ankle range of motion, Q-angle, and plantar pressure determined during running and cutting movements performed at maximal speed and using different shoes.  Foot sensitivity, ankle range of motion and Q-angle did not differ between the groups. During performance of soccer actions, young players showed higher peak pressure in the lateral region of the foot including the fifth metatarsal region. These higher peaks were minimized by manipulation of the footwear. In summary, young soccer athletes show dynamic plantar pressure patterns that are related to foot injury in the adult athlete, and this condition can be minimized by the manipulation of the footwear. Additional attention should be paid to the young athlete in soccer aiming to minimize long-term risk for stress injuries in the foot.


#9 Increased Myocardial Mass and Attenuation of Myocardial Strain in Professional Male Soccer Players and Competitive Male Triathletes
Reference: Int J Cardiovasc Imaging. 2020 Jun 20. doi: 10.1007/s10554-020-01918-1. Online ahead of print.
Authors: Jitka Starekova, Tilo Thottakara, Gunnar K Lund, Götz H Welsch, Fabian J Brunner, Kai Muellerleile, Gerhard Adam, Marc Regier, Enver Tahir
Download link: https://link.springer.com/content/pdf/10.1007/s10554-020-01918-1.pdf
Summary: The purpose of this prospective study was to analyze the relationship between ventricular morphology and parameters of cardiac function in two different athletic groups and controls, using feature tracking cardiac magnetic resonance (FT-CMR). Twenty-three professional soccer players (22 ± 4 years), 19 competitive triathletes (28 ± 6 years) and 16 controls (26 ± 3 years) were included in the study. CMR was performed using a 1.5 T scanner. Cardiac chamber volumes, mass and biventricular global myocardial strain were obtained and compared. In comparison to the control subjects, athletes were characterized by a higher cardiac volume (p < 0.0001), higher cardiac mass (p < 0.001), reduced longitudinal strain of the left and right ventricle (p < 0.05 and p < 0.01 respectively) and reduced left ventricular radial strain (p < 0.05). Soccer players revealed higher amounts of left ventricular mass (87 ± 15 vs. 75 ± 13 g/m2, p < 0.05) than triathletes. Moreover, they showed a greater decrease in left and right ventricular longitudinal strain (p < 0.05 and p < 0.05) as well as in radial left ventricular strain (p < 0.05) in comparison to triathletes. An increase in left ventricular mass correlated significantly with a decrease in longitudinal (r = 0.47, p < 0.001) and radial (r = - 0.28, p < 0.05) strain. In athletes, attenuation of strain values is associated with cardiac hypertrophy and differ between soccer players and triathletes. Further studies are needed to investigate whether it is an adaptive or maladaptive change of the heart induced by intense athletic training.


#10 Systematic Video Analysis of ACL Injuries in Professional Male Football (Soccer): Injury Mechanisms, Situational Patterns and Biomechanics Study on 134 Consecutive Cases
Reference:  Br J Sports Med. 2020 Jun 19;bjsports-2019-101247. doi: 10.1136/bjsports-2019-101247. Online ahead of print.
Authors: Francesco Della Villa, Matthew Buckthorpe, Alberto Grassi, Alberto Nabiuzzi, Filippo Tosarelli, Stefano Zaffagnini, Stefano Della Villa
Download link: https://bjsm.bmj.com/content/bjsports/early/2020/06/19/bjsports-2019-101247.full.pdf
Summary: A few small studies have reported on the mechanisms of ACL injury in professional male football. The purpose was to describe the mechanisms, situational patterns and biomechanics (kinematics) of ACL injuries in professional male football matches. We identified 148 consecutive ACL injuries across 10 seasons of professional Italian football. 134 (90%) injury videos were analysed for mechanism and situational pattern, while biomechanical analysis was possible in 107 cases. Three independent reviewers evaluated each video. ACL injury epidemiology (month), timing within the match and pitch location at the time of injury were also reported. 59 (44%) injuries were non-contact, 59 (44%) were indirect contact and 16 (12%) were direct contact. Players were frequently perturbed immediately prior to injury. We identified four main situational patterns for players who suffered a non-contact or an indirect contact injury: (1) pressing and tackling (n=55); (2) tackled (n=24); (3) regaining balance after kicking (n=19); and (4) landing from a jump (n=8). Knee valgus loading (n=83, 81%) was the dominant injury pattern across all four of these situational patterns (86%, 86%, 67% and 50%, respectively). 62% of the injuries occurred in the first half of the matches (p<0.01). Injuries peaked at the beginning of the season (September-October) and were also higher at the end of the season (March-May). 88% of ACL injuries occurred without direct knee contact, but indirect contact injuries were as frequent as non-contact injuries, underlying the importance of mechanical perturbation. The most common situational patterns were pressing, being tackled and kicking.

Tue

06

Oct

2020

Characterization of the Weekly External Load Profile of Professional Soccer Teams

 

The purpose was to analyze the day-to-day variance of a typical weekly external training workload of two professional soccer teams from Portugal and Netherlands

Wed

30

Sep

2020

Acceleration and sprint profiles of professional male football players in relation to playing position

The study aimed to describe positional differences in the acceleration and sprint profiles of professional footballers.

Tue

29

Sep

2020

Latest research in football - week 26 - 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 Evolution of Physical and Technical Performance Parameters in the Chinese Soccer Super League
Reference: Biol Sport. 2020 Jun;37(2):139-145. doi: 10.5114/biolsport.2020.93039. Epub 2020 Feb 11.
Authors: Changjing Zhou, Miguel-Ángel Gómez, Alberto Lorenzo
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249799/pdf/JBS-37-93039.pdf
Summary: Performance analysis in soccer has attained greater importance for coaching staff in order to gather and manage useful information (i.e., physical, technical, and tactical) of their teams during consecutive seasons. Accordingly, we examined the evolution of physical and technical performance parameters in the Chinese Soccer Super League (CSL). Data were collected from 1,429 CSL matches from the 2012 season to the 2017 season using the Amisco Pro (Amisco, Nice, France) system. Fourteen technical performance-related indicators and 11 physical performance-related indicators were analysed using a mixed linear model for repeated measures. Significant main effects of season were followed up using the Bonferroni correction (multiple comparisons). Although there were some irregularities, performance variables generally showed significant upward trends across the six seasons (p<0.05), resulting in significant increases from the 2012 season to the 2017 season in the total sprint distance (2,069.7±509.3 m vs. 2,272±493.6 m; p<0.001; effect size [ES]: 0.40), number of sprints (100.1±22.8 vs. 104.8±20.8, p<0.001; ES: 0.22), high-speed distance (2568.4±503.5 m vs. 2823.1±479.2 m; (p<0.001; ES: 0.52), and high-speed effort (187.5±36.1 to 204.7±33.7; p<0.001; ES: 0.49). Furthermore, there were ~23% more crosses (p<0.001; ES: 0.45), ~12% more shots on target (p<0.001; ES: 0.22), and ~11% more opponent penalty area entries (p<0.001; ES: 0.20) during the 2017 season than in the 2012 season. Coaches and sports scientists should be mindful of this evolution when preparing training sessions and recruiting new players, and even when predicting future trends in the Chinese Soccer Super League.


#2 The Cumulative and Residual Changes in Eccentric Knee Flexor Strength Indices Following Soccer-Specific Treadmill Running: Novel Considerations of Angle Specific Torque
Reference: J Sports Sci. 2020 Jun 7;1-9. doi: 10.1080/02640414.2020.1763053. Online ahead of print.
Authors: Richard Michael Page, Matt Greig
Summary: With potential implications for recovery and conditioning practices, the aim of this study was to assess the cumulative and residual response of angle specific eccentric knee flexor (eccKF) strength indices following soccer-specific activity. Thirteen semi-professional soccer players were therefore required to complete a 90-minute soccer-specific treadmill running. with eccKF isokinetic strength assessments completed pre-trial, immediately post-trial, and 48 hours post-trial. The strength assessments comprised the completion of 5 repetitions at angular velocities of 60 and 300 deg·s-1. Isokinetic data was analysed for measures of peak torque (PT), angle of peak torque (APT), functional range (FR), and angle specific torque (AST). Significant post-trial impairments were observed for measures of slow velocity PT60 (6.6%) and AST300 (12.5%). Further significant differences were observed 48 hours post-trial for PT300 (10.7%) and PT60 (12.8%) PT, APT60 (~15°), and AST300 (>13.6%). These data have implications for post exercise recovery monitoring and the prescription of recovery modalities and conditioning practices in the 2 days following match-play. The AST and APT responses highlight the importance of analysis of the entire strength-angle curve and at a range of angular velocities.


#3 Poor Hamstrings-To-Quadriceps Torque Ratios in Male Soccer Players: Weak Hamstrings, Strong Quadriceps, or Both?
Reference: Sports Biomech. 2020 Jun 8;1-11. doi: 10.1080/14763141.2020.1766100. Online ahead of print.
Authors: Carolina G Fritsch, Maurício P Dornelles, Gabriel Dos S Oliveira, Bruno M Baroni
Summary: This study aimed to evaluate the influence of hamstrings and quadriceps strength on the hamstrings-to-quadriceps conventional (H:Qcon) and functional (H:Qfun) ratios in male soccer players. Quadriceps concentric peak torque (PT) and hamstrings concentric and eccentric PT were assessed with isokinetic dynamometry at 60°/s in 101 players (202 legs). The cut-points of 0.50, 0.55 and 0.60 were used to assess muscle imbalance through the H:Qcon ratio, while 0.80, 0.85 and 0.90 were used for H:Qfun ratio. Legs with lower H:Qcon ratio had decreased hamstrings concentric PT (p < 0.01; moderate and large effect sizes) and increased quadriceps concentric PT (p < 0.01; moderate effect sizes) in all cut-points. Legs with lower H:Qfun ratio had decreased hamstrings eccentric PT (p < 0.01; large effect sizes) for all cut-points, and controversial results for quadriceps concentric PT (p < 0.01 only for 0.80 cut-point; small effect sizes). H:Qcon ratio presented only weak correlations with quadriceps (r = -0.37) and hamstrings (r = 0.45) concentric PT, while H:Qfun ratio had a negligible correlation with quadriceps concentric PT (r = -0.30) and a moderate correlation with hamstrings eccentric PT (r = 0.66). In conclusion, our findings support that hamstrings strength deficit is the key factor for low H:Q ratios in male soccer players, especially those with poor H:Qfun ratio.


#4 Bilateral Deficit and Bilateral Performance: Relationship With Sprinting and Change of Direction in Elite Youth Soccer Players
Reference: Sports (Basel). 2020 Jun 3;8(6):E82. doi: 10.3390/sports8060082.
Authors: Giampiero Ascenzi, Bruno Ruscello, Cristoforo Filetti, Daniele Bonanno, Valter Di Salvo, F Javier Nuñez, Alberto Mendez-Villanueva, Luis Suarez-Arrones
Download link: https://www.mdpi.com/2075-4663/8/6/82/pdf
Summary: The purpose of the study was to examine the differences in bilateral deficit (BLD) at different loadings during the half-squat jump (SJ) and horizontal countermovement jump (HCMJ) to determine if there is a relationship with linear sprint or change of direction (COD). The second goal was to check if fast players were more powerful in SJ and HCMJ than slow players in bilateral performance (BP). Twenty-seven male youth soccer players participated in the study. Players were divided in two groups, faster and slower, according to their sprint performance (10 and 40 m). BLD average power with body weight (BW) and 25%BW were significantly higher than 50%BW (p < 0.01). BLD during HCMJ was significantly higher than BLD during SJ with BW, 25%BW and 50%BW (p < 0.01). There were no statistical relationships between BLD and sprint or COD performance (p > 0.05). Fast players showed significantly higher SJ power with all the different loads and HCMJ than slow players (p < 0.01), and fast players lost more time executing COD-90° than slow players (p < 0.01). There were no statistical differences between fast and slow players in BLD. BLD seems to be dependent on motor task, contraction type and load and could not be a proper measure to estimate sprint and COD performance. Faster players are confirmed to be more powerful players than slow players, and decrements in COD could be a key benchmark to identify deficit between linear and COD performance.


#5 Comparison of 10 vs. 20 Min Neuromuscular Training for the Prevention of Lower Extremity Injuries in Male Youth Football: A Cluster Randomised Controlled Trial
Reference: J Sports Sci. 2020 Jun 10;1-9. doi: 10.1080/02640414.2020.1776459. Online ahead of print.
Authors: Anna Lina Rahlf, Astrid Zech
Summary: The aim of this study was to compare the effects of 20 min neuromuscular training with a programme of 10 min in youth football players. 342 (15.4 ± 1.7 years) male football players from 18 teams were included, and cluster-randomized by team into two intervention groups. Both groups performed an injury prevention programme twice a week over five months using the same exercises but a different duration. The first intervention group (INT10, n = 175) performed the programme for 10 min, the second intervention group (INT20, n = 167) for 20 min. Primary outcomes were lower extremity (LE) injuries. Secondary outcomes were injury type, severity, mechanism and compliance to the intervention. 13 teams with 185 players were included for final analysis. No significant group difference was found between INT10 (6.37 per 1000 h) and INT20 (7.20 per 1000 h) for the incidence rate ratio of the lower extremities (IRR = 1.03, 95% confidence interval 0.59, 1.79), nor for the distribution of injury location, type, severity or mechanism. The results show that performing preventive exercises for 10 min is no less effective than 20 min in youth football players. Shorter training sessions can, therefore, be effectively used for injury prevention.


#6 The Resumption of Sports Competitions After COVID-19 Lockdown: The Case of the Spanish Football League
Reference: Chaos Solitons Fractals. 2020 Sep;138:109964. doi: 10.1016/j.chaos.2020.109964. Epub 2020 Jun 4.
Authors: Javier M Buldú, Daniel R Antequera, Jacobo Aguirre
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7269962/pdf/main.pdf
Summary: In this work, we present a stochastic discrete-time SEIR Susceptible-Exposed-Infectious-Recovered model adapted to describe the propagation of COVID-19 during a football tournament. Specifically, we are concerned about the re-start of the Spanish national football league, La Liga, which is currently -May 2020- stopped with 11 fixtures remaining. Our model includes two additional states of an individual, confined and quarantined, which are reached when an individual presents COVID-19 symptoms or has undergone a virus test with a positive result. The model also accounts for the interaction dynamics of players, considering three different sources of infection: the player social circle, the contact with his/her team colleagues during training sessions, and the interaction with rivals during a match. Our results highlight the influence of the days between matches, the frequency of virus tests and their sensitivity on the number of players infected at the end of the season. Following our findings, we finally propose a variety of strategies to minimise the probability that COVID-19 propagates in case the season of La Liga was re-started after the current lockdown.


#7 Monitoring Matches and Small-sided Games in Elite Young Soccer Players
Reference: Int J Sports Med. 2020 Jun 26. doi: 10.1055/a-1165-1916. Online ahead of print.
Authors: Jonas Darbellay, Davide Malatesta, César Marius Philippe Meylan
Summary: The aim of this study was to compare the distances at various intensity in matches and small-sided games in elite-young soccer players using the metabolic power approach and running speed methods through fixed and individual speed zones. The second aim was to investigate the difference in high intensity external workload (% of total distances covered > 16 km/h or > 20 W/kg) between matches and small-sided games. Global positioning system data from 14 elite-youth players were analyzed during 13 matches and two types of small sided-games. Five intensity zones were used to compare the running distances between the metabolic power approach and the classic performance analysis. Metabolic power recorded more distances covered at high intensity than the running speed methods for every playing situations, except for the zone 5 of fixed speed (> 19 km/h) in matches (P<0.05). Smaller differences of external workload at high intensity were found when using the metabolic power approach compared to the traditional performance analysis. Our results highlight that the traditional analysis underestimates the athlete's high intensity efforts. The metabolic power approach seems more relevant to monitor matches and training situations but also to compare matches to small-sided games in elite-young soccer players.


#8 Level of Play and Coach-Rated Game Intelligence Are Related to Performance on Design Fluency in Elite Soccer Players
Reference: Sci Rep. 2020 Jun 25;10(1):9852. doi: 10.1038/s41598-020-66180-w.
Authors: T Vestberg, R Jafari, R Almeida, L Maurex, M Ingvar, P Petrovic 
Summary: Executive brain functions are innate mechanisms for regulating behavior. While the impact of suboptimal executive functions has been characterized in patients, their contribution to individual success has not been elucidated. We set out to understand how executive functions relate to successful human behavior by examining their relation to game intelligence in sport - the ability to read a game and quickly adapt the behavior. In elite soccer players (n = 51), those playing in national teams (national team players) significantly outperformed those only playing at premier league level (premier league players) in Design Fluency (DF), a complex visuo-spatial executive function test that includes measures of creativity and cognitive flexibility. Their result showed a moderate correlation with coach rated game intelligence, remained also when correcting for low level cognitive capacity and was most evident when considering cognitive flexibility. DF capacity also correlated with number of assists made during the season but not with number of made goals during the same period, linking the fast planning of several steps in DF to fast planning of several steps in the soccer game. Altogether, our data suggests that DF capacity relates to success in soccer both on a subjective and on an objective level.


#9 Understanding the Underlying Mechanisms of Quiet Eye: The Role of Microsaccades, Small Saccades and Pupil-Size Before Final Movement Initiation in a Soccer Penalty Kick
Reference: Eur J Sport Sci. 2020 Jun 25;1-27. doi: 10.1080/17461391.2020.1788648. Online ahead of print.
Authors: Piras Alessandro, Timmis Matthew, Trofè Aurelio, Raffi Milena
Summary: Experts keep a steady final fixation at a specific location just before final movement initiation, the so-called "quiet eye" (QE). However, the eyes are rarely "quiet", and small eye movements occur during visual fixation. The current research investigated the subtle eye movements and underlying mechanisms immediately prior to and during QE. The gaze behaviour of 8 intermediate-level goalkeepers was recorded as they moved (either left or right) in an attempt to predict the future direction of the ball during a soccer penalty kick. Goalkeepers were more likely to predict the direction of the penalty, which was coupled with delaying movement initiation. The temporal sequence of microsaccade rates dropped ∼1000 ms before goalkeepers' final movement initiation. Saccade rates increased, reaching a peak ∼500 ms before final movement initiation, concomitant with microsaccades reduction. Microsaccades predicted the goalkeepers' direction, oriented to the right when goalkeepers moved to the right, and conversely to the left when they moved to the left. Microsaccades may be modulated by attention and appear functionally related to saccadic intrusions. Pupil-size increased proportionally with the lead up to the instance of the penalty being kicked, reaching a plateau at final movement initiation. In conclusion, microsaccades and small saccades could improve the perception of the soccer penalty kick, helping athletes during the period that precedes the critical movement initiation, shifting from covert to overt attention for identifying the useful cues necessary to guide the action.


#10 Basic Cognitive Abilities Relevant to Male Adolescents' Soccer Performance
Reference: Percept Mot Skills. 2020 Jun 23;31512520930158. doi: 10.1177/0031512520930158. Online ahead of print.
Authors: Dragan Glavaš
Summary: While there is a theoretical and empirical consensus that specific cognitive abilities gained through deliberate sports practice influence sports performance, it is less clear whether basic cognitive abilities that are not specifically related to sports practice are relevant to sports performance. Accordingly, this research examined the roles of basic concentration and visuospatial ability in adolescent soccer performance. Participants were 46 adolescent male soccer players (Mage = 16.15 years, standard deviation = 1.13) who averaged 7.21 years (standard deviation = 2.2) of prior soccer training. We measured participant's basic cognitive abilities with the Corsi block and the concentration grid tasks, and we measured their soccer performance through five soccer skills. Concentration had no predictive role in elements of soccer performance, but visuospatial ability was significantly related to tactical abilities, technical skills, mental toughness, and situational awareness and thus, to overall soccer performance. These findings provided support for the importance of visuospatial ability but not concentration (as measured by the concentration grid) in young males' soccer performance.


#11 Sensory Reweighting for Upright Stance in Soccer Players: A Comparison of High and Low Exposure to Soccer Heading
Reference: J Neurotrauma. 2020 Jun 22. doi: 10.1089/neu.2020.7001. Online ahead of print.
Authors: Jaclyn B Caccese, Fernando V Santos, Felipe Yamaguchi, John J Jeka
Summary: The purpose of this study was to compare sensory reweighting for upright stance between soccer players who report higher soccer heading exposure to those who report lower soccer heading exposure. Thirty participants completed a self-reported questionnaire to estimate the number of soccer headers experienced over the prior year and were divided into "low exposure" and "high exposure" groups based on their responses. Sensory reweighting for upright stance was assessed by simultaneously perturbing visual, vestibular, and proprioceptive systems. The visual stimulus was a sinuosoidal translation of the visual scene at 0.2Hz, the vestibular stimulus was ±1mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36Hz, and the proprioceptive stimulus was Achilles tendon vibration at 0.28Hz. The visual stimulus was presented at two amplitudes (0.2m, 0.8m). Center of mass (COM) gain/phase to each modality, total power, 95% area and velocity were compared between "low exposure" (N=15, 6 males, 21.5±1.9years, 27.7±31.6headers) and "high exposure" groups (N=15, 10 males, 22.1±3.5years, 734.9±877.7headers). Without vibration, COM 95% area (F=5.861, p=.022*, partial η²=.173), velocity (F=14.198, p=.001, partial η²=.336), and total power (F=13.491, p=.001, partial η²=.325) for the "high exposure" group were higher than for the "low exposure" group and postural sway lagged the vestibular stimulus in the "high exposure" group rather than leading it as in the "low exposure" group (F=4.765, p=.038, partial η²=.145). There were no differences in sensory reweighting and no differences in COM gain/phase between groups. These findings lend empirical evidence to a detrimental effect of soccer heading exposure on balance control during upright stance.

Mon

28

Sep

2020

Spikes in acute:chronic workload ratio (ACWR) associated with a 5–7 times greater injury rate

A comprehensive 3-year study from English Premier League Footballers

Fri

25

Sep

2020

How Numerical Unbalance Constraints Physical and Tactical Individual Demands of Ball Possession Small-Sided Soccer Games

 

Is there an effect of unbalanced players numbers in SSG on workload and technical/tactical actions in football?

Tue

22

Sep

2020

Latest research in football - week 25 - 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 Football Fans' Emotions: Uncertainty Against Brand Perception
Reference: Front Psychol. 2020 May 15;11:659. doi: 10.3389/fpsyg.2020.00659. eCollection 2020.
Authors: Elena Shakina, Thadeu Gasparetto, Angel Barajas
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242735/pdf/fpsyg-11-00659.pdf
Summary: Football is an industry driven by emotions. Fans experience many different emotions related to their teams. This paper aims to inspect how emotions impact attendance at football matches, examining whether football fans prefer to watch highly competitive matches or matches between good teams with star-players. The paper also considers behavioral and emotional differences of match spectators when brand-teams play away or at home. Importantly, we are also looking for the effects that the expectations of these emotions have on the tickets' price mechanism. We use data from three seasons of the Brazilian State championship with information on more than 1,100 matches. The OLS estimator with the moderation marginal effects allows for analysis of a brand-team playing with different levels of uncertainty over the outcomes measured by the relative level of the divisions of rivals. We look for the difference between the marginal contribution of the brand-team and the uncertainty of outcomes that might change under some conditions. The analysis is performed later using two subsamples and, finally, we address the problem of endogeneity in price using an instrumental variable. From our results, the main findings are: first, that the price of tickets does not much affect the demand when a brand-team is playing. In case of competitive matches between non-brand-teams, price behavior correlates to the rationality of the demand curve having a negative impact. The fact that price is not relevant for matches with the brand-team comes to corroborate the idea that fans are driven more by emotions than by economic reasoning; second, the phenomena of highly competitive matches does not work when a brand-team is playing against a small one; and third, the effect of a brand-team playing is relatively more important than the uncertainty of outcome. The last two findings mean that the satisfaction of watching star-players or big-teams is stronger than the emotion brought by a competitive match.


#2 Acute Kinematics and Kinetics Changes to Wearable Resistance During Change of Direction Among Soccer Players
Reference: Res Sports Med. 2020 Jun 3;1-15. doi: 10.1080/15438627.2020.1770761. Online ahead of print.
Authors: Xueliang Li, Chunman Li  1 , Yixiong Cui  2 , Del P Wong  3
Summary: This study determined the acute changes in kinematics and kinetics when an additional load equivalent to 5% body mass was attached to the torso during change of direction (COD). In this within-subject repeated measures study, 14 male soccer players (age: 18.29 ± 0.32 years) volunteered to participate. Subjects performed COD under two conditions in randomized order: (1) no WR, and (2) with WR. No significant differences between the loaded and unloaded conditions in actual COD angle, approach speed, braking time, propulsive time, contact time, COD completion time (all p > 0.05, ES = 0.05-0.11), and all measured kinematic parameters (all p > 0.05, ES = 0-0.18). Nonetheless, ankle plantar/dorsi flexion ROM had possibly small increase in the loaded condition (ES = 0.24). Kinetics analysis has shown that the loaded condition was likely to have small increase in relative peak vertical propulsive ground reaction force (GRF, p = 0.11, ES = 0.41), and possible small increases in relative peak braking GRF (vertical: p = 0.21, ES = 0.42; total: p = 0.22, ES = 0.38), relative peak total propulsive GRF (p = 0.24, ES = 0.26), and relative braking impulse (horizontal, vertical, and total; p = 0.27-0.41, ES = 0.26-0.28). WR did not significantly change the acute movement techniques, meanwhile induced small increases in important kinetic stimuli for potential adaptation in COD.


#3 Reduced Telomere Shortening in Lifelong Trained Male Football Players Compared to Age-Matched Inactive Controls
Reference: Review Prog Cardiovasc Dis. 2020 Jun 1;S0033-0620(20)30117-1. doi: 10.1016/j.pcad.2020.05.009. Online ahead of print.
Authors: Marie Hagman, Christian Werner, Katharina Kamp, Bjørn Fristrup, Therese Hornstrup, Tim Meyer, Michael Böhm, Ulrich Laufs, Peter Krustrup
Summary: Current evidence points to cellular anti-ageing effects of regular endurance training which may differ from other sport modalities. Effects of football training on markers of cell senescence have not been tested. One hundred and forty healthy, non-smoking men participated in the study, including young elite football players aged 18-30 years (YF, n = 35, 21.6 ± 0.5 yrs), elderly football players aged 65-80 years (EF, n = 35, 71.9 ± 0.5 yrs), untrained young controls (YC, n = 35, 24.3 ± 0.6 yrs) and elderly controls (EC, n = 35, 70.1 ± 0.7 yrs). Besides body composition (DXA scan), resting heart rate (RHR), blood pressure (BP) and selected fasting blood variables, mononuclear cells (MNC) were isolated. MNC telomere length was determined by flow-fluorescence in-situ hybridization (FISH) and polymerase chain reaction (PCR). Telomerase activity was quantified using telomerase repeat amplification protocol (TRAP) assay. mRNA expression of anti- and pro-senescent factors was measured with real-time PCR. EF showed 2.5% higher (p = 0.047) granulocyte telomere length and 1.3% higher (p = 0.009) lymphocyte telomere length compared to EC. EF had 37% lower (p = 0.025) mRNA expression of the pro-senescent factor p16 compared to EC. No significant between-group differences (p > 0.050) were observed in telomerase activity or anti-senescent factors (TRF2, Ku70 and POT1a) for EF vs EC. YF had higher telomerase activity (4.2-fold, p = 0.001), telomere repeat binding factor (TRF) 2 mRNA expression (3.2-fold, p = 0.003), Ku70 mRNA expression (2.3-fold, p < 0.001) and POT1a mRNA expression (2.2-fold, p = 0.002) compared to YC, but there was no significant between-group difference in telomere length. This study is the first cross-sectional, controlled trial showing effects of lifelong football participation on telomere shortening and senescence markers in circulating cells, suggesting that football induces cellular anti-senescence mechanisms implying positive long-term cardiovascular health effects.


#4 Curve Sprinting in Soccer: Kinematic and Neuromuscular Analysis
Reference: Int J Sports Med. 2020 Jun 3. doi: 10.1055/a-1144-3175. Online ahead of print.
Authors: Alberto Filter, Jesús Olivares-Jabalera, Alfredo Santalla, Jaime Morente-Sánchez, Jose Robles-Rodríguez, Bernardo Requena, Irineu Loturco
Summary: Sprinting in curvilinear trajectories is an important soccer ability, corresponding to ~85% of the actions performed at maximum velocity in a soccer league. We compared the neuromuscular behavior and foot contact-time between outside leg and inside leg during curve sprinting to both sides in soccer players. Nine soccer players (age=23±4.12 years) performed: 3×Sprint linear, 3×Sprint right curve, and 3×Sprint left curve. An ANOVA with repeated measures was used to compare the differences between inside and outside leg, and Cohen's d was used to calculate the effect-size. Considering the average data, the performance classification (from best to worst) was as follows: 1. Curve "good" side (2.45±0.11 s), 2. Linear (2.47±0.13 s), and 3. Curve "weak" side (2.56±0.17 s). Comparing linear with curve sprinting, inside leg recorded significant differences ("good" and "weak"; effect size=1.20 and 2, respectively); in contrast, for outside leg, there were no significant differences ("good" and "weak"; effect size=0.30 and 0.49, respectively). Electromyography activity showed significant differences (p≤0.05) during curve sprinting between outside (higher in biceps femoris and gluteus medius) and inside leg (higher activity in semitendinosus and adductor). In summary, inside and outside leg play different roles during curved sprints, but inside leg is more affected by the change from straight to curve sprint.


#5 Recurrent Fifth Metatarsal Stress Fractures in a Professional Soccer Player With Hypoparathyroidism: A Case Report
Reference: BMC Musculoskelet Disord. 2020 Jun 3;21(1):347. doi: 10.1186/s12891-020-03383-2.
Authors: Itaru Kawashima, Atsushi Yamaga, Ryosuke Kawai, Yushi Hoshino, Shinya Ishizuka
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271481/pdf/12891_2020_Article_3383.pdf
Summary: Hypoparathyroidism is characterized by low or inappropriately normal levels of parathyroid hormone leading to hypocalcemia. In this report, a case of recurrent fifth metatarsal stress fractures in a professional soccer player with hypoparathyroidism is presented. A 23-year-old male professional soccer player developed left foot pain. He had no specific medical or family history. He was diagnosed with a fifth metatarsal stress fracture and underwent osteosynthesis with a cannulated cancellous screw 3 days after the injury. After three and a half months, the X-ray showed bone union, and he returned to full sports activity. However, he felt pain in his left foot again, and a re-fracture was found on X-ray a week later. Osteosynthesis was performed again. Two months after re-operation, the cause of re-fracture was investigated. Laboratory results showed abnormally low levels of serum calcium (8.4 mg/dL) and intact parathyroid hormone (i-PTH: 19.0 pg/mL). However, other laboratory examinations were normal. Therefore, he was diagnosed with primary hypoparathyroidism according to the diagnostic criteria. Medical treatment was started with alfacalcidol 1.0 μg/day. One month after starting medication, the serum calcium improved to 9.4 mg/dL. Four months after the re-operation, the X-ray showed bone union, and he was therefore allowed to play soccer. While he played professional soccer, there were no new subjective complaints. Hypoparathyroidism may be one of the risk factors for stress fractures. We believe that serum calcium levels should be checked in patients with stress fractures, and if the serum calcium is low, hypoparathyroidism should be considered.


#6 Epidemiological Data on LCL and PCL Injuries Over 17 Seasons in Men's Professional Soccer: The UEFA Elite Club Injury Study
Reference: Open Access J Sports Med. 2020 May 13;11:105-112. doi: 10.2147/OAJSM.S237997. eCollection 2020.
Authors: Matilda Lundblad, Martin Hägglund, Christoffer Thomeé, Eric Hamrin Senorski, Jan Ekstrand, Jón Karlsson , Markus Waldén
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7231769/pdf/oajsm-11-105.pdf
Summary: There is limited epidemiological information on injury rates and injury mechanisms for lateral collateral ligament (LCL) and posterior cruciate ligament (PCL) injuries in male professional soccer. In addition, time trends and lay-off times for these injuries have not yet been determined. The purpose was to determine injury rates and circumstances of LCL and PCL injuries over 17 seasons in men's professional soccer. A prospective cohort study, in which 68 professional European soccer teams were followed over 17 consecutive seasons (2001/2002 to 2017/2018). The teams' medical staff recorded player exposure and time-loss injuries. Lay-off time was reported as the median and the first and third quartile. Injury rate was defined as the number of injuries per 1000 player-hours. One hundred and twenty-eight LCL and 28 PCL injuries occurred during 2,554,686 h of exposure (rate 0.05 and 0.01/1000 h, respectively). The median lay-off time for LCL injuries was 15 (Q1=7, Q3=32) days, while it was 31 days for PCL injuries (Q1=15, Q3=74). The match injury rate for LCL injuries was 11 times higher than the training injury rate (0.21 vs 0.02/1000 h, rate ratio [RR] 10.5, 95% CI 7.3 to 15.1 p<0.001) and the match injury rate for PCL injuries was 20 times higher than the training injury rate (0.056 vs 0.003/1000 h, RR 20.1, 95% CI 8.2 to 49.6, p<0.001). LCL injuries saw a significant annual decrease of approximately 3.5% (p=0.006). In total, 58% (63/108) of all LCL injuries and 54% (14/26) of all PCL injuries were related to contact mechanism. This study with prospectively registered data on LCL and PCL injuries in men's professional soccer shows that the median lay-off from soccer for LCL and PCL injuries is approximately 2 and 4 weeks respectively. These rare knee ligament injuries typically occur during matches and are associated with a contact injury mechanism.


#7 ACTN3's R577x Single Nucleotide Polymorphism Allele Distribution Differs Significantly in Professional Football Players According to Their Field Position
Reference: Med Princ Pract. 2020 Jun 3. doi: 10.1159/000509089. Online ahead of print.
Authors: Enric Clos, Ricard Pruna, Matilda Lundblad, Rosa Artells, Nicola Maffulli
Download link: https://www.karger.com/Article/Pdf/509089
Summary: Football is characterised by intermittent high-intensity efforts varying according to the field position of a player. We wished to ascertain whether polymorphisms in the ACTN3 gene are associated to different playing positions in elite professional football players. Genotyping of the ACTN3 gene was conducted in 43 elite professional football players of a single team. Playing position was recorded based on the player's most frequent position. The genotype distribution was not significant between positions (p=0.057), while the allele distribution differed significantly (p=0.035). Goalkeepers (p=0.04, p=0.03), central defenders (p=0.03, p=0.01) and central midfielders (p=0.01, p=0.00) had a significantly different allele distribution compared with wide midfielders and forward players. Genetic biomarkers may be important when analysing performance capability in elite professional football. Identifying the genetic characteristics of a player to adapt his playing position may lead to a position orientation based on physical capabilities and tissue quality in young football players and to performance enhancement in those who are already playing in professional teams.


#8 Using Machine Learning to Improve Our Understanding of Injury Risk and Prediction in Elite Male Youth Football Players
Reference: J Sci Med Sport. 2020 May 18;S1440-2440(19)31676-7. doi: 10.1016/j.jsams.2020.04.021. Online ahead of print.
Authors: Jon L Oliver, Francisco Ayala, Mark B A De Ste Croix, Rhodri S Lloyd, Greg D Myer , Paul J Read
Summary: The purpose of this study was to examine whether the use of machine learning improved the ability of a neuromuscular screen to identify injury risk factors in elite male youth football players.  355 elite youth football players aged 10-18 years old completed a prospective pre-season neuromuscular screen that included anthropometric measures of size, as well as single leg countermovement jump (SLCMJ), single leg hop for distance (SLHD), 75% hop distance and stick (75%Hop), Y-balance anterior reach and tuck jump assessment. Injury incidence was monitored over one competitive season. Risk profiling was assessed using traditional regression analyses and compared to supervised machine learning algorithms constructed using decision trees. Using continuous data, multivariate logistic analysis identified SLCMJ asymmetry as the sole significant predictor of injury (OR 0.94, 0.92-0.97, p<0.001), with a specificity of 97.7% and sensitivity of 15.2% giving an AUC of 0.661. The best performing decision tree model provided a specificity of 74.2% and sensitivity of 55.6% with an AUC of 0.663. All variables contributed to the final machine model, with asymmetry in the SLCMJ, 75%Hop and Y-balance, plus tuck jump knee valgus and anthropometrics being the most frequent contributors. Although both statistical methods reported similar accuracy, logistic regression provided very low sensitivity and only identified a single neuromuscular injury risk factor. The machine learning model provided much improved sensitivity to predict injury and identified interactions of asymmetry, knee valgus angle and body size as contributing factors to an injurious profile in youth football players.


#9 Functional Neural Substrates of Football Fanaticism: Different Pattern of Brain Responses and Connectivity in Fanatics
Reference: Psychiatry Clin Neurosci. 2020 May 31. doi: 10.1111/pcn.13076. Online ahead of print.
Authors: Başar Bilgiç, Elif Kurt, Çağrı Can Makar, Cigdem Ulasoglu-Yildiz, Bedia Samancı, Hakan Gürvit, Tamer Demiralp, Murat Emre
Summary: Sports activities provide social interaction for humans. Commitment to a given team is a salient feature of being a sports fan and becomes a prominent part of self-identification for fanatics. Emotion, subjective hedonic experience, and non-romantic love are related to fan behaviors. Few studies have evaluated the neural basis of sports fanaticism. Thirty men, including 16 football fanatics and 14 non-fanatics, with a mean age of 27.4 ± 6.4 years (range, 20-48) were enrolled. Subjects underwent fMRI while watching a set of goals scored by favorite, rival, and neutral teams. The analysis of variance in GLM revealed a significant Group-by-Condition interaction effect in the bilateral dorsal anterior cingulate cortex (dACC), more prominent in the left hemisphere. In the post-hoc comparisons, fanatics showed increased activation in bilateral dACC, supplementary motor cortex (SMA), superior frontal cortex, right dorsolateral prefrontal cortex and right insula for favorite>neutral contrast and an increased activation in bilateral dACC and SMA for rival>neutral contrast. Seed-based connectivity analyses using the areas with significant activation differences revealed increased connectivity between dACC and several regions, including left posterior lateral temporal area, insula, and bilateral medial temporal, medial superior frontal areas as well as basal ganglia in fanatics compared to non-fanatics. Our results suggest that football fanatics exhibit different brain activation and connectivity pattern, both under favorable and unfavorable conditions. This brain activity and connectivity pattern under emotionally-laden conditions may represent higher responses to rewards, higher emotional valence attribution, and stronger motivational state of the football fanatics that might underlie their unusual behavioral responses.


#10 Sex-Based Differences in Anterior Cruciate Ligament Injuries Among United States High School Soccer Players: An Epidemiological Study
Reference: Orthop J Sports Med. 2020 May 28;8(5):2325967120919178. doi: 10.1177/2325967120919178. eCollection 2020 May.
Authors: Andrew S Gupta, Lauren A Pierpoint, R Dawn Comstock, Michael G Saper
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7262988/pdf/10.1177_2325967120919178.pdf
Summary: Anterior cruciate ligament (ACL) tears are common among high school athletes, with sex-based differences accounting for higher injury rates in girls. Previous epidemiological studies on ACL injuries focusing on adolescent athletes have looked at injuries across multiple sports, but few have analyzed ACL tears in solely high school soccer athletes.  The purpose was to examine sex-based differences in the epidemiology of ACL injuries among high school soccer players in the United States (US). ACL injury data for US high school soccer players were obtained from the internet-based National High School Sports-Related Injury Surveillance Study's High School RIO (Reporting Information Online) system. Athletic trainers from a random sample of 100 high schools from 8 strata based on US Census geographic region reported data for athlete-exposures (AEs) (practice or competition) and ACL injuries from 2007 through 2017. Injury rates were calculated as the number of ACL injuries per 100,000 AEs. Subgroup differences were evaluated with rate ratios (RRs) or injury proportion ratios (IPRs) and 95% CIs. Statistical differences in demographics between groups were examined using independent t tests. Comparisons of categorical data (ie, level of play) were performed using the Wald chi-square test. The reported number of ACL injuries corresponded to weighted national estimates of 41,025 (95% CI, 33,321-48,730) ACL injuries in boys' soccer and 110,028 (95% CI, 95,349-124,709) in girls' soccer during the study period. The rate of injuries was higher in girls' soccer (13.23/100,000 AEs) than boys' soccer (4.35/100,000 AEs) (RR, 3.04 [95% CI, 2.35-3.98]). The rate of ACL injuries was higher in competition compared with practice for girls (RR, 14.77 [95% CI, 9.85-22.15]) and boys (RR, 8.69 [95% CI, 5.01-15.08]). Overall, a smaller proportion of ACL injuries were caused by player-player contact for girls (30.1%) compared with boys (48.6%) (IPR, 0.62 [95% CI, 0.41-0.93]). ACL injury rates and patterns in high school soccer players differed between sex, type of exposure (practice vs competition), and mechanism of injury.

 

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21

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2020

Changes in lactate kinetics underpin soccer performance adaptations to cycling-based sprint interval training

The aim was to determine the effectiveness of sprint interval training on performance and lactate kinetics in soccer players.

Sat

19

Sep

2020

Analysis of Factors Determining Invasion into Attacking Areas and the Creation of Goal-Scoring Opportunities

Variables assessed passing strategies, field position and possession.

Wed

19

Aug

2020

Latest research in football week - 24 - 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 Regions at Risk in the Knee Joint of Young Professional Soccer Players: Longitudinal Evaluation of Early Cartilage Degeneration by Quantitative T2 Mapping in 3 T MRI
Reference: Cartilage. 2020 May 25;1947603520924773. doi: 10.1177/1947603520924773. Online ahead of print.
Authors: Hanna Schenk, David Simon, Leonie Waldenmeier, Christoph Evers , Rolf Janka, Goetz H Welsch, Milena L Pachowsky
Summary: The study aims to detect regions at risk for (pre-)osteoarthritis in the tibiofemoral joint of young professional soccer players by evaluating cartilage composition by T2 mapping in a 3 T magnetic resonance imaging setting. In this longitudinal study, 20 professional adolescent soccer players were included. Tibiofemoral cartilage was assessed by quantitative T2 mapping and T2 values were evaluated by regions of interest analysis. Statistical evaluation, using Wilcoxon signed-rank tests, was performed to compare global T2 values and subregional T2 values between a baseline and a follow-up investigation 4.3 years later. Based on the average of playing time (15 years) we divided the cohort in 2 groups and differences were evaluated. When comparing baseline and follow-up, our findings showed statistically significant increases of the global medial tibial and femoral T2 values. The most noticeable results of the subregional T2 analysis were statistically significant increases in the medial posterior zones (deep femoral 36.1 vs. 39.5, P = 0.001; superficial femoral 57.0 vs. 62.4, P = 0.034; deep tibial 28.3 vs. 34.1, P = 0.009; superficial tibial 43.2 vs. 55.3, P = 0.002). The elevation of T2 values in the medial, especially medial posterior, compartment of the knee joint indicates that these regions are at risk for early cartilage degeneration already at the time of adolescence. The findings can help individualize and optimize training concepts and to be aware of the chronic stress on these vulnerable areas. Prevention programs should be established in young players to avoid further cartilage damage.


#2 The Demands of the Extra-Time Period of Soccer: A Systematic Review
Reference: J Sport Health Sci. 2020 May 20;S2095-2546(20)30042-9.
doi: 10.1016/j.jshs.2020.03.008. Online ahead of print.
Authors: Adam Field, Robert Joseph Naughton, Matthew Haines, Steve Lui, Liam David Corr, Mark Russell, Richard Michael Page, Liam David Harper 
Download link: https://pdf.sciencedirectassets.com/282623/AIP/1-s2.0-S2095254620300429/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjEO3%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCXVzLWVhc3QtMSJIMEYCIQDRg4FAWJ2JSlvUe0Lgj05NwZY3iJ6RdNOxQDGiT13%2BTAIhAJC6OEYkDYYf7phTAg3iMaP7rdJES8Saz7LT3V%2FbQq6aKrQDCFYQAxoMMDU5MDAzNTQ2ODY1IgxsjddvZHy4uu7TevEqkQPi1tdm1BiVwcsIXSFwhIYyEF5G1zwXCWsSq7wIDKUoV0Cwlh1mVTLaT%2F%2FUT7D%2FAaK2KpjZr%2FVt1gtgYuGJyVZUT%2F4yWc5Vo5IwWZ104e96SO5Zs2TeGhDM8KBWja0CBbToft2uB5d0leEvOEu3do4swiaQeNMHjRXjzEjGLcLp8aEdDDs%2Foj4XEz8VcN4d9my6OJeR8RGx891wo%2Bw4gio1rcbjKqjFh5TjxvfiGz72xzfy1LZ9L64cRJMD9UVrQMjUqyzgNVW64msI6sOyW5TDJZyVOTKshWLZ0dfLFysKRvpyaC2bSnSkubUBUg5TIMheaxhWL%2FfDzhSwjriT1j56DUuEWIzR138%2FA6t0n279vv27i77xuGTYwRUZtZKY0brSHDaWYH98tM30bUFWnfVKFl2QOS0TEzF3ih5fVGyy3c5RYKVQen2xIb%2FN5eCemC940viP84mz%2FzJQrNaYRgMqHkdmYhDj%2FIF4dDbsBipMfSDOrok%2BKw1QJcSdGeWPXOji13BQBcQjCyTacjgJ8LRvCjDyttf2BTrqAR6ds3JMrlWuBGqJhZ4p%2F8L9BUePlp0zmOlxJ1XN4uR9RzaMztFoX0%2FSG4Nr%2FfvomA7vAVdgY1g9bg3hNh%2BvL7q6cbtnfYPPJAqdmqdLGX19H96qgUPeL9IdkJdlxzGKOpKqkS5k9WJ2hr7tEQa1SOnhugjqvlD4ffAjyAHwDQKH5Lpd576R%2BAljgh73SZtIyjKBaw39WN6M9pPJLOwDs69RYKuWw%2FF09k8%2FBFz8vnxPA3v7%2B1FuZ83z%2FafyKsj9WxWe%2B%2B1kB4yBR1ugSv5oZWdJ6%2F2J79%2BSJMQkp2Ks85LRAn3ypR0dAoWT%2Bg%3D%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20200602T060745Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTYV7OMK3OW%2F20200602%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=1e6916bebff9ecd160cb1608f8d48df201266f9f4414ce5a1805eddc64721147&hash=dcc6f99e827c03419b1e1baac5d3c796b0d4a731a9c5fcf59f3d10b34b99777b&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S2095254620300429&tid=spdf-fcd00ac4-b7ad-4c11-9356-69751a295540&sid=2b238ac368d48441770985e67aec66bf5d40gxrqb&type=client
Summary: Soccer match-play is typically contested over 90 min; however, in some cup and tournament scenarios, when matches are tied, they proceed to an additional 30 min, which is termed "extra-time" (ET). This systematic review sought to appraise the literature available on 120-min of soccer-specific exercise, with a view to identifying practical recommendations and future research opportunities. The review was conducted according to the PRISMA guidelines. Independent researchers performed a systematic search of PubMed, CINAHL and Psych Info in May 2019, with the following keywords entered in various combinations: "soccer," "football," "extra-time," "extra time," "120 minutes," "120 min, "additional 30 minutes," and "additional 30 min." The search yielded an initial 73 articles. Following the screening process, 11 articles were accepted for analyses. Articles were subsequently organized into the following 5 categories: movement demands of extra-time, performance responses to extra-time, physiologic and neuromuscular response during extra-time, nutritional inventions, and recovery and extra-time. The results highlighted that during competitive match-play, players cover 5%-12% less distance relative to match duration (i.e., meters per minute) during ET compared to the preceding 90 min. Reductions in technical performance (i.e., shot speed, number of passes and dribbles) were also observed during ET. Additionally, carbohydrate provision may attenuate and improve dribbling performance during ET. Moreover, objective and subjective measures of recovery may be further compromised following ET when compared to 90 min. Additional investigations are warranted to further substantiate these findings and identify interventions to improve performance during ET.


#3 Costs Resulting From Nonprofessional Soccer Injuries in Switzerland: A Detailed Analysis
Reference: J Sport Health Sci. 2020 May;9(3):240-247.
doi: 10.1016/j.jshs.2018.08.001. Epub 2018 Aug 23.
Authors: Angela Gebert, Markus Gerber, Uwe Pühse, Philippe Gassmann, Hanspeter Stamm, Markus Lamprecht
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242620/pdf/main.pdf
Summary: Soccer injuries constitute an important public health problem and cause a high economic burden. Nevertheless, comprehensive data regarding injury costs in nonprofessional soccer are missing. The aim of this study was to determine which groups of nonprofessional soccer athletes, injury types, and injury situations caused high injury costs. A cross-sectional, retrospective telephone survey was carried out with a random sample of persons who had sustained a soccer injury between July 2013 and June 2014 and who had reported this accident to the Swiss National Accident Insurance Fund (Suva). One year after the corresponding accident, every injury was linked to its costs and to the answers obtained in the interview about injury setting, injury characteristics, and injury causes. Finally, the costs of 702 injuries were analyzed. The average cost of an injury in nonprofessional soccer amounted to €4030 (bias-corrected and accelerated 95% confidence interval (BCa 95%CI): 3427-4719). Persons aged 30 years and older experienced 35% of soccer injuries but accounted for 49% of all costs. A total of 58% of all costs were the result of injuries that occurred during amateur games. In particular, game injuries sustained by players in separate leagues for players aged 30+/40+ years led to high average costs of €8190 (BCa 95%CI: 5036-11,645). Knee injuries accounted for 25% of all injuries and were responsible for 53% of all costs. Although contact and foul play did not lead to above-average costs, twisting or turning situations were highly cost relevant, leading to an average sum of €7710 (BCa 95%CI: 5376-10,466) per injury. Nonprofessional soccer players aged 30 years and older and particularly players in 30+/40+ leagues had above-average injury costs. Furthermore, the prevention of knee injuries, noncontact and nonfoul play injuries, and injuries caused by twisting and turning should be of highest priority in decreasing health care costs.


#4 Physical and Physiological Responses of U-14, U-16, and U-18 Soccer Players on Different Small-Sided Games
Reference: Sports (Basel). 2020 May 18;8(5):E66.
doi: 10.3390/sports8050066.
Authors: Jorge López-Fernández, Javier Sánchez-Sánchez, Jorge García-Unanue, Enrique Hernando, Leonor Gallardo
Download link: https://www.mdpi.com/2075-4663/8/5/66/pdf
Summary: As most existing studies in youth academies are focused on top players, the objective of this research is to analyze the physical and physiological demands of various small-sided games (SSGs) on different age categories within a sub-elite soccer academy. We evaluated 63 young players from a Spanish sub-elite academy (under 14 = 21; under 16 = 21; under 18 = 21). Players performed four different small-side games focused on possession game (3-a-side; 4-a-side; 5-a-side; 6-a-side). The global indicators of performance and high-intensity actions were recorded through global positioning systems, whereas the heart rate responses were measured using heart rate monitors. Results: Under 16 ran a greater distance at high-intensity velocity than under 14 in the small side games 3v3 and 6v6. Furthermore, under 16 also ran a greater distance at high-intensity velocity than under 18 in the small side game 3v3 (p < 0.01). Under 14 showed greater acceleration at the highest intensity (> 2.75 m/s2) than the other age groups, under 16 and U18 (p < 0.01; ES (effect size) > 1). According to the physiological load, SSG 3v3 presented lower outcomes in Zone 6 (> 95% HRmax) than the small side game 4v4 and the small side game 5v5, in both under 14 and under 16. The workload of SSGs varies depending on the number of players, but also depending on the players' ages. Therefore, when designing the SSGs it is important to consider both the players' ages and the workload that want to be achieved.


#5 The Intermittent Nature of Player Physical Output in Professional Football Matches: An Analysis of Sequences of Peak Intensity and Associated Fatigue Responses
Reference: Eur J Sport Sci. 2020 May 28;1-21. doi: 10.1080/17461391.2020.1776400. Online ahead of print.
Authors: Jan Schimpchen, Sudarshan Gopaladesikan, Tim Meyer
Summary: Professional footballers experience transient periods of in-game fatigue which might affect match outcomes. Further information regarding the degree of fatigue elicited by periods of peak physical intensity across different movement metrics is needed to allow for a more informed design of targeted training interventions. To that end, the purpose of this study was to identify sequences of player peak physical output in-game for three different rolling time windows (1-, 5-, 10-minutes) across three movement categories (total distance, high-intensity distance, average acceleration/deceleration) for 29 players during a full season of professional football matches. Physical performance was also assessed for the 5-minutes after peak intensity to identify possible signs of acute fatigue, while goal differential and match time were registered as contextual variables to analyze whether peak physical output fluctuations were game-state dependent. Total distance and average acceleration/deceleration were reduced by 11-18% in the first minute after peak intensity but returned to match average within the third minute. High-intensity distance remained reduced by 64-89% from the first minute after peak intensity to 6-31% at the fifth minute after. Both contextual factors had an influence on players' ability to perform at peak intensity, but only when considering total distance and average acceleration/deceleration. In contrast, high-intensity distance peak performance remained unaffected by contextual factors. These findings indicate that player in-game fatigue is most pronounced after periods of peak high-intensity running, highlighting the need for targeted training interventions to minimize subsequent reductions in players' physical output capabilities.


#6 Genetic Association Research in Football: A Systematic Review
Reference: Eur J Sport Sci. 2020 May 28;1-52. doi: 10.1080/17461391.2020.1776401. Online ahead of print.
Authors: Alexander B T McAuley, David C Hughes, Loukia G Tsaprouni, Ian Varley, Bruce Suraci, Thomas R Roos, Adam J Herbert, Adam L Kelly 
Summary: Genetic variation is responsible for a large amount of the inter-individual performance disparities seen in sport. As such, in the last ten years genetic association studies have become more common; with one of the most frequently researched sports being football. However, the progress and methodological rigor of genetic association research in football is yet to be evaluated. Therefore, the aim of this paper was to identify and evaluate all genetic association studies involving football players and outline where and how future research should be directed. Firstly, a systematic search was conducted in the Pubmed and SPORTDiscus databases, which identified 80 eligible studies. Progression analysis revealed that 103 distinct genes have been investigated across multiple disciplines; however, research has predominately focused on the association of the ACTN3 or ACE gene. Furthermore, 55% of the total studies have been published within the last four years; showcasing that genetic association research in football is increasing at a substantial rate. However, there are several methodological inconsistencies which hinder research implications, such as; inadequate description or omission of ethnicity and on-field positions. Furthermore, there is a limited amount of research on several key areas crucial to footballing performance, in particular; psychological related traits. Moving forward, improved research designs, larger sample sizes, and the utilisation of genome-wide and polygenic profiling approaches are recommended. Finally, we introduce the Football Gene Project, which aims to address several of these limitations and ultimately facilitate greater individualised athlete development within football.


#7 Erythrasma in Athletes and Football Players
Reference: Wien Med Wochenschr. 2020 May 26. doi: 10.1007/s10354-020-00753-2. Online ahead of print.
Authors: Lilia Zisova, Valentin Valchev, Georgi Kasabov
Summary: Erythrasma is a superficial skin infection that presents with red-brown, flaky macules. It is caused by the Gram-positive bacteria Corynebacterium minutissimum. The purpose of our study is to investigate the prevalence and incidence of erythrasma in active sportsmen, i.e., athletes and football players, comparing the results with the incidence of the disease in the general population. A total of 140 sportsmen, 110 male athletes and 30 football players, were examined by clinical examination, microscopic examination (Gram staining), and Wood's lamp examination. Erythrasma was diagnosed in 39% (43) of the athletes and in 40% (12) of the football players studied. Inguinal folds were found to be most commonly affected. The disease was often localized to more than one area. This erythrasma study conducted in Bulgaria is the first in active athletes. The worldwide prevalence of erythrasma in the general population varies from 4 to 15%. It was found that the incidence of erythrasma is high in men actively involved in sports. The results obtained are explained by the presence of many factors predisposing for the development of this disease in the athletes.


#8 Epidemiologic Assessment of Concussions in an NCAA Division I Women's Soccer Team
Reference: Orthop J Sports Med. 2020 May 15;8(5):2325967120921746. doi: 10.1177/2325967120921746. eCollection 2020 May.
Authors: Alexander E Weber, Nicholas A Trasolini, Ioanna K Bolia, Santano Rosario, John P Prodromo, Catherine Hill, Russ Romano, Charles Y Liu, James E Tibone, Seth C Gamradt
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7232119/pdf/10.1177_2325967120921746.pdf
Summary: Among collegiate sports, ice hockey and wrestling have been reported to have the highest rates of concussion injury. Recent literature has shown that among all sports, female soccer players had the highest rate of concussion injury at the high school level. Sport-specific analysis will increase our knowledge of epidemiologic characteristics of this serious injury in young soccer players, where "heading" is commonly involved during participation. Our hypothesis was that heading during soccer will be associated with increased frequency of concussion injury in collegiate female players compared with other mechanisms of injury, and concussion injury mechanism and rates will differ by setting of injury (practice or match) and player position. This was a retrospective review and epidemiologic analysis of all concussions documented from a single National Collegiate Athletic Association (NCAA) Division I female collegiate soccer team between 2004 and 2017. A total of 381 participants were reviewed, and concussion injury mechanism, setting (practice or match), player position, and number of games and practices missed due to injury were analyzed. Overall, 25 concussions in 22 players from the 2004 to 2017 seasons were identified, for an annual rate of 1.79 concussions per year. Collisions (36%) followed by headers (20%) were the most common mechanisms. Forwards sustained the most concussions (32%). Injuries were more common in games (56%) than practice (40%). Of note, the most common cause of concussion during practice was headers (40%). Of the concussions documented, 20 (91%) were the player's first concussion. On average, each concussion resulted in a player missing 3.96 games and 12.46 practices. Our results demonstrate that concussion rates in female NCAA soccer players vary by position and occur with different frequencies and mechanisms in practice and games. Interventions for concussion avoidance should aim to limit exposure to high-risk activity, including player-to-player contact in games and headers in practice. Although gameplay and collisions can be unpredictable and difficult to control, practice settings can be modified in an attempt to decrease risk.


#9 Deliberate Soccer Practice Modulates Attentional Functioning in Children
Reference: Front Psychol. 2020 May 12;11:761. doi: 10.3389/fpsyg.2020.00761. eCollection 2020.
Authors: Consuelo Moratal, Juan Lupiáñez, Rafael Ballester, Florentino Huertas
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7235161/pdf/fpsyg-11-00761.pdf
Summary: The main purpose of this study was to explore the association between the regular practice of open-skill sports (i.e., soccer) and executive control, along with other attentional functions (i.e., alerting and orienting) during preadolescence. The study was conducted on 131 participants (70 non-athletes and 61 soccer players). To measure cognitive performance, participants performed the Attentional Network Test-Interactions (ANT-I) task. Compared to non-athletes, soccer players showed overall faster responses and better executive control (e.g., reduced interference from distractors). Overall, our results provide new empirical evidence supporting the positive association between regular sports practice and cognitive performance, and more specifically executive functions. However, is important to note that the relationship between regular sport practice and cognition is complex and multifactorial. Our findings can be partly explained by the "cardiovascular fitness hypothesis" and the "cognitive component skills approach," suggesting that an externally paced sport environment with high physical fitness and perceptual-cognitive demands may be an appropriate setting to optimize the development of cognitive functioning during early adolescence.


#10 The Importance of Reactive Agility Tests in Differentiating Adolescent Soccer Players
Reference: Int J Environ Res Public Health. 2020 May 28;17(11):E3839. doi: 10.3390/ijerph17113839.
Authors: Nebojša Trajković, Goran Sporiš, Tomislav Krističević, Dejan M Madić, Špela Bogataj
Download link: https://www.mdpi.com/1660-4601/17/11/3839/pdf
Summary: The ability to differentiate the elite from nonelite athletes is not clearly defined. We investigated level differences in speed, change of direction speed (CODS), and reactive agility in a group of trained adolescent soccer players. A total of 75 adolescent male soccer players (aged 14-19 years) were recruited. The players were grouped based on the level of play to elite, sub-elite, and amateur players. Players were tested for 5-, 10- and 20-m sprints, CODS, and reactive agility tests (RAT). Elite players had faster reaction movement time during RAT with live opponent stimuli (p ≤ 0.01) compared to sub-elite and amateur players. Moreover, elite players showed a faster time during light stimuli (p ≤ 0.01) but only compared to amateur players. The times for 5-m and 10-m sprint groups did not differ (p > 0.05). The results demonstrated that the skilled players (elite and sub-elite) performed better in reactive agility tests, speed, and COD speed compared to amateur players. Additionally, we can conclude that total and reaction time in the agility test with live opponent stimuli can be a significant factor that differentiates between adolescent soccer players considering their level.


#11 Effects of Knowing the Task's Duration on Soccer Players' Positioning and Pacing Behaviour During Small-Sided Games
Reference: Int J Environ Res Public Health. 2020 May 28;17(11):E3843. doi: 10.3390/ijerph17113843.
Authors: Ricardo Ferraz, Bruno Gonçalves, Diogo Coutinho, Rafael Oliveira, Bruno Travassos, Jaime Sampaio, Mário C Marques
Download link: https://www.mdpi.com/1660-4601/17/11/3843/pdf
Summary: The study aimed to identify how the manipulation of knowledge regarding a training task duration constrains the pacing and tactical behaviour of soccer players when playing small-sided games (SSG). Twenty professional and experienced soccer players participated in a cross-sectional field study using three conditions: not informed on the duration of the SSG, which ended after 20 min (Unknown Condition); briefed about playing the SSG for 10 min, but after they completed the 10-min game, they were requested to complete another 10 min (Partial Condition) and informed before that they would play for 20 min (Known Condition). A global positioning system was used to measure the total distance covered and distances of different exercise training zones (walking to sprinting) and to access the dynamic players positioning through the distance from each player to all the teammates and opponents. Additionally, approximate entropy was measured to identify the regularity pattern of each gathered individual variable. The results indicate that the first 10 min of each scenario presented a higher physical impact independently of the initial information. During this time, the tactical behaviour also revealed higher variability. An increase in the distance of the teammates during the second period of 10-min for the Known scenario was also found, which may result from a lower pacing strategy. This study showed that the prior knowledge of the task duration led to different physical and tactical behaviours of the players. Furthermore, the relationship between the physical impact and the regularity of team game patterns should be well analysed by the coach, because the physical impact may be harmful to the development of the collective organization of the team.

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In-season Eccentric-Overload Training in Elite Footballers

Effects on body composition, strength and sprint performance.

Fri

24

Jul

2020

Preventive Effect of the Nordic Hamstring Exercise on Hamstring Injuries in Amateur Soccer Players

The study investigated the preventive effect of the nordic hamstring exercise on the incidence in male amateur footballers.

Mon

20

Jul

2020

Latest research in football - week 23 - 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 Endurance Abilities in Elite Female Soccer Players
Reference: Int J Sports Physiol Perform, 2020 May 29;1-7. doi: 10.1123/ijspp.2019-0526. Online ahead of print.
Authors: Carlo Castagna, Stefano D'Ottavio, Paolo Roberto Gabrielli, Susana Póvoas
Summary: The aim was to profile sprint endurance performance of elite-level female soccer players. Twenty-five female national-team soccer players (age 25.1 [2.7] y, body mass 59.6 [3.6] kg, height 168.5 [4.1] cm) were tested for sprint endurance, performing 5 maximal sprints, interspersed with 30 seconds of active recovery (5 × 30 m) and a 30-second all-out shuttle run in a soccer pitch. The Yo-Yo Intermittent Recovery Test level 1 (YYIR1) evaluated intermittent high-intensity endurance under the same field-testing conditions. Maximal anaerobic capacity was assessed while participants performed three 10-second all-out bouts separated by 20 seconds of passive recovery (3 × 10 s) on a nonmotorized treadmill. Huge interplayer variability was observed for sprint decrements in 3 × 10 seconds (coefficient of variation = 37%) and 5 × 30 m (coefficient of variation = 62%). The 3 × 10 performance was largely associated with 5 × 30-m mean and best time and very largely with 30 seconds. A very large and nearly perfect correlation was observed between 30 seconds and 5 × 30 mMean (r = -.86) and 5 × 30 mBest (r = -.92), respectively. The YYIR1 was moderately to largely associated with 5 × 30-m variables and 30 seconds, respectively. A nearly perfect association was observed between 5 × 30 mBest and 5 × 30 mMean (r = .97). Elite female soccer players' sprint endurance variables are characterized by remarkable variability. Associations between sprint endurance variables suggest physiological interdependence and a likelihood of a general ability in sustaining sprinting in this population.


#2 The Value of Preseason Screening for Injury Prediction: The Development and Internal Validation of a Multivariable Prognostic Model to Predict Indirect Muscle Injury Risk in Elite Football (Soccer) Players
Reference: Sports Med Open, 2020 May 27;6(1):22. doi: 10.1186/s40798-020-00249-8.
Authors: Tom Hughes , Richard D Riley, Michael J Callaghan, Jamie C Sergeant
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-020-00249-8
Summary: In elite football (soccer), periodic health examination (PHE) could provide prognostic factors to predict injury risk. The aim was to develop and internally validate a prognostic model to predict individualised indirect (non-contact) muscle injury (IMI) risk during a season in elite footballers, only using PHE-derived candidate prognostic factors. Routinely collected preseason PHE and injury data were used from 152 players over 5 seasons (1st July 2013 to 19th May 2018). Ten candidate prognostic factors (12 parameters) were included in model development. Multiple imputation was used to handle missing values. The outcome was any time-loss, index indirect muscle injury (I-IMI) affecting the lower extremity. A full logistic regression model was fitted, and a parsimonious model developed using backward-selection to remove factors that exceeded a threshold that was equivalent to Akaike's Information Criterion (alpha 0.157). Predictive performance was assessed through calibration, discrimination and decision-curve analysis, averaged across all imputed datasets. The model was internally validated using bootstrapping and adjusted for overfitting. During 317 participant-seasons, 138 I-IMIs were recorded. The parsimonious model included only age and frequency of previous IMIs; apparent calibration was perfect, but discrimination was modest (C-index = 0.641, 95% confidence interval (CI) = 0.580 to 0.703), with clinical utility evident between risk thresholds of 37-71%. After validation and overfitting adjustment, performance deteriorated (C-index = 0.589 (95% CI = 0.528 to 0.651); calibration-in-the-large = - 0.009 (95% CI = - 0.239 to 0.239); calibration slope = 0.718 (95% CI = 0.275 to 1.161)). The selected PHE data were insufficient prognostic factors from which to develop a useful model for predicting IMI risk in elite footballers. Further research should prioritise identifying novel prognostic factors to improve future risk prediction models in this field.


#3 Preseason Assessment of Anaerobic Performance in Elite Soccer Players: Comparison of Isokinetic and Functional Tests
Reference: Sports Biomech, 2020 May 28;1-15. doi: 10.1080/14763141.2020.1750681.
Authors: François Delvaux, Cédric Schwartz, Carlos Rodriguez, Bénédicte Forthomme, Jean-François Kaux, Jean-Louis Croisier
Summary: Isokinetic and functional jump tests are frequently performed for assessing the physical qualities of soccer players during preseason. The purpose of this investigation was to explore, in an elite soccer players population, the relationships between isokinetic strength and functional jump performances. Thirty-eight professional soccer players were evaluated as follows: isokinetic knee assessment in concentric (CON) mode (60, 240°/s) for quadriceps and hamstrings, and in eccentric (ECC) mode for the hamstrings only (30°/s); one-leg hop tests for distance (single hop (SH), triple hop (TH) and triple crossover hop (TCH)); one-leg vertical jump tests (countermovement jump, drop jump). Players with a low bodyweight normalised (BWN) quadriceps (Q) strength (<2.71 Nm/kg) performed, for a majority of the measured variables, significantly reduced jump performances compared to the players with high BWN Q strength (>3.14 Nm/kg; p < 0.05). Greater bilateral differences between uninjured and past injured lower limbs were found with isokinetics (Q CON 60°/s (mean bilateral difference (MBD): 10.3%; p < 0.01), Q CON 240°/s (MBD: 9.9%; p < 0.05), H ECC 30°/s (MBD: 16.1%; p < 0.001) than with functional tests (MBD: 2 to 9%; p > 0.05. In conclusion, due to their complementary role and implications for performance, functional and isokinetic tests should be associated in a preseason soccer players assessment.


#4 Eccentric-Overload Production During the Flywheel Squat Exercise in Young Soccer Players: Implications for Injury Prevention
Reference: Int J Environ Res Public Health. 2020 May 22;17(10):E3671. doi: 10.3390/ijerph17103671.
Authors: Javier Raya-González, Daniel Castillo, Marta Domínguez-Díez, José Luis Hernández-Davó
Download link: https://www.mdpi.com/1660-4601/17/10/3671/pdf
Summary: This study aimed to evaluate the differences in power production between movement phases (i.e., concentric and eccentric) during the execution of resistance exercises with a flywheel device, differentiating between execution regimes (i.e., bilateral, unilateral dominant leg and unilateral non-dominant leg). Twenty young elite soccer players (U-17) performed two sets of six repetitions of the bilateral half-squat (inertia 0.025 kg·m-2) and the lateral-squat exercise (inertia 0.010 kg·m-2) on a flywheel device. During the testing sessions, mean and peak power in concentric (MPcon) and eccentric (MPecc) phases were recorded. The non-dominant leg showed higher values in all power variables measured, although substantial differences were only found in MPecc (ES = 0.40, likely) and PPcon (ES = 0.36, possibly). On the other hand, for both exercises, MPcon was higher than MPecc (ES = -0.57 to -0.31, possibly/likely greater), while only PPecc was higher than PPcon in the dominant lateral-squat (ES = 0.44, likely). These findings suggest that young soccer players have difficulty in reaching eccentric-overload during flywheel exercises, achieving it only with the dominant leg. Therefore, coaches should propose precise preventive programs based on flywheel devices, attending to the specific characteristics of each limb, as well as managing other variables to elicit eccentric-overload.


#5 Workload Monitoring in Top-level Soccer Players During Congested Fixture Periods
Reference: Int J Sports Med. 2020 May 26. doi: 10.1055/a-1171-1865. Online ahead of print.
Authors: Antonio Gualtieri, Ermanno Rampinini, Roberto Sassi, Marco Beato
Summary: This study assessed the internal and external workload of starters and non-starters in a professional top-level soccer team during a congested fixture period. Twenty Serie A soccer players were monitored in this study during two mesocycles of 21 days each. Starters and non-starters were divided based on the match time played in each mesocycle. The following metrics were recorded: exposure time, total distance, relative total distance, high-speed running distance over 20 km·h-1, very high-speed running distance over 25 km·h-1, individual very high-speed distance over 80% of maximum peak speed, and rating of perceived exertion. Differences between starters and non-starters were found for: exposure time (effect size=large to very large), rating of perceived exertion (large to very large), total distance (large to very large), and individual very high-speed distance over 80% of maximum peak speed (moderate to large). Furthermore, differences for relative total distance, high-speed running distance over 20 km·h-1 and very high-speed running distance over 25 km·h-1 were small to moderate, but not significant. This study reports that during congested fixture periods, starters had higher exposure time, rating of perceived exertion, total distance, and individual very high-speed distance over 80% of maximum peak speed than non-starters.


#6 Role of Basal Hormones on Sweat Rate and Sweat Na+ Loss in Elite Women Soccer Players
Reference: Int J Sports Med. 2020 May 26. doi: 10.1055/a-1165-2072. Online ahead of print.
Authors: Mauricio Castro-Sepulveda, Jorge Cancino, Sebastian Jannas-Vela, Francisca Jesam, Casandra Lobos, Juan Del Coso, Hermann Zbinden-Foncea
Summary: We aimed to determine whether basal concentrations of testosterone, cortisol or the ratio testosterone/cortisol were related to sweat Na+ loss, sweat Na+ concentration ([Na+]) and sweat rate during exercise. Twenty-two female elite soccer players participated in the study. Testosterone and cortisol were measured in blood samples before exercise. Sweat samples were collected during a training session (~20°C, ~30% RH, and ~0.55 m/s of wind speed) to measure sweat [Na+]. Sweat rate was determined by considering the difference between post-and pre-body weight, along with the amount of liquid consumed. During exercise, sweat Na+ loss (0.33[0.19] g/h) and sweat rate (0.49[0.20] L/h) were related to basal testosterone concentration (1.4[0.4] pg/mL) (r=0.54; r=0.55, respectively; p<0.05), but not with basal cortisol concentration (119.2[24.2] ng/mL) nor testosterone/cortisol ratio (0.012[0.003]) (p>0.05). However, when Na+ loss was adjusted to sweat rate, no association was found between Na+ loss and testosterone (p>0.05). In addition, no differences were found between players with high vs. low Na+ loss adjusted to sweat loss in menstrual phase or intensity during exercise (p>0.05). In conclusion, these results suggest that in these specific environmental conditions, basal levels of testosterone might increase sweat rate and therefore, the amount of Na+ lost during exercise in elite women soccer players.


#7 Comparison of Lipid and Lipoprotein Values of Wrestlers and Soccer Players
Reference: Turk J Pharm Sci. 2020 Apr;17(2):172-176. doi: 10.4274/tjps.galenos.2018.66934. Epub 2020 Apr 24.
Authors: Semra Çetin, Cuma Ece, Meltem Paksoy, Hasan Nedim Çetin
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7227909/pdf/TJPS-17-172.pdf
Summary: The aim of this study was to compare the lipid and lipoprotein values of wrestlers and soccer players. A total of 35 subjects, 17 male wrestlers who are sporting for 11.5 years and 18 male soccer player students who are sporting for 11.9 years, participated in this study. Triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were determined by Hitachi 717 autoanalyzer. To determine the differences between the wrestlers and the soccer players the independent t-test was performed. There was a significant difference in body weight and body mass index between the wrestlers and the soccer players (p<0.05). Moreover, there were significant differences in plasma TC, LDL-C, and HDL-C values between the wrestlers and soccer players (all, p<0.05). However, there was no significant difference in plasma TG values between the wrestlers and the soccer players (p>0.05). On the other hand, TC and LDL-C values of the wrestlers were significantly higher than soccer players (p<0.05). The HDL-C values of the soccer players were significantly higher the wrestlers (p<0.05). The ratio TC/HDL-C of the wrestlers was markedly higher than soccer players (p<0.05). TC, TG, HDL-C, and LDL-C values of the soccer players were in better ranges than wrestlers. This situation can be caused by the effect of different sports branches as well as the training differences. The lipid and lipoprotein values of the wrestlers and soccer players showed that they do not carry a risk of cardiovascular disease. In addition, it can be recommended that wrestlers should do jogging or aerobic training in their daily regular training.


#8 Effects of Maturation on Knee Biomechanics During Cutting and Landing in Young Female Soccer Players
Reference: PLoS One. 2020 May 26;15(5):e0233701. doi: 10.1371/journal.pone.0233701. eCollection 2020.
Authors: Audrey E Westbrook, Jeffrey B Taylor, Anh-Dung Nguyen, Mark V Paterno, Kevin R Ford 
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0233701&type=printable
Summary: Young female soccer players are at high risk of anterior cruciate ligament injury due to the fast-paced nature of the sport and surplus of unplanned movements during play. Neuromuscular training programs that aim to reduce this injury by targeting the associated biomechanical movements are a potential solution. While previous studies have examined the lack of dynamic knee control during landing, there are few that outline the role that maturation can play during unanticipated cutting. Therefore, the purpose of this study was to determine if young female soccer players across multiple phases of maturation exhibited the before seen differences in knee control during a drop landing as well as an unanticipated cutting task. 139 female soccer players volunteered to participate in this study and were classified in three maturational groups based on percent adult stature: prepubertal (PRE), pubertal (PUB), and post-pubertal (POST). Each group performed a drop vertical jump (DVJ) and an unanticipated cutting task (CUT). Standard 3D motion capture techniques were used to determine peak knee flexion/abduction angles and moments during each task. Within tasks, POST exhibited significantly greater peak abduction angles and moments compared to PUB/PRE. While each maturational group exhibited greater peak knee abduction angles during the DVJ compared to the CUT, peak knee abduction moments during the CUT were greater compared to the DVJ. Participants within each maturational group exhibited greater knee flexion during the DVJ compared to the CUT, however there were no differences identified between groups. During both tasks, POST/PUB exhibited greater peak knee flexion moments compared to PRE, as well as POST compared to PUB. Overall, each group exhibited significantly greater peak knee flexion moments during the CUT compared to the DVJ. These observed differences indicate the need for neuromuscular training programs that target both jumping and cutting techniques to reduce ACL injuries.


#9 Effects of Different Plyometric Training Frequencies on Measures of Athletic Performance in Prepuberal Male Soccer Players
Reference: J Strength Cond Res. 2020 Jun;34(6):1609-1617. doi: 10.1519/JSC.0000000000002486.
Authors: Raja Bouguezzi, Helmi Chaabene, Yassine Negra, Rodrigo Ramirez-Campillo, Zied Jlalia, Bessem Mkaouer, Younés Hachana
Summary: This study aimed to compare the effects of 1 vs. 2 sessions of equal-weekly volume plyometric training (PT) across 8 weeks on measures of athletic performance (i.e., sprint time, change of direction [CoD], jumping ability, and muscle strength) in prepuberal male soccer players. Thirty participants were randomly assigned either to 1 session PT group (1SPT [n = 15]) or 2 sessions PT group (2SPT [n = 15]). Plyometric training was integrated into their regular soccer training routine. Pretraining and posttraining tests for the assessment of sprint time (e.g., 5, 10, 20, and 30-m), CoD (e.g., T-test and modified Illinois change of direction test [MICODT]), jumping ability (e.g., standing long jump [SLJ], countermovement jump [CMJ], and squat jump [SJ]), muscle strength (reactive strength index [RSI]), and kicking distance were conducted. Results showed a main effect of time for 5-m sprint-time performance (F(1,56) = 4.00, effect size [ES] = 0.53 [medium], p = 0.05), T-test (F(1,56) = 23.19, ES = 1.28 [large], p < 0.001), MICODT (F(1,56) = 5.72, ES = 0.94 [large], p = 0.02), SLJ (F(1,56) = 16.63, ES = 1.09 [large], p < 0.001), CMJ (F(1,56) = 15.43, ES = 1.04 [large], p < 0.001), SJ (F(1,56) = 20.27, ES = 1.20 [large], p < 0.001), RSI (F(1,56) = 26.26, ES = 1.36 [large], p < 0.001), and kicking distance (F(1,56) = 47.19, ES = 1.83 [large], p < 0.001). There were no training group × time interactions in all the measured outcomes. In conclusion, when an equated moderate volume of jumps is performed, higher PT frequency across 8 weeks has no extra effects on prepuberal male soccer players' measures of athletic performance. The present findings may help optimizing PT interventions dedicated to prepuberal male soccer players.


#10 GreenSea: Visual Soccer Analysis Using Broad Learning System
Reference: IEEE Trans Cybern. 2020 May 21;PP.  doi: 10.1109/TCYB.2020.2988792. Online ahead of print.
Authors: Bin Sheng, Ping Li, Yuhan Zhang, Lijuan Mao, C L Philip Chen
Summary: Modern soccer increasingly places trust in visual analysis and statistics rather than only relying on the human experience. However, soccer is an extraordinarily complex game that no widely accepted quantitative analysis methods exist. The statistics collection and visualization are time consuming which result in numerous adjustments. To tackle this issue, we developed GreenSea, a visual-based assessment system designed for soccer game analysis, tactics, and training. The system uses a broad learning system (BLS) to train the model in order to avoid the time-consuming issue that traditional deep learning may suffer. Users are able to apply multiple views of a soccer game, and visual summarization of essential statistics using advanced visualization and animation that are available. A marking system trained by BLS is designed to perform quantitative analysis. A novel recurrent discriminative BLS (RDBLS) is proposed to carry out long-term tracking. In our RDBLS, the structure is adjusted to have better performance on the binary classification problem of the discriminative model. Several experiments are carried out to verify that our proposed RDBLS model can outperform the standard BLS and other methods. Two studies were conducted to verify the effectiveness of our GreenSea. The first study was on how GreenSea assists a youth training coach to assess each trainee's performance for selecting most potential players. The second study was on how GreenSea was used to help the U20 Shanghai soccer team coaching staff analyze games and make tactics during the 13th National Games. Our studies have shown the usability of GreenSea and the values of our system to both amateur and expert users.


#11 How Manipulation of Playing Area Dimensions in Ball Possession Games Constrains Physical Effort and Technical Actions in under-11, under-15 and under-23 Soccer Players
Referernce: Res Sports Med. 2020 May 26;1-15. doi: 10.1080/15438627.2020.1770760.

Authors: Nuno André Nunes, Bruno Gonçalves, Keith Davids, Pedro Esteves, Bruno Travassos
Summary: The aim of this study was to investigate the effects of playing area manipulation (20 × 15 m, 25 × 20 m and 30 × 25 m) on external workloads (total distance covered, distance covered while walking, running and sprinting, number of sprints, maximum sprint speed), internal load perceptions (rating of perceived exertion) and technical actions of passing (number of passes with dominant and non-dominant foot, and maximum passing speed) during 4v4 ball possession small-sided and conditioned games in under-11, under-15 and under-23 soccer players. Results showed higher values in the large playing area for under-11 in the distance covered in different speed zones, sprint number and RPE (all p <.001) for under-15 in sprints number (p <.01) and maximum sprint speed (p =.02), and for under-23 in both RPE and sprint numbers (p <.01). Although no significant differences were found on technical actions, it was still possible to notice some effects through pairwise comparison. High-intensity running was promoted on larger playing areas, where under-11 s were also able to perform more technical actions of passing. Opposite, under-23s were able to perform more passing on smaller playing areas, where under-11 s perceived the exercise more intense. The impact of different playing areas was reduced for the under-15.


#12 Transformational Parenting and Coaching on Mental Toughness and Physical Performance in Adolescent Soccer Players: The Moderating Effect of Athlete Age
Reference: Eur J Sport Sci. 2020 May 25;1-10. doi: 10.1080/17461391.2020.1765027.
Authors: Ross M Murray, James H Dugdale, Christine M Habeeb, Calum A Arthur 
Summary: Both parent and coach leadership behaviours are instrumental to adolescent athlete development. Researchers, however, are yet to examine parent and coach leadership influences simultaneously, and at different stages of adolescents' psychological and physical development. Therefore, the purpose of this study was to understand if the effects of transformational parenting, and transformational coaching on mental toughness and performance varied at different ages during adolescence. Early adolescent (ages 10-14) and late adolescent (ages 15-18) soccer players (n = 334) completed questionnaires assessing their perceptions of their mother's, father's, and coach's transformational leadership, as well as a questionnaire assessing mental toughness. Participants also completed a comprehensive battery of physical fitness tests relevant to soccer. Results indicated that transformational fathering was more strongly associated with levels of mental toughness for early adolescent athletes than it was for later adolescent athletes. Results also indicated that transformational coaching was more strongly associated with physical performance for later adolescent athletes than it was for early adolescents. Overall, these results can inform development models and provide support for future longitudinal studies to assess the impact of parent and coach transformational leadership across different stages of athlete development.

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2020

Association of Physical and Technical Activities With Partial Match Status in a Soccer Professional Team

The purpose was to investigate the association between physical and technical activities and match status.

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2020

Imagery Effects on the Performance of Skilled and Novice Football Players

The purpose was to investigate the effect of an imagery training programme on the performance of a soccer task by skilled and novice players.

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2020

Latest research in football - week 22 - 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 Determining the Reliability and Usability of Change of Direction Speed Tests in Adolescent Female Soccer Players: A Systematic Review
Reference: J Sports Med Phys Fitness. 2020 May;60(5):720-732. doi: 10.23736/S0022-4707.20.10178-6.
Authors: Elena Pardos-Mainer , José A Casajús , Cristina Julián , Chris Bishop, Oliver Gonzalo-Skok 
Summary: This review aimed 1) to describe the most common tests used for assessing change of direction (COD) performance; 2) to detail the reliability of current COD tests; 3) to provide an overview of current intervention strategies used to improve COD performance in adolescent female soccer players. A computerized search was conducted in the PubMed, Cochrane Plus and Web of Science (from 1995 to January 2020) for English and Spanish language and peer-reviewed investigations. A total of 221 studies were identified, with only 16 meeting the specific search criteria. The main findings were that eleven different tests have been used to assess COD performance with intraclass correlation coefficient and coefficient of variation values between 0.72-0.99 and 1-10.6%, respectively. The number of CODs performed during each test ranged from 1 to 9 within a range of 45º to 180º and with a duration <5 s, 5-9 s and >10 s. Findings indicate that the reliability of the COD tests seems to depend on: the equipment used, the surface tested on and the technical level of the soccer player. These results should be interpreted with caution as they may be influenced by the period of growth and maturation, the playing position of the player and the period of the soccer season. Finally, strength and power drills could be considered as appropriate to improve COD performance.


#2 Game-based vs Mulitaleral Approach: Effects of a 12-week Program on Motor Skill Acquisition and Physical Fitness Development in Soccer School Children
Reference: J Sports Med Phys Fitness. 2020 May 20.  doi: 10.23736/S0022-4707.20.10726-6. Online ahead of print.
Authors: Federico Abate Daga, Luca Baseggio, Massimiliano Gollin, Luca Beratto
Summary: The purpose of this study was to investigate the effects of a 12-week- game-based training versus a traditional multilateral approach on motor skills acquisition and physical fitness, in a group of U9 children playing soccer. 40 Children 9 years old or younger (U9) recruited from a local soccer school were assigned in a 1:1 ratio to a game-based training program (GB) or a multilateral training (MA) approach. The training programs lasted 12 weeks, and players were tested at baseline and at the end of the program (12-week follow-up). The outcomes were: standing long jump test, shuttle dribble test, 10x5 shuttle run test and Mini-Cooper test. Within-group comparisons showed statistically-significant improvements in both of the groups: standing long lump (p < 0.0001), shuttle dribble test (p < 0.0001), shuttle run test (p < 0.0001) and Mini-Cooper test (p < 0.0001). Furthermore, the MA group showed better performance in the shuttle run test after 12 weeks of training compared to the GB group (p= 0.0002; +8%).  A multilateral approach promotes physical development in U9 soccer players without affecting learning of soccer skills. Therefore, a multilateral approach should be included in soccer training programs to ensure an optimal development in young soccer players.


#3 Effects of in Season Multi-Directional Plyometric Training on Vertical Jump Performance, Change of Direction Speed and Dynamic Postural Control in U-21 Soccer Players
Reference: Front Physiol. 2020 Apr 30;11:374.  doi: 10.3389/fphys.2020.00374. eCollection 2020.
Authors: Mohamed Chedly Jlid, Jérémy Coquart, Nicola Maffulli, Thierry Paillard, Gian Nicola Bisciotti, Karim Chamari
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212831/pdf/fphys-11-00374.pdf
Summary: The aim of the study was to assess the effects of multi-directional plyometric training (MPT) on vertical jump height, change of direction speed (CODS), and dynamic postural control (DPC) of soccer players under 21 year (U-21). Twenty-seven male soccer players were randomly allocated to either an experimental group (EG; n = 14; age: 19.0 ± 0.9 years) or a control group (CG; n = 13; age: 19.0 ± 0.7 years). The EG introduced 6 weeks MPT, 2 days per week into their in-season training, while CG continued training without change. Measurements of vertical jump height, CODS and DPC were completed at the beginning and end of the 6 week MPT. ANOVA demonstrated a significant group × time interaction for SJ (F = 6.03, p = 0.021), CMJ (F = 9.10, p = 0.006), and T-Test (F = 10.46, p = 0.002). The Bonferroni Post Hoc test demonstrated significant increase for the three tests in both group (EG and CG). For SJ (EG: p < 0.001; CG: p < 0.001), CMJ (EG: p < 0.001; CG: p = 0.005) and T-Test (EG: p < 0.001; CG: p = 0.02). For DPC on the dominant leg, there was a significant group × time interaction for four axes [anterior (F = 5.48, p = 0.028), antero-lateral (F = 4.82, p = 0.038), postero-lateral (F = 4.82, p = 0.038), and medial (F = 6.77, p = 0.015)]. The Bonferroni Post Hoc test demonstrated significant increase in EG (p < 0.001), but no significant change in CG in four axes (anterior, antero-lateral, postero-lateral and medial). Furthermore DPC on the non-dominant leg, there was a significant group × time interaction for three axes [lateral (F = 8.09, p = 0.009), postero-lateral (F = 11.92, p = 0.002), and medial (F = 5.84, p = 0.023)]. The Bonferroni Post Hoc test demonstrated significant increase in EG (p < 0.001), but no significant change in CG in three axes (lateral, postero-lateral, and medial). In conclusion, incorporating MPT into the in-season regimen of under 21 soccer players improved performance of various indices related to soccer activity (i.e., CMJ, CODS, 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 soccer players.


#4 A Possible Antioxidant Role for Vitamin D in Soccer Players: A Retrospective Analysis of Psychophysical Stress Markers in a Professional Team
Reference: Int J Environ Res Public Health. 2020 May 16;17(10):E3484. doi: 10.3390/ijerph17103484.
Authors: Davide Ferrari, Giovanni Lombardi, Marta Strollo, Marina Pontillo, Andrea Motta, Massimo Locatelli
Download link: https://www.mdpi.com/1660-4601/17/10/3484/pdf
Summary: The health benefits of physical activity are recognized, however, high levels of exercise may lead to metabolic pathway imbalances that could evolve into pathological conditions like the increased risk of neurological disease observed in professional athletes. We analyzed the plasma/serum levels of 29 athletes from a professional soccer team playing in the Italian first league and tested the levels of psychophysical stress markers (vitamin D, creatine kinase, reactive oxygen species (ROS) and testosterone/cortisol ratio) during a period of 13 months. The testosterone/cortisol ratio was consistent with an appropriate training program. However, most of the athletes showed high levels of creatine kinase and ROS. Despite the large outdoor activity, vitamin D values were often below the sufficiency level and, during the "vitamin D winter", comparable with those of the general population. Interestingly, high vitamin D values seemed to be associated to low levels of ROS. Based on the results of our study we proposed a vitamin D supplementation as a general practice for people who perform high levels of physical exercise. Beside the known effect on calcium and phosphate homeostasis, vitamin D supplementation should mitigate the high reactivity of ROS which might be correlated to higher risk of neurodegenerative diseases observed in professional athletes.


#5 Latarjet Procedures on anterior shoulder instability in professional soccer players
Reference: Acta Ortop Bras. Mar-Apr 2020;28(2):84-87.
doi: 10.1590/1413-785220202802225433.
Authors: Guilherme Augusto Stirma, Ewerton Borges DE Souza Lima, Deginaldo Holanda Chaves, Paulo Santoro Belangero, Carlos Vicente Andreoli, Benno Ejnisman
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224322/pdf/1809-4406-aob-28-02-84.pdf
Summary: Anterior glenohumeral instability is a frequent cause of professional soccer players' removal, reduced performance, and prolonged recovery. Players are subjected to intense physical contact and high performance, thus demanding lower rates of recurrence after surgical correction so they can return to sport quickly. The purpose was to assess professional soccer players treated by the Lartajet technique considering the rate and time of return to sports activities, complications or failures. Analysis held between 2010 and 2018 of professional soccer players diagnosed with anterior shoulder instability operated by the open procedure of Lartajet in our service. The mean return to professional sports was 93.5 days. The mean time of surgery in relation to the first dislocation was 12.4 months. Each athlete had 4.3 shoulder dislocations until the procedure was performed. The rate of recurrence was zero and subluxation was not observed. The Latarjet procedure allowed all professional athletes to return to competitive activities quickly, without dislocations and subluxation, negative seizure and without complications during follow-up.

 
#6 Heart Rate-Index Estimates Aerobic Metabolism in Professional Soccer Players
Reference: J Sci Med Sport. 2020 Apr 27;S1440-2440(19)31624-X.  doi: 10.1016/j.jsams.2020.04.015. Online ahead of print.
Authors: Alessandro L Colosio, Maarten Lievens, Silvia Pogliaghi, Jan G Bourgois, Jan Boone
Summary: This study aimed at proposing a new heart rate (HR) method to track aerobic metabolism in soccer by: (i) validating a recently developed HR index (HRindex) in professional soccer players, (ii) comparing HRindex vs the most common HR parameters and (iii) testing the agreement between measured and estimated VO2 values using HRindex. 184 professional soccer players performed a step incremental running test on a treadmill while VO2 and HR were recorded. HRindex was calculated (actual HR/resting HR) and its relationship with VO2 was compared with the relationships with the metabolism of actual HR, net HR, and % of HR reserve. Finally, HRindex was used to predict VO2=((HRindex·6)-5)·3.5) and measured and estimated VO2 were compared by 2W RM-ANOVA and Bland-Altman analysis. HRindex/VO2 relationship explained 85% of the variability in data, showing a higher performance than actual HR (77%) and similar values to the other parameters. Measured and estimated VO2 were not significantly different ≤14kmh-1, whereas at speeds ≥14kmh-1 measured VO2 was higher than estimated VO2. Finally, measured and estimated VO2 were highly correlated (R2=0.85, p=0.000), and showed no significant bias (bias=-1.03, z=-0.69, precision=3.75mlkgmin-1). We validated the HRindex/VO2 relationship in professional soccer players. HRindex showed better agreement with metabolism than actual HR and similar agreement to the other HR parameters. HRindex allowed to estimate VO2, but at very high-intensity HRindex underestimated VO2. Future studies should test this in real game conditions. HRindex could offer a time-efficient and easy-to-use "field" method to monitor aerobic metabolism in soccer.


#7 Risk Factors in Elite, Adolescent Male Soccer Players: Prospective Study
Reference: Clin Pediatr (Phila). 2020 Jun;59(6):596-605. doi: 10.1177/0009922820916895.
Authors: Dai Sugimoto, Adam J Loiacono, Alexandra Blenis, Jennifer M Morse, Dennis R Borg, William P Meehan 3rd
Summary: The aim was to find risk factors for soccer-related musculoskeletal injuries among elite, adolescent male soccer players. Prior to the season, various physical, clinical, and functional measurements were taken. One season was used as an injury surveillance period. Then, after the season, measures of potential risk factors were compared between (1) those players who sustained musculoskeletal injuries and (2) those who remained injury free. Among 61 players, 37.7% (23/61) sustained soccer-related musculoskeletal injuries. After adjusting for covariates in a logistic regression model, presence of previous hip and low back injury (adjusted odds ratio [aOR] = 8.93, P = .046) and Functional Movement Screen (FMS) scores (aOR = 1.92, P = .022) were independently associated with musculoskeletal injures. Elite, adolescent male soccer players with a history of hip and back injury are at greater risk of sustaining a soccer-related musculoskeletal injury. In addition, our study indicated greater risk of sustaining a future soccer-related injury as FMS scores increase.


#8 Estimating Postmatch Fatigue in Soccer: The Effect of Individualization of Speed Thresholds on Perceived Recovery
Reference: Int J Sports Physiol Perform. 2020 May 18;1-7.  doi: 10.1123/ijspp.2019-0399. Online ahead of print.
Authors: Gustavo Tomazoli, Joao B Marques, Abdulaziz Farooq, Joao R Silva
Summary: The aim was to investigate the effectiveness of different individualization methods of speed zones during match play to estimate postmatch perceptual recovery in soccer. Twelve players under the age of 19 y undertook field-based assessments to determine their maximal aerobic speed (MAS) and maximal sprint speed (MSS). External load (extracted from 10-Hz GPS over 10 official matches) was measured and classified into 4 categories as follows: low-speed running, moderate-speed running, high-speed running, and sprinting. Match running distribution into different speed zones was categorized using either MAS, MSS, MAS and MSS as measures of locomotor capacities, and absolute values. Players perceived recovery status was recorded immediately postmatch (Post) and 24 (G+24H) and 48 hours (G+48H) after each game. Different individualization methods resulted in distinct match outputs in each locomotor category. Perceived recovery status was lower (P < .001) at Post (3.8 [1.32], 95% confidence interval [CI], 3.6 to 4.2), G+24H (5.2 [1.48], 95% CI, 4.9 to 5.6), and G+48H (6.0 [1.22], 95% CI, 5.7 to 6.3) compared with prematch values (7.1 [1.05], 95% CI, 6.8 to 7.3). The absolute perceived recovery-status score was better associated with high-speed running using the locomotor-capacities method at Post (β = -1.7, 95% CI, -3.2 to -0.22, P = .027), G+24H (β = -2.08, 95% CI, -3.22 to -0.95, P = .001), and G+48H (β = -1.32, 95% CI, -2.2 to -0.4, P = .004) compared with other individualization methods. The authors' results suggest that locomotor capacities may better characterize the match intensity distribution (particularly for the high-speed running and sprinting categories) and should be preferred over MAS and MSS to estimate perceived recovery.


#9 Youth Soccer Parents' Perceptions of Long-Term Effects of Concussion
Reference: Dev Neuropsychol. Apr-Jun 2020;45(3):110-117.  doi: 10.1080/87565641.2020.1766464. Epub 2020 May 18.
Authors: Philip Schatz, Mary Corcoran, Anthony P Kontos, R J Elbin
Summary: Increased focus on sports-related concussion (SRC) in football in the media, and mandatory concussion education for parents of youth sport athletes, may result in parental concern that youth athletes will experience long-term effects from concussion. We sought to identify beliefs about long-term effects of concussion in parents of youth soccer athletes. Four hundred and eleven parents from soccer leagues in three states completed a survey assessing parents' perceptions and knowledge of long-term effects of SRC. Nearly all youth soccer parents surveyed (96.5%) believe there are long-term effects from SRCs, 76% reported concern their child would sustain a concussion, and 71% had talked with their child about concussion symptoms/reporting. Parents ranked tackle football as having the highest risk for concussion, followed by soccer, ice hockey, cheerleading, and lacrosse. Parents of children that had previously sustained a concussion were 8.3x more likely to be concerned their child would sustain a concussion, and parents with a personal history of concussion were 2x more likely to consider not allowing their child to participate in youth sports. There are wide-spread beliefs among youth soccer parents regarding long-term effects of SRCs, and concerns their children will sustain concussions while participating in youth sports.


#10 An Injury Audit in High-Level Male Youth Soccer Players From English, Spanish, Uruguayan and Brazilian Academies
Reference: Phys Ther Sport. 2020 May 4;44:53-60. doi: 10.1016/j.ptsp.2020.04.033. Online ahead of print.
Authors: Elliott C R Hall, Jon Larruskain, Susana M Gil, Jose A Lekue, Philipp Baumert, Edgardo Rienzi, Sacha Moreno, Marcio Tannure, Conall F Murtagh, Jack D Ade, Paul Squires, Patrick Orme, Liam Anderson, Craig M Whitworth-Turner, James P Morton, Barry Drust, Alun G Williams, Robert M Erskine
Summary: The purpose was to identify the most common injury types/locations in high-level male youth soccer players (YSP). Six hundred and twenty-four high-level male YSP [Under 9 (U9) to U23 year-old age groups] from academies in England, Spain, Uruguay and Brazil. Injury type, location and severity were recorded during one season. Injury severity was compared between age groups, while injury type and location were compared between nations. Four hundred and forty-three training or match injuries were recorded, giving an injury rate of 0.71 per player. Non-contact injuries were most common (58.5%), with most (44.2%) resolved between 8 and 28 days. Most injuries (75.4%) occurred in the lower limbs, with muscle (29.6%) the most commonly injured tissue. U14 and U16 suffered a greater number of severe injuries relative to U12 and U19/U20/U23/Reserves. Tendon injury rate was higher in Brazil vs. Spain (p < 0.05), with low back/sacrum/pelvis injury rate highest in Spain (p < 0.05). The proportion of severe injuries in U14 and U16 suggests YSP injury risk is maturation-dependent. Minimal differences in type and location between high-level YSP from four different countries suggest injury rates in this population are geographically similar.


#11 Vaccination Practices and Influenza in Professional Football Players in Greece
Reference: Occup Med (Lond). 2020 May 20;kqaa004.  doi: 10.1093/occmed/kqaa004. Online ahead of print.
Authors: D Papagiannis, G Rachiotis, A Xanthopoulos, A Simou, C Zilidis, F Triposkiadis
Download link: https://watermark.silverchair.com/kqaa004.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAApAwggKMBgkqhkiG9w0BBwagggJ9MIICeQIBADCCAnIGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMARfBCRVTVlEjxw8zAgEQgIICQ9BddycOxi2bk_zYbWpVQ0R2l5mFFiUvBv0DlZTEfi5XVjDNw_rK_eed0PPPAjE32epHxrSBAsPx_Y6C5B22WnXM0bSMbfgACW3V716VQOpoQSb3q80OCArl7uGfB9RxU9gsMrS5Q1naSYE2se2XOeKUup6sV0-po9kAYEr7KIZ4fkZh6L91R8AvILLyJcbQDDSnRY-3GRRNZu3ZtBNiz-ZBLC0VlImxJLcWUoX8TZduelTXWtc4iXkksAoInu-1ryAmVgZoY-v-dfKMpPsTaCiGfnSVETb1Xj6wB5MlLhM1xCPhVEcZwUGlZvLr-Qfwn661QpEVX3-EU4rNFtsSOIQSb54TJbPlfZSgP-nmdMUf-uEiFiS_9FvwTPc-ES11XdHbbyiC4y6NNmm0alSi5yjayT68CH5_D5qA0O6hHtXARc7vJXxVJKoUAzvAwvR-H51ss-OL20K_Als9HjoBRbvKALbf6BVWLEKQOCAAoDi8sxKHN5ILwt6Lt1S-wlNFWD-nY6AYHYTmfCPd83FfQDPm4KLa9AMriTGCMylkL6qVAozW4pUd9RDEHSTdJKcd7hsjkKsOE5huwuFxAl58GXCP1JrQX7LIsq2lKQefbQ7ulcbpdmno7SM9EYUCc4KZe-rLT97Uw4z05udE7SyRhjMMtWKL0ZA54llAv8Xph9qV4QA0YiCEq5Id8A4ynHn39Kf8AY0xCgGhx23bTcoTVvr8C284q5EYgVlAXbUllogcs1q7bbX9GRnqZ7LS_Qvi9H86JQ
Summary: There is limited data on vaccination practices for professional footballers globally. The aim was to record vaccination practices employed by medical staff of individual football teams of the Super League Greece, and absenteeism of footballers related to influenza illness. A brief questionnaire was distributed to chief medical officers (CMOs) of the sixteen teams of the Super League Greece. Participants were asked to report vaccines they recommended for footballers. In addition, the questionnaire included questions on new cases of influenza and absenteeism due to influenza. Descriptive statistics (absolute and relative frequencies) were used for the presentation of the results. Overall, 87% of the CMOs recommended seasonal influenza vaccine, 62% hepatitis B vaccine and 50% pneumococcal vaccine. Fourteen CMOs (87%) reported that the occurrence of seasonal influenza in the 2016-17 northern hemisphere season ranged from one to five cases, while two medical officers (12%) reported zero workdays lost due to influenza. Our survey shows considerable variation in vaccination practices of CMOs of the Super League Greece. The results of this survey should stimulate further evaluation of vaccination policy and influenza-related absenteeism in footballers.


#12 Pre-season Football Preparation in the Era of COVID-19: Croatian Football Association Model
Reference: J Glob Health. 2020 Jun;10(1):010352. doi: 10.7189/jogh.10.010352.
Authors: Dragan Primorac, Vid Matišić, Vilim Molnar, Zoran Bahtijarević, Ozren Polašek
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7211417/pdf/jogh-10-010352.pdf

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13

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2020

Movement economy in football

Some considerations and limitations

Sat

11

Jul

2020

High-speed running and sprinting as an injury risk factor in football

The study investigated the association between high-speed running and sprinting and injuries in football.

Thu

09

Jul

2020

Latest research in football - week 21 - 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 Are European Soccer Players Worth More If They Are Born Early in the Year? Relative Age Effect on Player Market Value
Reference: Int J Environ Res Public Health. 2020 May 9;17(9). pii: E3301. doi: 10.3390/ijerph17093301.
Authors: Perez-Gonzalez B, Fernandez-Luna A, Castillo D, Burillo P
Download link: https://www.mdpi.com/1660-4601/17/9/3301/pdf
Summary: The relative age effect (RAE) consists of the lower presence of members of an age group born in the months furthest from the age cut-off date established. In youth soccer, it is known that because of this effect the birth dates of more players in a team are closer to the cutoff of 1 January. These older players, due to their physical and psychological advantages, are more likely to be identified as talent. This study aimed to examine whether RAE can be identified in professional players of the top five European soccer leagues (Spain, Italy, England, Germany, and France) and to assess its influence on the perceived market value of the players. Market value data for 2577 players were obtained from the Transfermarkt database. A significant RAE was produced in all leagues (p < 0.05). However, this bias did not affect the market value of the professional elite soccer players examined here. Our observations indicate that, while the identification and promotion of talent at young ages are often biased by RAE, once players have reached the professional stage, the market value assigned to them is based more on factors other than their date of birth.


#2 Weekly Load Variations of Distance-Based Variables in Professional Soccer Players: A Full-Season Study
Reference: Int J Environ Res Public Health. 2020 May 9;17(9). pii: E3300. doi: 10.3390/ijerph17093300.
Authors: Clemente FM, Silva R, Castillo D, Los Arcos A, Mendes B, Afonso J
Download link: https://www.mdpi.com/1660-4601/17/9/3300/pdf
Summary: The aim of this study was two-fold: (1) to analyze the variations of acute load, training monotony, and training strain among early (pre-season), mid (first half of season), and end season (second half of season) periods; (2) to compare these training indicators for playing positions in different moments of the season. Nineteen professional players (age: 26.5 ± 4.3 years; experience as professional: 7.5 ± 4.3 years) from a European First League team participated in this study. The players were monitored daily over a 45-week period for the total distance (TD), distance covered (DC) at 14 km/h-1 or above (DC > 14 km/h), high-speed running above 19.8 km/h-1 (HSR) distance, and number of sprints above 25.2 km/h-1. The acute load (sum of load during a week), training monotony (mean of training load during the seven days of the week divided by the standard deviation of the training load of the seven days), and training strain (sum of the training load for all training sessions and matches during a week multiplied by training monotony) workload indices were calculated weekly for each measure and per player. Results revealed that training monotony and training strain for HSR were meaningfully greater in pre-season than in the first half of the in-season (p ≤ 0.001; d = 0.883 and p ≤ 0.001; d = 0.712, respectively) and greater than the second half of the in-season (p ≤ 0.001; d = 0.718 and p ≤ 0.001; d = 0.717). The training monotony for the sprints was meaningfully greater in pre-season than in the first half of in-season (p < 0.001; d = 0.953) and greater than the second half of in-season (p ≤ 0.001; d = 0.916). Comparisons between playing positions revealed that small-to-moderate effect sizes differences mainly for the number of sprints in acute load, training monotony, and training strain. In conclusion, the study revealed that greater acute load, training monotony, and training strain occurred in the pre-season and progressively decreased across the season. Moreover, external defenders and wingers were subjected to meaningfully greater acute load and training strain for HSR and number of sprints during the season compared to the remaining positions.


#3 'Soccer toe': Chronic physeal injury of the great toe metatarsal in a skeletally immature child - A case report
Reference: SA J Radiol. 2020 Apr 22;24(1):1834. doi: 10.4102/sajr.v24i1.1834. eCollection 2020.
Authors: Schapiro A, Laor T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203536/pdf/SAJR-24-1834.pdf
Summary: Chronic physeal stress injuries in children can result from ongoing, repetitive compression, distraction and/or shear forces during sports-related activity, and manifest as physeal widening on imaging. We present an 11-year-old soccer athlete with focal physeal widening of her great toe metatarsal and postulate that ongoing or repetitive stress from soccer play may manifest as this imaging appearance. We suggest that recognition of this entity in growing children might explain pain, if present, and guide conservative treatment.


#4 How Training Tools Physically Linking Soccer Players Improve Interpersonal Coordination
Reference: J Sports Sci Med. 2020 May 1;19(2):245-255. eCollection 2020 Jun.
Authors: Yokoyama K, Tabuchi N, Araújo D, Yamamoto Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7196758/pdf/jssm-19-245.pdf
Summary: Interpersonal coordination is an important skill for promoting collective behavior in team sports. This study tested the impact of two types of tools in facilitating triadic coordination. 16 males aged under 12 years were divided into four groups with similar skill levels and average ages. Each group performed a three-versus-one ball passing task under three conditions: a one-elastic-band tool linking the three players, a three-elastic-bands tool linking the three players, and without a tool linking the three players. The dependent variables were ball passing frequency, frequency and amplitude of inner angles of the triangle formed by the players, and duration of the synchronized patterns of the inner angles. The results show that neither tool increased ball-passing frequency or the duration of synchronized patterns. However, both tools increased the frequency of inner angles, and the three-elastic-bands tool decreased the amplitude of inner angles. From these results, we conclude that elastic-band tools affect spatial and temporal triadic formation by means of haptic and visual information. Specifically, compared with the one-elastic-band tool, the three-elastic-bands tool stabilizes the triadic spatial formation. We also explore the implications for how these tools can be used in practice.


#5 A Low-Glycemic Index, High-Fiber, Pulse-Based Diet Improves Lipid Profile, but Does Not Affect Performance in Soccer Players
Reference: Nutrients. 2020 May 6;12(5). pii: E1324. doi: 10.3390/nu12051324.
Authors: Mizelman E, Chilibeck PD, Hanifi A, Kaviani M, Brenna E, Zello GA
Download link: https://www.mdpi.com/2072-6643/12/5/1324/pdf
Summary: Pulses (i.e., lentils, chickpeas, beans, peas) are low-glycemic index, high-fiber foods that are beneficial for improving blood lipids. Young soccer players typically have low dietary fiber intake, perhaps because of concerns regarding gastro-intestinal problems during exercise performance. Twenty-seven (17 females) soccer players were randomized to receive a pulse-based diet or their regular diet for four weeks in a cross-over study and evaluated for changes in blood lipids and athletic performance, with 19 (22 ± 6y; 12 females) completing the study (eight participants withdrew because of lack of time). Women increased high density lipoproteins (+0.5 ± 0.7 vs. -0.6 ± 0.3 mmol/L; p < 0.01) and reduced total cholesterol to high density lipoprotein ratio (-2.4 ± 2.9 vs. +2.6 ± 2.2; p < 0.01) on the pulse-based vs. regular diet, respectively, while there were no differences between diet phases in men. Athletic performance assessed by distance covered during games by a global positioning system was not significantly different during the pulse-based vs. regular diet (9180 ± 1618 vs. 8987 ± 1808 m per game; p = 0.35). It is concluded that a pulse-based diet can improve blood lipid profile without affecting athletic performance in soccer players.


#6 Women's Football: An Examination of Factors That Influence Movement Patterns
Reference: J Strength Cond Res. 2020 May 13. doi: 10.1519/JSC.0000000000003638. [Epub ahead of print]
Authors: Griffin J, Larsen B, Horan S, Keogh J, Dodd K, Andreatta M, Minahan C
Summary: The popularity and professionalism of women's football has increased in conjunction with participation rates over the last 10 years, with projected female participation rates to double worldwide by 2026. Scientific interest has also increased, in part due to Fédération Internationale de Football Association now allowing global positioning system (GPS) units to be worn during all competitive matches, resulting in investigations into the match demands of women's football. Therefore, the purpose of the present review is to provide a summary of the literature specific to the movement patterns of women's football matches. Contemporary scientific investigation using GPS match data has led to a greater understanding of the movement patterns of football. Greater emphasis has been placed on high-speed running and sprinting during matches because of the strong link to scoring opportunities and being a distinguishing factor between international and national along with elite and subelite competition levels. Further research, however, is warranted in regard to accelerations and decelerations, given the high metabolic and mechanical loads and contribution to high-speed running and sprinting. With an influx of research into the movement patterns of match-play, investigators have begun to examine factors affecting match performance such as positional demands, age, level of competition, opponent, scoreline, and phase of the game. An understanding of the factors that influence match demands is vital to ultimately be able to understand the effects on performance and how manipulating these factors may improve football performance and reduce the risk of injury.


#7 Influence of Academic Performance, Level of Play, Sports Success, and Position of Play on the Motivation of the Young Football Player
Reference: Int J Environ Res Public Health. 2020 May 12;17(10). pii: E3374. doi: 10.3390/ijerph17103374.
Authors: Ureña-Lopera C, Morente-Oria H, Chinchilla-Minguet JL, Castillo-Rodríguez A
Download link: https://www.mdpi.com/1660-4601/17/10/3374/pdf
Summary: Motivation in athletes is a state that fluctuates due to multiple factors that can, in turn, negatively or positively influence sports performance. The aim of this study was twofold, being, on the one hand, to analyze the motivation of soccer players of developmental age in two different contexts (training time (baseline) and the precompetitive time) depending on the category, sports success and playing position, and, on the other hand, to find relations of the motivation dimensions with the academic performance and physical characteristics of the soccer players. One hundred and forty-one under 16 (U16) soccer players were selected (age: 14.7 ± 0.5; height: 170.4 ± 7.2 cm; weight: 61.6 ± 10.0 kg). Data on academic performance, physical and socio-demographic characteristics were recorded, and in two differentiated moments, the motivation dimensions, both in training and in competition. The results showed that the general motivation decreases with the competition, and in particular, the intrinsic motivation, where the precompetitive evaluation is lower than the basal, in both categories (p < 0.05). In addition, demotivation is explained by 10.2%, 19.8%, and 23.9% by fat mass, by academic performance, and by category, respectively; and the extrinsic motivation of external regulation is explained in 26.0% by the academic performance factor (p < 0.01). U16 soccer players show lower levels of motivation at moments prior to the sports competition, and these dimensions of motivation are explained by the category, academic performance, and fat mass.


#8 Acute Effects of a Single Football Training or Match on Passive Hip Rotation Range of Motion in Semi-Professional Football Players: A Pilot Study
Reference: Medicina (Kaunas). 2020 May 10;56(5). pii: E228. doi: 10.3390/medicina56050228.
Authors: De-la-Cruz-Torres B, Abuín-Porras V, Blanco-Morales M, de-la-Cueva-Reguera M, Calvo-Lobo C, López-López D, Romero-Morales C
Download link: https://www.mdpi.com/1010-660X/56/5/228/pdf
Summary: The repetitive loading forces generated during football activities may induce alterations in the hip rotation range of motion (ROM) in players. The objective of this study was to evaluate the acute effects of a training and a match on bilateral passive hip rotation ROM in both lower limbs in soccer. Twenty-eight male players were divided into two groups: 14 players (28 limbs) with normal bilateral hip rotation ROM (NH group) and 14 players (28 limbs) with restricted bilateral hip ROM (RH group). Passive bilateral hip rotation ROM was measured, by goniometer, before and after training or a match. Internal-rotation ROM (ROMIR), external-rotation ROM (ROMER), total ROM (ROMTOT) and relative internal rotation (ROMREL) were calculated. The NH group did not show substantial changes in hip ROM after a training nor a match. After a training session, only the RH group exhibited a substantial increase in ROMIR, ROMER and ROMTOT. After a match, only the RH group exhibited a substantial increase in ROMER and ROMTOT and exhibited a substantial decrease in ROMREL. Comparing both groups, there were significant differences within ROM changes for ROMER and ROMTOT after training and for ROMER and ROMREL after a match. Despite the small sample size of the present study, the findings indicate that a single football activity leads to significant changes in hip rotation ROM in players with restricted bilateral hip external-rotation ROM. However, these changes did not reach reference cut-off scores.


#9 Responsiveness of Device-Based and Self-Report Measures of Physical Activity to Detect Behavior Change in Men Taking Part in the Football Fans in Training (FFIT) Program
Reference: J Meas Phys Behav. 2020 Mar;3(1):67-77. doi: 10.1123/jmpb.2019-0018.
Authors: Donnachie C, Hunt K, Mutrie N, Gill JMR, Kelly P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212021/pdf/EMS85589.pdf
Summary: The capacity of physical activity (PA) measures to detect changes in PA within interventions is crucial. This is the first study to examine the responsiveness of activPAL3™ and the International Physical Activity Questionnaire (IPAQ; Short Form) in detecting PA change during a 12-week group-based, men-only weight management program-Football Fans in Training (FFIT). Participants wore an activPAL3™ and completed the IPAQ pre- and post-program (n = 30). Relationships between change scores were assessed by Spearman's correlations. Mean or median changes in PA were measured using paired samples t-tests and Wilcoxon signed-rank tests. Responsiveness to change was assessed utilizing Standardized Response Mean (SRM). Both device-based and self-report measures demonstrated significant changes pre-post intervention, although these changes were not significantly correlated. The SRM values for changes in activPAL3™ metrics were: 0.54 (MET-mins/day); 0.53 (step counts/day); and 0.44 (MVPA/day), indicating a small to medium responsiveness to change. SRM values for changes in IPAQ scores were: 0.59 (for total PA mins/day); 0.54 (for total MET-mins/day); 0.59 (for walking MET-mins/day); 0.38 (for vigorous MET-mins/day); and 0.38 (for moderate MET-mins/day), revealing a small to medium responsiveness to change. These findings reveal that two commonly used device-based and self-report measures demonstrated responsiveness to changes in PA. While inclusion of both device-based and self-report measures is desirable within interventions it is not always feasible. The results from this study support that self-reported measures can detect PA change within behavioral interventions, although may have a tendency to overestimate changes compared with device-based measures on absolute values, but not standardized response values.


#10 Physical Fitness, Body Composition, and Adherence to the Mediterranean Diet in Young Football Players: Influence of the 20 mSRT Score and Maturational Stage
Reference: Int J Environ Res Public Health. 2020 May 7;17(9). pii: E3257. doi: 10.3390/ijerph17093257.
Authors: Manzano-Carrasco S, Felipe JL, Sanchez-Sanchez J, Hernandez-Martin A, Gallardo L, Garcia-Unanue J
Download link: https://www.mdpi.com/1660-4601/17/9/3257/pdf
Summary: This study aimed to analyze the differences in physical fitness variables, body composition, and adherence to the Mediterranean diet according to the cardiorespiratory fitness and the maturational stage in young football players. A total of 194 male football players (aged 8-16) from three football sport schools participated in this study. Data on cardiorespiratory fitness (the 20-m shuttle run test), anthropometric measurements, handgrip strength, respiratory capacity (forced spirometry), and adherence to the Mediterranean diet (KIDMED questionnaire) were collected. Players were divided into two groups depending on their maturational stage (prepubertal n = 127 and pubertal n = 67). The results show a direct relationship between low levels of cardiorespiratory fitness and body mass index, as well as body fat and leg fat. Similarly, players with lower cardiorespiratory fitness presented higher values of handgrip strength in the prepubertal state. On the other hand, improvements in respiratory values were observed in the pubertal state with the rest of the parameters when the cardiorespiratory fitness was increased. Therefore, the promotion of recreational football that encourage and develop cardiorespiratory fitness is a key factor and can be used as an effective sport activity to promote physical fitness and healthy habits in children and adolescents as well as within the population that is already physically active.


#11 Purposeful Heading in Youth Soccer: Time to Use Our Heads
Reference: J Orthop Sports Phys Ther. 2020 May 22;1-8. doi: 10.2519/jospt.2020.9680. Online ahead of print.
Authors: Kerry Peek, James M Elliott , Andrew Gardner
Summary: Repeated purposeful heading in soccer has come under increased scrutiny as concerns surrounding the association with long-term neurodegenerative disorders in retired players continues to grow. Whilst a causal link between heading and brain health has not been established, the 'Precautionary Principle' supports the notion that soccer governing bodies and associations should consider implementing pragmatic strategies, which can reduce head impact during purposeful heading in youth soccer whilst this relationship is being investigated. This viewpoint discusses the current evidence to support low-risk head impact reduction strategies during purposeful heading to protect young developing players; and how such strategies could be implemented now while research and debate continues on this topic.

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Mental fatigue impairs technical performance

Passing and shooting in the LSST and LSPT.

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2020

Running-based high-intensity interval training vs. small-sided game training programs

Effects on the physical performance, psychophysiological responses and technical skills in young soccer players.

Wed

24

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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.

Fri

29

May

2020

Heavy sled training improved sprint performance

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

Tue

26

May

2020

Game style in football

What is it and are there quantifiable variables

Fri

22

May

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.

Fri

22

May

2020

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), at