Blog archive

Tue

29

May

2018

Football is...(#62)

The role of anthropometry for certain positions - debatable?

Mon

28

May

2018

Latest research in football - week 17 - 2018

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 Assessing Repeated-Sprint Ability in Division I Collegiate Women Soccer Players
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002527. [Epub ahead of print]
Authors: Lockie RG, Liu TM, Stage AA, Lazar A, Giuliano DV, Hurley JM, Torne IA, Beiley MD, Birmingham-Babauta SA, Stokes JJ, Risso FG, Davis DL, Moreno MR, Orjalo AJ
Summary: Repeated-sprint ability (RSA) is a key component of soccer, and is the capacity to repeatedly produce near-maximal to maximal sprints with short recovery periods. Repeated-sprint ability has received little analysis in collegiate women soccer players. The purpose of this study was to investigate relationships between RSA and tests of soccer-specific performance. Nineteen players from the same Division I collegiate women's soccer team were recruited. The RSA test consisted of six 20-m sprints completed on 15-second cycles. The measurements taken were total time (TT) and percent decrement (PD; percent change from first to last sprint). Subjects also completed tests of: lower-body strength (1 repetition maximum [1RM] back squat); jump performance (vertical and standing long jumps); linear (0-5, 0-10, and 0-30 m sprint intervals) and change-of-direction (505 from each leg) speed; and soccer-specific fitness (Yo-Yo intermittent recovery test level 1 [YYIRT1]). Pearson's correlations (p ≤ 0.05) were used to calculate relationships between RSA TT and PD with the performance tests. Total time exhibited significant relationships with the 0-10 (r = 0.50) and 0-30 m (r = 0.71) sprint intervals, and the left-leg 505 (r = 0.57). However, lower-body strength measured by the 1RM back squat and jump performance did not relate to TT. Percent decrement correlated only with the left-leg 505 (r = 0.53) and no other performance test. This included the YYIRT1, although both PD and YYIRT1 performance are limited by fatigue. The results from this study indicated that faster linear sprinting speed could positively influence RSA in Division I collegiate women soccer players.


#2 EEG alpha activity during imagining creative moves in soccer decision-making situations
Reference: Neuropsychologia. 2018 Apr 24. pii: S0028-3932(18)30166-0. doi: 10.1016/j.neuropsychologia.2018.04.025. [Epub ahead of print]
Authors: Fink A, Rominger C, Benedek M, Perchtold CM, Papousek I, Weiss EM, Seidel A, Memmert D
Summary: This study investigated task-related changes of EEG alpha power while participants were imagining creative moves in soccer decision-making situations. After presenting brief video clips of a soccer scene, participants had to imagine themselves as the acting player and to think either of a creative/original or an obvious/conventional move (control condition) that might lead to a goal. Performance of the soccer task generally elicited comparatively strong alpha power decreases at parietal and occipital sites, indicating high visuospatial processing demands. This power decrease was less pronounced in the creative vs. control condition, reflecting a more internally oriented state of information processing characterized by more imaginative mental simulation rather than stimulus-driven bottom-up processing. In addition, more creative task performance in the soccer task was associated with stronger alpha desynchronization at left cortical sites, most prominently over motor related areas. This finding suggests that individuals who generated more creative moves were more intensively engaged in processes related to movement imagery. Unlike the domain-specific creativity measure, individual's trait creative potential, as assessed by a psychometric creativity test, was globally positively associated with alpha power at all cortical sites. In investigating creative processes implicated in complex creative behavior involving more ecologically valid demands, this study showed that thinking creatively in soccer decision-making situations recruits specific brain networks supporting processes related to visuospatial attention and movement imagery, while the relative increase in alpha power in more creative conditions and in individuals with higher creative potential might reflect a pattern relevant across different creativity domains.


#3 Inter-season variability in isokinetic strength and poor correlation with nordic hamstring eccentric strength in football players
Reference: Scand J Med Sci Sports. 2018 Apr 25. doi: 10.1111/sms.13201. [Epub ahead of print]
Authors: van Dyk N, Witvrouw E, Bahr R
Summary: In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aims to investigate the variability of isokinetic muscle strength over time, e.g. between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with one/two seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25Nm, 15%), whether separated by one or two seasons. Considering hamstring injuries, the same pattern was observed among injured (n=60) and uninjured (n=228) players. A poor correlation (r=0.35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes were not correlated (r=0.037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by one or two seasons, irrespective of injury. Also, eccentric hamstring strength and limb-to-limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests. This article is protected by copyright. All rights reserved.


#4 Variability of activity profile during medium-sided games in professional soccer
Reference: J Sports Med Phys Fitness. 2018 Apr 24. doi: 10.23736/S0022-4707.18.08376-7. [Epub ahead of print]
Authors: Rago V, Silva JR, Mohr M, Barreira D, Krustrup P, Rebelo AN
Summary: In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason. Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers). Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3 %). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59). During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.


#5 Landing Kinematics in Elite Male Youth Soccer Players of Different Chronologic Age and Stage of Maturation
Reference: J Athl Train. 2018 Apr 25. doi: 10.4085/1062-6050-493-16. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players. The aim was to use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation. A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV) participated in the study. Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe). A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups. Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.


#6 Team Dynamics, Running, and Skill-Related Performances of Brazilian U11 to Professional Soccer Players During Official Matches
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002577. [Epub ahead of print]
Authors: Palucci Vieira LH, Aquino R, Moura FA, Barros RML, Arpini VM, Oliveira LP, Bedo BLS, Santiago PRP
Summary: Analyses of movements during soccer competition have been used previously to help develop conditioning programs. However, this has not been extensively studied in youth populations. Therefore, the purposes of this study were to examine (1) dynamics of collective tactical movements, (2) running, and (3) skill-related performances during soccer matches disputed by children to senior players. A total of 120 Brazilian players in the age groups U11, U13, U15, U17, U20, and professional (PRO) were monitored during official competition matches (N = 12). Using semiautomatic video-based tracking (30 Hz), match running variables including total distance traveled, average speed, maximum sprint speed, and high-intensity activities were evaluated. Tactical metrics were computed as team surface area, spread, and median frequency. Through notational analysis, technical skills such as involvements with the ball, passes, ball touches, duels, and goal attempts were also recorded. One-way analysis of variance and magnitude-based inferences were used to detect differences between ages. Although the average speed, team surface area, and spread tended to present stabilized increases from the U15 (e.g., U15 > U13 > U11), maximal sprinting speed (PRO > U17 > U15, U13, U11) and percentage at very high-intensity activities (U20 > PRO, U17 > U15 > U13 > U11) demonstrated continuous gains. Median frequencies were higher in the younger groups (U13, U15, U17 > U20, PRO), although the percentage of successful passes was higher in the older groups (PRO > U17, U15 > U13, U11). We concluded that Brazilian U11 to PRO players present different performance profiles for running, collective movement dynamics, and technical skills, and that the rate of development regarding these components varies. Coaches should be aware of these differences to select and adapt training content for each age group.


#7 New Tool to Control and Monitor Weighted Vest Training Load for Sprinting and Jumping in Soccer
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002580. [Epub ahead of print]
Authors: Carlos-Vivas J, Freitas TT, Cuesta M, Perez-Gomez J, De Hoyo M, Alcaraz PE
Summary: The purpose of this study was to develop 2 regression equations that accurately describe the relationship between weighted vest loads and performance indicators in sprinting (i.e., maximum velocity, Vmax) and jumping (i.e., maximum height, Hmax). Also, this study aimed to investigate the effects of increasing the load on spatio-temporal variables and power development in soccer players and to determine the "optimal load" for sprinting and jumping. Twenty-five semiprofessional soccer players performed the sprint test, whereas a total of 46 completed the vertical jump test. Two different regression equations were developed for calculating the load for each exercise. The following equations were obtained: % body mass (BM) = -2.0762·%Vmax + 207.99 for the sprint and % BM = -0.7156·%Hmax + 71.588 for the vertical jump. For both sprinting and jumping, when the load increased, Vmax and Hmax decreased. The "optimal load" for resisted training using weighted vest was unclear for sprinting and close to BM for vertical jump. This study presents a new tool to individualize the training load for resisted sprinting and jumping using weighted vest in soccer players and to develop the whole force-velocity spectrum according to the objectives of the different periods of the season.


#8 Injury prevention and return to play strategies in elite football: no consent between players and team coaches
Reference: Arch Orthop Trauma Surg. 2018 Apr 20. doi: 10.1007/s00402-018-2937-6. [Epub ahead of print]
Authors: Loose O, Achenbach L, Fellner B, Lehmann J, Jansen P, Nerlich M, Angele P, Krutsch W
Summary: Injuries are a common problem in football. To improve prevention strategies, the players' (p) and coaches' (c) views need to be disclosed as they have a strong impact on return to play decisions. The aim of this study is to reveal current opinions with regard to injury prevention and return to play strategies to introduce new strategies in elite football. In a retrospective data analysis of elite salaried football players (n = 486) and team coaches (n = 88), a detailed investigation by means of a standardized questionnaire was carried out. In a preseason period of the 2015/16 season and as part of a large interventional research project in elite salaried German football, a request about players' and team coaches' knowledge and opinions was performed. Topics such as injury prevention, return to play after injuries, the importance of screening tests, general problems of injuries in football, or the decision-making in terms of prevention and return to play in elite football were investigated. The study revealed a high interest in injury prevention and screening tests among players and coaches (p 82.5%; c 99.1%). The participants of the study reported warm-up exercises (p 76.4%; c 74.7%), regeneration training (p 54.1%; c 56.3%), and core stability (p 53.8; c 70.1%) as the most important prevention methods, but the additional investigation of the teams' current daily training routine showed that the transfer is incomplete. Coaches are more familiar with scientific published warm-up programs like FIFA 11 + than players (42.5 vs. 12.6; p < 0.001). Knee injuries (p 90.7%; c 93.1%) and ACL injuries in particular were reported as the most severe and common problem in elite football. Players and coaches expressed different attitudes concerning return to play decisions. While players want to decide themselves (81.4%), team coaches consult medical advice ahead of the decision of return to play after injuries (83.5%; p < 0.001). Decisions against the doctor's recommendation are often made by both groups (p 64.4% vs. c 87.1%; p < 0.001). The basic knowledge of prevention and injuries is sufficient in elite football, but the transfer from theoretical knowledge to practical routine is suboptimal. The study also shows possibilities to improve the prevention process and communication between players, coaches, doctors, and physiotherapists, while there is no consent between players and coaches regarding return to play decision.


#9 Dynamics of submaximal effort soccer instep kicking
Reference: J Sports Sci. 2018 May 1:1-8. doi: 10.1080/02640414.2018.1470216. [Epub ahead of print]
Authors: Nunome H, Inoue K, Watanabe K, Iga T, Akima H
Summary: During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.


#10 Periodic Health Examination and Injury Prediction in Professional Football (Soccer): Theoretically, the Prognosis is Good
Reference: Sports Med. 2018 Apr 27. doi: 10.1007/s40279-018-0928-y. [Epub ahead of print]
Authors: Hughes T, Sergeant JC, van der Windt DA, Riley R, Callaghan
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0928-y.pdf
Summary: In professional soccer and other elite sports, medical and performance screening of athletes (also termed periodic health examination or PHE) is common practice. The purposes of this are: (1) to assist in identifying prevalent conditions that may be a threat to safe participation, (2) to assist in setting benchmark targets for rehabilitation or performance purposes and (3) to assist clinicians in determining which athletes may be at risk of future injury and selecting appropriate injury prevention strategies to reduce the perceived risk. However, when using PHE as an injury prevention tool, are clinicians seeking to identify potential causes of injury or to predict future injury? This Current Opinion aims to examine the conceptual differences between aetiology and prediction of injury while relating these areas to the capabilities of PHE in practice. We also introduce the concept of prognosis-a broader approach that is closely related to prediction-and why this may have greater applicability to PHE of professional athletes.

Thu

24

May

2018

Latest research in football - week 16 - 2018

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 Association between Cumberland Ankle Instability Tool score and postural stability in collegiate soccer players with and without functional ankle instability
Reference: Phys Ther Sport. 2018 Mar 23;32:29-33. doi: 10.1016/j.ptsp.2018.03.002. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Yoshida N, Miyakawa S
Summary: The purpose of this study was to investigate the association between Cumberland Ankle Instability Tool (CAIT) scores and postural stability during a diagonal landing, and to investigate whether postural stability is altered in collegiate soccer players with and without functional ankle instability (FAI). Ninety-one soccer players were classified into a FAI group (history of at least two ankle sprains and a CAIT-Japanese version score ≤25, n = 28), a copers group (history of one ankle sprain and a CAIT-Japanese version score ≥26, n = 32), or a control group (no history of ankle sprain, n = 31). Time to anteroposterior stabilisation (TTSAP) and mediolateral stabilisation (TTSML) were measured during the diagonal single-leg landing. The CAIT scores were correlated with TTSAP (P < 0.05, rs = -0.214) and TTSML (P < 0.01, rs = -0.566). TTSAP was longer in the FAI group than in the control group, and TTSML was longer in the FAI group than in the other groups. Our findings indicate the presence of an association between the CAIT-J score and TTSML, as well as postural stability deficits in collegiate soccer players with FAI during diagonal landings.


#2 Isolated Subscapularis Tendon Tear in a Skeletally Immature Soccer Player
Reference: Joints. 2017 Dec 11;6(1):68-70. doi: 10.1055/s-0037-1608952. eCollection 2018 Mar.
Authors: Avanzi P, Dei Giudici L, Giovarruscio R, Gigante A, Zorzi C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5906114/pdf/10-1055-s-0037-1608952.pdf
Summary: Subscapularis injury in adolescents, usually associated to an avulsion fracture of the lesser humeral tuberosity, accounts for less than 2% of all fractures of the proximal humerus. Isolated tears of the subscapularis tendon without a history of dislocation and associated avulsion fractures are an even rarer occurrence, and treatment is controversial. This article describes a rare case of a 12-year-old suffering from an isolated subscapularis tear and discusses its management. The patient was evaluated at presentation, and at 1 to 2.5 months after he underwent a cuff tear arthroscopic repair with a single "all suture" anchor loaded with two wires, active/passive range of motion (A/PROM), Constant-Murley score, and American Shoulder and Elbow Surgeons (ASES) score were noted. Patient reported an excellent outcome, recovered the whole ROM, was pain free, and returned to the previous level of activity. Isolated avulsion of the subscapularis tendon requires a high index of suspicion for a proper diagnosis as early treatment is required for a good recovery. Arthroscopy reserves more advantages in proper hands, restoring the previous levels of function and activity. An increase in attention for this condition is mandatory in a society where many adolescents are getting more and more active in high levels of sport activities.


#3 The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Reference: PLoS One. 2018 Apr 19;13(4):e0196253. doi: 10.1371/journal.pone.0196253. eCollection 2018.
Authors: Brustio PR, Lupo C, Ungureanu AN, Frati R, Rainoldi A, Boccia G
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196253&type=printable
Summary: The relative age effect (RAE; i.e., an asymmetry in the birth distribution) is a bias observed in sport competitions that may favour relatively older athletes in talent identification. Therefore, the aim of this study was to investigate the presence of RAE in elite soccer players competing in the Italian championships, even considering the discriminations of younger and older Serie A players (in relation to the median age of the sample), and different positional roles (i.e., goalkeeper, defender, midfielder, forward) for each observed category. A total of 2051 players competing into the 2017-2018 Italian under-15 (n = 265), under-16 (n = 362), under-17 (n = 403), Primavera (n = 421) and Serie A (n = 600) championships were analysed. The birth-date distributions, grouped in four quartiles (i.e., January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4), were compared to a uniform distribution using Chi-squared analysis. The week of birth was analysed using Poisson regression. The results showed a large over-representation of players born in Q1 in all soccer player categories. However, the effect size of this trend resulted smaller as age increased. Individuals born in Q1 have about two-folds more chances to become a Serie A player compared to those born in Q4. The Poisson regression analysis showed that RAE was greater for defenders than for forwards among all categories. Therefore, a strongly biased selection emerged among elite soccer players competing in Italian championships, highlighting how young individuals born in the first three months have many more chances to become elite players compared to the others.


#4 Ratios of torques of antagonist muscle groups in female soccer players
Reference: Acta Bioeng Biomech. 2018;20(1):153-158.
Authors: Struzik A, Siemienski A, Bober T, Pietraszewski B
Summary: An increase in the value of the hamstring-to-quadriceps (H/Q) ratio with an increase in angular velocity may effectively prevent injuries of the back of the thigh. Previous studies have found that the conventional H/Q ratio was unaltered along with an increasing angular velocity in females. Therefore, this study aimed to investigate the relationships between the conventional H/Q ratio and angular velocity in a group of female soccer players. The study was carried out on a group of 16 female soccer players (age: 20.7 ± 3.9 years, body height: 166.1 ± 5.8 cm, body mass: 58.4 ± 6.2 kg, training experience: 8.8 ± 4.1 years). Measurements of peak torque of extensors and flexors of the knee joint under static conditions and under isokinetic conditions (at angular velocities of 30°/s, 60°/s, 90°/s and 120°/s) were carried out using a Biodex dynamometer. There was a statistically significant increase in the conventional H/Q ratio with an increase in angular velocity. These differences occurred between measurements at angular velocities of 0°/s and 30°/s, and 30°/s and 60°/s. As previously found for males, an increase in conventional H/Q ratio with increased angular velocity was also present in this group of female players. This phenomenon should reduce the number of injuries of the muscles of back of the thigh. Coaches should pay attention to increasing the level of strength in the group of knee joint flexor muscles so as to make the value of the H/Q ratio appropriately high and increasing with increasing angular velocity.


#5 Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football
Reference: Scand J Med Sci Sports. 2018 Apr 19. doi: 10.1111/sms.13197. [Epub ahead of print]
Authors: Raisanen AM, Arkkila H, Vasankari T, Steffen K, Parkkari J, Kannus P, Forsman H, Pasanen K
Summary: This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA) during the single-leg squat and sustaining an acute lower extremity injury or acute non-contact lower extremity injury. Secondly, side-to-side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex and leg dominance on the FPKPA. A total of 558 youth football players (U11 to U14), participated in the single-leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA. Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear but the oldest girls displayed the smallest mean FPKPA in the study (12.2°+ 8.3°). The FPKPA was greater on the dominant kicking leg compared to the non-dominant support leg (P<0.001 for boys, P=0.001 for girls). However, side-to-side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single-leg squat was not associated with lower extremity injuries among young football players. As the single-leg squat to 90° knee flexion was too demanding for many subjects, easier single-leg squat test procedure or a different movement control test, such as a double-legged squat, could be more suitable for the young football players.


#6 Is the message getting through? Awareness and use of the 11+ injury prevention programme in amateur level football clubs
Reference: PLoS One. 2018 Apr 19;13(4):e0195998. doi: 10.1371/journal.pone.0195998. eCollection 2018.
Authors: Wilke J, Niederer D, Vogt L, Banzer W
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0195998&type=printable
Summary: A large body of evidence suggests that the 11+ warm-up programme is effective in preventing football-related musculoskeletal injuries. However, despite considerable efforts to promote and disseminate the programme, it is unclear as to whether team head coaches are familiar with the 11+ and how they rate its feasibility. The present study aimed to gather information on awareness and usage among German amateur level football coaches. A questionnaire was administered to 7893 individuals who were in charge of youth and adult non-professional teams. Descriptive and inferential statistics were used to analyse the obtained data. A total of 1223 coaches (16%) returned the questionnaire. There was no risk of a non-response bias (p>.05). At the time of the survey, nearly half of the participants (42.6%) knew the 11+. Among the coaches who were familiar with the programme, three of four reported applying it regularly (at least once per week). Holding a license (φ = .28, p < .0001), high competitive level (Cramer-V = .13, p = .007), and coaching a youth team (φ = .1, p = .001) were associated with usage of 11+. Feasibility and suitability of the 11+ were rated similarly by aware and unaware coaches. Although a substantial share of German amateur level coaches is familiar with the 11+, more than half of the surveyed participants did not know the programme. As the non-usage does not appear to stem from a lack of rated feasibility and suitability, existing communication strategies might need to be revised.


#7 Muscle injuries in professional football : Treatment and rehabilitation
Reference: Unfallchirurg. 2018 Apr 17. doi: 10.1007/s00113-018-0501-z. [Epub ahead of print]  [Article in German]
Authors: Riepenhof H, Del Vescovo R, Droste JN, McAleer S, Pietsch A
Summary: Muscle injuries are common in professional sports, especially in football. Recent epidemiological studies showed that muscle injuries account for more than 30% of professional football injuries (1.8-2.2/1000 h exposure); however, even though there are significant differences within a European comparison, a single professional football team diagnosed on average 12 muscle injuries per season, corresponding to more than 300 availability days lost. The aim of this work is to present the diagnosis, general treatment and comprehensive management of muscle injuries in professional football. The present work is based on current scientific findings, experiences of the authors and examples from routine practice in the management of muscle injuries in a professional sports environment. The authors present a model of gradual progression for the treatment of muscular injuries and their rehabilitation. Due to the time-pressured nature of the professional sports environment, often promoted by coaches and media, this model could help lead players to recover as quickly as possible and return to competitive sports without relapse or sequel injury. This model integrates the player into the treatment plan. The progression sequences in the rehabilitation should be made clear to players and other parties involved, which are crucial for optimal healing. Even if absolute certainty cannot be achieved, i.e. the occurrence of re-injury or secondary injury, this model attempts to minimize the level of risk involved for the returning athlete. Since it is hardly possible to act strictly in line with more conservative guidelines due to the particular circumstances of the professional sport environment, the experiences of the authors are presented in the sense of best practice in order to support future decision-making processes.


#8 Post-Game High Protein Intake May Improve Recovery of Football-Specific Performance during a Congested Game Fixture: Results from the PRO-FOOTBALL Study
Reference: Nutrients. 2018 Apr 16;10(4). pii: E494. doi: 10.3390/nu10040494.
Authors: Poulios A, Fatouros IG, Mohr M, Draganidis DK, Deli C, Papanikolaou K, Sovatzidis A, Nakopoulou T, Ermidis G, Tzatzakis T, Laschou VC, Georgakouli K, Koulouris A, Tsimeas P, Chatzinikolaou A, Karagounis LG, Batsilas D, Krustrup P, Jamurtas AZ
Download link: www.mdpi.com/2072-6643/10/4/494/pdf
Summary: The effects of protein supplementation on performance recovery and inflammatory responses during a simulated one-week in-season microcycle with two games (G1, G2) performed three days apart were examined. Twenty football players participated in two trials, receiving either milk protein concentrate (1.15 and 0.26 g/kg on game and training days, respectively) (PRO) or an energy-matched placebo (1.37 and 0.31 g/kg of carbohydrate on game and training days, respectively) (PLA) according to a randomized, repeated-measures, crossover, double-blind design. Each trial included two games and four daily practices. Speed, jump height, isokinetic peak torque, and muscle soreness of knee flexors (KF) and extensors (KE) were measured before G1 and daily thereafter for six days. Blood was drawn before G1 and daily thereafter. Football-specific locomotor activity and heart rate were monitored using GPS technology during games and practices. The two games resulted in reduced speed (by 3-17%), strength of knee flexors (by 12-23%), and jumping performance (by 3-10%) throughout recovery, in both trials. Average heart rate and total distance covered during games remained unchanged in PRO but not in PLA. Moreover, PRO resulted in a change of smaller magnitude in high-intensity running at the end of G2 (75-90 min vs. 0-15 min) compared to PLA (P = 0.012). KE concentric strength demonstrated a more prolonged decline in PLA (days 1 and 2 after G1, P = 0.014-0.018; days 1, 2 and 3 after G2, P = 0.016-0.037) compared to PRO (days 1 after G1, P = 0.013; days 1 and 2 after G2, P = 0.014-0.033) following both games. KF eccentric strength decreased throughout recovery after G1 (PLA: P=0.001-0.047-PRO: P =0.004-0.22) in both trials, whereas after G2 it declined throughout recovery in PLA (P = 0.000-0.013) but only during the first two days (P = 0.000-0.014) in PRO. No treatment effect was observed for delayed onset of muscle soreness, leukocyte counts, and creatine kinase activity. PRO resulted in a faster recovery of protein and lipid peroxidation markers after both games. Reduced glutathione demonstrated a more short-lived reduction after G2 in PRO compared to PLA. In summary, these results provide evidence that protein feeding may more efficiently restore football-specific performance and strength and provide antioxidant protection during a congested game fixture.


#9 Hip and groin time-loss injuries decreased slightly but injury burden remained constant in men's professional football: the 15-year prospective UEFA Elite Club Injury Study
Reference: Br J Sports Med. 2018 Apr 24. pii: bjsports-2017-097796. doi: 10.1136/bjsports-2017-097796. [Epub ahead of print]
Authors: Werner J, Hagglund M, Ekstrand J, Walden M
Summary: Hip and groin injuries are common in men's professional football, but the time-trend of these injuries is not known. The aim of the study was to investigate hip and groin injury rates, especially time-trends, in men's professional football over 15 consecutive seasons. 47 European teams were followed prospectively for a varying number of seasons between 2001/2002 and 2015/2016, totalling 268 team seasons. Time-loss injuries and individual player exposure during training and matches were recorded. Injury rate was defined as the number of injuries/1000 hours and injury burden as the number of lay-off days/1000  hours. Time-trends for total hip and groin injuries and adductor-related injury rates were analysed using Poisson regression, and injury burden was analysed using a negative binomial regression model. Hip and groin injuries contributed 1812 out of 12 736 injuries (14%), with adductor-related injury as the most common of hip and groin injuries (n=1139, 63%). The rates of hip and groin injury and adductor-related injury were 1.0/1000 hours and 0.6/1000 hours, and these rates decreased significantly with on average 2% (Exp(b)=0.98, 95% CI 0.97 to 0.99, P=0.003) and 3% (Exp(b)=0.97, 95% CI 0.95 to 0.99, P<0.001) per season (year on year), respectively. The seasonal trend of hip and groin injury burden did not improve (Exp(b)=0.99, 95% CI 0.97 to 1.01, P=0.40). Hip and groin injuries constitute a considerable part of all time-loss injuries in men's professional football. Although there was a promising slight decreasing trend in the rates of hip and groin injury (as a category) and adductor-related injury (as a specific diagnosis), the injury burden remained at a consistent level over the study period.


#10 Body composition and somatotypes of male Zimbabwean Premier League football referees
Reference: J Sports Med Phys Fitness. 2018 Apr 20. doi: 10.23736/S0022-4707.18.08326-3. [Epub ahead of print]
Authors: Banda M, Grobbelaar HW, Terblanche E
Summary: Elite athletes need to optimise their body composition to deliver world class performances and this argument could be extended to elite referees as well. Unfortunately, there is a scarcity of body composition information among football referees. The aim of the study was to determine and compare the body composition and somatotypes of male football referees and assistant referees who officiated in the 2013 Zimbabwe Premier Football League. Forty-one participants (21 referees, 20 assistant referees; 8 FIFA, 33 ZIFA licenced referees) with a mean age of 34.89 ± 5.13 years took part. They had on average 10.85 ± 3.85 years of refereeing experience. The ISAK restricted anthropometric profile was used to measure body mass, height, skinfolds, girths and bone breadths, from which body mass index (BMI), waist-to-hip ratio (WHR), percentage body fat and somatotype were calculated. The referees were significantly taller than the assistant referees. The FIFA referees had moderately more desirable anthropometric profiles than the ZIFA referees. With a mean somatotype of 2.62-4.65-2.65, the total sample could be classified as balanced mesomorphs. They had lower BMI and body fat percentages than that observed among referees from other nationalities in the available literature. The results add to the paucity of information on the body composition of football officials. Referees aiming to excel at higher levels need to obtain and maintain an ideal body composition since elite level football is intense and requires high fitness levels.

Thu

17

May

2018

Latest research in football - week 14 - 2018

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 Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players
Reference: Hum Mov Sci. 2018 Apr 3;59:81-87. doi: 10.1016/j.humov.2018.03.016. [Epub ahead of print]
Authors: Coratella G, Beato M, Schena F
Summary: The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.


#2 "Good, better, creative": the influence of creativity on goal scoring in elite soccer
Reference: J Sports Sci. 2018 Apr 6:1-5. doi: 10.1080/02640414.2018.1459153. [Epub ahead of print]
Authors: Kempe M, Memmert D
Summary: This study investigated the level of creativity of goals scored in football. Therefore, all goals in the Football FIFA World Cup 2010 and 2014, as well as the Football UEFA Euro 2016 were qualitatively examined. Three Football experts evaluated the last eight actions before each goal using a creativity scale ranging from 0 to 10 (0 = not creative, 10 = highly creative) of all goals scored via open play (311 goals in 153 matches). Level of creativity was revealed using an Analysis of Variance and the frquency of high highly creative goals using a Kruskall- Wallis Test. The results showed that the closer the actions to a goal, the more creative they were evaluated. Teams that advanced to the later rounds of the tournament demonstrated greater creativity than teams that failed to do so. High creativity in the last two actions before the actual shot on goal proved to be the best predictor for game success. In conclusion, this study is the first one to show that creativity seems to be a factor for success in high level football. Thereby it provides an empirical basis for the ongoing debate on the importance of creativity training in football.


#3 Mental Fatigue and Soccer: Current Knowledge and Future Directions
Reference: Sports Med. 2018 Apr 5. doi: 10.1007/s40279-018-0908-2. [Epub ahead of print]
Authors: Smith MR, Thompson C, Marcora SM, Skorski S, Meyer T, Coutts AJ
Summary: Fatigue is a complex state with multiple physiological and psychological origins. However, fatigue in soccer has traditionally been investigated from a physiological perspective, with little emphasis on the cognitive demands of competition. These cognitive demands may induce mental fatigue, which could contribute to the fatigue-related performance decrements observed during and after soccer matches. Recent research investigating the relationship between mental fatigue and soccer-specific performance supports this suggestion. This leading article provides an overview of the research in this emerging field, outlining the impact of mental fatigue on soccer-specific physical, technical, decision-making, and tactical performances. The second half of this review provides directions for future research in response to the limitations of the existing research. Emphasis is placed on translating the current body of knowledge into practical applications and developing a greater understanding of the mechanisms underpinning the negative impact of mental fatigue on soccer performance. A conceptual model is presented to help direct this future research.


#4 Specific Changes in Young Soccer Player's Fitness After Traditional Bilateral vs. Unilateral Combined Strength and Plyometric Training
Reference: Front Physiol. 2018 Mar 22;9:265. doi: 10.3389/fphys.2018.00265. eCollection 2018.
Authors: Ramirez-Campillo R, Sanchez-Sanchez J, Gonzalo-Skok O, Rodriguez-Fernandez A, Carretero M, Nakamura FY
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874317/pdf/fphys-09-00265.pdf
Summary: The aim of this study was to compare changes in young soccer player's fitness after traditional bilateral vs. unilateral combined plyometric and strength training. Male athletes were randomly divided in two groups; both received the same training, including strength training for knee extensors and flexors, in addition to horizontal plyometric training drills. The only difference between groups was the mode of drills technique: unilateral (UG; n = 9; age, 17.3 ± 1.1 years) vs. bilateral (TG; n = 9; age, 17.6 ± 0.5 years). One repetition maximum bilateral strength of knee muscle extensors (1RM_KE) and flexors (1RM_KF), change of direction ability (COD), horizontal and vertical jump ability with one (unilateral) and two (bilateral) legs, and limb symmetry index were measured before and after an 8-week in-season intervention period. Some regular soccer drills were replaced by combination of plyometric and strength training drills. Magnitude-based inference statistics were used for between-group and within-group comparisons. Beneficial effects (p < 0.05) in 1RM_KE, COD, and several test of jumping performance were found in both groups in comparison to pre-test values. The limb symmetry index was not affected in either group. The beneficial changes in 1RM_KE (8.1%; p = 0.074) and 1RM_KF (6.7%; p = 0.004), COD (3.1%; p = 0.149), and bilateral jump performance (from 2.7% [p = 0.535] to 10.5% [p = 0.002]) were possible to most likely beneficial in the TG than in the UG. However, unilateral jump performance measures achieved likely to most likely beneficial changes in the UG compared to the TG (from 4.5% [p = 0.090] to 8.6% [p = 0.018]). The improvements in jumping ability were specific to the type of jump performed, with greater improvements in unilateral jump performance in the UG and bilateral jump performance in the TG. Therefore, bilateral strength and plyometric training should be complemented with unilateral drills, in order to maximize adaptations.


#5 Switching between pitch surfaces: practical applications and future perspectives for soccer training
Reference: J Sports Med Phys Fitness. 2018 Apr 4. doi: 10.23736/S0022-4707.18.08278-6. [Epub ahead of print]
Authors: Rago V, Silva JR, Brito J, Barreira D, Mohr M, Krustrup P, Rebelo AN
Summary: Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training / competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising on different pitch surfaces in soccer. Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations or injury outcomes according to different pitch surfaces. A total of 224 studies were retrieved from a literature search. Twenty articles met the inclusion criteria: 9 for acute physical and physiological responses, 2 for training adaptations and 9 for injury assessment. The literature lacks consistent evidence regarding the effects of pitch surface on performance and health outcomes in soccer players. However, it seems that occasionally switching training surfaces seems a valuable strategy for focusing on specific musculoskeletal queries and enhancing players' fitness. For instance, sand training may be occasionally proposed as complementary training strategy, given the recruitment of additional musculature probably not involved on firmer surfaces, but the possible training-induced adaptations of non-conventional soccer surfaces (e.g., sand) might potentially result into a negative transfer on AT or NG. Since the specific physical demands of soccer can differ between surfaces, coaches should resort to the use of non-traditional surfaces with parsimony, emphasizing the specific surface-related motor tasks, normally observed on natural grass or artificial turf. Further studies are required to better understand the physiological effects induced by systematic surface-specific training, or switching between pitch surfaces.


#6 Shoulder and elbow injuries in soccer goalkeepers versus field players in the National Collegiate Athletic Association, 2009-2010 through 2013-2014
Reference: Phys Sportsmed. 2018 Apr 4. doi: 10.1080/00913847.2018.1462083. [Epub ahead of print]
Authors: Goodman AD, Etzel C, Raducha JE, Owens BD
Summary: Examination of the incidence of shoulder and elbow injuries in the collegiate soccer player population is limited, as is comparison between goalkeepers and field players. We hypothesized that goalkeepers would have a higher incidence of shoulder and elbow injuries than field players. Furthermore, we sought to determine the incidence of shoulder and elbow injuries among National Collegiate Athletic Association (NCAA) soccer players, and to determine injury risk factors. The NCAA Injury Surveillance Program database was analyzed for injuries to NCAA men's and women's soccer players during the 2009-2010 through 2013-2014 academic years. The incidence of injury was calculated per 10,000 athletic exposures (AE) for goalkeepers versus field players, activity, and injury characteristics, and compared using univariate analysis and risk-ratios to determine injury risk factors. While the overall incidence of shoulder and elbow injuries in soccer players was 2.7/10,000AE [95% CI 2.62-2.78], the incidence among goalkeepers was 4.6-fold higher (8.3 vs. 1.8/10,000AE, p<0.0001). Goalkeepers had significantly higher incidences of injury in practice (21.3-fold) and in the preseason (16.1-fold) than field players. Women goalkeepers were disproportionately affected, with injury incidences 7.7-fold higher than women field players, and 1.9-fold higher than male goalkeepers. Acromioclavicular joint injuries, rotator cuff tears/sprains, and elbow and shoulder instability constituted the majority of the goalkeeper injuries. Shoulder and elbow injuries in NCAA soccer players are significantly more common in goalkeepers than field players. Incidence varies widely by position and injury, with a number of associated risk factors. Soccer players sustaining these injuries, along with their coaches and medical providers, may benefit from this injury data to best manage expectations and outcomes. Soccer governing bodies may use this to track injury incidence and response to preventative measures.


#7 The effects of maturation on jumping ability and sprint adaptations to plyometric training in youth soccer players
Reference: J Sports Sci. 2018 Apr 3:1-7. doi: 10.1080/02640414.2018.1459151. [Epub ahead of print]
Authors: Asadi A, Ramirez-Campillo R, Arazi H, Saez de Villarreal E
Summary: The aim of this study was to investigate the effects of maturation on power and sprint performance adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity [PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤ 0.05) and small to moderate effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64; 0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = -0.58; -0.66), and 20-m sprint with ball (ES = -0.44; -0.8; -0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-PHV in vertical jump and sprint performance after training (P ≤ 0.05). Short-term plyometric training had positive effects on sprinting and jumping-power which are important determinants of match-winning actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems effective in improving power and sprint performance in youth soccer players.


#8 Passing Decisions in Football: Introducing an Empirical Approach to Estimating the Effects of Perceptual Information and Associative Knowledge
Reference: Front Psychol. 2018 Mar 22;9:361. doi: 10.3389/fpsyg.2018.00361. eCollection 2018.
Authors: Steiner S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874613/pdf/fpsyg-09-00361.pdf
Summary: The importance of various information sources in decision-making in interactive team sports is debated. While some highlight the role of the perceptual information provided by the current game context, others point to the role of knowledge-based information that athletes have regarding their team environment. Recently, an integrative perspective considering the simultaneous involvement of both of these information sources in decision-making in interactive team sports has been presented. In a theoretical example concerning passing decisions, the simultaneous involvement of perceptual and knowledge-based information has been illustrated. However, no precast method of determining the contribution of these two information sources empirically has been provided. The aim of this article is to bridge this gap and present a statistical approach to estimating the effects of perceptual information and associative knowledge on passing decisions. To this end, a sample dataset of scenario-based passing decisions is analyzed. This article shows how the effects of perceivable team positionings and athletes' knowledge about their fellow team members on passing decisions can be estimated. Ways of transfering this approach to real-world situations and implications for future research using more representative designs are presented.


#9 Concurrent validation of an inertial measurement system to quantify kicking biomechanics in four football codes
Reference: J Biomech. 2018 Mar 21. pii: S0021-9290(18)30212-4. doi: 10.1016/j.jbiomech.2018.03.031. [Epub ahead of print]
Authors: Blair S, Duthie G, Robertson S, Hopkins W, Ball K
Summary: Wearable inertial measurement systems (IMS) allow for three-dimensional analysis of human movements in a sport-specific setting. This study examined the concurrent validity of a IMS (Xsens MVN system) for measuring lower extremity and pelvis kinematics in comparison to a Vicon motion analysis system (MAS) during kicking. Thirty footballers from Australian football (n = 10), soccer (n = 10), rugby league and rugby union (n = 10) clubs completed 20 kicks across four conditions. Concurrent validity was assessed using a linear mixed-modelling approach, which allowed the partition of between and within-subject variance from the device measurement error. Results were expressed in raw and standardised units for assessments of differences in means and measurement error, and interpreted via non-clinical magnitude-based inferences. Trivial to small differences were found in linear velocities (foot and pelvis), angular velocities (knee, shank and thigh), sagittal joint (knee and hip) and segment angle (shank and pelvis) means (mean difference: 0.2-5.8%) between the IMS and MAS in Australian football, soccer and the rugby codes. Trivial to small measurement errors (from 0.1 to 5.8%) were found between the IMS and MAS in all kinematic parameters. The IMS demonstrated acceptable levels of concurrent validity compared to a MAS when measuring kicking biomechanics across the four football codes. Wearable IMS offers various benefits over MAS, such as, out-of-laboratory testing, larger measurement range and quick data output, to help improve the ecological validity of biomechanical testing and the timing of feedback. The results advocate the use of IMS to quantify biomechanics of high-velocity movements in sport-specific settings.

Wed

16

May

2018

Football is...(#61)

Long throw-ins might create goal scoring opportunities

Mon

14

May

2018

Latest research in football - week 12 - 2018

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 Seasonal Changes in Fitness, Anthropometrics, and Body Composition in Collegiate Division Ii Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002578. [Epub ahead of print]
Authors: Peart AN, Nicks CR, Mangum M, Tyo BM
Summary: The purpose of this study was to investigate anthropometrics, body composition, aerobic and anaerobic fitness of collegiate Division II female soccer players throughout a calendar year. Eighteen (20 ± 0.9y) NCAA division II female soccer players from the same team participated in the study. Anthropometrics and body composition variables were assessed in addition to the Counter Movement Jump (CMJ), Wingate Anaerobic Test (WAT), and peak oxygen uptake (VO2peak). Data were collected over five time points: end of competitive seasons (ECS1 and ECS2), beginning of off-season (BOS), end of off-season (EOS), and pre-season (PS). Repeated-measures analysis of variance (ANOVA) were conducted to compare test scores among all five data collection points. Where appropriate, Bonferroni post-hoc tests were used to determine which points were significantly different. Hip circumference (HC) decreased significantly (p < 0.001) from EOS (98.47 ± 6.5 cm) to PS (94.46 ± 6.8 cm). Fat mass (FM) (12.73 ± 5.4 kg) was significantly different in ECS2 compared to BOS and EOS means (p ≤ 0.05) and percentage of body fat (%BF) (20.08 ± 5.44) significantly different in ECS2 compared to ECS1, BOS, and EOS means (p ≤ 0.05), while fat-free mass (FFM) was maintained from ECS1 to ECS2. CMJ, WAT, and VO2peak performance did not significantly change from ECS1 to ECS2. Anthropometrics and body composition results are similar to previous studies measuring Division II to professional female soccer players. CMJ results remained consistent and are comparable to results on Division I female soccer players. Coaches and researchers can use these data to help design and evaluate training programs throughout a calendar year.


#2 The Effect of Match-Factors on the Running Performance of Elite Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002584. [Epub ahead of print]
Authors: Trewin J, Meylan C, Varley MC, Cronin J, Ling D
Summary: The purpose of this study was to examine the effects of match-factors on the match-running of elite female soccer players. Players from the same women's national team (n = 45) were monitored during 47 international fixtures (files = 606) across four years (2012-2015) using 10-Hz global positioning system devices. A mixed model was used to analyse the effects of altitude, temperature, match-outcome, opposition ranking and congested schedules. At altitude (>500 m) a small increase in the number of accelerations (ES = 0.40) and a small decrease in total distance (ES = -0.54) was observed, whereas at higher temperatures there were decreases in all metrics (ES = -0.83 to -0.16). Playing a lower-ranked team in a draw resulted in a moderate increase in high-speed running (ES = 0.89), with small to moderate decreases in total distance and low-speed running noted in a loss or a win. Winning against higher-ranked opponents indicated moderately higher total distance and low-speed running (ES = 0.75), compared to a draw. Whilst the number of accelerations were higher in a draw against lower-ranked opponents, compared to a win and a loss (ES = 0.95 and 0.89 respectively). Practitioners should consider the effect of match-factors on match-running in elite female soccer.


#3 Sequencing Effects of Plyometric Training Applied Before or After Regular Soccer Training on Measures of Physical Fitness in Young Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002525. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Gentil P, Loturco I, Sanchez-Sanchez J, Izquierdo M, Moran J, Nakamura FY, Chaabene H, Granacher U
Summary: The objective was to compare the effects of short-term (i.e., 7 week) plyometric training applied before (PJT-B) or after (PJT-A) soccer practice on components of physical fitness in young soccer players, a single-blind randomized controlled trial was conducted. Post-pubertal boys aged 17.0±0.5 years were allocated to three groups: PJT-B (n=12), PJT-A (n=14), and control (CON; n=12). The outcome measures included tests to evaluate 20-m speed, standing long jump [SLJ], squat jump [SJ], countermovement jump [CMJ], and drop jump [DJ], 20-m multistage shuttle running speed [MSSRT], and Illinois change of direction speed [ICODT]. While the CON performed soccer-specific training, the PJT-A and PJT-B groups conducted the same soccer-specific sessions but replaced ∼11% of their time with plyometric training. The PJT-B group performed plyometric exercises after a warm-up program, and the PJT-A group conducted plyometric exercises ∼10 minutes after the completion of soccer training. Analyses of variance (ANOVAs) were used to detect differences between groups in all variables for pre- and post-training tests. Main effects of time (all p<.01; d=0.19-0.79) and group x time interactions (all p<.05; d=0.17-0.76) were observed for all examined variables. Post hoc analyses revealed significant increases in the PJT-B group (SLJ: 9.4%, d=1.7; CMJ: 11.2%, d=0.75; 20-m MSSRT: 9.0%, d=0.77) and the PJT-A group (SLJ: 3.1%, d=0.7; CMJ: 4.9%, d=0.27; 20-m MSSRT: 9.0%, d=0.76). Post hoc analyses also revealed significant increases in the PJT-B group (20-m speed: -7.4%, d=0.75; 20-cm DJ reactive strength index: 19.1%, d=1.4; SJ: 6.3%, d=0.44; ICODT results: -4.2%, d=1.1). In general, our study revealed that plyometric training is effective in improving measures of physical fitness in young male soccer players when combined with regular soccer training. More specifically, larger training induced effects on physical fitness were registered if plyometric training was conducted prior to soccer specific training.


#4 Postactivation Potentiation Following Acute Bouts of Plyometric versus Heavy-Resistance Exercise in Collegiate Soccer Players
Reference: Biomed Res Int. 2018 Feb 7;2018:3719039. doi: 10.1155/2018/3719039. eCollection 2018.
Authors: Sharma SK, Raza S, Moiz JA, Verma S, Naqvi IH, Anwer S, Alghadir AH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5820625/pdf/BMRI2018-3719039.pdf
Summary: Postactivation potentiation is referred to as an acute and temporary enhancement of muscle performance resulting from previous muscle contraction. The purpose of this study was to compare the acute effect of plyometric exercise (PLY) and heavy-resistance exercise (RES) on the blood lactate level (BLa) and physical performance. Fourteen male collegiate soccer players were randomized to perform either RES or PLY first and then crossed over to perform the opposite intervention. PLY consisted of 40 jumps, whereas RES comprised ten single repetitions at 90% of one repetition maximum. BLa and physical performance (countermovement jump height and 20-m sprint) were measured before and at 1 and 10 min following the exercise. No significant difference was observed in the BLa for both exercises (PLY and RES). Relative to baseline, countermovement jump (CMJ) height was significantly better for the PLY group after 1 min (P = 0.004) and after 10 min (P = 0.001) compared to that of the RES group. The 20-m sprint time was significantly better for PLY at 10 min (P = 0.003) compared to that of RES. The present study concluded that, compared to RES, PLY causes greater potentiation, which leads to improved physical performance.


#5 Aerobic fitness in professional soccer players after anterior cruciate ligament reconstruction
Reference: PLoS One. 2018 Mar 22;13(3):e0194432. doi: 10.1371/journal.pone.0194432. eCollection 2018.
Authors: Almeida AM, Santos Silva PR, Pedrinelli A, Hernandez AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864031/pdf/pone.0194432.pdf
Summary: Although anterior cruciate ligament (ACL) reconstruction is considered a successful procedure in restoring knee stability, few studies have addressed the issue of aerobic capacity after ACL surgery. Soccer players need technical, tactical and physical skills to succeed, such as good knee function and aerobic capacity. Our purpose is to evaluate aerobic fitness in ACL injured professional football players and six months after ACL reconstruction compared to a control group. Twenty athletes with ACL injury were evaluated and underwent ACL reconstruction with hamstrings autograft, and were compared to twenty healthy professional soccer players. The methods used to evaluate aerobic fitness were maximum oxygen uptake (VO2max) and ventilatory thresholds with a treadmill protocol, before and six months after surgery, compared to a control group. Knee function questionnaires, isokinetic strength testing and body composition evaluation were also performed. Median ACL-injured patients age was 21 years old, and controls 20.5 years old. (n.s.). Preoperative VO2max in the ACL injured group was 45.2 ± 4.3 mL/kg/min, postoperative 48.9 ± 3.8 mL/kg/min and controls 56.9 ± 4.2 mL/kg/min. (p< .001 in all comparisons). Body composition evaluation was similar in all situations. Knee function questionnaires and quadriceps peak torque deficit improved after surgery but were significantly lower compared to controls. Aerobic fitness is significantly reduced in professional soccer players with ACL injury, and six months of rehabilitation was not enough to restore aerobic function after ACL reconstruction, compared to non-injured players of the same level.


#6 Validation of Field Methods to Assess Body Fat Percentage in Elite Youth Soccer Players
Reference: Int J Sports Med. 2018 Mar 21. doi: 10.1055/s-0044-101145. [Epub ahead of print]
Authors: Munguia-Izquierdo D, Suarez-Arrones L, Di Salvo V, Paredes-Hernandez V, Alcazar J, Ara I, Kreider R, Mendez-Villanueva A
Summary: This study determined the most effective field method for quantifying body fat percentage in male elite youth soccer players and developed prediction equations based on anthropometric variables. Forty-four male elite-standard youth soccer players aged 16.3-18.0 years underwent body fat percentage assessments, including bioelectrical impedance analysis and the calculation of various skinfold-based prediction equations. Dual X-ray absorptiometry provided a criterion measure of body fat percentage. Correlation coefficients, bias, limits of agreement, and differences were used as validity measures, and regression analyses were used to develop soccer-specific prediction equations. The equations from Sarria et al. (1998) and Durnin & Rahaman (1967) reached very large correlations and the lowest biases, and they reached neither the practically worthwhile difference nor the substantial difference between methods. The new youth soccer-specific skinfold equation included a combination of triceps and supraspinale skinfolds. None of the practical methods compared in this study are adequate for estimating body fat percentage in male elite youth soccer players, except for the equations from Sarria et al. (1998) and Durnin & Rahaman (1967). The new youth soccer-specific equation calculated in this investigation is the only field method specifically developed and validated in elite male players, and it shows potentially good predictive power.


#7 Cardiac deformation parameters and rotational mechanics by cardiac magnetic resonance feature tracking in pre-adolescent male soccer players
Reference: Cardiol Young. 2018 Mar 21:1-3. doi: 10.1017/S1047951118000343. [Epub ahead of print]
Authors: Malek LA, Barczuk-Falęcka M, Brzewski M
Summary: The purpose of the study was to analyse whether prolonged and regular physical training in children leads to changes in myocardial systolic deformation and rotational mechanics. For that purpose, cardiac MRI feature tracking was performed retrospectively in 35 pre-adolescent male soccer players and 20 matched controls. There were no changes in global strain, but left ventricular twist and apical rotation were greater in soccer players, which adds to the features of paediatric athlete's heart.


#8 Effect of Core Muscle Strengthening Exercises (Including Plank and Side Plank) on Injury Rate in Male Adult Soccer Players: A Systematic Review
Reference: Sportverletz Sportschaden. 2018 Mar;32(1):35-46. doi: 10.1055/a-0575-2324. Epub 2018 Mar 20. [Article in German; Abstract available in German from the publisher]
Authors: Blasimann A, Eberle S, Scuderi MM
Summary: Soccer is seen as highly intensive sport with an increased injury rate. Male adults are the players with the highest injury incidence. Accordingly, the importance of core muscle strengthening to prevent injury has increased in the past few years. Up to date, core muscle strengthening plays an important role in different prevention programs, such as the "FIFA 11 +". The aim of this systematic review was to investigate the effect of core muscle strengthening on injury rate in male adult soccer players, including at least the known and easy exercises "plank" and "side plank", on injury rate in male adult soccer players. The databases PubMed, PEDro, Cochrane Library, SPORTDiscus and Cinahl were searched systematically. Included studies had to comprise exercises for core muscles as an intervention (as a part of a prevention program) for adult male soccer players. The control group had to continue their usual exercise routine. The exercises "plank" and "side plank" were mandatory elements of the training program. The number of injuries and/or the injury rate (per 1000 hours) were defined as outcomes. The quality of the included studies was assessed with the PEDro scale and the Risk of Bias tool. Seven studies with 2491 participants in total could be included. Two studies found a significant decrease in the injury rate in the intervention group (p < 0.05, p < 0.001 respectively). In two studies, no significance level was reported, but the training showed preventive effects in the intervention group. In the other three studies, no significant changes in the injury rate were found (p > 0.05). The seven included studies differed greatly with respect to the applied methods, the chosen interventions and the obtained results. Furthermore, core muscles were never trained separately but were always part of a program containing other preventive elements. Therefore, it was difficult to compare the studies. However, prevention programs including strengthening exercises for core muscles tend to positively affect the injury rate. Based on the literature found, the research question cannot definitively be answered. In the future, further studies are needed which investigate the effect of isolated core muscle training on the injury rate of soccer players.


#9 In-season monitoring of hip and groin strength, health and function in elite youth soccer: Implementing an early detection and management strategy over two consecutive seasons
Reference: J Sci Med Sport. 2018 Mar 14. pii: S1440-2440(18)30071-9. doi: 10.1016/j.jsams.2018.03.004. [Epub ahead of print]
Authors: Wollin M, Thorborg K, Welvaert M, Pizzari T
Summary: The primary purpose of this study was to describe an early detection and management strategy when monitoring in-season hip and groin strength, health and function in soccer. Secondly to compare pre-season to in-season test results. Twenty-seven elite male youth soccer players (age: 15.07±0.73years) volunteered to participate in the study. Monitoring tests included: adductor strength, adductor/abductor strength ratio and hip and groin outcome scores (HAGOS). Data were recorded at pre-season and at 22 monthly intervals in-season. Thresholds for alerts to initiate further investigations were defined as any of the following: adductor strength reductions >15%, adductor/abductor strength ratio <0.90, and HAGOS subscale scores <75 out of 100 in any of the six subscales. Overall, 105 alerts were detected involving 70% of players. Strength related alerts comprised 40% and remaining 60% of alerts were related to HAGOS. Hip adductor strength and adductor/abductor strength ratio were lowest at pre-season testing and had increased significantly by month two (p<0.01, mean difference 0.26, CI95%: 0.12, 0.41N/kg and p<0.01, mean difference 0.09, CI95%: 0.04, 0.13 respectively). HAGOS subscale scores were lowest at baseline with all, except Physical Activity, showing significant improvements at time-point one (p<0.01). Most (87%) time-loss were classified minimal or mild. In-season monitoring aimed at early detection and management of hip and groin strength, health and function appears promising. Hip and groin strength, health and function improved quickly from pre-season to in-season in a high-risk population for ongoing hip and groin problems.


#10 Exploring the effects of mental and muscular fatigue in soccer players' performance
Reference: Hum Mov Sci. 2018 Apr;58:287-296. doi: 10.1016/j.humov.2018.03.004. Epub 2018 Mar 15.
Authors: Coutinho D, Goncalves B, Wong DP, Travassos B, Coutts AJ, Sampaio J
Summary: This study examined the effects of induced mental and muscular fatigue on soccer players' physical activity profile and collective behavior during small-sided games (SSG). Ten youth soccer players performed a 5vs5 SSG under three conditions: a) control, playing without any previous activity; b) muscular fatigue, playing after performing a repeated change-of-direction task; c) mental fatigue, playing after completing a 30 min Stroop color-word task. Players' positional data was used to compute time-motion and tactical-related variables. The muscular fatigue condition resulted in lower distances covered in high speeds (∼27%, 0.3; ±0.5) than the control condition. From the tactical perspective, the muscular fatigue condition resulted in lower distance between dyads and players spent ∼7% more time synchronized in longitudinal displacements than the control condition (0.3; ±0.3). Additionally, players spent ∼14% more time synchronized with muscular fatigue than with mental fatigue (0.7; ±0.3). The mental fatigue condition resulted in a very likely more predictable pattern in the distance between dyads than in muscular fatigue condition (0.4; ±0.2). Also, the mental fatigue possibly decreased the teams' stretch index when compared with control (0.2; ±0.3) and likely increased compared with muscular fatigue (0.5; ±0.5). The better levels of longitudinal synchronization after muscular fatigue, might suggest the usage of tactical-related tasks after intense exercise bouts. The lower physical performance and time spent longitudinally synchronized after mental fatigue, should alert to consider this variable before matches or training activities that aim to improve collective behavior.


#11 Is Bony Hip Morphology Associated With Range of Motion and Strength in Asymptomatic Male Soccer Players?
Reference: J Orthop Sports Phys Ther. 2018 Mar 16:1-29. doi: 10.2519/jospt.2018.7848. [Epub ahead of print]
Authors: Mosler AB, Agricola R, Thorborg K, Weir A, Whiteley RJ, Crossley KM, Holmich P
Summary: Study Design Cross-sectional cohort study. Background Athletes with femoroacetabular impingement (FAI) syndrome have cam and/or pincer morphology, pain on orthopaedic testing, and often have reduced hip range of motion (ROM) and strength. However, cam and pincer morphology are also common in asymptomatic hips. Therefore, it is currently unknown whether the ROM and strength deficits observed in athletes with FAI syndrome result from the variance in their bony hip morphology or hip condition. Objectives To investigate the relationship between musculoskeletal screening findings and bony hip morphology in asymptomatic male soccer players. Methods Male professional soccer players in Qatar were screened specifically for hip/groin pain in 2 consecutive seasons. The screening battery included: pain provocation, ROM and strength tests, and hip radiographs. Univariate and multivariate regression analyses using generalised estimating equations evaluated the relationship between musculoskeletal screening findings and each bony hip morphological variant (cam, large cam, pincer, and acetabular dysplasia). Results Asymptomatic hips with cam and large cam morphology were associated with lower ROM in internal rotation and bent knee fall out, and a higher likelihood of pain on provocation testing. Pincer morphology was associated with lower abduction ROM and higher abduction strength. Acetabular dysplasia was associated with higher abduction ROM. Each association was weak and demonstrated poor or failed discriminatory power. Conclusion Bony hip morphology is associated with hip joint ROM and abduction strength, but musculoskeletal screening tests have a poor ability to discriminate between the different morphologies.


#12 Higher compliance to a neuromuscular injury prevention program improves overall injury rate in male football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Mar 19. doi: 10.1007/s00167-018-4895-5. [Epub ahead of print]
Authors: Silvers-Granelli HJ, Bizzini M, Arundale A, Mandelbaum BR, Snyder-Mackler L
Summary: The 11+ injury prevention program has been shown to decrease injury rate. However, few studies have investigated compliance and if it is correlated to time loss. The purpose of this study was to (1) analyze how differences in compliance may impact injury rate and (2) if compliance may impact time loss due to injury. This study was a Level 1 prospective cluster randomized controlled trial conducted in NCAA men's football (soccer) teams that examined the efficacy of the 11+ injury prevention program. The two outcome variables examined were number of injuries and number of days missed from competition. Twenty-seven teams (n = 675 players) used the 11+ program. Compliance, injuries and time loss were recorded. There were three compliance categories, low (LC, 1-19 doses/season), moderate (MC, 20-39 doses/season), and high (HC, > 40 doses/season). There was a significant difference among the groups for injuries, p = 0.04, pη2  = 0.23. The LC group [mean (M) = 13.25, 95% confidence interval (CI) 9.82-16.68, injury rate (IR) = 10.35 ± 2.21] had a significantly higher injury rate than the HC group (M = 8.33, 95%CI 6.05-10.62, IR = 10.35 ± 2.21), p = 0.02. The MC group (M = 11.21, 95%CI 9.38-13.05, IR = 8.55 ± 2.46) was not significantly different than the LC group, p = 0.29, but was significantly greater than the HC group, p = 0.05. When examined as a continuous variable, compliance was significantly negatively related to injury rate (p = 0.004). It was also significantly negatively related to number of days missed (p = 0.012). When compliance was high, there was a significant reduction in injury and time loss. This evidence reinforces the importance of consistent injury prevention program utilization. Clinically, these findings have important implications when discussing the importance of consistent utilization of an injury prevention protocol in sport.


#13 Training Effects of the FIFA 11+ Kids on Physical Performance in Youth Football Players: A Randomized Control Trial
Reference: Front Pediatr. 2018 Mar 5;6:40. doi: 10.3389/fped.2018.00040. eCollection 2018.
Authors: Pomares-Noguera C, Ayala F, Robles-Palazon FJ, Alomoto-Burneo JF, Lopez-Valenciano A, Elvira JLL, Hernandez-Sanchez S, De Ste Croix M
Summary: The objective was to analyze the training effects of the FIFA 11+ kids on several parameters of physical performance in male youth football players. Twenty-three youth players were randomized within each team into two groups (control vs. intervention). The intervention group performed the FIFA 11+ kids programme 2 times a week for 4 weeks; the control groups completed their normal warm-up routines. Thirteen physical performance measures {range of motion (hip, knee, and ankle joints), dynamic postural control (measured throughout the Y balance test), 20 m sprint time, slalom dribble with a ball, agility, vertical jumping height [counter movement jump (CMJ) and drop jump (DJ)], horizontal jump distance, accuracy when volleying a ball [measured throughout the Wall Volley test]} were assessed. All physical performance parameters were compared via magnitude-based inference analysis. Significant between-group differences in favor of the FIFA 11+ players were found for dynamic postural control {anterior [mean and 90% confidence intervals (CI) = 1 cm, from -1.6 to 3.5 cm] and posteromedial (mean and 90% CI = 5.1 cm, from -1.8 to 12 cm) and posterolateral (mean and 90% CI = 4.8 cm, from 0.6 to 9.0 cm) distances}, agility run (mean and 90% CI = 0.5 s, from -0.9 to 0 s), vertical jump height [CMJ (mean and 90% CI = 3.1 cm, from 0.2 to 6.1 cm) and DJ (mean and 90% CI = 1.7 cm, from -0.5 to 3.9 cm)], and horizontal jump distance (mean and 90% CI = 2.5 cm, from -8 to 15 cm). The control groups showed better performance in 20 m sprint time (mean and 90% CI = -0.05 s, from -0.11 to 0.07) and wall volley tests (mean and 90% CI = 0.2, from -0.2 to 0.6) compared to the intervention group. The main findings of this study suggest that just 4 weeks of implementation of the FIFA 11+ kids produces improved physical performance compared with traditional warm-up routines in youth soccer players.

Sun

13

May

2018

Football is...(#60)

Off-season = detraining

Thu

10

May

2018

Latest research in football - week 11 - 2018

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 reliability and validity of a video-based method for assessing hamstring strength in football players
Reference: J Exerc Sci Fit. 2017 Jun;15(1):18-21. doi: 10.1016/j.jesf.2017.04.001. Epub 2017 Apr 28.
Authors: Lee JWY, Li C, Yung PSH, Chan KM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812858/pdf/main.pdf
Summary: Evaluating hamstring strength by isokinetic dynamometry is limited by various practical issues such as time and cost. A video-based Nordic hamstring exercise is introduced as an alternative option. The aims of this study are to evaluate 1.) the between-session reliability and 2.) concurrent validity of the testing method compared to a standardized isokinetic dynamometry. Thirty male elite footballers were recruited for the study. From the Nordic hamstring exercise, the video-analysis-determined Nordic break-point angles where the participant could no longer withstand the force of the fall (eccentric mode) and the number of seconds that the player could hold at 30° forward flexion angle (isometric mode) were measured. Intra-class correlation coefficients for between-session reliability, Pearson r correlations between the current method and isokinetic dynamometry were calculated. The reliability of the eccentric mode was moderate (ICC (2,1) = 0.82) while that of isometric mode was poor (ICC (2,1) = 0.57). The Nordic break-point angle of the eccentric mode significantly correlated with the concentric and eccentric hamstring peak torque (r = 0.48 and 0.58, p < 0.001), while the isometric was not (r = 0.02 - 0.07, p > 0.05). The eccentric mode of the video-based hamstring strength test was a moderately reliable and valid method to measure the eccentric hamstring strength in elite football players.


#2 Activity profile and physiological responses of Korean amateur football referees during matches
Reference: J Phys Ther Sci. 2018 Feb;30(2):351-354. doi: 10.1589/jpts.30.351. Epub 2018 Feb 28.
Authors: Choi Y, Roh J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5851381/pdf/jpts-30-351.pdf
Summary: The present study aimed to analyze and compare the activity profile and physiological responses of amateur football referees during competitive matches of high school and college students. Thirty referees (high school, 15; college, 15) were included in this study. The total distance covered, movement speed, and heart rate were measured using a global positioning system-enabled wireless heart rate monitor. The blood lactate concentration was measured immediately after the first and second half. College football referees covered a higher total distance than did their high school counterparts (7,547 m vs. 6,719 m). The maximal heart rate of college football referees was low in the first half alone, and the percentage of the heart rate within the "maximum" range was low throughout the game.  Refereeing imposes a significantly high physical load on the body while tracking player and ball movement. The present study suggests the need for developing and distributing physical training programs tailored for refereeing.


#3 Influence of Football on Physiological Cardiac Indexes in Professional and Young Athletes
Reference: Front Physiol. 2018 Feb 28;9:153. doi: 10.3389/fphys.2018.00153. eCollection 2018.
Authors: Francavilla CV, Sessa F, Salerno M, Albano GD, Villano I, Messina G, Triolo F, Todaro L, Ruberto M, Marsala G, Cascio O, Mollica MP, Monda V, Cibelli G, Valenzano A, Zammit C, Monda M, Messina A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835836/pdf/fphys-09-00153.pdf
Summary: After long-term intensive training, considerable morphological and functional heart changes occur in professional athletes. Such changes arise progressively and regress upon interruption of the physical activity. Morphological and functional alterations on heart are known as "Athlete's heart" condition. This study aims to compare echocardiographic parameters in two different groups of professional athletes. Furthermore, a prospective study is performed analyzing the echocardiographic changes occurring in 12 professional players in 3 years of follow-up. 78 football players were examined from July 2011 to May 2016 (40 enrolled in Group A and 38 in Group B). Twelve players of GROUP A were followed for 3 consecutive seasons. The general clinical examination, the cardiopulmonary evaluation, the ECG, the ergometer stress test, the spirometric examination and the standard cardiac eco color doppler test were recorded. Left ventricle dimensions, left atrium dimensions, and interventricular septum dimensions were higher in A players than in B players. Moreover, following up 12 players for 3 years, a statistically significant increase of such values was observed. In A players, higher dimensions of the left chambers and the interventricular septum were observed, compared to B players. No statistically significant difference was found regarding the ejection fraction. The 3 years follow-up showed a statistically significant increase of both left chambers and interventricular septum dimensions, particularly in the second and third year. These findings demonstrated that A players have higher echocardiographic parameters respect to B players. The results of this study support the scientific theory that long-term intensive training influences heart function, inducing "athlete's heart" with morphological adaptations. No significant echocardiographic variation within the examined sample was observed for different roles (goalkeeper, defender, midfielder, or attacker) or skills of individual players.


#4 Age-Predicted Maximal Heart Rate Equations Are Inaccurate for Use in Youth Male Soccer Players
Reference: Pediatr Exerc Sci. 2018 Mar 15:1-5. doi: 10.1123/pes.2017-0281. [Epub ahead of print]
Authors: Cicone ZS, Sinelnikov OA, Esco MR
Summary: The purpose of this study was to compare the differences between measured (MHRobt) and predicted (MHRpred) maximal heart rate (MHR) in youth athletes. In total, 30 male soccer players [14.6 (0.6) y] volunteered to participate in this study. MHRobt was determined via maximal-effort graded exercise test. Age-predicted MHR (MHRpred) was calculated for each participant using equations by Fox, Tanaka, Shargal, and Nikolaidis. Mean differences were compared using Friedman's 2-way analysis of variance and post hoc pairwise comparisons. Agreement between MHRobt and MHRpred values was calculated using the Bland-Altman method. There were no significant differences between MHRobt and MHRpred from the Fox (P = .777) and Nikolaidis (P = .037) equations. The Tanaka and Shargal equations significantly underestimated MHRobt (P < .001). All 4 equations produced 95% limits of agreement of ±15.0 beats per minute around the constant error. The results show that the Fox and Nikolaidis equations produced the smallest mean difference in predicting MHRobt. However, the wide limits of agreement suggests that none of the equations adequately account for individual variability in MHRobt. Practitioners should avoid applying these equations in youth athletes and utilize a lab or field testing protocol to obtain MHR.


#5 Laterality-Specific Training Improves Mental Rotation Performance in Young Soccer Players
Reference: Front Psychol. 2018 Feb 27;9:220. doi: 10.3389/fpsyg.2018.00220. eCollection 2018.
Authors: Pietsch S, Jansen P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835319/pdf/fpsyg-09-00220.pdf
Summary: This study investigates the influence of specific soccer training with the non-dominant leg on mental rotation performance of 20 adolescent soccer players between 10 and 11 years of age. While the experimental group performed soccer specific tasks only with the non-dominant foot once a week for 10 weeks, the control group absolved the same exercises with the dominant foot for the same period of time. Both groups performed a mental rotation task and shot, dribbling and ball control tests before and after the 10 week intervention. The most relevant result was that the experimental group showed a significantly larger increase in mental rotation ability than the control group.


#6 The Influence of Task Conditions on Side Foot-Kick Accuracy among Swedish First League Women's Soccer Players
Reference: J Sports Sci Med. 2018 Mar 1;17(1):74-81. eCollection 2018 Mar.
Authors: Carlsson T, Isberg J, Nilsson J, Carlsson M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844211/pdf/jssm-17-74.pdf
Summary: The purpose of this study was to investigate the influence of the task conditions on 20-m side foot-kick accuracy among Swedish first league women's soccer players. Twenty-three players performed three side foot-kick tests under different task conditions: stationary ball using match-relevant ball speed (SBRS) and maximal ball speed (SBMS) and a 5-m run with the ball from different approach angles (0°, 30°, and 60°) to a predetermined position, where passing of the ball on the move was executed using match-relevant ball speed (RBRS). With each test, the players performed 30 side-foot kicks, alternating between kicking legs with the aim of hitting a target stick. The accuracy was determined using video analysis. The side foot-kick accuracy was significantly greater for SBRS, compared to RBRS and SBMS. For all three test variables, the preferred leg displayed greater accuracy. The preferred leg's accuracy was greater for the approach angle of 30° compared to both 0° and 60°. A significant deviation from the target stick was found for the straight-ahead approach, in which the right-foot and left-foot kicks deviated to respectively the left and right of the stick; in contrast, for the approach angle of 60°, the deviation from the target stick was on the opposite side of the approach side for both legs.


#7 Effect of 8 Weeks Soccer Training on Health and Physical Performance in Untrained Women
Reference: J Sports Sci Med. 2018 Mar 1;17(1):17-23. eCollection 2018 Mar.
Authors: Ortiz JG, da Silva JF, Carminatti LJ, Guglielmo LGA, Diefenthaeler F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844205/pdf/jssm-17-17.pdf
Summary: This study aims to analyze the physiological, neuromuscular, and biochemical responses in untrained women after eight weeks of regular participation in small-sided soccer games compared to aerobic training. Twenty-seven healthy untrained women were divided into two groups [soccer group (SG = 17) and running group (RG = 10)]. Both groups trained three times per week for eight weeks. The variables measured in this study were maximal oxygen uptake (VO2max), relative velocity at VO2max (vVO2max), peak velocity, relative intensity at lactate threshold (vLT), relative intensity at onset of blood lactate accumulation (vOBLA), peak force, total cholesterol, HDL, LDL, triglycerides, and cholesterol ratio (LDL/HDL). VO2max, vLT, and vOBLA increased significantly in both groups (12.8 and 16.7%, 11.1 and 15.3%, 11.6 and 19.8%, in SG and RG respectively). However, knee extensors peak isometric strength and triglyceride levels, total cholesterol, LDL, and HDL did not differ after eight weeks of training in both groups. On the other hand, the LDL/HDL ratio significantly reduced in both groups. In conclusion, eight weeks of regular participation in small-sided soccer games was sufficient to increase aerobic performance and promote health benefits related to similar aerobic training in untrained adult women.


#8 Muscle Strength Is a Poor Screening Test for Predicting Lower Extremity Injuries in Professional Male Soccer Players: A 2-Year Prospective Cohort Study
Reference: Am J Sports Med. 2018 Mar 1:363546518756028. doi: 10.1177/0363546518756028. [Epub ahead of print]
Authors: Bakken A, Targett S, Bere T, Eirale C, Farooq A, Mosler AB, Tol JL, Whiteley R, Khan KM, Bahr R
Summary: Lower extremity muscle strength tests are commonly used to screen for injury risk in professional soccer. However, there is limited evidence on the ability of such tests in predicting future injuries. The purpose of the study was to examine the association between hip and thigh muscle strength and the risk of lower extremity injuries in professional male soccer players. Professional male soccer players from 14 teams in Qatar underwent a comprehensive strength assessment at the beginning of the 2013/2014 and 2014/2015 seasons. Testing consisted of concentric and eccentric quadriceps and hamstring isokinetic peak torques, eccentric hip adduction and abduction forces, and bilateral isometric adductor force (squeeze test at 45°). Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff throughout each season. Univariate and multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% CIs. In total, 369 players completed all strength tests and had registered injury and exposure data. Of these, 206 players (55.8%) suffered 538 lower extremity injuries during the 2 seasons; acute muscle injuries were the most frequent. Of the 20 strength measures examined, greater quadriceps concentric peak torque at 300 deg/s (HR, 1.005 [95% CI, 1.00-1.01]; P = .037) was the only strength measure identified as significantly associated with a risk of lower extremity injuries in multivariate analysis. Greater quadriceps concentric peak torque at 60 deg/s (HR, 1.004 [95% CI, 1.00-1.01]; P = .026) was associated with the risk of overuse injuries, and greater bilateral adductor strength adjusted for body weight (HR, 0.75 [95% CI, 0.57-0.97; P = .032) was associated with a lower risk for any knee injury. Receiver operating characteristic curve analyses indicated poor predictive ability of the significant strength variables (area under the curve, 0.45-0.56). There was a weak association with the risk of lower extremity injuries for 2 strength variables: greater quadriceps concentric muscle strength at (1) high and (2) low speeds. These associations were too small to identify an "at-risk" player. Therefore, strength testing, as performed in the present study, cannot be recommended as a screening test to predict injuries in professional male soccer.


#9 Close Encounter With a Prickly Soccer Ball: An Injury from an Indian Crested Porcupine
Reference: Wilderness Environ Med. 2018 Mar 9. pii: S1080-6032(18)30003-6. doi: 10.1016/j.wem.2018.01.003. [Epub ahead of print]
Authors: Thalgaspitiya SPB, Wijerathne BTB, Thennakoon BDB
Summary: The Indian crested porcupine, Hystrix indica, is a large rodent with the unique feature of long quills. These quills are an integral part of its defense mechanism against predators. Injuries resulting from human contact with quills may cause pain, bleeding, and swelling. Quill-related injuries are common among animals such as dogs, cats, and some wild animals. The mechanism of injury, consequences, and management of injuries to humans from H indica quills are rarely described. In this report, we describe the injuries and management of a man who sustained injury from H indica quills.

#10 Inferior heel pain in soccer players: a retrospective study with a proposal for guidelines of treatment
Reference: BMJ Open Sport Exerc Med. 2018 Feb 7;4(1):e000085. doi: 10.1136/bmjsem-2015-000085. eCollection 2018.
Authors: Saggini R, Migliorini M, Carmignano SM, Ancona E, Russo C, Bellomo RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841518/pdf/bmjsem-2015-000085.pdf
Summary: The cause of heel pain among soccer players is multifactorial and is related to repetitive microtrauma due to impact forces involving technical moves, but also the playground, the exercise mode, the recovery time, the climatic conditions and the footwear used. The aim was to investigate the aetiology of plantar heel pain of soccer players with the objective of proposing an example of guidelines for treatment. We investigated the prevalence and characteristics of inferior heel pain of 1473 professional, semiprofessional and amateur players. All evaluated subjects were submitted to a specific rehabilitation protocol that involved advanced physical therapies and viscoelastic insoles depending on the aetiology of pain. Clinical and instrumental examinations revealed that 960 of 1473 athletes had inferior heel pain. These patients were divided into seven groups based on aetiology: sural nerve compression, abductor digiti minimi compression, atrophy and inflammation of the fat pad, plantar fasciitis, stress injury of the heel spur, stress fracture of the heel bone and heel spur. The proposed rehabilitation treatment aims for a reduction of pain and an early return to sports, with excellent results. According to what was observed in the present study, related also to the specific treatment of inferior heel pain, and considering the technological progress achieved in recent years, we can now propose an integrated therapeutic approach to treatment of heel pain, properly differentiated according to specific aetiology.

Fri

04

May

2018

Football is ...(#59)

Training utilizing repeated sprint can have multiple benefits.

Wed

02

May

2018

Latest research in football - week 10- 2018

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 Kicking Performance in Young U9 to U20 Soccer Players: Assessment of Velocity and Accuracy Simultaneously
Reference: Res Q Exerc Sport. 2018 Mar 7:1-11. doi: 10.1080/02701367.2018.1439569. [Epub ahead of print]
Authors: Vieira LHP, Cunha SA, Moraes R, Barbieri FA, Aquino R, Oliveira LP, Navarro M, Bedo BLS, Santiago PRP
Summary: The purpose of this study was to compare the kicking performance of young soccer players in the U9 to U20 age groups. Three hundred and sixty-six Brazilian players were evaluated on an official pitch using three-dimensional kinematics to measure (300 Hz) ball velocity (Vball), foot velocity (Vfoot), Vball/Vfoot ratio, last stride length, and distance between the support foot and the ball. Simultaneously, a two-dimensional procedure was also conducted to compute (60 Hz) the mean radial error, bivariate variable error, and accuracy. Possible age-related differences were assessed through one-way analysis of variance and magnitude-based inferences. Ball velocity increased by 103% (p < .001, η2 = .39) from the U11 age group (48.54 ± 8.31 km/hr) to the U20 age group (98.74 ± 16.35 km/hr). Foot velocity presented a 59% increase (p < .001, η2 = .32) from the U11 age group (49.08 ± 5.16 km/hr) to U20 (78.24 ± 9.49 km/hr). This finding was due to improvement in the quality of foot-ball impact (Vball/Vfoot ratio) from U11 (0.99 ± 0.13 a.u.) to U20 (1.26 ± 0.11 a.u.; p < .001, η2 = .25). Parameters such as mean radial error and accuracy appeared to be impaired during the growth spurt (U13-U15). Last stride length was correlated, low to moderately high, with Vball in all age groups (r = .36-.79). In summary, we concluded that simple biomechanical parameters of kicking performance presented distinct development. These results suggest that different training strategies specific for each age group could be applied. We provide predictive equations to aid coaches in the long-term monitoring process to develop the kick in soccer or search for talented young players.


#2 The biomechanical characteristics of elite deaf and hearing female soccer players: comparative analysis
Reference: Acta Bioeng Biomech. 2017;19(4):127-133.
Authors: Szulc AM, Busko K, Sandurska E, Kolodziejczyk M
Summary: The aim of this study was to examine the differences in body composition, strength and power of lower limbs, height of jump measured for the akimbo counter movement jumps, counter movement jump and spike jumps between deaf and hearing elite female soccer players. Twenty deaf (age: 23.7±5.0 years, hearing loss: 96±13.9 dB) and 25 hearing (age: 20.3±3.8 years) participated in the study. Their WHR and BMI were calculated. Body fat was measured using the BIA method. The maximal power and height of jump were measured by force plate. Biodex dynamometer was used to evaluate isokinetic isometric strength of the hamstrings and quadriceps. Significant differences between hearing and deaf soccer players in anthropometric values were for the waist and calf circumferences and the WHR index ( p < 0.01, effect size 0.24-0.79). Statistically significant differences were observed for flexion of the lower limb in the knee joint for the relative joint torque and relative power obtained for the angular velocity of 300 degˑs-1 for both lower limbs (p < 0.01, effect size 0.19-0.48) and for 180 degˑs-1 during flexion of the left limb (p = 0.02, effect size 0.13). The hearing female football players developed significantly greater MVC in all the cases. Statistically significant differences between deaf and hearing athletes were found for spike jump for maximal power (1828.6 ± 509.4 W and 2215.2 ± 464.5 W, respectively; p = 0.02, effect size 0.14). Hearing impairment does not limit the opportunities for development of physical fitness in the population of deaf women.


#3 Effect of Muscular Strength, Asymmetries and Fatigue on Kicking Performance in Soccer Players
Reference: Int J Sports Med. 2018 Mar 5. doi: 10.1055/s-0043-123648. [Epub ahead of print]
Authors: Maly T, Sugimoto D, Izovska J, Zahalka F, Mala L
Summary: The aim of this study was to determine the effect of muscular strength, strength asymmetries, and fatigue on the speed and accuracy of an instep kick in soccer players. We measured ball velocity (BV) and kicking accuracy (KA) in the preferred (PL) and non-preferred leg (NPL) before (PRE) and after (POST) physical load in the PL. Maximum peak muscle torque of the knee extensors and flexors in the PL and NPL as well as ipsilateral knee flexors and knee extensors ratio (H:Q ratio) for both legs were assessed. BV was significantly decreased in POST physical load (5.82%, BVPRE=30.79±1.70 m·s-1, BVPOST=29.00±1.70 m·s-1, t19=3.67, p=0.00, d=1.05). Instep kick accuracy after the physical load worsened by an average of 10% in the most accurate trials. Results revealed a significant decrease in instep kick accuracy after physical loading (KAPRE=2.74±0.70 m, KAPOST=3.85±1.24 m, t19=-3.31, p=0.00, d=1.10). We found an insignificant correlation between H:Q ratio and KA in PRE test value, whereas a lower ipsilateral ratio (higher degree of strength asymmetry) in the POST physical load significantly correlated with KA in all angular velocities (r=-0.63 up to -0.67, p=0.00).


#4 The independent effects of match location, match result and the quality of opposition on subjective wellbeing in under 23 soccer players: a case study
Reference: Res Sports Med. 2018 Mar 4:1-14. doi: 10.1080/15438627.2018.1447476. [Epub ahead of print]
Authors: Abbott W, Brownlee TE, Harper LD, Naughton RJ, Clifford T
Summary: This study examined if subjective wellbeing in soccer players was affected by match location, match result and opposition quality before a match (PRE), 1 day after (POST-1), and 3 days after a match (POST-3). Eleven professional male soccer players from the under 23 squad playing in the Premier League 2 division completed a wellbeing questionnaire before and after 17 matches. Match training load (session-rating perceived exertion) was not different, regardless of the location, result, or quality of opposition faced (P > 0.05). Subjective wellbeing was not different at PRE (P > 0.05); however, at POST-1 and POST-3, stress and mood were ≥20% lower after playing away from home or losing (P < 0.05). Stress, mood and sleep were ≥12% worse after playing against a higher-level opposition at POST-1. Coaches need to be aware that match location, match result and the quality of the opposition can influence post-match wellbeing, irrespective of match load.


#5 Childhood football play and practice in relation to self-regulation and national team selection; a study of Norwegian elite youth players
Reference: J Sports Sci. 2018 Mar 9:1-7. doi: 10.1080/02640414.2018.1449563. [Epub ahead of print]
Authors: Erikstad MK, Hoigaard R1, Johansen BT, Kandala NB, Haugen T
Summary: Childhood sport participation is argued to be important to understand differences in self-regulation and performance level in adolescence. This study sought to investigate if football-specific activities in childhood (6-12 years of age) is related to self-regulatory skills and national under 14- and 15-team selection in Norwegian elite youth football. Data of practice histories and self-regulatory skills of 515 youth football players selected at Norwegian regional level were collected and further analysed using multilevel analyses. The results revealed that high self-regulated players were more likely to be selected for national initiatives, and increased their involvement in peer-led football practice and adult-led football practice during childhood, compared to players with lower levels of self-regulation. While national level players reported higher levels of peer-led football play in childhood, the interaction effect suggest that the regional level players increased their involvement in peer-led play during childhood compared to national level players. In conclusion, the findings indicate that childhood sport participation may contribute to later differences in self-regulation, and highlights the importance of childhood engagement in football-specific play and practice in the development of Norwegian youth football players.


#6 "The Early Specialised Bird Catches the Worm!" - A Specialised Sampling Model in the Development of Football Talents
Reference: Front Psychol. 2018 Feb 21;9:188. doi: 10.3389/fpsyg.2018.00188. eCollection 2018.
Authors: Sieghartsleitner R, Zuber C, Zibung M, Conzelmann A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5826374/pdf/fpsyg-09-00188.pdf
Summary: Characteristics of learning activities in early sport participation play a key role in the development of the sporting talent. Therefore, pathways of specialisation or diversification/sampling are as well debated as the implementation of practice- or play-oriented activities. The related issues are currently perceived as a two-dimensional construct of domain specificity and performance orientation. In this context, it has been shown that early specialisation, with experiences in practice and play, has led to Swiss junior national team football players reaching higher success levels as adults. This study aimed to examine whether a similar approach improves chances of even being selected for junior national teams from a broader sample. Hence, 294 youth players answered retrospective questionnaires on their early sport participation when entering the Swiss football talent development programme. Using the person-oriented Linking of Clusters after removal of a Residue (LICUR) method, volumes of in-club practice, free play and activities besides football until 12 years of age were analysed along with age at initial club participation. According to the results, clusters of Football enthusiasts (p = 0.01) with the most free play and above average in-club practice and Club players (p = 0.02) with the most in-club practice and average free play had a greater chance of reaching junior national team level. Thus, high levels of domain-specific activities seem to increase the chances of junior national team participation. Furthermore, the most successful constellation (Football enthusiasts) may illustrate the relevance of domain-specific diversity, induced by several types of practice and play. In line with previous studies, specialising in football and sampling different experiences within this specific domain seems to be the most promising pathway. Therefore, we argue that the optimal model for the development of football talents is a specialised sampling model.


#7 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.


#8 Neophyte experiences of football match analysis: a multiple case study approach
Reference: Res Sports Med. 2018 Mar 5:1-17. doi: 10.1080/15438627.2018.1447473. [Epub ahead of print]
Authors: McKenna M, Cowan D, Stevenson D, Baker J
Summary: Performance analysis is extensively used in sport, but its pedagogical application is little understood. Given its expanding role across football, this study explored the experiences of neophyte performance analysts. Experiences of six analysis interns, across three professional football clubs, were investigated as multiple cases of new match analysis. Each intern was interviewed after their first season, with archival data providing background information. Four themes emerged from qualitative analysis: (1) "building of relationships" was important, along with trust and role clarity; (2) "establishing an analysis system" was difficult due to tacit coach knowledge, but analysis was established; (3) the quality of the "feedback process" hinged on coaching styles, with balance of feedback and athlete engagement considered essential; (4) "establishing effect" was complex with no statistical effects reported; yet enhanced relationships, role clarity, and improved performances were reported. Other emic accounts are required to further understand occupational culture within performance analysis.


#9 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.

Tue

01

May

2018

Football is....(#58)

Dynamic stretching as part of the warm-up, starting slow and controlled.

Mon

30

Apr

2018

Latest research in football - week 9 - 2018

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 Vertical and Horizontal Asymmetries are Related to Slower Sprinting and Jump Performance in Elite Youth Female Soccer Players
Reference: J Strength Cond Res. 2018 Feb 27. doi: 10.1519/JSC.0000000000002544. [Epub ahead of print]
Authors: Bishop C, Read P, McCubbine J, Turner A
Summary: Inter-limb asymmetries have been shown to be greater during vertical jumping compared to horizontal jumping. Notable inter-limb differences have also been established at an early age in male youth soccer players. Furthermore, given the multi-planar nature of soccer, establishing between-limb differences from multiple jump tests is warranted. At present, a paucity of data exists regarding asymmetries in youth female soccer players and their effects on physical performance. The aims of this study were to quantify inter-limb asymmetries from unilateral jump tests and examine their effects on speed and jump performance. Nineteen elite youth female soccer players performed a single leg countermovement jump (SLCMJ), single, triple, and crossover hops for distance and a 20 m sprint test. Test reliability was good to excellent (ICC = 0.81-0.99) and variability acceptable (CV = 1.74-5.42%). A one-way ANOVA highlighted larger asymmetries from the SLCMJ compared to all other jump tests (p < 0.05). Pearson's correlations portrayed significant relationships between vertical asymmetries from the SLCMJ and slower sprint times (r = 0.49-0.59). Significant negative relationships were also found between horizontal asymmetries during the triple hop test and horizontal jump performance (r = -0.47 to -0.58) and vertical asymmetries during the SLCMJ and vertical jump performance (r = -0.47 to -0.53). The results from this study highlight that the SLCMJ appears to be the most appropriate jump test for identifying between-limb differences with values ∼12% showing negative associations with sprint times. Furthermore, larger asymmetries are associated with reduced jump performance and would appear to be direction-specific. Practitioners can use this information as normative data to be mindful of when quantifying inter-limb asymmetries and assessing their potential impact on physical performance in youth female soccer players.


#2 Oxidative stress biomarkers after a single maximal test in blind and non-blind soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08030-1. [Epub ahead of print]
Authors: Viana Gomes D, Santos Vigario P, Lima Piazera BK, Pereira Costa F, Vaisman M, Salerno Pinto V
Summary: Compare oxidative stress biomarkers, antioxidant capacity, muscle damage and hormone response between vision impaired and non-vision impaired athletes after a single maximal exercise test. Eight vision impaired and fifteen non-vision impaired athletes performed a maximal aerobic test with blood collected before and after. Non-vision impaired athletes displayed greater aerobic capacity than blind individuals (p<0.05). Lactate increased by four-fold, while CK and GGT as well as the oxidative stress biomarkers and antioxidants were unchanged. Cortisol increased, but testosterone and their ratio were not altered. Differences were observed for ALT and AST, which were increased only in non-blind athletes. Our data suggest that blind soccer players, in comparison to those with vision, experienced less cellular damage.


#3 The effect of acute match play loading on hip adductor strength & flexibility in soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08194-X. [Epub ahead of print]
Author: Light N
Summary: Deficits in adductor strength and flexibility are known risk factors for soccer hip/groin injury, yet little is known about the acute effects of soccer match play on these physical features. The aim of this study therefore was to examine the changes in adductor strength and flexibility before; during and immediately after soccer match play. Design: Twenty, male university soccer players (age = 22.35 ± 1.98 years) participated in this field-based, within subject, repeated measures study. Each participant performed three adductor squeeze tests at both 0° and 45° hip flexed test positions alongside a bent knee fall out test. Adductor squeeze scores were quantified using pressure sphygmomanometer and BKFO values recorded in centimetres. Each test was performed before (0 mins) half time (45 mins) and at full time (90 mins) of a competitive match. Adductor strength decreased by 17.7% in 0° test position and 19.1% in 45° test position at 90 minutes of soccer play, whilst BKFO scores increased by 15% indicating a reduction in adductor flexibility. Statistical analysis showed significant effects of time Vs adductor strength and squeeze test position (P=<0.005), Positive correlations between time played and BKFO scores, and BKFO scores vs adductor squeeze scores at 0 and 45 minutes (P=<0.005) were also observed. University soccer players exhibit decreased adductor squeeze test and BKFO values as soccer match duration increases. These findings may have implications hip/groin injury management and recovery strategies, post or during soccer matches.


#4 Subungual Exostosis in a Young Soccer Player
Reference: Open Access Maced J Med Sci. 2017 Dec 30;6(1):52-54. doi: 10.3889/oamjms.2018.002. eCollection 2018 Jan 25.
Authors: Tchernev G, Grigorov Y, Philipov S, Chokoeva A, Wollina U, Lotti T, Cardoso J, Yungareva I, Lozev I, Maximov GK
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5816314/pdf/OAMJMS-6-52.pdf
Summary: Subungual exostosis is a relatively uncommon, benign osteocartilaginous tumor of the distal phalanx of the toes or fingers in young adults, considered as a rare variant of osteochondroma. Differential diagnoses include subungual verruca (viral wart), pyogenic granuloma, osteochondroma, amelanotic subungual melanoma and glomus tumour. Misdiagnosis and total onychodystrophy frequently occur as a result of late treatment or inadequate treatment strategy. Dermoscopy could be a useful technique, involved in the diagnostic process, although X-ray examination and histopathology are mandatory for the diagnosis. We report a rare case of subungual exostosis of the great toe associated with repeated trauma of the nail bed. The lack of radiographic and histopathological examination could lead to misdiagnosis and inadequate treatment. Although completely benign, subungual exostosis should be considered in differential diagnosis of nail bed tumors in young adults, in order to avoid associated complications and unneeded aggressive surgical interventions. Complete excision of the lesion and delicate separation from the underlying nail bed structures results in total resolve of the problem, by providing the lowest risk of recurrences.



#5 Acute lateral ankle sprain prediction in collegiate women’s soccer players
Reference: Int J Sports Phys Ther. 2018 Feb;13(1):12-18.
Authors: McCann RS, Kosik KB, Terada M, Beard MQ, Buskirk GE, Gribble PA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5808007/pdf/ijspt-13-12.pdf
Summary: Women's soccer has among the highest injury rates in collegiate sports, and lateral ankle sprains (LAS) are among the most commonly occurring injuries in that athletic population. However, no established LAS prediction model exists for collegiate women's soccer players.The purpose of this study was to develop a prediction model for acute LAS injuries in collegiate women's soccer players utilizing previous ankle sprain history, height, mass, and BMI as potential predictors.The authors' hypothesized that collegiate women's soccer players with greater height, mass, and body mass index (BMI), as well as a previous history of ankle sprain would have greater odds of sustaining a LAS.  Forty-three NCAA Division I women's soccer players' (19.7 ± 1.1yrs, 166.8 ± 3.7cm, 60.8 ± 4.4kg) height, mass, and BMI were measured one week before beginning preseason practices. Additionally, participants reported whether or not they had sustained a previous ankle sprain. The team athletic trainer tracked LASs over the competitive season. Independent t-tests, binary logistic regression analyses, receiver operating characteristic (ROC) curves, and diagnostic statistics assessed the ability of the variables to differentiate between those that did and did not sustain a LAS. Participants that sustained a LAS (n = 8) were significantly taller than those that did not sustain a LAS (n = 35) (t41 = -2.87, p = 0.01, d = 0.83[0.03,1.60]). A logistic regression analysis (odds ratio=1.30[1.00,1.70]) and area under the ROC curve analysis (AUROC=0.73[0.58,0.89], p=0.04) further exhibited predictive value of height. A height cutoff score of 167.6cm demonstrated excellent sensitivity (0.88), moderate specificity (0.51), and a favorable diagnostic odds ratio (7.5). A logistic regression analysis (odds ratio=1.87[1.22,1.98]) exhibited predictive value of previous ankle sprain history. That variable was also associated with good sensitivity (0.75) and specificity (0.71) within the model, as well as a favorable DOR (7.37). Mass and BMI demonstrated no predictive value for LAS. Taller collegiate women's soccer players and those with previous ankle sprain history may have a greater predisposition to LAS.


#6 Characteristics of goalkeepers' injuries: retrospective, self-reported study among adolescence football players
Reference: J Sports Med Phys Fitness. 2018 Feb 26. doi: 10.23736/S0022-4707.18.07849-0. [Epub ahead of print]
Authors: Blazkiewicz A, Grygorowicz M, Bialostocki A, Czaprowski D
Summary: Characteristic types of actions and training/matches loads of football goalkeepers show that goalkeeper's performance differs from other football's formations. Such situation may predispose to the occurrence of other kinds of injuries in this position. The aim of this study was to analyse epidemiology of injuries in young football goalkeepers. 48 football goalkeepers (aged:15.2±1.9 years) were filled the questionnaire aimed at collecting information about all injuries sustained within 12 months before the data collection. The anthropometric data, football experience and information regarding the injury types and occurrence were analysed. The injury rate proportion for acute and overuse injuries and values of injuries including the burden of the match game and training were evaluated. The level of significance was set at p<0.05. 33(68.8%) questionnaires were given back. 24(72.7%) goalkeepers reported the history of football related injury within a year before the survey. 52 injuries were reported. Significantly higher number of acute (76.9%) vs. overuse (23.1%) injuries was described (p=0.0012). Acute injuries involved fractures/subluxations of the fingers and thigh muscle strain/tears. The group of overuse injuries was dominated by trauma of the knee and pelvic girdle muscles. Majority of injuries occurred during training (88,5% of all injuries), and there was significant higher number of injuries sustained on artificial vs. natural grass for all, acute and overuse types of injuries (p<0,0001). Young football goalkeepers suffer mostly acute injuries (within the fingers of hands and muscles of thighs). It might be associated with specific characteristic of performance related to goalkeeper`s position.


#7 The elite player performance plan: the impact of a new national youth development strategy on injury characteristics in a premier league football academy
Reference: J Sports Sci. 2018 Feb 24:1-8. doi: 10.1080/02640414.2018.1443746. [Epub ahead of print]
Authors: Tears C, Chesterton P, Wijnbergen M
Summary: The objective of this study was to investigate the injury incidence and patterns in elite youth football at a category 1 Premier League Academy before and after the introduction of a new development strategy, the Elite Player Performance Plan (EPPP). A prospective study was performed over six consecutive seasons encompassing three years before and after the introduction of the EPPP. The findings revealed a most likely moderate increase in total exposure per player per season when the post-EPPP football exposure (640.86 ± 83.25 hours per player per year) was compared with the pre-EPPP football exposure (539.08 ± 71.59). The total injury incidence pre-EPPP was 3.0/1000 hours compared to 2.1/1000 hours post-EPPP (rate ratio 1.43). 6% of all injuries were re-injuries (20.24 ± 33.43 days) but did not result in a substantially longer absence (16.56 ± 15.77 days). The injury burden decreased for the U12-U15 from pre- to post-EPPP, whereas the injury burden increased for the U16-U18 (respectively 125 and 47% higher). These findings suggest that following the introduction of the EPPP there has been a reduction in injuries in the younger age groups U12-U15 but in the older age groups U16-U18 there has been an increase in the severity of the injuries sustained at this club.


#8 The influence of joint rigidity on impact efficiency and ball velocity in football kicking
Reference: J Biomech. 2018 Feb 20. pii: S0021-9290(18)30112-X. doi: 10.1016/j.jbiomech.2018.02.015. [Epub ahead of print]
Authors: Peacock JCA, Ball K
Summary: Executing any skill with efficiency is important for performance. In football kicking, conflicting and non-significant results have existed between reducing ankle plantarflexion during foot-ball contact with impact efficiency, making it unclear as to its importance as a coaching instruction. The aims of this study were to first validate a mechanical kicking machine with a non-rigid ankle, and secondly compare a rigid to a non-rigid ankle during the impact phase of football kicking. Measures of foot-ball contact for ten trials per ankle configuration were calculated from data recorded at 4000 Hz and compared. The non-rigid ankle was characterised by initial dorsiflexion followed by plantarflexion for the remainder of impact, and based on similarities to punt and instep kicking, was considered valid. Impact efficiency (foot-to-ball speed ratio) was greater for the rigid ankle (rigid = 1.16 ± 0.02; non-rigid = 1.10 ± 0.01; p < 0.001). The rigid ankle was characterised by significantly greater effective mass and significantly less energy losses. Increasing rigidity allowed a greater portion of mass from the shank to be used during the collision. As the ankle remained in plantarflexion at impact end, stored elastic energy was not converted to ball velocity and was considered lost. Increasing rigidity is beneficial for increasing impact efficiency, and therefore ball velocity.


#9 Cardiac Magnetic Resonance Assessment of the Structural and Functional Cardiac Adaptations to Soccer Training in School-Aged Male Children
Reference: Pediatr Cardiol. 2018 Mar 8. doi: 10.1007/s00246-018-1844-5. [Epub ahead of print]
Authors: Barczuk-Falęcka M, Malek LA, Krysztofiak H, Roik D, Brzewski M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00246-018-1844-5.pdf
Summary: Physical training is associated with changes in cardiac morphology called the "athlete's heart", which has not been sufficiently studied in children. The aim of the study was to analyze cardiac adaptation to exercise in pre-adolescent soccer players. Thirty-six soccer players (mean age 10.1 ± 1.4 years) and 24 non-athlete male controls (10.4 ± 1.7 years) underwent cardiac magnetic resonance. Measurements of myocardial mass, end-diastolic and end-systolic volume, stroke volume and ejection fraction for left and right ventricle (LV, RV) were performed. Additionally, left and right atrial (LA, RA) areas and volumes were analysed. Relative wall thickness (RWT) was calculated to describe the pattern of cardiac remodeling. Interventricular wall thickness and LV mass were significantly higher in athletes, but remained within the reference (6.9 ± 0.8 vs. 6.2 ± 0.9 mm/√m2, p = 0.003 and 57.1 ± 7.4 vs. 50.0 ± 7.1 g/m2, p = 0.0006, respectively) with no changes in LV size and function between groups. The RWT tended to be higher among athletes (p = 0.09) indicating LV concentric remodeling geometry. Soccer players had significantly larger RV size (p < 0.04) with similar function and mass. Also, the LA volume (p = 0.01), LA area (p = 0.03) and LA diameter (p = 0.009) were significantly greater in players than in controls. Cardiac adaptations in pre-adolescent soccer players are characterized by an increased LV mass without any changes in LV size and systolic function, which is typical of resistance training with tendency to concentric remodeling. This is accompanied by increase of LA and RV size. It should be taken into account during annual pre-participation evaluation.


#11 No better moment to score a goal than just before half time? A soccer myth statistically tested
Reference: PLoS One. 2018 Mar 8;13(3):e0194255. doi: 10.1371/journal.pone.0194255. eCollection 2018.
Authors: Baert S, Amez S
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0194255&type=printable
Summary: We test the soccer myth suggesting that a particularly good moment to score a goal is just before half time. To this end, rich data on 1,179 games played in the UEFA Champions League and UEFA Europa League are analysed. In contrast to the myth, we find that, conditional on the goal difference and other game characteristics at half time, the final goal difference at the advantage of the home team is 0.520 goals lower in case of a goal just before half time by this team. We show that this finding relates to this team's lower probability of scoring a goal during the second half.

Wed

18

Apr

2018

Latest research in football - week 8,5 - 2018

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 Normalized STEAM-based diffusion tensor imaging provides a robust assessment of muscle tears in football players: preliminary results of a new approach to evaluate muscle injuries
Reference: Eur Radiol. 2018 Feb 8. doi: 10.1007/s00330-017-5218-9. [Epub ahead of print]
Authors: Giraudo C, Motyka S, Weber M, Karner M, Resinger C, Feiweier T, Trattnig S, Bogner W
Summary: The purpose of the study was to assess acute muscle tears in professional football players by diffusion tensor imaging (DTI) and evaluate the impact of normalization of data. Eight football players with acute lower limb muscle tears were examined. DTI metrics of the injured muscle and corresponding healthy contralateral muscle and of ROIs drawn in muscle tears (ROItear) in the corresponding healthy contralateral muscle (ROIhc_t) in a healthy area ipsilateral to the injury (ROIhi) and in a corresponding contralateral area (ROIhc_i) were compared. The same comparison was performed for ratios of the injured (ROItear/ROIhi) and contralateral sides (ROIhc_t/ROIhc_i). ANOVA, Bonferroni-corrected post-hoc and Student's t-tests were used. Analyses of the entire muscle did not show any differences (p>0.05 each) except for axial diffusivity (AD; p=0.048). ROItear showed higher mean diffusivity (MD) and AD than ROIhc_t (p<0.05). Fractional anisotropy (FA) was lower in ROItear than in ROIhi and ROIhc_t (p<0.05). Radial diffusivity (RD) was higher in ROItear than in any other ROI (p<0.05). Ratios revealed higher MD and RD and lower FA and reduced number and length of fibre tracts on the injured side (p<0.05 each). DTI allowed a robust assessment of muscle tears in athletes especially after normalization to healthy muscle tissue.


#2 Sideline Concussion Assessment: The King-Devick Test in Canadian Professional Football
Reference: J Neurotrauma. 2018 Feb 8. doi: 10.1089/neu.2017.5490. [Epub ahead of print]
Authors: Naidu D, Mrazik M, Borza C, Kobitowich T
Summary: Reasons for Study: Sideline assessment tools are an important component of concussion evaluations. To date there has been little data evaluating the clinical utility of these tests in professional football. The purpose of this study was to evaluate the clinical utility of the King-Devick Test (KD) in evaluating concussions in professional football players. Baseline data was collected over 2 consecutive seasons in the Canadian Football League as part of a comprehensive medical baseline evaluation. A pilot study with the KD began in 2015 with 306 participants and the next year (2016) there were 917 participants. In addition, a sample of 64 participants completed testing after physical exertion (practice or game). Participants with concussion demonstrated significantly higher (slower) results compared with baseline and the exercise group (F[2,211] = 5.94, p = 0.003). The data revealed a specificity of 84% and sensitivity of 62% for our sample. Reliability from season to season was good (ICC2,1 = 0.88, 95% CI: 0.83, 0.91). On average participants improved performances by a mean of 1.9 seconds (range -26.6 to 23.8) in subsequent years. High reliability was attained in the exercise group. (ICC2,1 = 0.93, 95% CI: 0.89, 0.96). The K-D test presents as a reliable measure although sensitivity and specificity data from our sample indicate it should be used in conjunction with other measures for diagnosing concussion. Further research is required to identify stability of results over multiple usages.


#3 Multivariate analysis of factors related to radiographic knee osteoarthritis based on the comparison between football players and matched nonsportsmen
Reference: Int Orthop. 2018 Feb 6. doi: 10.1007/s00264-018-3797-y. [Epub ahead of print]
Authors: Lv H, Chen W, Yuwen P, Yang N, Yan X, Zhang Y
Summary: Knee osteoarthritis (KOA) is the most common joint pathology worldwide and a major cause of later disability. It is unknown if the bone mass density (BMD) is correlated with KOA. This study aimed to investigate the prevalence of radiographic KOA among retired professional football players by comparing with matched nonsportsmen, and assess the correlation between BMD and KOA. A cross-sectional, descriptive study was performed on a group of retired professional football players without history of knee injury. A control group of nonsporting volunteers was matched to the football player group in terms of age, height, weight, and body mass index (BMI). Uni- and multivariate analyses were performed to identify risk factors for KOA and predictors for knee function. Eighty-six retired male professional football players, with a mean age of 53 (51-58) years and an average period of professional career of 19.8 ± 6.3 years, were enrolled into the study group. Eighty-six subjects were included in the control group. Radiographic KOA was more common in the control group (45.3%) than in the study group (15.1%; χ 2  = 18.633, P < 0.001). While the HSS, IKS score, and BMD of spine, femoral neck, and trochanter were all higher among sportsmen than the nonsportsmen (z = 10.250, z = 10.450, z = 7.237, z = 8.826, z = 8.776, all P < 0.001). Independent risk factors for ROA were age (55-60 + years, aOR 9.159, P < 0.001) and BMD (decrease, aOR 16.226, P = 0.001; osteoporosis, aOR 8.176, P = 0.005). The mathematical model of multiple linear regression for the HSS and IKS score were Y = 127.217-3.334 age + 8.971 BMD + 4.752 occupation and Y = 57.784-3.022 age + 7.241 BMD + 4.730 occupation, respectively. This study reveals that low BMD and advanced age are independent risk factors for KOA. High BMD and regular exercise have a positive impact on knee function as evaluated with the use of HSS and IKS. Our findings guarantee further study to investigate the possibility that KOA may be caused by low BMD.


#4 Structural differences in the lower extremities in children aged 7-9 years, caused by playing football: A cross-sectional study
Reference: Foot (Edinb). 2017 Nov 17;34:78-82. doi: 10.1016/j.foot.2017.11.004. [Epub ahead of print]
Authors: Diaz-Miguel S, Lopezosa-Reca E, Benhamu-Benhamu S, Ortega-Avila AB, Garcia-De-La-Pena R, Gijon-Nogueron G
Summary: Physical activity during childhood can be beneficial in the long term. However, this practice can influence the child's physiological development. The aim of this study was to determine whether the practice of soccer, in moderation, could be a risk factor for the inadequate development of the lower limb. The study group was composed of 115 children, of whom 59 (mean age 8.03±0.89years) practised soccer 3 times a week and had a positive Physical Activity Questionnaire for Adolescents (PAQ-A) score, while a further 56 (mean age 7.96±0.87years) did not perform any additional physical activity and had a negative PAQ-A score. A foot posture analysis, based on the foot posture index (FPI), the valgus index, the orientation of the subtalar joint (STJ) and the Q angle of the knee, was carried out. For the group of soccer players, the following results were obtained: FPI 4.79±2.38 (R) and 3.95±2.31 (L); valgus index 13.56°±1.66° (R) and 13.42°±1.48° (L); STJ test 79% pronated; Q angle 13.13°±2.06° (R) and 13.18°±1.93° (L). For the non-players, the corresponding values were: FPI 3.62±2.82 (R) and 3.74±2.77 (L); valgus index 12.76°±1.71° (R) and 12.84°±1.72° (L); STJ test 50% pronated; Q angle 13.87°±3.01° (R) and 13.86°±2.94° (L). There is a degree of difference between the two groups, but the values do not vary greatly from those considered normal for this age group. Any alterations in this respect can be assumed to be caused at older ages than those analysed.


#5 Prevalence of dermatomycoses in professional football players : A study based on data of German Bundesliga fitness check-ups (2013-2015) compared to data of the general population.
[Article in German]
Reference: Hautarzt. 2018 Feb 7. doi: 10.1007/s00105-017-4120-3. [Epub ahead of print]
Authors: Buder V, Augustin M, Schafer I, Welsch G, Catala-Lehnen P, Herberger K
Summary: The prevention, early diagnosis and treatment of onychomycosis is of great importance for professional athletes to avoid physical limitations by complications. So far, there is only little data on the prevalence of dermatomycosis in professional athletes. The aim of the study was to detect the prevalence of dermatomycosis in professional football players compared to the general population. The prospective, non-interventional, controlled study on the prevalence of dermatomycosis in professional football players was carried out on football players of a German Bundesliga team compared with a previously studied, equivalently aged German working population. A questionnaire survey, a dermatological check-up and a microbiological detection of pathogens in cases of suspicion were performed. Data of 84 football players (n = 45 in 2013; n = 39 in 2015) were compared to data of n = 8186 male employees between 17 and 35 years of age. In the group of athletes, there were findings of 60.7% onychomycosis, 36.9% of tinea pedis and 17.8% of pityriasis versicolor. In the group of the age-equivalent general German working population the findings were: onychomycosis 3.3%, tinea pedis 3.2%, pityriasis versicolor 1.4%. Our study shows a clearly higher risk for fungal diseases of the skin especially on the feet of professional football players. The results show a necessity for elucidation within prevention and the establishment of an appropriate therapy of dermatomycosis for professional football players.


#6 Depression and anxiety symptoms in 17 teams of female football players including 10 German first league teams
Reference: Br J Sports Med. 2018 Feb 2. pii: bjsports-2017-098033. doi: 10.1136/bjsports-2017-098033. [Epub ahead of print]
Authors: Junge A, Prinz B
Summary: Information on the prevalence of mental health problems of elite athletes is inconclusive, most probably due to methodological limitations, such as low response rates, heterogeneous samples. The aim of the study was to evaluate the prevalence and risk factors of depression and anxiety symptoms in high-level female football players. Female football players of 10 German first league (Bundesliga) and 7 lower league teams were asked to answer a questionnaire on players' characteristics, the Center of Epidemiologic Studies Depression Scale (CES-D) and the Generalised Anxiety Disorder (GAD-7) scale. A total of 290 players (184 first and 106 lower league players) took part in the study. The CES-D score indicated mild to moderate symptoms of depression in 48 (16.6%) and severe symptoms in 41 (14.1%) players. The GAD-7 score indicated an at least moderate generalised anxiety disorder in 24 (8.3%) players. The prevalence of depression symptoms and generalised anxiety disorders was similar to the female general population of similar age. However, significantly more second league players reported symptoms of depression than first league players, and thus the prevalence of depression symptoms in second league players was higher than in the general population. Only a third of the 45 (15.7%) players who stated that they currently wanted or needed psychotherapeutic support received it. The prevalence of depression and generalised anxiety symptoms in elite football players is influenced by personal and sport-specific variables. It is important to raise awareness of athletes' mental health problems in coaches and team physicians, to reduce stigma and to provide low-threshold treatment.


#7 Using Cartilage MRI T2-Mapping to Analyze Early Cartilage Degeneration in the Knee Joint of Young Professional Soccer Players
Reference: Cartilage. 2018 Feb 1:1947603518756986. doi: 10.1177/1947603518756986. [Epub ahead of print]
Authors: Waldenmeier L, Evers C, Uder M, Janka R, Hennig FF, Pachowsky ML, Welsch GH
Summary: The objective was to evaluate and characterize the appearance of articular cartilage in the tibiofemoral joint of young professional soccer players using T2-relaxation time evaluation on magnetic resonance imaging (MRI). Design In this study, we included 57 male adolescents from the youth academy of a professional soccer team. The MRI scans were acquired of the knee joint of the supporting leg. An "early unloading" (minute 0) and "late unloading" (minute 28) T2-sequence was included in the set of images. Quantitative T2-analysis was performed in the femorotibial joint cartilage in 4 slices with each 10 regions of interest (ROIs). Statistical evaluation, using Wilcoxon signed-rank tests, was primarily performed to compare the T2 values of the "early unloading" and "late unloading." Results When comparing "early unloading" with "late unloading," our findings showed a significant increase of T2-relaxation times in the weightbearing femoral cartilage of the medial ( P < 0.001) and lateral ( P < 0.001) compartment of the knee and in the tibial cartilage of the medial compartment ( P < 0.001). Conclusion In this study, alterations of the cartilage were found with a maximum in the medial condyle where the biomechanical load of the knee joint is highest, as well as where most of the chronic cartilage lesions occur. To avoid chronic damage, special focus should be laid on this region.


#8 A Trunk Stabilization Exercise Warm-up May Reduce Ankle Injuries in Junior Soccer Players
Reference: Int J Sports Med. 2018 Feb 15. doi: 10.1055/s-0044-100923. [Epub ahead of print]
Authors: Imai A, Imai T, Iizuka S, Kaneoka K
Summary: The aim of this study was to investigate the efficacy of a trunk stabilization exercise warm-up program in reducing the incidence of lower extremity injuries among male junior soccer players. Two junior soccer teams participated in this study. The intervention (INT) team performed three trunk stabilization exercises before practice sessions and games, while a control (CON) team performed their usual warm-up without trunk exercises. Both teams engaged in regular soccer training and games, and were followed for the incidence of injury. As a result, overall injury incidence rates (IRs) were 2.65 injuries/1,000 h and 4.94 injuries/1,000 h in the INT and CON teams, respectively (incidence rate ratio [IRR]=0.54, 95% confidence interval [CI]=0.32-0.89, p=0.013). The IR of acute injuries was significantly lower in the INT team (1.91 injuries/1,000 h) than in the CON team (4.06 injuries/1,000 h) (IRR=0.47, 95%CI=0.26-0.84, p=0.009). Regarding injury sites, the IRs of ankle injuries in the INT team (0.32 injuries/1,000 h) were significantly lower than that in the CON team (2.28 injuries/1,000 h) (IRR=0.14, 95%CI=0.04-0.47, p<0.001). These results suggest that a warm-up program comprising trunk stabilization exercises alone can prevent acute injuries, especially ankle injuries.


#9 Effect of oxygen therapy on chest pain in patients with ST elevation myocardial infarction: results from the randomized SOCCER trial
Reference: Scand Cardiovasc J. 2018 Feb 13:1-5. doi: 10.1080/14017431.2018.1439183. [Epub ahead of print]
Authors: Khoshnood A, Akbarzadeh M, Carlsson M, Sparv D, Bhiladvala P, Mokhtari A, Erlinge D, Ekelund U
Summary: Oxygen (O2) have been a cornerstone in the treatment of acute myocardial infarction. Studies have been inconclusive regarding the cardiovascular and analgesic effects of oxygen in these patients. In the SOCCER trial, we compared the effects of oxygen treatment versus room air in patients with ST-elevation myocardial infarction (STEMI). There was no difference in myocardial salvage index or infarct size assessed with cardiac magnetic resonance imaging. In the present subanalysis, we wanted to evaluate the effect of O2 on chest pain in patients with STEMI. Normoxic patients with first time STEMI were randomized in the ambulance to standard care with 10 l/min O2 or room air until the end of the percutaneous coronary intervention (PCI). The ambulance personnel noted the patients´ chest pain on a visual analog scale (VAS; 1-10) before randomization and after the transport but before the start of the PCI, and also registered the amount of morphine given. 160 patients were randomized to O2 (n = 85) or room air (n = 75). The O2 group had a higher median VAS at randomization than the air group (7.0 ± 2.3 vs 6.0 ± 2.9; p = .02) and also received a higher median total dose of morphine (5.0 mg ± 4.4 vs 4.0 mg ± 3.7; p = .02). There was no difference between the O2 and air groups in VAS at the start of the PCI (4.0 ± 2.4 vs 3.0 ± 2.5; p = .05) or in the median VAS decrease from randomization to the start of the PCI (-2.0 ± 2.2 vs -1.0 ± 2.9; p = .18). Taken together with previously published data, these results do not support a significant analgesic effect of oxygen in patients with STEMI.


#10 The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training
Reference: Int J Sports Physiol Perform. 2018 Feb 12:1-25. doi: 10.1123/ijspp.2017-0763. [Epub ahead of print]
Authors: Chatzinikolaou A, Michaloglou K, Avloniti A, Leontsini D, Deli CK, Vlachopoulos D, Gracia-Marco L, Arsenis S, Athanailidis I, Draganidis D, Jamurtas AZ, Williams CA, Fatouros IG
Summary:  The purpose was to investigate the effect of a complex, short-term strength/power training protocol on performance and body composition of elite early-adolescent soccer players. Twenty-two players (14-15 years) were randomly assigned to (a) an experimental (EG, n=12, participated in a 5-week training protocol with traditional multi-joint power resistance exercises, Olympic-style lifts, plyometric drills and speed work, four times/week) or (b) a control group (CG, n=10). Strength and power performance [jumping, speed, change of direction, repeated sprint ability, endurance, isokinetic strength of knee flexors and extensors, maximal strength in various lifts, speed-endurance) were evaluated pre- and post-training. Cessation of training for five weeks in the CG induced a marked performance deterioration (~5-20%). Training not only prevented strength performance deterioration but also increased it (~2-30%). Endurance and RSA declined to a smaller extent in EG compared to CG (15% vs. 7.5%). Isometric strength, and body composition remained unaltered in both groups. Results demonstrate that (i) young players exhibit a high level of trainability of their strength/power performance (but not endurance) in response a short-term complex training protocol during early adolescence, (ii) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective, (iii) it appears that lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors, (iv) cessation of training for only five weeks results in marked deterioration of strength/power and endurance performance and (v) improvement of strength/power performance may be related to neural-based adaptation since body composition remained unaffected.


#11 Osteochondral lesion of the distal tibial plafond in an adolescent soccer player: a case report
Reference: J Can Chiropr Assoc. 2017 Dec;61(3):261-268.
Authors: Corso M, DeGraauw C, Hsu W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799846/pdf/jcca-61-261.pdf
Summary: Osteochondral lesions of the tibial plafond account for approximately 2.6% of osteochondral lesions in the ankle. There are few cases describing this lesion in the literature, with little information on mechanism of injury, history/physical findings or recommendations for management. A 17-year-old male competitive soccer player presented with a 6-7 month history of medial ankle pain after an inversion sprain. He presented with locking and giving way of the ankle with weight-bearing and pushing off the foot to the contralateral side. Radiographs were negative for fracture or osteochondral involvement. Magnetic resonance imaging revealed an osteochondral lesion of the tibial plafond with no injury to the talar dome. This case discusses the clinical presentation, imaging findings, management and outcomes of this osteochondral lesion of the distal tibial plafond.


#12 Modelling the impact of players' workload on the injury-burden of English Premier League football clubs
Reference: Scand J Med Sci Sports. 2018 Feb 23. doi: 10.1111/sms.13078. [Epub ahead of print]
Authors: Fuller CW
Summary: The loss of players through injury is known to affect team performance in many sports; it is important therefore for professional teams to be able to quantify the likely injury-burden that will be encountered throughout a season. A kinetic model, based on the rates at which match and training injuries are sustained and resolved, a team's squad size and the 2017/18 season fixture schedule for teams competing in the English Premier League, is used to produce daily forecasts of injury-burden experienced by a typical team. The incidences and median severities of match (incidence: 26.9 injuries/1000 player-match-hours, 95% CI: 21.5 to 33.7; severity: 17.5 days, 95% CI: 13.0 to 28.0) and training (incidence: 4.3 injuries/1000 player-training-hours, 95% CI: 3.4 to 5.5; severity: 14.0 days, 95% CI: 11.0 to 22.0) injuries were determined using data collected from four English Premier League football clubs during the 2016/17 season. Time-to-recovery curves for the match and training injuries sustained in the Premier League closely matched the time-to-recovery curves predicted by the kinetic model used in this study. The kinetic model predicted higher match and lower training injury burdens and a higher overall injury burden for successful teams competing in both national and European club competitions compared to teams competing only in national competitions. The model also showed that, in terms of injury-burden, there were no benefits in adopting a 4-week mid-season break during the season: reducing the number of clubs competing in the Premier League would, however, reduce the overall injury burden during a season. This article is protected by copyright. All rights reserved.

Tue

17

Apr

2018

Latest research in football - week 8 - 2018

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 Psychological Characteristics in Talented Soccer Players - Recommendations on How to Improve Coaches' Assessment
Reference: Front Psychol. 2018 Feb 5;9:41. doi: 10.3389/fpsyg.2018.00041. eCollection 2018.
Authors: Musculus L, Lobinger BH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5807374/pdf/fpsyg-09-00041.pdf
Summary: Psychological characteristics, including personality traits and psychological skills, have been shown to be relevant predictors of soccer performance. In research, general and sport specific standardized self-report questionnaires have been applied in psychological diagnostics of sports talent. However, with regard to the assessment of psychological characteristics of talented soccer players, a gap between research and practice is apparent. While soccer clubs often ask their coaches to assess their players on self-designed, unevaluated scouting sheets, research widely neglects expert coaches' and clubs' perspectives on relevant performance characteristics. As we believe that expert coaches' assessments could be a valid predictor of a player's current performance and future success, we provide recommendations on how to improve coaches' assessment of psychological characteristics. As the quality of the assessment of psychological characteristics is crucial, we provide recommendations on how to ensure the central diagnostic standards: objectivity, reliability, and validity in talent assessment. Further, we argue that assessing psychological characteristics should combine self ratings of players and external ratings of coaches in talent development. Sport psychologists should assist clubs and coaches in improving the diagnostics of psychological characteristics as well as in embedding psychological diagnostics and interventions in the talent development process.


#2 Influence of biological maturity on the match performance of 8 to 16 year old elite male youth soccer players
Reference: J Strength Cond Res. 2018 Feb 14. doi: 10.1519/JSC.0000000000002510. [Epub ahead of print]
Authors: Goto H, Morris JG, Nevill ME
Summary: The aim of this study was to examine the influence of biological maturity on match performance in elite youth male soccer players. The participants were 80 Premier League Academy outfield players (8-16 years old). Biological maturity was determined by calculating estimated chronological age at peak height velocity. The U9 and U10 squads played 6-a-side and the U11-U16 squads played 11-a-side inter-academy matches. All matches were analyzed using a 1 Hz Global Positioning System (SPI elite, GPSport, Australia) with squad specific speed zones which were calculated based on 5 m flying sprint speed in the last 5 m of 10 m sprint test. In the U9/U10s, earlier maturers were given a longer pitch time by coaches (∼4 min per match, p = 0.029) and covered a greater total distance (∼9%, ∼400 m, p = 0.037) and a greater distance by walking (∼13%, ∼100 m, p = 0.024) and jogging (∼12%, ∼200 m, p = 0.014) during a match compared to later maturers. In the U13/U14s, earlier maturers covered a greater distance per hour of a match by high speed running compared to later maturers (∼25%, ∼130 m, p = 0.028) and spent a longer percentage of time in high speed running during a match compared to later maturers (3.4% vs. 2.7%, p = 0.034). Thus, coaches should take care to provide all players with a similar pitch-time and should be aware in the talent identification and development process, particularly with the U13/U14 age group, that maturity can influence high speed match running performance.


#3 Detection of Spatiotemporal Asymmetry in Pro Level Soccer Players
Reference: J Strength Cond Res. 2018 Mar;32(3):798-804. doi: 10.1519/JSC.0000000000001811.
Authors: Knudsen NS, Andersen TB
Summary: Several papers have focused on change of direction (COD) asymmetry investigated through standardized tests, and used this information to provide some spatiotemporal insight during games. The aim of this study was to investigate asymmetry in the reachable areas of the players through actual position data from soccer games. Sixteen professional players from the Danish Superliga participated in this study, but 5 were excluded because of lack of participation throughout the investigated games. The reachable areas of the players were investigated at varying sprint velocities (1-7 m·s) and within varying time intervals (0.5-4 seconds). The analysis found 7 players having spatiotemporal asymmetries in their reachable areas (0.5-3%) and shift of center of reachable area (4-29 cm). Four players (LB, RB, DM, and CF) had spatiotemporal asymmetries that could be attributed to COD and thus physiological asymmetries, whereas 3 players (LCB, LW, and RW) had spatiotemporal asymmetries that might be caused by their position or by use of tactic. This type of asymmetry was named a tactical spatiotemporal asymmetry. Coaches with knowledge about spatiotemporal asymmetries can use these actively in their tactical approach using the players' asymmetries in synergy, using opponents' asymmetries or improving the existing postgame spatiotemporal analyzing tools.


#4 Capture of Time-Loss Overuse Soccer Injuries in the National Collegiate Athletic Association's Injury Surveillance System, 2005-2006 Through 2007-2008
Reference: J Athl Train. 2018 Feb 21. doi: 10.4085/1062-6050-191-16. [Epub ahead of print]
Authors: Roos K, Kucera K, Golightly Y, Myers JB, Rosamond W, Marshall SW
Summary:  Overuse injuries are reported to account for nearly 50% of sports injuries and, due to their progressive nature and the uncertainty regarding date of onset, are difficult to define and categorize. Comparing the capture rates of overuse injuries between injury-surveillance systems and medical records can clarify completeness and determinants of how overuse injuries are represented in injury-surveillance data. The objective was to estimate the capture rate of time-loss medical-attention overuse injuries in men's and women's soccer in the National Collegiate Athletic Association Injury Surveillance System (NCAA ISS) compared with medical records maintained by certified athletic trainers and assess the differences in completeness of capture and factors contributing to those differences. Fifteen NCAA institutions provided NCAA ISS and medical record data from men's and women's soccer programs from 2005-2006 through 2007-2008. National Collegiate Athletic Association men's and women's soccer players participated in this study.  Time-loss medical-attention overuse injuries were defined as injuries with an overuse mechanism of injury in the NCAA ISS or medical records. Capture rates were calculated as the proportion of total overuse injuries classified as having overuse mechanisms in the NCAA ISS and the NCAA ISS and medical records combined. The NCAA ISS captured 63.7% of the total estimated overuse mechanisms of injury in men's and women's soccer players. The estimated proportion of overuse injury mechanisms captured by both the NCAA ISS and medical records was 37.1%. The NCAA ISS captured more overuse injury mechanisms in men's soccer than in women's soccer (79.2% versus 45.0%, χ2 = 9.60; P = .002) athletes.  From 2005-2006 through 2007-2008, the NCAA ISS captured only two thirds of time-loss medical-attention overuse mechanisms of injury in men's and women's soccer players. Future researchers should consider supplementing injury-surveillance data with a clinical record review to capture the burden of these injuries.


#5 Is the technical performance of young soccer players influenced by hormonal status, sexual maturity, anthropometric profile, and physical performance?
Reference: Biol Sport. 2017 Dec;34(4):305-311. doi: 10.5114/biolsport.2017.69817. Epub 2017 Sep 20.
Authors: Moreira A, Massa M, Thiengo CR, Rodrigues Lopes RA, Lima MR, Vaeyens R, Barbosa WP, Aoki MS
Summary: The aim of this study was to examine the influence of hormonal status, anthropometric profile, sexual maturity level, and physical performance on the technical abilities of 40 young male soccer players during small-sided games (SSGs). Anthropometric profiling, saliva sampling, sexual maturity assessment (Tanner scale), and physical performance tests (Yo-Yo and vertical jumps) were conducted two weeks prior to the SSGs. Salivary testosterone was determined by the enzyme-linked immunosorbent assay method. Technical performance was determined by the frequency of actions during SSGs. Principal component analyses identified four technical actions of importance: total number of passes, effectiveness, goal attempts, and total tackles. A multivariate canonical correlation analysis was then employed to verify the prediction of a multiple dependent variables set (composed of four technical actions) from an independent set of variables, composed of testosterone concentration, stage of pubic hair and genitalia development, vertical jumps and Yo-Yo performance. A moderate-to-large relationship between the technical performance set and the independent set was observed. The canonical correlation was 0.75 with a canonical R2 of 0.45. The highest structure coefficient in the technical performance set was observed for tackles (0.77), while testosterone presented the highest structure coefficient (0.75) for the variables of the independent set. The current data suggest that the selected independent set of variables might be useful in predicting SSG performance in young soccer players. Coaches should be aware that physical development plays a key role in technical performance to avoid decision-making mistakes during the selection of young players.


#5 Expression analysis of selected classes of circulating exosomal miRNAs in soccer players as an indicator of adaptation to physical activity
Reference: Biol Sport. 2017 Dec;34(4):331-338. doi: 10.5114/biolsport.2017.69820. Epub 2017 Sep 1.
Authors: Domanska-Senderowska D, Jastrzębski Z, Kiszalkiewicz J, Brzezianski M, Pastuszak-Lewandoska D, Radziminki L, Brzezianska-Lasota E, Jegier A
Summary: Recently studies have shown that, depending on the type of training and its duration, the expression levels of selected circulating myomiRNAs (c-miR-27a,b, c-miR-29a,b,c, c-miR-133a) differ and correlate with the physiological indicators of adaptation to physical activity. To analyse the expression of selected classes of miRNAs in soccer players during different periods of their training cycle. The study involved 22 soccer players aged 17-18 years. The multi-stage 20-m shuttle run test was used to estimate VO2 max among the soccer players. Samples serum were collected at baseline (time point I), after one week (time point II), and after 2 months of training (time point III). The analysis of the relative quantification (RQ) level of three exosomal myomiRNAs, c-miRNA-27b, c-miR-29a, and c-miR-133, was performed by quantitative polymerase chain reaction (qPCR) at three time points - before the training, after 1 week of training and after the completion of two months of competition season training. The expression analysis showed low expression levels (according to references) of all evaluated myomiRNAs before the training cycle. Analysis performed after a week of the training cycle and after completion of the entire training cycle showed elevated expression of all tested myomiRNAs. Statistical analysis revealed significant differences between the first and the second time point in soccer players for c-miR-27b and c-miR-29a; between the first and the third time point for c-miR-27b and c-miR-29a; and between the second and the third time point for c-miR-27b. Statistical analysis showed a positive correlation between the levels of c-miR-29a and VO2 max. Two months of training affected the expression of c-miR-27b and miR-29a in soccer players. The increased expression of c-miR-27b and c-miR-29 with training could indicate their probable role in the adaptation process that takes place in the muscular system. Possibly, the expression of c-miR-29a will be found to be involved in cardiorespiratory fitness in future research.


#6 The Impact of Soccer Match Play on the Muscle Damage Response in Youth Female Athletes
Reference: Int J Sports Med. 2018 Feb 23. doi: 10.1055/s-0044-101147. [Epub ahead of print]
Authors: Hughes JD, Denton K, S Lloyd R, Oliver JL, De Ste Croix M
Summary: Post-match assessment of creatine kinase (CK) activity and delayed-onset muscle soreness (DOMS) are common markers of exercise-induced muscle damage and recovery status in soccer players. These responses have not been examined in youth female players. This study examined the effect of competitive match play on CK activity and DOMS in elite youth players. Thirty-four elite female players, divided into three chronological age groups (U13, n=11; U15, n=10; U17 n=12). Players completed baseline testing for CK and DOMS that was repeated immediately (for DOMS), 80, 128 and 168 h post-competitive match play for CK. Significant time effects were reported for CK (P=0.006) and DOMS (P<0.01). Significant differences between baseline and 168 h post-match were reported for CK (P<0.01), with significant group differences between the U13 and U17 groups for CK (P<0.01). All parameters returned to baseline in U17s at 168 h, but increased CK was evident for U13s and U15s at 168 h. In conclusion, seven days may be insufficient for biochemical recovery in youth female athletes. Therefore, monitoring strategies to assess muscle damage between training and match play should be considered to track recovery and potentially reduce muscular injury risk.


#7 Age-Related Differences in Functional Hamstring/Quadriceps Ratio Following Soccer Exercise in Female Youth Players: An Injury Risk Factor
Reference: Pediatr Exerc Sci. 2018 Feb 27:1-7. doi: 10.1123/pes.2017-0034. [Epub ahead of print]
Authors: De Ste Croix M, Priestley A, Lloyd R, Oliver J
Summary: Fatigue negatively alters dynamic knee control, and the functional hamstring/quadriceps ratio (H/QFUNC) plays an important role in stabilizing the joint. The aim of this study was to investigate the influence of soccer-specific exercise on H/QFUNC in under (U) 13-, U15-, and U17-year-old female soccer players. A total of 36 female players performed concentric and eccentric actions of the hamstrings at 60°, 120°, and 180°/s before and after an age group-specific field-based soccer protocol. H/QFUNC was determined in the first 30° of knee flexion. Significant angle × velocity (P = .001) and time × angle (P = .033) interaction effects were found indicating a lower H/QFUNC with increased movement velocity at 0°-10° as opposed to greater knee flexion angles. Fatigue-related effects were only evident near full knee extension. Probabilistic inferences indicated that changes in H/QFUNC were generally unclear in U13s, likely detrimental in U15s, and very likely beneficial in U17s. Altered muscular control following soccer-specific exercise is age dependent with players' 1-year post-peak height velocity at greatest risk of injury. Injury prevention and screening need to be age and maturation appropriate, should consider the effects of fatigue, and include movements near full extension.


#8 Discovery of a Sweet Spot on the Foot with a Smart Wearable Soccer Boot Sensor That Maximizes the Chances of Scoring a Curved Kick in Soccer
Reference: Front Physiol. 2018 Feb 13;9:63. doi: 10.3389/fphys.2018.00063. eCollection 2018.
Authors: Fuss FK, Duking P, Weizman Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5816831/pdf/fphys-09-00063.pdf
Summary: This paper provides the evidence of a sweet spot on the boot/foot as well as the method for detecting it with a wearable pressure sensitive device. This study confirmed the hypothesized existence of sweet and dead spots on a soccer boot or foot when kicking a ball. For a stationary curved kick, kicking the ball at the sweet spot maximized the probability of scoring a goal (58-86%), whereas having the impact point at the dead zone minimized the probability (11-22%). The sweet spot was found based on hypothesized favorable parameter ranges (center of pressure in x/y-directions and/or peak impact force) and the dead zone based on hypothesized unfavorable parameter ranges. The sweet spot was rather concentrated, independent of which parameter combination was used (two- or three-parameter combination), whereas the dead zone, located 21 mm from the sweet spot, was more widespread.


#9 Anterior cruciate ligament ruptures in German elite soccer players: Epidemiology, mechanisms, and return to play
Reference: Knee. 2018 Feb 22. pii: S0968-0160(18)30031-0. doi: 10.1016/j.knee.2018.01.010. [Epub ahead of print]
Authors: Schiffner E, Latz D, Grassmann JP, Schek A, Thelen S, Windolf J, Schneppendahl J, Jungbluth P
Summary: Anterior cruciate ligament ruptures (ACLRs) are severe sports-related injuries with significant consequences for affected players and teams. This study aims to identify the epidemiology and injury-related lay-off after ACLR in professional male soccer players from the first-division German Bundesliga. Exposure times and incidence of anterior cruciate ligament ruptures were collected during 7.5 consecutive seasons using two media-based registers. A total of 72 total ACLRs were registered in 66 different players with an incidence of 0.040 per 1000h of exposure (95% CI 0.009-0.12). On average there were 9.6 ACLRs per season and 0.53 per team and season. The mean age of players affected was 24 (standard deviation±3.6) years. The number of ACLRs recorded per season fluctuated during the period observed. Goalkeepers are significantly (P<0.05) less prone to suffer an ACLR compared to outfield players. Understanding ACLR loading mechanisms, knowing risk factors for the injury and mean off time after ACLR are essential information for the coach, the medical staff, the elite soccer players, the insurance and team managers. Our results are in accordance with reports based on information from medical team staff. Therefore, our analysis of ACLR based on media sources may serve as an alternative for injury reports in elite soccer. The information of this study may be helpful for the medical staff taking care of professional soccer players and for orthopedic surgeons performing ACL reconstructions in this patient population.

Tue

17

Apr

2018

Football is...(#57)

High pace dribbling to penetrate lines

Mon

16

Apr

2018

Latest research in football - week 6 - 2018

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 cluster set warm-up configurations on sprint performance in collegiate male soccer players
Reference: Appl Physiol Nutr Metab. 2018 Jan 24. doi: 10.1139/apnm-2017-0610. [Epub ahead of print]
Authors: Nickerson BS, Mangine GT, Williams TD, Martinez IA
Summary: The purpose of this study was to determine if back squat cluster sets (CS) with varying inter-repetition rest periods would potentiate greater sprint performance compared to a traditional set parallel back squat in collegiate soccer players. Twelve collegiate male soccer players (21.0 ± 2.0 years; 180.0 ± 9.0 cm; 79.0 ± 9.5 kg) performed a 20-meter sprint prior to (PRE) a potentiation complex and at 1-, 4-, 7-, and 10-minutes post-exercise on three separate, randomized occasions. On each occasion, the potentiation complex consisted of 1 set of 3 repetitions at 85% one-repetition maximum (1RM) for the traditional parallel back squat. However, on one occasion the 3-repetition set was performed in a traditional manner (i.e., continuously), whereas on the other two occasions, 30- (CS30) and 60-seconds (CS60) of rest were allotted between each repetition. Repeated measures analysis of variance revealed greater (p = 0.022) mean barbell velocity on CS60 compared to the traditional set. However, faster (p < 0.040) 20-meter sprint times were observed for CS30 (3.15±0.16 sec) compared to traditional (3.20±0.17 sec) only at 10-minutes post-exercise. No other differences were observed. These data suggest that a single cluster set of three repetitions with 30-second inter-repetition rest periods at 85% 1RM acutely improves 20-meter sprinting performance. Strength and conditioning professionals and their athletes might consider its inclusion during the specific warm-up to acutely improve athletic performance during the onset (≤ 10 minutes) of training or competition.


#2 The Effects of Cupping on Hamstring Flexibility in Collegiate Soccer Players
Reference: J Sport Rehabil. 2018 Jan 24:1-18. doi: 10.1123/jsr.2017-0199. [Epub ahead of print]
Authors: Williams JG, Gard HI, Gregory JM, Gibson A, Austin J
Summary: Collegiate soccer players suffer hamstring injuries due to inflexibility and repetitive motions involving intense hamstring lengthening and contraction during sport. Although a popular intervention for muscular injury, there exists limited evidence of the effects of therapeutic cupping on hamstring flexibility. The objective was to determine the effect of cupping therapy on hamstring flexibility in collegiate soccer players. Twenty-five, asymptomatic, NCAA Division III soccer players (10 males, 15 females) (age = 19.4 ± 1.30 years, height = 175.1 ± 8.2 cm, mass = 69.5 ± 6.6 kg) participated in this study.  A 7-minute therapeutic cupping treatment was delivered to the treatment group. Four 2-inch cups were fixed atop trigger point locations within the hamstring muscle bellies of participants' dominant legs. Control group participants received no intervention between pre- and post-test measurements. Pretest and posttest measurements of hamstring flexibility, using a Passive Straight Leg Raise (PSLR), were performed on both groups were used as outcome measures. PSLR measurements were conducted by blinded examiners using a digital inclinometer. An independent samples t-test was used to analyze changes in hamstring flexibility from pre- to post-treatment with p-values set a priori at 0.05. An independent samples t-test demonstrated no significant difference in change in hamstring flexibility between participants in the treatment group and those in the control group (t23 = -.961, p = .35). The findings of this study demonstrated no statistically significant changes in hamstring flexibility following a cupping treatment.


#3 Reliability of internal and external load parameters in recreational football (soccer) for health
Reference: Res Sports Med. 2018 Jan 24:1-7. doi: 10.1080/15438627.2018.1431532. [Epub ahead of print]
Authors: Beato M, Jamil M, Devereux G
Summary: There is limited research focussed around the analysis of internal and external load parameters during football health programmes. The aim of this study was to assess the reliability of internal and external load parameters in this activity. Thrity subjects were enrolled (mean ± SDs; age = 43 ± 3 years, weight = 84 ± 14 kg, height = 176 ± 7 cm, BMI = 27.1 ± 3, VO2max = 40.7 ± 3.4 ml.kg.min-1). The football matches (five a-side) took place on an artificial grass outdoor field (pitch size of 36 × 18.5 m). Participants completed the match (60 min) and replicated the same match a week later. The analysis took into account several parameters: heart rate (HR), total distance (TD), high speed running (HSR), number of accelerations (>2 m.s-2) and metabolic power (MP). We found a good score of reliability in several parameters: TD (ICC = 0.66), accelerations (ICC = 0.62), mean HR (ICC = 0.82), HSR (ICC = 0.77) and MP (ICC = 0.66). The results reported in this study revealed good scores of absolute reliability and small/trivial effect size.


#4 Activity monitoring in men's college soccer: a single season longitudinal study
Reference: Res Sports Med. 2018 Jan 23:1-13. doi: 10.1080/15438627.2018.1431535. [Epub ahead of print]
Authors: Slater LV, Baker R, Weltman AL, Hertel J, Saliba SA, Hart JM
Summary: Performance in soccer has been characterized previously using time-motion analyses; however, it is unclear if men's college soccer shares performance characteristics with women's college or men's professional soccer. The purpose of this study was to compare proportions of matches spent walking, jogging, running, and sprinting in men's college soccer. Twenty-two male college soccer players wore global positioning system units during matches. Proportions of walking, jogging, running, high-speed running, and sprinting were calculated for each player based on time period (first half, second half, extra time) and outcome (win, loss, tie). Multivariate analyses of variance were run for each time period to compare positions. Means, 95% confidence intervals, and effect sizes were calculated for each position based on time period and match outcome. There were differences in low-speed and high-speed activities based on position, with forwards and midfielders demonstrating increased high-speed activities. Positional differences may require different physiological profiles and should be a consideration during training.


#5 Noninvasive Ventilation in Hypoxemic Patients: an Ongoing Soccer Game or a Lost One?
Reference: Turk J Anaesthesiol Reanim. 2017 Dec;45(6):329-331. doi: 10.5152/TJAR.2017.241102. Epub 2017 Dec 1.
Authors: Gregoretti C, Cortegiani A, Raineri SM, Giarrjatano A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772410/pdf/tard-45-6-329.pdf


#6 Acute Effects of Ballistic vs Passive Static Stretching Involved in A Pre-Match Warm-Up Regarding Vertical Jump and Linear Sprint Performance in Soccer Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002477. [Epub ahead of print]
Authors: Mariscal SL, Garcia VS, Fernandez-Garcia JC, Saez de Villarreal E
Summary: The purpose of this study was to compare the effects of introducing passive static and ballistic stretching in a standard soccer match warm-up. The variables addressed were the Counter Movement Jump (CMJ), Abalakov jump and the 40 m linear sprint. The sample was composed of 33 male subjects, divided in two age groups. U16 and adult players formed the groups, in order to cross check if there were differences between them. Each group was further subdivided into two groups regarding the type of stretching carried out during the stretching phase. Prior to the warm-up, the tests previously described were assessed. In the experimental phase, standard stretching was carried out consisting of: an initial phase in which players had to execute continuous running; a general phase in which players had to make articulate moves; a technical phase, in which players had to execute exercises with the ball; a 5 vs. 5 small sided game was carried out during the tactical phase; and, in the final phase, activation exercises and sprints were carried out by the players. Eventually, the same variables were assessed again once the warm-up was finished. There were no statistically significant differences between the two types of stretching included in the pre-match warm-up. It can be concluded that ballistic and passive static stretching (<10s) did not cause, under these circumstances, any effect in the assessed variables related to soccer performance (linear sprint, CMJ and Abalakov). This has to be considered by coaches when devising soccer related warm-ups.


#7 Optimal Reactive Strength Index: Is it an Accurate Variable to Optimize Plyometric Training Effects on Measures of Physical Fitness in Young Soccer Players?
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002467. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Garcia-Pinillos F, Sanchez-Sanchez J, Yanci J, Castillo D, Loturco I, Chaabene H, Moran J, Izquierdo M
Summary: This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) versus an optimal drop-box height (i.e, 10-cm to 40-cm: generating an optimal [OPT] reactive strength index [RSI]) in youth soccer players' physical fitness. Athletes were randomly allocated to a control-group (CG: n=24; age=13.7 years), a fixed drop-box height group (FIXED, n=25; age=13.9 years) or an optimal drop-box height group (OPT, n=24; age=13.1 years). Before and after 7 weeks of training, tests for the assessment of jumping (countermovement jump [CMJ], five multiple bounds [MB]), speed (20-m sprint time), change of direction (Illinois change of direction test [CODT]), strength (RSI and 5 maximal squat repetition test [5RM]), endurance (2.4 km time trial), and kicking ability (maximal kicking distance) were undertaken. Analyses revealed main effects of time for all dependent variables (p<0.001, d=0.24-0.72), except for 20-m sprint time. Analyses also revealed group×time interactions for CMJ (p<0.001, d=0.51), DJ (p<0.001, d=0.30), 20-m sprint time (p<0.001, d=0.25), CODT (p<0.001, d=0.22), and 5RM (p<0.01, d=0.16). Post-hoc analyses revealed increases for the FIXED group (CMJ: 7.4%, d=0.36; DJ: 19.2%, d=0.49; CODA: -3.1%, d=-0.21; 5RM: 10.5%, d=0.32) and the OPT group (CMJ: 16.7%, d=0.76; DJ: 36.1%, d=0.79; CODA: -4.4%, d=-0.34; 5RM: 18.1%, d=0.47). Post-hoc analyses also revealed increases for the OPT group in 20-m sprint time (-3.7%, d=0.27). Therefore, to maximize the effects of plyometric training, an OPT approach is recommended. However, using adequate fixed drop-box heights may provide a rational and practical alternative.


#8 Accuracy, intra- and inter-unit reliability, and comparison between GPS and UWB-based position-tracking systems used for time-motion analyses in soccer
Reference: Eur J Sport Sci. 2018 Jan 31:1-8. doi: 10.1080/17461391.2018.1427796. [Epub ahead of print]
Authors: Bastida Castillo A, Gomez Carmona CD, De la Cruz Sanchez E, Pino Ortega J
Summary: There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20 ± 1.6 years, 1.76 ± 0.08 cm, and 69.5 ± 9.8 kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig-zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57-5.85%), test-retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69-6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03).


#9 Osteoarthritis of the hip and knee in former male professional soccer players
Reference: Br Med Bull. 2018 Jan 29. doi: 10.1093/bmb/ldy001. [Epub ahead of print]
Authors: Petrillo S, Papalia R, Maffulli N, Volpi P, Denaro V
Summary: Professional soccer (PS) players are at great risk of osteoarthritis (OA) of the knee and hip. Sources of data: Following the PRISMA guidelines, the key words 'osteoarthritis' and 'soccer' or 'football' were matched with 'players' or 'former' or 'retired' and with 'hip' or 'knee' on December 24, 2017 in the following databases: PubMed, Cochrane, Google scholar, Embase and Ovid. Only comparative studies reporting the prevalence rate of OA of both hip and knee joint in former PS athletes (fPSa) and age and sex matched controls were considered. In fPSa, the prevalence rate of OA of both hip and knee is significantly higher compared to age and sex matched controls. The pathological pathways responsible for the development of OA of the hip and knee in PS athletes (PSa) are still not clearly understood. The prevalence rate of clinical OA of the hip was 8.6% in fPSa and 5.6% in controls (odd ratio (OR) = 1.5; 95% CI: 1.06-2.31). The radiographic rate of OA was 21.2% in fPSa and 9.8% in controls (OR = 2.4; 95% CI: 1.66-3.69). A total of 14.6 and 53.7% of fPSa presented clinical and radiographic signs of OA of the knee, respectively, vs 12.9% (OR = 1.16; 95% CI: 0.86-1.55) and 31.9% (OR = 2.47; 95% CI: 2.03-3.00) of controls. Sonographic evidence of OA of the knee was found in 52% of fPSa and 33% of controls (OR = 2.2; 95% CI: 1.24-3.89). Preventive training programmes should be developed to reduce the number of fPSa presenting early OA.


#10 Key team physical and technical performance indicators indicative of team quality in the soccer Chinese super league
Reference: Res Sports Med. 2018 Jan 31:1-10. doi: 10.1080/15438627.2018.1431539. [Epub ahead of print]
Authors: Yang G, Leicht AS, Lago C, Gomez MA
Summary: The aim of this study was to identify the key physical and technical performance variables related to team quality in the Chinese Super League (CSL). Teams' performance variables were collected from 240 matches and analysed via analysis of variance between end-of-season-ranked groups and multinomial logistic regression. Significant physical performance differences between groups were identified for sprinting (top-ranked group vs. upper-middle-ranked group) and total distance covered without possession (upper and upper-middle-ranked groups and lower-ranked group). For technical performance, teams in the top-ranked group exhibited a significantly greater amount of possession in opponent's half, number of entry passes in the final 1/3 of the field and the Penalty Area, and 50-50 challenges than lower-ranked teams. Finally, time of possession increased the probability of a win compared with a draw. The current study identified key performance indicators that differentiated end-season team quality within the CSL.


#11 Influence of well-being variables and recovery state in physical enjoyment of professional soccer players during small-sided games
Reference: Res Sports Med. 2018 Jan 28:1-12. doi: 10.1080/15438627.2018.1431540. [Epub ahead of print]
Authors: Selmi O, Goncalves B, Ouergui I, Sampaio J, Bouassida A
Summary: This study aimed to assess the effects of the total quality of recovery and well-being indices (self-ratings of sleep during the preceding night, stress, fatigue and delayed onset muscle soreness) on rating of perceived exertion (RPE) and physical enjoyment (PE) during small-sided games. A total of 20 professional soccer players (25 ± 0.8 years) completed four 5-a-side game sessions of 25-min duration each (4 × 4 min work with 3-min passive recovery in-between). All variables were collected before each game session with the exception of RPE and Physical Activity Enjoyment Scale that were collected after. The results demonstrate that recovery state and pre-fatigue states were not contributing signals of affected internal intensity and enjoyment of players. The study established the objectivity and utility of RPE as a useful tool for determining internal intensity during soccer-specific training as well as PE for assessing emotional response during exercise or training session.


#12 Effects of Soccer Training on Anthropometry, Body Composition, and Physical Fitness during a Soccer Season in Female Elite Young Athletes: A Prospective Cohort Study
Reference: Front Physiol. 2017 Dec 22;8:1093. doi: 10.3389/fphys.2017.01093. eCollection 2017.
Authors: Lesinski M, Prieske O, Helm N, Granacher U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5770736/pdf/fphys-08-01093.pdf
Summary: The objectives of this study were to (i) describe soccer training (e.g., volume, types), anthropometry, body composition, and physical fitness and (ii) compute associations between soccer training data and relative changes of anthropometry, body composition, and physical fitness during a soccer season in female elite young athletes. Seasonal training (i.e., day-to-day training volume/types) as well as variations in anthropometry (e.g., body height/mass), body composition (e.g., lean body/fat mass), and physical fitness (e.g., muscle strength/power, speed, balance) were collected from 17 female elite young soccer players (15.3 ± 0.5 years) over the training periods (i.e., preparation, competition, transition) of a soccer season that resulted in the German championship title in under-17 female soccer. Training volume/types, anthropometrics, body composition, and physical fitness significantly varied over a soccer season. During the two preparation periods, higher volumes in resistance and endurance training were performed (2.00 ≤ d ≤ 18.15; p < 0.05), while higher sprint and tactical training volumes were applied during the two competition periods (2.22 ≤ d ≤ 11.18; p < 0.05). Body height and lean body mass increased over the season (2.50 ≤ d ≤ 3.39; p < 0.01). In terms of physical fitness, significant performance improvements were found over the soccer season in measures of balance, endurance, and sport-specific performance (2.52 ≤ d ≤ 3.95; p < 0.05). In contrast, no statistically significant changes were observed for measures of muscle power/endurance, speed, and change-of-direction speed. Of note, variables of muscle strength (i.e., leg extensors) significantly decreased (d = 2.39; p < 0.01) over the entire season. Our period-specific sub-analyses revealed significant performance improvements during the first round of the season for measures of muscle power/endurance, and balance (0.89 ≤ d ≤ 4.01; p < 0.05). Moreover, change-of-direction speed significantly declined after the first round of the season, i.e., transition period (d = 2.83; p < 0.01). Additionally, significant medium-to-large associations were observed between training and anthropometrics/body composition/physical fitness (-0.541 ≤ r ≤ 0.505). Soccer training and/or growth/maturation contributed to significant variations in anthropometry, body composition, and physical fitness outcomes throughout the different training periods over the course of a soccer season in female elite young soccer players. However, changes in components of fitness were inconsistent (e.g., power, speed, strength). Thus, training volume and/or types should be carefully considered in order to develop power-, speed- or strength-related fitness measures more efficiently throughout the soccer season.


#13 Orthopaedics injuries in male professional football players in Brazil: a prospective comparison between two divisions
Reference: Muscles Ligaments Tendons J. 2018 Jan 10;7(3):524-531. doi: 10.11138/mltj/2017.7.3.524. eCollection 2017 Jul-Sep.
Authors: Arliani GG, Lara PHS, Astur DC, Pedrinelli A, Pagura JR, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5774927/pdf/524-531.pdf
Summary: Football is a high-speed contact sport and the risk of injury is high. The objective of this study was to compare the two main divisions (A1 and A2) of the São Paulo Football Championship and to perform a correlation analysis of the variables studied. A prospective study was conducted using an electronic questionnaire previously developed by the Medical Committee of the São Paulo Football Federation. The questionnaire was sent to the doctors of the teams playing in the A1 and A2 divisions of the São Paulo Football Championship after each round. Setting: 2016 São Paulo Football Championship. The comparison of divisions A1 and A2 showed few significant differences among the various variables analysed in this study. The only significant differences were for right-side involvement in division A1 (p=0.044) and morning matches in division A2 (p<0.001). The correlation analysis of the variables studied showed expected associations, including sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains. Despite the differences between the two divisions regarding budgets and team characteristics, there was a little difference in the variables analysed and there were associations such as sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains.

 


American Football
#1 Incidence, Severity, and Time Loss Associated With Collegiate Football Fractures, 2004-2005 to 2013-2014
Reference: Am J Sports Med. 2018 Jan 1:363546517749914. doi: 10.1177/0363546517749914. [Epub ahead of print]
Authors: Cairns MA, Hasty EK, Herzog MM, Ostrum RF, Kerr ZY
Summary: The inherent risk of any time loss from physical injury in football has been extensively discussed, with many such injuries having a profound effect on the lives of National Collegiate Athletic Association (NCAA) football players. However, the incidence of fractures in collegiate football has not been well established. The purpose of the study was to examine the epidemiology of fractures in NCAA football. Fracture data reported in college football during the 2004-2005 to 2013-2014 academic years were analyzed from the NCAA Injury Surveillance Program (NCAA-ISP). Fracture rates per 1000 athlete-exposures, surgery and time loss distributions, injury rate ratios, injury proportion ratios (IPRs), and 95% CIs were reported. Overall, 986 fractures were reported. The rate of competition fractures was larger than the rate of practice fractures (1.80 vs 0.17 per 1000 athlete-exposures; injury rate ratio = 10.56; 95% CI, 9.32-11.96). Fractures of the hand/fingers represented 34.6% of all injuries, while fibula fractures (17.2%) were also common. A majority (62.5%) of all fractures resulted in time loss >21 days. Altogether, 34.4% of all fractures required surgery, and 6.3% were recurrent. The proportion of fractures resulting in time loss >21 days was higher for fractures requiring surgery than fractures not requiring surgery (85.0% vs 50.7%; IPR = 1.68; 95% CI, 1.53-1.83). The proportion of recurrent and nonrecurrent fractures requiring surgery did not differ (35.5% vs 34.3%; IPR = 1.03; 95% CI, 0.73-1.46); however, recurrent fractures were more likely to require surgery than nonrecurrent fractures when restricted to the hand/fingers (66.7% vs 27.2%; IPR = 2.45; 95% CI, 1.36-4.44). Fractures in collegiate football were sustained at a higher rate in competition than practice and frequently required extended time lost from participation, particularly among those requiring surgery. Prevention strategies are warranted to reduce incidence and severity of fractures.


#2 Association Between Playing American Football in the National Football League and Long-term Mortality
Reference: JAMA. 2018 Feb 1. doi: 10.1001/jama.2018.0140. [Epub ahead of print]
Authors: Venkataramani AS, Gandhavadi M, Jena AB
Summary: Studies of the longevity of professional American football players have demonstrated lower mortality relative to the general population but they may have been susceptible to selection bias. The objective was to examine the association between career participation in professional American football and mortality risk in retirement. Retrospective cohort study involving 3812 retired US National Football League (NFL) players who debuted in the NFL between 1982 and 1992, including regular NFL players (n = 2933) and NFL "replacement players" (n = 879) who were temporarily hired to play during a 3-game league-wide player strike in 1987. Follow-up ended on December 31, 2016. NFL participation as a career player or as a replacement player. The primary outcome was all-cause mortality by December 31, 2016. Cox proportional hazards models were estimated to compare the observed number of years from age 22 years until death (or censoring), adjusted for birth year, body mass index, height, and position played. Information on player death and cause of death was ascertained from a search of the National Death Index and web-based sources. Of the 3812 men included in this study (mean [SD] age at first NFL activity, 23.4 [1.5] years), there were 2933 career NFL players (median NFL tenure, 5 seasons [interquartile range {IQR}, 2-8]; median follow-up, 30 years [IQR, 27-33]) and 879 replacement players (median NFL tenure, 1 season [IQR, 1-1]; median follow-up, 31 years [IQR, 30-33]). At the end of follow-up, 144 NFL players (4.9%) and 37 replacement players (4.2%) were deceased (adjusted absolute risk difference, 1.0% [95% CI, -0.7% to 2.7%]; P = .25). The adjusted mortality hazard ratio for NFL players relative to replacements was 1.38 (95% CI, 0.95 to 1.99; P = .09). Among career NFL players, the most common causes of death were cardiometabolic disease (n = 51; 35.4%), transportation injuries (n = 20; 13.9%), unintentional injuries (n = 15; 10.4%), and neoplasms (n = 15; 10.4%). Among NFL replacement players, the leading causes of death were cardiometabolic diseases (n = 19; 51.4%), self-harm and interpersonal violence (n = 5; 13.5%), and neoplasms (n = 4; 10.8%). Among NFL football players who began their careers between 1982 and 1992, career participation in the NFL, compared with limited NFL exposure obtained primarily as an NFL replacement player during a league-wide strike, was not associated with a statistically significant difference in long-term all-cause mortality. Given the small number of events, analysis of longer periods of follow-up may be informative.


#3 Anthropometric and Athletic Performance Combine Test Results Among Positions within Grade Levels of High School-Aged American Football Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002481. [Epub ahead of print]
Authors: Leutzinger TJ, Gillen ZM, Miramonti AM, McKay BD, Mendez AI, Cramer JT
Summary: The purpose of the present study was to investigate differences among player positions at three grade levels in elite, collegiate-prospective American football players. Participants' data (n = 7,160) were analyzed for this study [mean height (Ht) ± standard deviation (SD) = 178 ± 7 cm, weight (Wt) = 86 ± 19 kg]. Data were obtained from 12 different high school American football recruiting combines hosted by Zybek Sports (Boulder, Colorado). Eight two-way (9x3) mixed factorial ANOVAs [position (defensive back (DB), defensive end (DE), defensive lineman (DL), linebacker (LB), offensive lineman (OL), quarterback (QB), running back (RB), tight end (TE), and wide receiver (WR) x grade (freshmen, sophomores, and juniors)] were used to test for differences among the mean test scores for each combine measure [Ht, Wt, 40-yard (40yd) dash, pro-agility drill (PA), L-cone drill (LC), vertical jump (VJ), and broad jump (BJ)]. There were position-related differences (p ≤ 0.05) for Ht, 40yd dash, and BJ, within each grade level and for Wt, PA, LC, and VJ independent of grade level. Generally, the results showed that OL were the tallest, weighed the most, and exhibited the lowest performance scores among positions. RBs were the shortest, while DBs and WRs weighed the least, and exhibited the highest performance scores among positions. These results demonstrate the value of classifying high school-aged American football players according to their specific position rather than categorical groupings such as 'line' vs. 'skill' vs. 'big skill' when evaluating anthropometric and athletic performance combine test results.


#4 Initial symptom presentation after high school football-related concussion varies by time point in a season: an initial investigation
Reference: Sports Med Open. 2018 Jan 31;4(1):8. doi: 10.1186/s40798-018-0121-8.
Authors: Brett BL, Kuhn AW, Yengo-Kahn AM, Kerr ZY, Bonfield CM, Solomon GS, Zuckerman SL
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0121-8?site=sportsmedicine-open.springeropen.com
Summary: Schedule-based and in-season factors (e.g., competition type) have been shown to be associated with symptom reporting patterns and injury severity in sport-related concussion (SRC). To determine if acute neurocognitive and symptom presentation following SRC differ by time point within a high school football season. Multicenter ambispective cohort of high school football players who sustained a SRC (N = 2594). Timing (early, mid, and late season) of SRC was based on median dates for the start of the pre-season, regular season, and playoffs of each states' football schedules. Analysis of covariance (ANCOVA) investigated differences across season period groups for: (1) neurocognitive test scores, (2) total symptom scores (TSS), and (3) individual symptom increases from baseline within 1-week post-injury. Significant group differences were observed in TSS, F(2, 2589) = 15.40, p <  0.001, ηp2 = 0.01, and individual symptom increases from baseline, F(2, 2591) = 16.40, p <  0.001, ηp2 = 0.01. Significant increases were seen from baseline to both midseason and late season in both TSS, χ2 = 24.40, p <  0.001, Φ = 0.10 and individual symptoms, χ2  = 10.32, p = 0.006, Φ = 0.10. Post hoc tests indicated a linear trend, with late-season injured athletes reporting approximately twice the TSS (13.10 vs. 6.77) and new symptoms (5.70 vs. 2.68) as those with early-season injuries. In a cohort of American high school football student-athletes, those suffering SRC in the late-season time period had increased acute symptom burden. SRC sustained later in-season may require more conservative management.


Wed

28

Feb

2018

Latest research in football - week 5 - 2018

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 Iron, Hematological Parameters and Blood Plasma Lipid Profile in Vitamin D Supplemented and Non-Supplemented Young Soccer Players Subjected to High-Intensity Interval Training
Reference: J Nutr Sci Vitaminol (Tokyo). 2017;63(6):357-364. doi: 10.3177/jnsv.63.357.
Authors: Jastrzebska M, Kaczmarczyk M, Suarez AD, Sanchez GFL, Jastrzebska J, Radziminski L, Jastrzebski Z
Download link: https://www.jstage.jst.go.jp/article/jnsv/63/6/63_357/_pdf/-char/en
Summary: Vitamin D deficiency has been associated with increased risk for cardiovascular disease and anemia. Vitamin D-related changes in lipid profile have been studied extensively but the relationship between vitamin D and lipid metabolism is not completely understood. As both vitamin D and intermittent training may potentially affect iron and lipid metabolism, the aim of the study was to evaluate whether a daily supplementation of vitamin D can modulate the response of hematological and lipid parameters to high-intensity interval training (HIIT) in soccer players. Thirty-six young elite junior soccer players were included in the placebo-controlled, double-blind study. Participants were non-randomly allocated into either a supplemented group (SG, n=20, HIIT and 5,000 IU of vitamin D daily) or placebo group (PG, n=16, HIIT and sunflower oil). Hematological parameters were ascertained before and after the 8-wk training. The change score (post- and pre-training difference) was calculated for each individual and the mean change score (MCS) was compared between SG and PG using the t test and analysis of covariance. There were no differences between SG and PG at baseline. The red and white cell count, hemoglobin, hematocrit, MCHC, ferritin, and HDL-cholesterol changed significantly over the 8-wk HIIT. However, no significant differences in MCS were observed between SG and PG for any variable. A daily vitamin D supplement did not have any impact on alteration in hematological or lipid parameters in young soccer players in the course of high-intensity interval training.


#2 Impact of the EURO-2016 football cup on emergency department visits related to alcohol and injury
Reference: Eur J Public Health. 2018 Jan 15. doi: 10.1093/eurpub/ckx233. [Epub ahead of print]
Authors: Noel GN, Roch AR, Michelet PM, Boiron LB, Gentile SG, Viudes GV
Summary: In Marseille, the 2016 EURO football cup days were independently associated with a 43% increase in alcohol-related visits in the Emergency Department (ED). Patients admitted for alcohol consumption were younger (41 vs. 46.6;P < 0.001), more often male (82.8% vs. 60.1%; P < 0.001) and more often admitted as inpatients (24.0% vs. 16.5%; P = 0.03) than those admitted for injury. Unlike reported in previous studies, injury-related visits did not increase. This could be explained by coding practice variability between EDs (alcohol or injury). To account for this variability, both diagnosis groups must be separately included when using ED data for preparing and monitoring major gatherings.


#3 Exploring the effects of playing formations on tactical behaviour and external workload during football small-sided games
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002445. [Epub ahead of print]
Authors: Baptista J, Travassos B, Goncalves B, Mourao P, Viana JL, Sampaio J
Summary: This study aimed to identify the effects of playing formations on tactical behaviour and external workload during football small-sided games. Twenty-three semi-professional footballers integrated three different playing formations in a 7-a-side small-sided game, according to their specific player positions: team 4:3:0 (4 defenders, 3 midfielders); team 4:1:2 (4 defenders, 1 midfielder, 2 forwards); and team 0:4:3 (4 midfielders, 3 forwards). Based on players' movement trajectories, the following individual and collective tactical variables were calculated: total distance covered and distance covered while walking, jogging, running and sprinting, distance from each player to both own and opponent's team centroid (Dist CG and Dist OPP CG, respectively), individual area, team length, team width and surface area. Approximate entropy (ApEn) was computed to identify the regularity of each variable. The team 4:3:0 promoted players' space exploration with moderate physical efforts. The team 4:1:2 promoted compactness and regularity of the team with increase in the physical efforts. The team 0:4:3 promoted team balance and adaptability on space coverage with increase in physical efforts. Concluding, different playing formations support different game dynamics, and variations on external load were directly linked with the variations on tactical behaviour. The analysis tactical behaviour through quantification of variability of patterns of play and quantification of distance covered at different velocities were the most useful information for the analysis of the effects of practice task manipulations. Therefore, in a practical sense, strength and conditioning coaches should plan and monitor these tasks in interaction with the head coaches.


#4 The Importance of Strength and Power on Key Performance Indicators in Elite Youth Soccer
Reference: J Strength Cond Res. 2018 Jan 24. doi: 10.1519/JSC.0000000000002446. [Epub ahead of print]
Authors: Wing CE, Turner AN, Bishop CJ
Summary: The purpose of this investigation was to examine the importance of strength and power in relation to key performance indicators (KPI's) within competitive soccer match play. This was achieved through using an experimental approach where fifteen subjects were recruited from a professional soccer club's scholarship squad during the 2013/14 season. Following anthropometric measures, power and strength were assessed across a range of tests which included the squat jump (SJ), countermovement jump (CMJ), 20 metre (m) sprint and arrowhead change of direction test. A predicted 1-repetition maximum (RM) was also obtained for strength by performing a 3RM test for both the back squat and bench press and a total score of athleticism (TSA) was provided by summing z-scores for all fitness tests together, providing one complete score for athleticism. Performance analysis data was collected during 16 matches for the following KPIs: passing, shooting, dribbling, tackling and heading. Alongside this, data concerning player ball involvements (touches) was recorded. Results showed that there was a significant correlation (p < 0.05) between CMJ (r = 0.80), SJ (r = 0.79) and TSA (r = 0.64) in relation to heading success. Similarly, a significant correlation (p < 0.05) between predicted 1RM squat strength and tackle success (r = 0.61). These data supports the notion that strength and power training are important to soccer performance, particularly when players are required to win duels of a physical nature. There were no other relationships found between the fitness data and the KPI's recorded during match play which may indicate that other aspects of player's development such as technical skill, cognitive function and sensory awareness are more important for soccer-specific performance.


#5 The Effect of Heat Stress on Measures of Running Performance and Heart Rate Responses During A Competitive Season in Male Soccer Players
Reference: J Strength Cond Res. 2018 Jan 24. doi: 10.1519/JSC.0000000000002441. [Epub ahead of print]
Authors: Coker NA, Wells AJ, Gepner Y
Summary: Measures of running performance (RP) and heart rate responses (HR) to matchplay during three different heat stress (HS) conditions were assessed in seven National Collegiate Athletic Association (NCAA) Division I male soccer players. Total distance (TD), as well as distance covered within distinct velocity zones [walking (WALK), jogging (JOG), low speed running (LSR), high-speed running (HSR), sprinting (SPRINT), low-intensity running (LIR), and high-intensity running (HIR)] were assessed using GPS units over 12 matches. HS was monitored during each match, and matches were defined as low (HSlow, n=4), moderate (HSmod, n=4), or high (HShigh, n=4) HS. Minutes played were significantly different across HS conditions (p=0.03). Therefore, distance covered within each movement velocity was assessed relative to minutes played, and as a percentage of total playing time. WALKrel was significantly greater during HShigh compared to HSlow (p=0.035). LIRrel was significantly greater during HSmod (p=0.015) compared to HSlow. A trend was observed for %WALK being higher during HShigh compared to HSlow (p=0.066). %LIR was significantly greater during HShigh compared to HSlow (p=0.048). HIR was not significantly different across HS conditions. Percent of time spent >85% HRmax was significantly greater during HShigh (p=0.002) and HSmod (p<0.001) compared to HSlow. Percent of time spent between 65-84% HRmax was significantly greater during HSlow compared to HShigh (p<0.001). Results indicate that HS resulted in increased LIR and %HR≥85, while HIR was maintained. HIR performance may be conserved through decreased playing time and/or the adoption of pacing strategies. This may assist coaches in altering player management strategies to optimize team performance.


#6 Combined Anterolateral, Anterior, and Anteromedial Ankle Impingement in an Adolescent Soccer Player-A Case Report and Review of the Literature
Reference: Clin J Sport Med. 2018 Jan 24. doi: 10.1097/JSM.0000000000000576. [Epub ahead of print]
Authors: Cosma DI, Vasilescu DE, Corbu A, Todor A, Valeanu M, Ulici A
Summary: A unique case of combined anterolateral, anterior, and anteromedial ankle impingement in an adolescent soccer player is presented in this article. To the best of our knowledge, this is the only report of circumferential, massive, anterior ankle impingement in children described in the literature. The importance of proper diagnosis and treatment of such a lesion is illustrated in this case report. We also emphasize that clinical examination combined with 3D computed tomography scan reconstruction is an excellent and cost-effective imaging modality that can help with the diagnosis of anterior ankle impingement. Finally, open surgical treatment showed excellent results in an elite athlete.


#7 Match Situations Leading to Head Injuries in Professional Male Football (Soccer)-A Video-based Analysis Over 12 Years
Reference: Clin J Sport Med. 2018 Jan 19. doi: 10.1097/JSM.0000000000000572. [Epub ahead of print]
Authors: Beaudouin F, Aus der Funten K, Troß 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 study.  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). 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.


#8 Linear Acceleration in Direct Head Contact Across Impact Type, Player Position, and Playing Scenario in Collegiate Women's Soccer
Reference: J Athl Train. 2018 Jan 26. doi: 10.4085/1062-6050-90-17. [Epub ahead of print]
Authors: Caccese JB, Lamond LC, Buckley TA, Glutting J, Kaminski TW
Summary: Heading, an integral component of soccer, exposes athletes to a large number of head impacts over a career. The literature has begun to indicate that cumulative exposure may lead to long-term functional and psychological deficits. Quantifying an athlete's exposure over a season is a first step in understanding cumulative exposure. The objective was to measure the frequency and magnitude of direct head impacts in collegiate women's soccer across impact type, player position, and game or practice scenario. Twenty-three collegiate women's soccer athletes participated in this study. Athletes wore Smart Impact Monitor accelerometers during all games and practices Impacts were classified during visual, on-field monitoring of athletic events. All direct head impacts that exceeded the 10 g threshold were included in the final data analysis. The dependent variable was linear acceleration, and the fixed effects were (1) type of impact: clear, pass, shot, unintentional deflection, or head-to-head contact; (2) field position: goalkeeper, defense, forward, or midfielder; (3) playing scenario: game or practice. Shots (32.94 g ± 12.91 g, n = 38, P = .02) and clears (31.09 g ± 13.43 g, n = 101, P = .008) resulted in higher mean linear accelerations than passes (26.11 g ± 15.48 g, n = 451). Head-to-head impacts (51.26 g ± 36.61 g, n = 13, P < .001) and unintentional deflections (37.40 g ± 34.41 g, n = 26, P = .002) resulted in higher mean linear accelerations than purposeful headers (ie, shots, clears, and passes). No differences were seen in linear acceleration across player position or playing scenario. Nonheader impacts, including head-to-head impacts and unintentional deflections, resulted in higher mean linear accelerations than purposeful headers, including shots, clears, and passes, but occurred infrequently on the field. Therefore, these unanticipated impacts may not add substantially to an athlete's cumulative exposure, which is a function of both frequency and magnitude of impact.


#9 Preseason Maximal Aerobic Power in Professional Soccer Players Among Different Divisions
Reference: J Strength Cond Res. 2018 Feb;32(2):356-363. doi: 10.1519/JSC.0000000000001810.
Authors: Marcos MA, Koulla PM, Anthos ZI
Summary: The purpose of this study was to examine and compare the anthropometric, maximal oxygen uptake (V[Combining Dot Above]O2max), and positional differences of first division (D1) professional football players from players of second (D2) and third (D3) divisions in Cyprus football leagues. Four hundred twenty-one professional male football players participated in this study. All subjects underwent anthropometric and body composition evaluation. In addition, they performed an incremental cardiopulmonary exercise testing (CPET) on a treadmill for V[Combining Dot Above]O2max evaluation. The results were analyzed using 1-way analysis of variance, between subjects design revealing significant effects among the divisions. Tukey's honest significant difference (HSD) tests demonstrated that players from D1 scored significantly higher on V[Combining Dot Above]O2max and lasted significantly longer on the treadmill than participants of D2 and D3 (p ≤ 0.05). Similar findings were demonstrated when D2 was contrasted against D3 players. Goalkeepers, defenders, and forwards demonstrated significantly higher anthropometric measurements, whereas wingers and midfielders demonstrated significantly higher V[Combining Dot Above]O2max (p ≤ 0.05) than goalkeepers and defenders. The findings of this study clearly demonstrated that cardiovascular fitness, as determined by CPET, is an important fitness parameter that differentiates professional football players who play at a more advanced level. This could be attributed to the different seasonal schedules that allow for longer transition time for lower division players and thus favoring greater detraining effects. Emphasis should be given by fitness professionals on transition period training to minimize the detraining effects especially in lower divisions.


#10 Performance Differences Among Skilled Soccer Players of Different Playing Positions During Vertical Jumping and Landing
Reference: J Strength Cond Res. 2018 Feb;32(2):304-312. doi: 10.1519/JSC.0000000000002343.
Authors: Harry JR, Barker LA, James R, Dufek JS
Summary: Both jumping and landing performance of skilled soccer players is diminished when task demands are increased. However, it is unclear if performance changes are specific to players of certain playing positions. Therefore, we assessed jumping and landing performance among skilled soccer players of different playing positions. Twenty-five National Collegiate Athletic Association (NCAA) Division 1 male soccer players (179.5 ± 7.8 cm, 75.5 ± 7.1 kg, 19.7 ± 1.2 years) performed maximum effort vertical jump landings (VJLs), whereas vertical ground reaction force (vGRF) data were obtained. Participants were stratified into goalkeeping (GK), defensive (DEF), midfield (MID), and attacking (ATT) group according to their primary playing position. One-way analyses of variance (α = 0.05) and effect sizes (ESs; large ≥ 0.80) were used to compare differences among groups. The jumping phase variables evaluated were jump height, unloading and amortization vGRF magnitudes, eccentric rate of force development, and the reactive strength index. Landing phase variables included the peak vGRF magnitude, vGRF loading rate, vGRF attenuation rate, and landing time. No statistically significant differences were detected for any jumping or landing variable (p ≥ 0.05). However, a number of large magnitude differences were detected during landing after ES calculations. Specifically, greater peak vGRF magnitudes were detected in DEF vs. both MID (ES = 1.08) and ATT (ES = 0.93), a greater vGRF loading rate occurred in DEF vs. MID (ES = 0.93), and a greater vGRF attenuation rate occurred in DEF vs. both MID (ES = 1.00) and AT (ES = 0.80). It is concluded that highly skilled soccer players possess position-specific abilities with respect to the landing phase of VJL. Skilled soccer players might experience enhanced training outcomes after VJL training regimens tailored to the specific demands of their primary playing position.


#11 Importance of Speed and Power in Elite Youth Soccer Depends on Maturation Status
Reference: J Strength Cond Res. 2018 Feb;32(2):297-303. doi: 10.1519/JSC.0000000000002367.
Authors: Murtagh CF, Brownlee TE, OʼBoyle A, Morgans R, Drust B, Erskine RM
Summary: Importance of speed and power in elite youth soccer depends on maturation status. J Strength Cond Res 32(2): 297-303, 2018-Maturation status is a confounding factor when identifying talent in elite youth soccer players (ESP). By comparing performance of ESP and control participants (CON) matched for maturation status, the aims of our study were to establish the importance of acceleration, sprint, horizontal-forward jump, and vertical jump capabilities for determining elite soccer playing status at different stages of maturation. Elite youth soccer players (n = 213; age, 14.0 ± 3.5 years) and CON (n = 113; age, 15.0 ± 4.4 years) were grouped using years from/to predicted peak height velocity (PHV) to determine maturation status (ESP: pre-PHV, n = 100; mid-PHV, n = 25; post-PHV, n = 88; CON: pre-PHV, n = 44; mid-PHV, n = 15; post-PHV, n = 54). Participants performed 3 reps of 10- and 20-m sprint, bilateral vertical countermovement jump (BV CMJ), and bilateral horizontal-forward CMJ (BH CMJ). Elite youth soccer players demonstrated faster 10-m (p < 0.001) and 20-m sprint (p < 0.001) performance than CON at all stages of maturation. Mid-PHV and post-PHV ESP achieved greater BV CMJ height (p < 0.001) and BH CMJ distance (ESP vs. CON; mid-PHV: 164.32 ± 12.75 vs. 136.53 ± 21.96 cm; post-PHV: 197.57 ± 17.05 vs. 168.06 ± 18.50 cm; p < 0.001) compared with CON, but there was no difference in BV or BH CMJ between pre-PHV ESP and CON. Although 10 and 20 m and sprint performance may be determinants of elite soccer playing status at all stages of maturation, horizontal-forward and vertical jumping capabilities only discriminate ESP from CON participants at mid- and post-PHV. Our data therefore suggest that soccer talent identification protocols should include sprint, but not jump assessments in pre-PHV players.


#12 Direct player observation is needed to accurately quantify heading frequency in youth soccer
Reference: Res Sports Med. 2018 Jan 24:1-8. doi: 10.1080/15438627.2018.1431534. [Epub ahead of print]
Authors: Harriss A, Walton DM, Dickey JP
Summary: In soccer, heading may be related to subsequent neurological impairment. Accurate measures of heading exposure are therefore important. This study evaluated whether 12 female youth players accurately recalled their average number of headers over an entire soccer season (20 games total). Their self-reported average number of headers per game was multiplied by the number of games that they participated in, and were compared to actual number of headers extracted from game video. All players overestimated the number of headers compared to game video. Linear regression analysis indicated that self-reported headers overestimated the number of headers by 51%. While self-reports are a convenient way to estimate heading behaviour, they do not accurately represent the number of headers that players perform. Self-reports of heading exposure should be interpreted with caution.


#13 Dietary habits and energy balance in an under 21 male international soccer team
Reference: Res Sports Med. 2018 Jan 25:1-10. doi: 10.1080/15438627.2018.1431537. [Epub ahead of print]
Authors: Caruana Bonnici D, Akubat I, Greig M, Sparks A, Mc Naughton LR
Summary: Soccer presents a metabolic challenge which is not necessarily matched by players' habitual dietary intake. To examine the effects of a bespoke diet, 22 players completed the Ball Sport Endurance and Sprint Test (BEAST90mod) protocol, followed by 4 days of regulated nutritional intake. The diet consisted of 10 g∙kg-1 body mass (BM) and 1.7 g∙kg-1 BM of carbohydrate and protein, respectively. On day 5, players followed a prematch nutritional strategy of 7 g∙kg-1 BM of carbohydrate and 1 g∙kg-1 BM of protein divided into three meals and then repeated the BEAST90mod. The players' pre-intervention intake consisted of 49 ± 7.1% or 3.5 g ± 1.0 g∙kg-1 BM for carbohydrate and 19 ± 3.8% of total daily energy intake or 1.3 g ± 0.5 g∙kg-1 BM for protein. Following the tailor-made dietary intervention, players ran an additional 887 ± 233 m (8.1%; d = 2.4). An acute dietary intervention provided a positive effect on a valid simulated soccer match play test.


American Football
#1 Fatal Exertional Heat Stroke and American Football Players: The Need for Regional Heat-Safety Guidelines
Reference: J Athl Train. 2018 Jan 13. doi: 10.4085/1062-6050-445-16. [Epub ahead of print]
Authors: Grundstein AJ, Hosokawa Y, Casa DJ
Summary: Weather-based activity modification in athletics is an important way to minimize heat illnesses. However, many commonly used heat-safety guidelines include a uniform set of heat-stress thresholds that do not account for geographic differences in acclimatization. The purpose was to determine if heat-related fatalities among American football players occurred on days with unusually stressful weather conditions based on the local climate and to assess the need for regional heat-safety guidelines. Incidents of fatal exertional heat stroke (EHS) in American football players were obtained from the National Center for Catastrophic Sport Injury Research 5 and the Korey Stringer Institute. Sixty-one American football players at all levels of competition with fatal EHSs from 1980 to 2014. We used the wet-bulb globe temperature (WBGT) and a z-score WBGT standardized to local climate conditions from 1991 to 2010 to assess the absolute and relative magnitudes of heat stress, respectively. We observed a poleward decrease in exposure WBGTs during fatal EHSs. In milder climates, 80% of cases occurred at above-average WBGTs, and 50% occurred at WBGTs greater than 1 standard deviation from the long-term mean; however, in hotter climates, half of the cases occurred at near-average or below-average WBGTs. The combination of lower exposure WBGTs and frequent extreme climatic values in milder climates during fatal EHSs indicates the need for regional activity-modification guidelines with lower, climatically appropriate weather-based thresholds. Established activity-modification guidelines, such as those from the American College of Sports Medicine, work well in the hotter climates, such as the southern United States, where hot and humid weather conditions are common.


#2 Balance Regularity Among Former High School Football Players With or Without a History of Concussion
Reference: J Athl Train. 2018 Jan 13. doi: 10.4085/1062-6050-326-16. [Epub ahead of print]
Authors: Schmidt JD, Terry DP, Ko J, Newell KM, Miller LS
Summary: Subclinical postural-control changes may persist beyond the point when athletes are considered clinically recovered postconcussion. The purpose was to compare postural-control performance between former high school football players with or without a history of concussion using linear and nonlinear metrics. A total of 11 former high school football players (age range, 45-60 years) with 2 or more concussions and 11 age- and height-matched former high school football players without a history of concussion. No participant had college or professional football experience. Participants completed the Sensory Organization Test. We compared postural control (linear: equilibrium scores; nonlinear: sample and multiscale entropy) between groups using a 2 × 3 analysis of variance across conditions 4 to 6 (4: eyes open, sway-referenced platform; 5: eyes closed, sway-referenced platform; 6: eyes open, sway-referenced surround and platform). We observed a group-by-condition interaction effect for medial-lateral sample entropy ( F2,40 = 3.26, P = .049, ηp2 = 0.140). Participants with a history of concussion presented with lower medial-lateral sample entropy values (0.90 ± 0.41) for condition 5 than participants without a history of concussion (1.30 ± 0.35; mean difference = -0.40; 95% confidence interval [CI] = -0.74, -0.06; t20 = -2.48, P = .02), but conditions 4 (mean difference = -0.11; 95% CI: -0.37, 0.15; t20 = -0.86, P = .40) and 6 (mean difference = -0.25; 95% CI: -0.55, 0.06; t20 = -1.66, P = .11) did not differ between groups. Postconcussion deficits, detected using nonlinear metrics, may persist long after injury resolution. Subclinical concussion deficits may persist for years beyond clinical concussion recovery.

 

Tue

27

Feb

2018

Football is...(#56)

Floaters in SSG...

Mon

26

Feb

2018

Latest research in football - week 4 - 2018

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 Relative Age Effect on Soccer Players in Formative Stages with Different Sport Expertise Levels
Reference: J Hum Kinet. 2017 Dec 28;60:167-173. doi: 10.1515/hukin-2017-0100. eCollection 2017 Dec.
Authors: Praxedes A, Moreno A, Garcia-Gonzalez L, Pizarro D, Del Villar F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765797/pdf/hukin-60-167.pdf
Summary: The Relative Age Effect (RAE) in sport has been targeted by many research studies. The objective of this study was to analyze, in amateur clubs, the RAE of soccer players, according to the sport expertise level of the team (e.g., A, B, C and subsequent) that they belong to within the same game category. 1,098 soccer players in formative stages took part in the study, with ages varying between 6 and 18 years old (U8 to U19 categories). All of them were members of 4 Spanish federated clubs. The birth dates were classified into 4 quartiles (Q1 = Jan-Mar; Q2 = Apr-Jun; Q3 = Jul-Sept; Q4 = Oct-Dec)according to the team they belonged to. The results obtained in the chi-squared test and d value (effect size) revealed the existence of RAE in the teams with the highest expertise level, "A" (X2 = 15.342, p = .002, d = 0.4473) and "B" (X2 = 10.905, p = .012, d = 0.3657). However, in the lower level teams, "C and subsequent", this effect was not observed. Present findings show that players born during the first months of the year tend to be selected to play in teams with a higher sport expertise level of each category, due to their physical maturity. Consequently, this causes differences in terms of the experience they accumulate and the motivation that this creates in these players.


#2 Physical Performance and Anthropometric Characteristics of Male South African University Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:153-158. doi: 10.1515/hukin-2017-0098. eCollection 2017 Dec.
Authors: Kubayi A, Paul Y, Mahlangu P, Toriola A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765795/pdf/hukin-60-153.pdf
Summary: Soccer is the most popular sport worldwide. Despite its global acclaim, scientific studies of soccer have tended to focus on tactics and techniques, thereby neglecting the physical and physiological profile of the players. Therefore, the purpose of this study was to examine physical and anthropometric characteristics of male South African university soccer players. Twenty-seven male soccer players aged 19 to 24 (mean age: 22.1 years; s = 1.5 years) volunteered to participate in the study. The results showed that goalkeepers (77.5 ± 9.7 kg) and defenders (68.2 ± 6.5 kg) were the heaviest compared to players in other playing positions. The goalkeepers also had the highest percentage of body fat (11.3 ± 2.3%), in contrast to midfielders who had the lowest body fat content (9.1 ± 0.9%). With regard to flexibility, defenders (45.1 ± 4.9 cm) and midfielders (45.9 ± 5.4 cm) performed better than goalkeepers (37.1 ± 4.3 cm) and strikers (40.1 ± 3.4 cm). Midfielders (57.2 ± 3.1 ml1·kg-1·min1) and defenders (56.1 ± 5.1 ml1·kg-1·min1) had significantly higher values of maximal oxygen uptake (VO2max) than goalkeepers (47.9 ± 0.2 ml-1·kg-1·min-1) and strikers (49.8 ± 6.2 ml-1·kg-1·min-1). No significant (p > 0.05) differences were observed for all other variables, with the exception of body height, body mass, and VO2max. It was therefore concluded that sports scientists and coaches should tailor conditioning programmes in soccer according to players' positions in view of the implications for successful performance.


#3 Effects of Passive and Active Rest on Physiological Responses and Time Motion Characteristics in Different Small Sided Soccer Games
Reference: J Hum Kinet. 2017 Dec 28;60:123-132. doi: 10.1515/hukin-2017-0095. eCollection 2017 Dec.
Authors: Arslan E, Alemdaroglu U, Koklu Y, Hazir T, Muniroglu S, Karakoc B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765792/pdf/hukin-60-123.pdf
Summary: The purpose of this study was to investigate the effects of resting regimes on physiological responses and time motion characteristics between bouts during small sided games (SSGs) in young soccer players. Sixteen players (average age 16.87 ± 0.34 years; body height 176.69 ± 3.21 cm; body mass 62.40 ± 2.59 kg; training experience 3.75 ± 0.44 years) performed four bouts 2-a-side, 3-a-side and 4-a-side games with three minutes active (SSGar: Running at 70% of HRmax) and passive (SSGpr) rest between bouts at two-day intervals. The heart rate (HR) along with total distance covered in different speed zones - walking (W, 0-6.9 km·h-1), low-intensity running (LIR, 7.0-12.9 km·h-1), moderate-intensity running (MIR, 13.0-17.9 km·h-1) and high-intensity running (HIR, >18km·h-1), were monitored during all SSGs, whereas the rating of perceived exertion (RPE, CR-20) and venous blood lactate (La-) were determined at the end of the last bout of each SSG. The results demonstrated that all SSGpr elicited significantly higher physiological responses compared to SSGar in terms of the RPE and La- (p < 0.05). In addition, 2-a-side SSGpr induced significantly lower %HRmax responses and total distance covered than 2-a-side SSGar (p < 0.05). Moreover, the distance covered at HIR was significantly higher in 4-a-side SSGar than 4-side SSGpr. The results of this study indicate that both SSGs with passive and active rest can be used for soccer specific aerobic endurance training. Furthermore, all SSGs with active recovery should be performed in order to increase players and teams' performance capacity for subsequent bouts.


#4 Multivariate Profiles of Selected versus Non-Selected Elite Youth Brazilian Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:113-121. doi: 10.1515/hukin-2017-0094. eCollection 2017 Dec.
Authors: Aquino R, Alves IS, Padilha MB, Casanova F, Puggina EF, Maia J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765791/pdf/hukin-60-113.pdf
Summary: This study determined whether a multivariate profile more effectively discriminated selected than non-selected elite youth Brazilian soccer players. This examination was carried out on 66 youth soccer players (selected, n = 28, mean age 16.3 ± 0.1; non-selected, n = 38, mean age 16.7 ± 0.4) using objective instruments. Multivariate profiles were assessed through anthropometric characteristics, biological maturation, tactical-technical skills, and motor performance. The Student's t-test identified that selected players exhibited significantly higher values for height (t = 2.331, p = 0.02), lean body mass (t = 2.441, p = 0.01), and maturity offset (t = 4.559, p < 0.001), as well as performed better in declarative tactical knowledge (t = 10.484, p < 0.001), shooting (t = 2.188, p = 0.03), dribbling (t = 5.914, p < 0.001), speed - 30 m (t = 8.304, p < 0.001), countermovement jump (t = 2.718, p = 0.008), and peak power tests (t = 2.454, p = 0.01). Forward stepwise discriminant function analysis showed that declarative tactical knowledge, running speed -30 m, maturity offset, dribbling, height, and peak power correctly classified 97% of the selected players. These findings may have implications for a highly efficient selection process with objective measures of youth players in soccer clubs.


#5 High-Intensity Small-Sided Games versus Repeated Sprint Training in Junior Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:101-111. doi: 10.1515/hukin-2017-0104. eCollection 2017 Dec.
Authors: Eniseler N, Şahan C, Ozcan I, Dinler K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765790/pdf/hukin-60-101.pdf
Summary: The aim of this study was to compare the effects of high-intensity small-sided games training (SSGT) versus repeated-sprint training (RST) on repeated-sprint ability (RSA), soccer specific endurance performance and short passing ability among junior soccer players. The junior soccer players were recruited from of a professional team (age 16.9 ± 1.1 years). The tests included the repeated-shuttle-sprint ability test (RSSAT), Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and Loughborough Soccer Passing Test (LSPT). Nineteen participants were randomly assigned to either the small-sided games training (SSGTG) (n = 10) or repeated-sprint training group (RSTG) (n = 9). Small-sided games or repeated-sprint training were added to the regular training sessions for two days of the regular practice week. The Wilcoxon signed-rank and Mann-Whitney U tests were used to examine differences in groups and training effects. A time x training group effect was found in the improvement of short-passing ability for the smallsided games training group which showed significantly better scores than the repeated-sprint training group (p ≤ 0.05). Both groups showed similar improvements in RSAdecrement (p < 0.05). Only the repeated-sprint training group improved in the Yo-Yo IR1 (p < 0.05). This study clearly shows that high-intensity small-sided games training can be used as an effective training mode to enhance both repeated sprint ability and short-passing ability.


#6 Association between Match Activity Variables, Measures of Fatigue and Neuromuscular Performance Capacity Following Elite Competitive Soccer Matches
Reference: J Hum Kinet. 2017 Dec 28;60:93-99. doi: 10.1515/hukin-2017-0093. eCollection 2017 Dec.
Authors: Varley I, Lewin R, Needham R, Thorpe RT, Burbeary R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765789/pdf/hukin-60-093.pdf
Summary: The aim of the study was to assess the relationships between match activity variables, subsequent fatigue and neuromuscular performance capacity in elite soccer players. Subjects (n = 10) were professional soccer players participating in the English Championships. Match activity variables and markers of fatigue status were measured before and following two matches. Creatine kinase (CK) and muscle soreness were measured at baseline, immediately following, as well as 40 and 64 h post-match. Countermovement jump performance and perceived ratings of wellness were measured at baseline, then 40 and 64 h post-match. Relationships were shown between CK and the total number of accelerations and decelerations immediately (r = 0.63; large), 40 h (r = 0.45; moderate) and 64 h post-match (r = 0.35; moderate) (p < 0.05). Relationships between CK and total sprint distance (r = 0.39; moderate) and the number of sprints (r = 0.35; moderate) 40 h post-match (p < 0.05) were observed. Furthermore, relationships were shown between the perceived rating of wellness and number of accelerations 40 (r = 0.52; large) and 64 h (r = 0.40; moderate) post-match, sprint distance 40 h post-match (r = 0.40; moderate) and the total number of sprints 40 h post-match (r = 0.51; large) (p < 0.05). The quantification of match activity variables, particularly the total number of accelerations and decelerations and the number of sprints, provides insights into the fatigue status in elite soccer players 40 and 64 h post-match.


#7 Physiological Demands, Morphological Characteristics, Physical Abilities and Injuries of Female Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:77-83. doi: 10.1515/hukin-2017-0091. eCollection 2017 Dec.
Authors: Milanovic Z, Sporis G, James N, Trajkovic N, Ignjatovic A, Sarmento H, Trecroci A, Mendes BMB
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765787/pdf/hukin-60-077.pdf
Summary: The popularity of female soccer is increasing as well as the number of females playing soccer. Similarly, over the last twenty or so years, research in soccer has increased significantly, but a large disparity exists in the volume of studies involving male and female players. As a consequence of this, female players remain less well understood compared to males. The purpose of the present narrative review was to describe morphological characteristics, physiological demands, physical abilities and injuries in female soccer players. Physiological demands are similar between men's and women's soccer, but competitive women's matches were characterized by nearly 33% less distance covered, although at higher intensity levels (maximum speeds greater than 15 km/h) than typically found in the men's game. Sub-elite female players also tended to run less at higher intensity levels at the end of both halves in comparison with elite female players. High intensity running is an important factor of success in soccer since many critical moments of the game occur under this condition. The ability to rapidly change direction also determined elite, sub-elite and amateur levels. The implementation of functional training, which focused on soccer-specific drills and plyometric exercises, to improve explosive power, may improve conditioning in female soccer players as well as decrease the risk of injuries which was 3-8 times higher in females compared to males. This review presents an in-depth overview of the most influential factors for determining success in female soccer.


#8 Effects of Plyometric and Resistance Training on Muscle Strength, Explosiveness and Neuromuscular Function in Young Adolescent Soccer Players
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002428. [Epub ahead of print]
Authors: McKinlay BJ, Wallace P, Dotan R, Long D, Tokuno C, Gabriel D, Falk B
Summary: This study examined the effect of 8-weeks of free-weight-resistance (RT) and plyometric (PLYO) training on maximal strength, explosiveness and jump performance compared with no added training (CON), in young male soccer players. Forty-one 11[FIGURE DASH]13-year-old soccer players were divided into three groups (RT, PLYO, CON). All participants completed isometric and dynamic (240°/s) knee extensions pre- and post-training. Peak torque (pT), peak rate of torque development (pRTD), electromechanical-delay (EMD), rate of muscle activation (Q50), m. vastus-lateralis thickness (VLT), and jump performance were examined. pT, pRTD and jump performance significantly improved in both training groups. Training resulted in significant (p<0.05) increases in isometric pT (23.4 vs. 15.8%) and pRTD (15.0 vs. 17.6%), in RT and PLYO, respectively. During dynamic contractions, training resulted in significant increases in pT (12.4 and 10.8% in RT and PLYO, respectively), but not pRTD. Jump performance increased in both training groups (RT=10.0%, PLYO=16.2%), with only PLYO significantly different from CON. Training resulted in significant increases in VLT (RT=6.7%. PLYO=8.1%). There were no significant EMD changes. In conclusion, 8-week free-weight resistance and plyometric training resulted in significant improvements in muscle strength and jump performance. Training resulted in similar muscle hypertrophy in the two training modes, with no clear differences in muscle performance. Plyometric training was more effective in improving jump performance, while free-weight resistance training was more advantageous in improving peak torque, where the stretch reflex was not involved.


#9 Comparison of step-by-step kinematics in repeated 30m sprints in female soccer players
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002429. [Epub ahead of print]
Authors: van den Tillaar R
Summary: The aim of this study was to compare kinematics in repeated 30m sprints in female soccer players. Seventeen subjects performed seven 30m sprints every 30s in one session. Kinematics were measured with an infrared contact mat and laser gun, and running times with an electronic timing device. The main findings were that sprint times increased in the repeated sprint ability test. The main changes in kinematics during the repeated sprint ability test were increased contact time and decreased step frequency, while no change in step length was observed. The step velocity increased in almost each step until the 14, which occurred around 22m. After this, the velocity was stable until the last step, when it decreased. This increase in step velocity was mainly caused by the increased step length and decreased contact times. It was concluded that the fatigue induced in repeated 30m sprints in female soccer players resulted in decreased step frequency and increased contact time. Employing this approach in combination with a laser gun and infrared mat for 30m makes it very easy to analyse running kinematics in repeated sprints in training. This extra information gives the athlete, coach and sports scientist the opportunity to give more detailed feedback and help to target these changes in kinematics better to enhance repeated sprint performance.


#10 Mild jugular compression collar ameliorated changes in brain activation of working memory after one soccer season in female high school athletes
Reference: J Neurotrauma. 2018 Jan 15. doi: 10.1089/neu.2017.5262. [Epub ahead of print]
Authors: Yuan W, Dudley J, Barber-Foss K, Ellis JD, Thomas S, Galloway RT, DiCesare C, Leach J, Adams J, Maloney T, Gadd B, Smith D, Epstein J, Grooms DR, Logan K, Howell DR, Altaye M, Myer GD
Summary: Recent neuroimaging studies have suggested that repetitive sub-concussive head impacts, even after only one sport season, may lead to pre- to post-season structural and functional alterations in male high school football athletes. However, data on female atheletes is limited. In the current investigation, we aimed to (1) assess the longitudinal pre- to post-season changes in fMRI of working memory and working memory performance, (2) quantify the association between the pre- to post-season change in fMRI of working memory and the exposure to head impact and working memory performance, and (3) assess whether wearing a neck collar designed to reduce intracranial slosh via mild compression of the jugular veins can ameliorate the changes in fMRI brain activation observed in the non-collar group after a full soccer season. A total of 48 female high school soccer athletes (age range: 14.00 - 17.97 years) were included in the study. These athletes were assigned to the non-collar group (n=21) or to the collar group (n=27). All athletes undewent MRI at both pre-season and post-season. In each session, a fMRI verbal N-Back task was used to engage working memory. A significant pre- to post-season increase in fMRI BOLD signal was demonstrated when performing the N-back working memory task in the non-collar group but not in the collar group, despite the comparable exposure of head impacts during the season between the two groups. The collar group demonstrated significantly smaller pre- to post-season change in fMRI BOLD signal than the non-collar group, suggesting a potential protective effect from the collar device. Significant correlations were also found between the pre- to post-season increase in fMRI brain activation and the decrease in task accuracy in the non-collar group, indicating an association between the compensatory mechanism in underlying neurophysiology and the alteration in the behavioral outcomes.


#11 Effects of resisted sprint training on sprinting ability and change of direction speed in professional soccer players
Reference: J Sports Sci. 2018 Jan 15:1-7. doi: 10.1080/02640414.2018.1426346. [Epub ahead of print]
Authors: Gil S, Barroso R, Crivoi do Carmo E, Loturco I, Kobal R, Tricoli V, Ugrinowitsch C, Roschel H
Summary: Resisted sprint training consists of performing overloaded sprints, which may produce greater effects than traditional sprint training. We compared a resisted sprint training with overload control versus an unresisted sprint training program on performance in soccer players. Eighteen elite athletes were randomly assigned to resisted (RST) or unresisted sprint training protocol (UR). Before and after a 6-week training period, sprinting ability, change of direction speed (COD), vertical jumps (SJ and CMJ), mean power (MP) and mean propulsive power (MPP) at distinct loads were assessed. Both groups improved sprinting ability at all distances evaluated (5m: UR = 8%, RST = 7%; 10m: UR = 5%, RST = 5%; 15m: UR = 4%, RST = 4%; 20m: UR = 3%, RST = 3%; 25m: UR = 2%, RST = 3%;), COD (UR = 6%; RST = 6%), SJ (UR = 15%; RST = 13%) and CMJ (UR = 15%; RST = 15%). Additionally, both groups increased MP and MPP at all loads evaluated. The between-group magnitude-based inference analysis demonstrated comparable improvement ("trivial" effect) in all variables tested. Finally, our findings support the effectiveness of a short-term training program involving squat jump exercise plus sprinting exercises to improve the performance of soccer players.


#12 Does inside passing contribute to the high incidence of groin injuries in soccer? A biomechanical analysis
Reference: J Sports Sci. 2018 Jan 15:1-9. doi: 10.1080/02640414.2017.1423193. [Epub ahead of print]
Authors: Dupre T, Funken J, Muller R, Mortensen KRL, Lysdal FG, Braun M, Krahl H, Potthast W
Summary: Groin injuries are common in soccer and often cause time-loss from training. While groin injuries have been linked to full effort kicking, the role of inside passing is unclear. Therefore, the purpose of this study was to investigate hip joint kinematics and muscle force, stress and contraction velocity for adductor longus and gracilis during inside passing. 3D kinematics of ten soccer players (23.4 yrs; 77.5 kg; 1.81 m) were captured with a motion capture system inside a Footbonaut. Muscle force and contraction velocity were determined with AnyBody Modelling System. Gracilis muscle forces were 9% lower compared to adductor longus (p = 0.005), but muscle stress was 183% higher in gracilis (p = 0.005). Contraction velocity reveals eccentric contraction of gracilis in the last quarter of the swing phase. Considering the combination of eccentric contraction, high muscle stress and the repetitive nature of inside passing, gracilis accumulates high loads in matches and training. These results indicate that the high incidence of groin injuries in soccer could be linked to isolated pass training. Practitioners need to be aware of the risk and refrain from sudden increases in the amount of pass training. This gives the musculoskeletal system time to adapt and might avoid career threatening injuries.

 



American Football
#1 Making Football Safer: Assessing the current NFL policy on the type of helmets allowed on the playing field
Reference: J Neurotrauma. 2018 Feb 8. doi: 10.1089/neu.2017.5446. [Epub ahead of print]
Authors: Colello R D.Phil., Colello IA, AbdelHameid D, Cresswell KG, Merchant R, Beckett E
Summary: In an effort to reduce concussions in football, a helmet safety-rating system was developed in 2011 that rated helmets based on their ability to reduce g-forces experienced by the head across a range of impact forces measured on the playing field. Although this was considered a major step in making the game safer, the NFL continues to allow players the right to choose what helmet to wear during play. This prompted us to ask: what helmets do NFL players wear and does this helmet policy make the game safer? Accordingly, we identified the helmets worn by nearly 1000 players on Weeks 13 and 1 of the 2015-2016 and 2016-2017 seasons, respectively. Using stop-motion footage, we found that players wore a wide range of helmets with varying safety ratings influenced, in part, by the player's position and age. Moreover, players wearing lower safety-rated helmets were more likely to receive a concussion than those wearing higher safety-rated helmets. Interestingly, many players suffering a concussion in 2015 did not switch to a higher safety-rated helmet in 2016. Using a helmet-to-helmet impactor, we found that the g-forces experienced in the highest safety-rated helmets were roughly 30% less than that for the lowest safety-rated helmets. These results suggest that the current NFL helmet policy puts players at increased risk of receiving a concussion as many players are wearing low safety-rated helmets, which transmits more energy to the brain than higher-safety-rated helmets, following collision. Thus, the NFL should mandate that players only wear helmets that receive the highest safety rating. This policy change would likely represent the simplest and most straightforward way to reduce concussions in football.

 



Gaelic Football
#1 An Acceleration Profile of Elite Gaelic Football with Special Reference to Position of Play
Reference: J Strength Cond Res. 2018 Feb 1. doi: 10.1519/JSC.0000000000002479. [Epub ahead of print]
Authors: Ryan M, Malone S, Donnellan A, Collins K
Summary: The current study aimed to characterize the positional match-play demands of elite Gaelic football players with special reference to acceleration utilizing predetermined 5- min periods (epochs). Thirty-five male Gaelic players (Mean ± SD, age: 24 ± 6 years; height: 180 ± 7 cm; mass: 81 ± 7 kg) across five playing positions (full-back, half-back, midfield, half-forward, full-forward) were monitored during the investigation. Player movement was recorded during nineteen matches using 4-Hz global positioning system technology (GPS; VXSport, New Zealand) resulting in 154 player observations. GPS was used to record total distance (m), high-speed running (HSR; m; ≥17 kmh), very high-speed running distance, (VHSR; m; ≥22 kmh), the number of accelerations (n), duration of accelerations (s), peak acceleration (m), and distance of accelerations (m). Acceleration profiles were position dependent with midfielders found to have a high accumulation of acceleration movements when compared to all other positions (p < 0.05). Declines of -2% to -32% for acceleration distance (m) depending on positional line of play were observed during match-play. Less HSR and VHSR, was performed by the full-back line (HSR; -39%, VHSR; -36%) and full-forward line (-35%; -29%) when compared to half-back, midfielders and half-forwards (p=0.01, d = 1.35 to 1.77). Similar trends were reported for peak acceleration distance (p=0.01, d = 1.15 to 1.93). The current investigation provides a greater understanding of temporal differences in acceleration profiles of playing position. We show that half-back, midfield and half-forwards have the highest acceleration movements these data can assist coaches in appropriately preparing players for the required acceleration distances required during match-play.


#2 The Pre-Competition Macronutrient Intake of Elite Gaelic Football Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Feb 6:1-20. doi: 10.1123/ijsnem.2017-0292. [Epub ahead of print]
Authors: Cassidy C, Collins K, Shortall M
Summary: Competition related dietary intake has not yet been investigated in Gaelic football. The present study examined the pre-competition macronutrient intake of elite male Gaelic football players. Forty players from two teams completed a food diary on the two days preceding competition (DAY-1 & DAY-2) and on match date pre-match (MATCH-DAY). Carbohydrate intake was significantly greater on DAY-2 compared to DAY-1, for both absolute [295 ± 98 vs. 318 ± 77 g] (p = 0.048; -23.6 g [-47.3 to 0.2]; Cohen's d = 0.27) and relative intake [3.4 ± 1.1 vs. 3.7 ± 1.0 g.kg-1] (p = 0.027; -0.3 g.kg-1 [-0.6 to -0.03]; Cohen's d = 0.32). The number of players in accordance with and not in accordance with the guidelines for carbohydrate intake on DAY-2 was significantly different to an expected frequency distribution [χ2 (1) = 32.400; p = <0.001; ϕ = 0.9] with a greater number of players not meeting the guidelines [observed N = 2 vs. 38]. The number of players in accordance with and not in accordance with the recommendations for carbohydrate intake on MATCH-DAY was significantly different to an expected frequency distribution [χ2 (1) = 8.100; p = 0.004; ϕ = 0.45] with a greater number of players meeting the guidelines [observed N = 29 vs. 11]. The major finding from the current investigation was that a significantly greater number of players did not meet carbohydrate intake guidelines on the day before competition. Individualised nutritional interventions are required in order to modify current pre-match dietary intake.

Fri

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2018

Football is...(#55)

Cognition in football - some thoughts

Wed

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Feb

2018

Latest research in football - week 3 - 2018

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 Mixed Training Methods: Effects of Combining Resisted Sprints or Plyometrics with Optimum Power Loads on Sprint and Agility Performance in Professional Soccer Players
Reference: Front Physiol. 2017 Dec 12;8:1034. doi: 10.3389/fphys.2017.01034. eCollection 2017.
Authors: Loturco I, Kobal R, Kitamura K, Cal Abad CC, Faust B, Almeida L, Pereira LA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732948/pdf/fphys-08-01034.pdf
Summary: The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.


#2 Time course of oxidative stress, inflammation and muscle damage markers for five days after a soccer match: effects of sex and playing position
Reference: J Strength Cond Res. 2018 Jan 3. doi: 10.1519/JSC.0000000000002436. [Epub ahead of print]
Authors: Souglis A, Bogdanis GC, Chryssanthopoulos C, Apostolidis N, Geladas ND
Summary: This study examined the influence of sex and playing position on the time-course of selected oxidative stress, inflammation and muscle damage markers following an official soccer match. Sixty professional soccer players (30 male and 30 female) were divided into three groups, according to their playing position: defenders, midfielders and attackers. Each group consisted of 10 male and 10 female players. Sixty healthy volunteers (30 males and 30 females) served as control. Blood samples were taken before and after the match and daily for five days after the match. Analysis of variance revealed different responses over time between sex and playing positions, as shown by the 3-way interaction, for creatine kinase (CK), protein carbonyls (PC), catalase, fibrinogen (FIB), uric acid (UA), lactate dehydrogenase (LDH), reduced glutathione, C-reactive protein and interleukin-6 (IL-6) (p < 0.01).Male players had higher values compared with females of the same playing position, for all oxidative, inflammatory and muscle damage indices (p<0.01). Also, in both sexes, midfielders had higher peaks in all indices compared with defenders (p < 0.05). Five days after the game CK and UA concentrations had not returned to pre-game levels in any exercise group, whereas PC were still elevated in male midfielders and attackers (p < 0.05).These results show that sex and playing position influence the time-course of selected oxidative stress, inflammation and muscle damage markers following an official soccer game. This information should be taken into account by practitioners for the design of training programs following match play.


#3 Comparison between traditional strength training and complex contrast training on soccer players
Reference: J Sports Med Phys Fitness. 2018 Jan 4. doi: 10.23736/S0022-4707.18.07934-3. [Epub ahead of print]
Authors: Spineti J, Figueiredo T, Willardson JM, Bastos de Oliveira V, Assis M, Fernandes DE Oliveira L, Miranda H, Machado de Ribeiro Reis V, Simao R
Summary: The purpose of this study was to compare traditional strength training (TST) versus and contrast training (CCT) on sprint, change of direction speed (COD) and squat jump (SJ) in young male soccer players. Twenty-two soccer players (age: 18.4 ± 0.4 years, body mass: 70.2 ± 9.1 kg, height: 179.9 ± 7.5 cm), were randomly assigned to one of two groups: TST (n=12) and CCT (n = 10). The study was conducted using a randomized experimental design over an eight- week period. The participants assigned to the CCT group performed high-power exercises paired with high-velocity exercises. The participants assigned to the TST group performed resistance exercises in a straight-set forma. During the study period, sprint tests for 5, 10, 20 and 30 m split times, COD and SJ were applied. A two-way ANOVA was applied, and the alpha level was p <0.05. The results demonstrated that the CCT regimen elicited significant within-group differences in 5 m sprint time (1.032 s to 0.997 s, pre- and post-intervention, respectively, effect size (ES) = -0.5, medium; p = 0.04), COD (5.963 s to 5.639 s, pre- and post-intervention, respectively, ES = -2.7, large; p<0.001) and SJ (30.9 cm to 34.4 cm, pre- and post-intervention, respectively, ES = 0.8, large; p<0.001). Conversely, the TST did not elicit significant within-group differences for any of the dependent variables. No differences were found between post-test time point. In conclusion, the CCT protocol could be used to improve sprint, in male soccer players.


#4 Differential Learning as a Key Training Approach to Improve Creative and Tactical Behavior in Soccer
Reference: Res Q Exerc Sport. 2018 Jan 19:1-14. doi: 10.1080/02701367.2017.1412063. [Epub ahead of print]
Authors: Santos S, Coutinho D, Goncalves B, Schollhorn W, Sampaio J, Leite N
Summary: The aim of this study was to identify the effects of a differential-learning program, embedded in small-sided games, on the creative and tactical behavior of youth soccer players. Forty players from under-13 (U13) and under-15 (U15) were allocated into control and experimental groups and were tested using a randomized pretest to posttest design using small-sided games situations. The experimental group participated in a 5-month differential-learning program embodied in small-sided games situations, while the control group participated in a typical small-sided games training program. In-game creativity was assessed through notational analyses of the creative components, and the players' positional data were used to compute tactical-derived variables. The findings suggested that differential learning facilitated the development of creative components, mainly concerning attempts (U13, small; U15, small), versatility (U13, moderate; U15, small), and originality (U13, unclear; U15, small) of players' actions. Likewise, the differential-learning approach provided a decrease in fails during the game in both experimental groups (moderate). Moreover, differential learning seemed to favor regularity in pitch-positioning behavior for the distance between players' dyads (U13, small; U15, small), the distance to the team target (U13, moderate; U15, small), and the distance to the opponent target (U13, moderate; U15, small). The differential-learning program stressed creative and positional behavior in both age groups with a distinct magnitude of effects, with the U13 players demonstrating higher improvements over the U15 players. Overall, these findings confirmed that the technical variability promoted by differential learning nurtures regularity of positioning behavior.


#5 The neuromuscular, biochemical, endocrine and mood responses to small-sided games training in professional soccer
Reference: J Strength Cond Res. 2018 Jan 17. doi: 10.1519/JSC.0000000000002424. [Epub ahead of print]
Authors: W S, An T, M W, M R, Mj J, Lp K
Summary: The 24h responses to small-sided games (SSG) soccer training were characterized. Professional soccer players (n=16) performed SSG's (4vs4 + goalkeepers; 6x7-min, 2-min inter-set recovery) with performance (peak-power output, PPO; jump height, JH), physiological (blood creatine kinase: CK, lactate; salivary testosterone, cortisol), and mood measures collected before (baseline), and after (immediately; 0h, +2h, +24h). For PPO and JH, possibly small-moderate reductions occurred at 0h (-1.1W·kg; ±0.9W·kg, -3.2cm; ±1.9cm, respectively), before returning to baseline at +2h (trivial) and declining thereafter (small-moderate effect) at +24h (-0.9W·kg; ±0.8W·kg, -2.5cm; ±1.2cm, respectively). Lactate increased at 0h (likely-large; +1.3mmol·L; ±0.5mmol·L), reduced at +2h (likely-small; -0.5mmol·L; ±0.2mmol·L), and returned to baseline at 24h (trivial). A very-likely small increase in CK occurred at 0h (+97u·L; ±28u·L), persisting for +24h (very-likely small; +94u·L; ±49u·L). Possibly-small increases in testosterone (+20pg·ml; ±29pg·ml) occurred at 0h, before likely-moderate declines at +2h (-61pg·ml; ±21pg·ml) returning to baseline at +24h (trivial). For cortisol, possibly-small decreases occurred at 0h (-0.09ug·dl; -±0.16ug·dl), before likely-large decreases at +2h (-0.39ug·dl; ±0.12ug·dl), which persisted for 24h (likely-small; -0.12ug·dl; ±0.11ug·dl). Mood was disturbed by SSG's at 0h (likely-moderate; +13.6AU, ±5.6AU) and +2h (likely-small; +7.9AU; ±5.0AU), before returning to baseline at +24h (trivial). The movement demands of SSG's result in a bimodal recovery pattern of neuromuscular function and perturbations in physiological responses and mood for up to 24h. Accordingly, when programming soccer training, SSG's should be periodized throughout the competitive week with submaximal technical/tactical activities.


#6 Effects of Contrast Strength vs. Plyometric Training on Lower Limb Explosive Performance, Ability to Change Direction and Neuromuscular Adaptation in Soccer Players
Reference: J Strength Cond Res. 2018 Jan 17. doi: 10.1519/JSC.0000000000002425. [Epub ahead of print]
Authors: Hammami M, Gaamouri N, Shephard RJ, Chelly MS
Summary: The aim was to compare the effects of two differing 8-week in-season strength training programs (contrast strength training [CST] vs. plyometric training [PT]) on selected performance tests (5 and 40m sprints, S 4 X 5 m change of direction test, squat (SJ) and countermovement (CMJ) jumps , leg peak power on a cycle ergometer force-velocity test, 1-repetition maximal (1-RM) half squat, and electromyographic [EMG] activity of the vastus lateralis, vastus medialis and rectus femoris muscles during vertical jump tests). Forty male soccer players (age = 15.8 ± 0.4 years; body mass = 58.8 ± 6.3 kg; body height = 1.74 ± 0.06 m; body fat = 10.5 ± 1.9 %) were divided between a contrast strength (CSG, n = 14), plyometric (PG, n = 14) and control groups (CG, n = 12). Both training programs enhanced sprint performance (p<0.001 in 5m; p≤0.05 in 40m) and change of direction test scores (p<0.001) relative to controls. PG and CSG increased SJ height relative to the CG, with a slightly greater response in CSG compared to PG (p≤0.05). The majority of CMJ scores increased significantly in both CSG and PG relative to the CG, with no inter-group differences in training response. The majority of force-velocity scores increased significantly in the CSG relative to PG and CG. The EMG parameters also increased in the CSG relative to both PG and CG. In summary, most measures of athletic performance in male soccer players were enhanced after CST and PT. However, the improvement of physical performance was better with eight weeks of CST than with PT. Thus, coaches should be encouraged to include CST as an element of in-season conditioning.


#7 Preseason Adductor Squeeze Strength in 303 Spanish Male Soccer Athletes: A Cross-sectional Study
Reference: Orthop J Sports Med. 2018 Jan 11;6(1):2325967117747275. doi: 10.1177/2325967117747275. eCollection 2018 Jan.
Authors: Esteve E, Rathleff MS, Vicens-Bordas J, Clausen MB, Holmich P, Sala L, Thorborg K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5768277/pdf/10.1177_2325967117747275.pdf
Summary: Hip adductor muscle weakness and a history of groin injury both have been identified as strong risk factors for sustaining a new groin injury. Current groin pain and age have been associated with hip adductor strength. These factors could be related, but this has never been investigated. The purpose was to investigate whether soccer athletes with past-season groin pain and with different durations of past-season groin pain had lower preseason hip adductor squeeze strength compared with those without past-season groin pain. We also investigated whether differences in preseason hip adductor squeeze strength in relation to past-season groin pain and duration were influenced by current groin pain and age. In total, 303 male soccer athletes (mean age, 23 ± 4 years; mean weight, 74.0 ± 7.9 kg; mean height, 178.1 ± 6.3 cm) were included in this study. Self-reported data regarding current groin pain, past-season groin pain, and duration were collected. Hip adductor squeeze strength was obtained using 2 different reliable testing procedures: (1) the short-lever (resistance placed between the knees, feet at the examination bed, and 45° of hip flexion) and (2) the long-lever (resistance placed between the ankles and 0° of hip flexion) squeeze tests. There was no difference between those with (n = 123) and without (n = 180) past-season groin pain for hip adductor squeeze strength when adjusting for current groin pain and age. However, athletes with past-season groin pain lasting longer than 6 weeks (n = 27) showed 11.5% and 15.3% lower values on the short-lever (P = .006) and long-lever (P < .001) hip adductor squeeze strength tests, respectively, compared with those without past-season groin pain. Male soccer athletes with past-season groin pain lasting longer than 6 weeks are likely to begin the next season with a high-risk groin injury profile, including a history of groin pain and hip adduction weakness.


#8 Are Current Physical Match Performance Metrics in Elite Soccer Fit for Purpose or is the Adoption of an Integrated Approach Needed?
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-23. doi: 10.1123/ijspp.2017-0433. [Epub ahead of print]
Authors: Bradley PS, Ade JD
Summary: Time-motion analysis is a valuable data-collection technique used to quantify the physical match performance of elite soccer players. For over 40 years researchers have adopted a 'traditional' approach when evaluating match demands by simply reporting the distance covered or time spent along a motion continuum of walking through to sprinting. This methodology quantifies physical metrics in isolation without integrating other factors and this ultimately leads to a one-dimensional insight into match performance. Thus, this commentary proposes a novel 'integrated' approach that focuses on a sensitive physical metric such as high-intensity running but contextualizes this in relation to key tactical activities for each position and collectively for the team. In the example presented, the 'integrated' model clearly unveils the unique high-intensity profile that exists due to distinct tactical roles, rather than one-dimensional 'blind' distances produced by 'traditional' models. Intuitively this innovative concept may aid the coaches understanding of the physical performance in relation to the tactical roles and instructions given to the players. Additionally, it will enable practitioners to more effectively translate match metrics into training and testing protocols. This innovative model may well aid advances in other team sports that incorporate similar intermittent movements with tactical purpose. Evidence of the merits and application of this new concept are needed before the scientific community accepts this model as it may well add complexity to an area that conceivably needs simplicity.


#9 Effects of Late-Night Training on "Slow-Wave Sleep Episode" and Hour-by-Hour Derived Nocturnal Cardiac Autonomic Activity in Female Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-26. doi: 10.1123/ijspp.2017-0681. [Epub ahead of print]
Authors: Costa JA, Brito J, Nakamura FY, Oliveira EM, Rebelo AN
Summary: The purpose was to assess the sensitivity of nocturnal heart rate variability (HRV) monitoring methods to the effects of late-night soccer training sessions in female athletes. Eleven female soccer players competing in the 1st division of the Portuguese soccer league wore HR monitors during night-sleep throughout a one-week competitive in-season microcycle, after late-night training sessions (n = 3) and rest days (n = 3). HRV was analyzed through "slow-wave sleep episode" (SWSE; 10 min duration) and "hour-by-hour" (all the RR intervals recorded throughout the hours of sleep). Training load was quantified by session rating of perceived exertion (sRPE: 281.8 ± 117.9 to 369.0 ± 111.7 a.u.) and training impulse (TRIMP: 77.5 ± 36.5 to 110.8 ± 31.6 a.u.), added to subjective well-being ratings (Hopper index: 11.6 ± 4.4 to 12.8 ± 3.2 a.u.). These variables were compared between training and rest days using repeated measures ANOVA. The ln-transformed SWSE cardiac autonomic activity (lnRMSSD varying between 3.92 ± 0.57 and 4.20 ± 0.60 ms; ηp2 = 0.16 [0.01-0.26]), lnHF, lnLF, lnSD1 and lnSD2 and the non-transformed LF/HF were not different among night-training session days and resting days (P > 0.05). Considering the hour-by-hour method (lnRMSSD varying between 4.05 ± 0.35 and 4.33 ± 0.32 ms; ηp2 = 0.46 [0.26-0.52]), lnHF, lnLF, lnSD1 and lnSD2 and the non-transformed LF/HF were not different among night-training session days and resting days (P > 0.05). Late-night soccer training does not seem to affect nocturnal SWSE and "hour-by-hour" HRV indices in highly-trained athletes.


#10 Post-match Perceived Exertion, Feeling and Wellness in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-22. doi: 10.1123/ijspp.2017-0725. [Epub ahead of print]
Authors: Fessi MS, Moalla W
Summary: The aim of this study was to assess post-match perceived exertion, feeling and wellness according to the match outcome (winning, drawing or losing) in professional soccer players. Twelve outfield players were followed during 52 official matches where the outcomes (win, draw or lose) were noted. Following each match players completed both a 10-point scale rating of perceived exertion (RPE) and an 11-point scale rating of perceived feeling. Rating of perceived sleep quality, stress, fatigue and muscle soreness were collected separately on a 7-point scale the day following each match. Player RPE was higher by a very largely magnitude following a loss compared to a draw or a win and higher by a small magnitude after a draw compared to a win. Players felt more pleasure after a win compared to a draw or loss and more displeasure after a loss compared to draw. The players reported a largely and moderately better-perceived sleep quality, less stress and fatigue following a win compared to draw or a loss, and a moderately bad-perceived sleep quality, higher stress and fatigue following a draw compared to a loss. In contrast, only a trivial-small change was observed in perceived muscle soreness between all outcomes. Matches outcomes moderately to largely affect RPE, perceived feeling, sleep quality, stress and fatigue whereas perceived muscle soreness remains high regardless of the match outcome. However, winning a match decreases the strain and improves both pleasure and wellness in professional soccer players.

Wed

31

Jan

2018

Latest research in football - week 2 - 2018

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 Demands of Amputee Soccer Impair Muscular Endurance and Power Indices But Not Match Physical Performance
Reference: Adapt Phys Activ Q. 2018 Jan 5:1-17. doi: 10.1123/apaq.2016-0147. [Epub ahead of print]
Authors: Simim MAM, da Mota GR, Marocolo M, da Silva BVC, de Mello MT, Bradley PS
Summary: We investigated the match demands (distances covered and acute physiological responses) of amputee soccer and its impact on muscular endurance and power. Measures such as heart rate, blood lactate concentration, subjective rating of perceived exertion, and time-motion characteristics were recorded in 16 Brazilian amputee soccer players during matches. Before and after matches, players completed a battery of tests: push-ups, countermovement vertical jump performance, and medicine ball throwing. Small differences were found between the first and second half for the distance covered in total and across various speed categories. Heart rate responses, blood lactate concentrations, and peak speed did not differ between halves, and all neuromuscular performance measures decreased after the match particularly after push-ups, although the rating of perceived exertion increased markedly compared with prematches. Although match physical performances were consistent across halves, the overall demands impaired test performance, especially for upper limb and closed kinetic chain exercise.


#2 Carbohydrates for Soccer: A Focus on Skilled Actions and Half-Time Practices
Reference: Nutrients. 2017 Dec 25;10(1). pii: E22. doi: 10.3390/nu10010022.
Authors: Hills SP, Russell M
Download link: www.mdpi.com/2072-6643/10/1/22/pdf
Summary: Carbohydrate consumption is synonymous with soccer performance due to the established effects on endogenous energy store preservation, and physical capacity maintenance. For performance-enhancement purposes, exogenous energy consumption (in the form of drinks, bars, gels and snacks) is recommended on match-day; specifically, before and during match-play. Akin to the demands of soccer, limited opportunities exist to consume carbohydrates outside of scheduled breaks in competition, such as at half-time. The link between cognitive function and blood glucose availability suggests that carbohydrates may influence decision-making and technical proficiency (e.g., soccer skills). However, relatively few reviews have focused on technical, as opposed to physical, performance while also addressing the practicalities associated with carbohydrate consumption when limited in-play feeding opportunities exist. Transient physiological responses associated with reductions in activity prevalent in scheduled intra-match breaks (e.g., half-time) likely have important consequences for practitioners aiming to optimize match-day performance. Accordingly, this review evaluated novel developments in soccer literature regarding (1) the ergogenic properties of carbohydrates for skill performance; and (2) novel considerations concerning exogenous energy provision during half-time. Recommendations are made to modify half-time practices in an aim to enhance subsequent performance. Viable future research opportunities exist regarding a deeper insight into carbohydrate provision on match-day.


#3 Talent Identification and Development in Male Football: A Systematic Review
Reference: Sports Med. 2018 Jan 3. doi: 10.1007/s40279-017-0851-7. [Epub ahead of print]
Authors: Sarmento H, Anguera MT, Pereira A, Araujo D
Summary: Expertise has been extensively studied in several sports over recent years. The specificities of how excellence is achieved in Association Football, a sport practiced worldwide, are being repeatedly investigated by many researchers through a variety of approaches and scientific disciplines. The aim of this review was to identify and synthesise the most significant literature addressing talent identification and development in football. We identified the most frequently researched topics and characterised their methodologies. A systematic review of Web of Science™ Core Collection and Scopus databases was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The following keywords were used: "football" and "soccer". Each word was associated with the terms "talent", "expert*", "elite", "elite athlete", "identification", "career transition" or "career progression". The selection was for the original articles in English containing relevant data about talent development/identification on male footballers. The search returned 2944 records. After screening against set criteria, a total of 70 manuscripts were fully reviewed. The quality of the evidence reviewed was generally excellent. The most common topics of analysis were (1) task constraints: (a) specificity and volume of practice; (2) performers' constraints: (a) psychological factors; (b) technical and tactical skills; (c) anthropometric and physiological factors; (3) environmental constraints: (a) relative age effect; (b) socio-cultural influences; and (4) multidimensional analysis. Results indicate that the most successful players present technical, tactical, anthropometric, physiological and psychological advantages that change non-linearly with age, maturational status and playing positions. These findings should be carefully considered by those involved in the identification and development of football players. This review highlights the need for coaches and scouts to consider the players' technical and tactical skills combined with their anthropometric and physiological characteristics scaled to age. Moreover, research addressing the psychological and environmental aspects that influence talent identification and development in football is currently lacking. The limitations detected in the reviewed studies suggest that future research should include the best performers and adopt a longitudinal and multidimensional perspective.


#4 Monitoring loads and non-contact injury during the transition from club to National team prior to an international football tournament: A case study of the 2014 FIFA World Cup and 2015 Asia Cup
Reference: J Sci Med Sport. 2017 Dec 20. pii: S1440-2440(17)31825-X. doi: 10.1016/j.jsams.2017.12.002. [Epub ahead of print]
Authors: McCall A, Jones M, Gelis L, Duncan C, Ehrmann F, Dupont G, Duffield R
Summary: Injured and non-injured national team footballers were compared for external and internal loads during transition from club to National team training camp. Load and injury data were collected from the same National team prior to and during training camps of 2 tournaments; World (n=17) and Asian Cups (n=16). External (number sessions) and internal (s-RPE) loads were collected 4-weeks prior to and during camps. The acute:chronic load ratio was calculated for the first week of camp based on the mean of previous 4-weeks. Respective loads and ratios were compared between injured and non-injured players for non-contact injuries occurring during camp. Seven non-contact injuries occurred during World Cup camp and 1 during Asian Cup (preventing statistical analyses). Small-to-moderate effect sizes were found for lower chronic internal loads (ES=0.57; 90% CI: 0.39-1.08) and higher acute:chronic ratio (ES=0.45; 90% CI: 0.31-0.87) for injured compared to non-injured players. Moderate-large effects (ES=0.83; 90% CI: 0.56-1.60) were evident for increased acute:chronic ratio for number of sessions in injured compared to non-injured players. However, small-moderate effect sizes were present for lower chronic training and match loads (ES=0.55; 90% CI: 0.38-1.06) in injured players prior to the World Cup camp, alongside an increased number of sessions in week 1 of camp (ES=0.47; 90% CI: 0.33-0.91). Players incurring non-contact injury during training camp prior to an international tournament performed less prior chronic external and internal load and a concomitant higher relative increase in camp, thus representing a practical marker to monitor in national teams.


#5 Ecological validity and reliability of an age-adapted endurance field test in young male soccer players
Reference: J Strength Cond Res. 2018 Jan 11. doi: 10.1519/JSC.0000000000002255. [Epub ahead of print]
Authors: Castagna C, Krustrup P, D'Ottavio S, Pollastro C, Bernardini A, Araujo Povoas SC
Summary: The purpose of this study was to examine the reliability and the association with relevant match activities (ecological validity) of an age-adapted field test for intermittent high-intensity endurance known as Yo-Yo intermittent recovery level 1 children test (YYIR1C) in young male soccer players. Twenty-eight young male outfield soccer players (age 11.1±0.9 years, height 142±4.4 cm, body mass 37.0±5.9 kg) with at least 2 years of experience in soccer competitions were tested twice using YYIR1C and an age-adapted competitive small-sided game (i.e., 9v9), 7 days apart in a random order. The YYIR1C performance showed an excellent relative (ICC=0.94) and a good absolute reliability (TEM as %CV=5.1%). Very large and significant associations were found between YYIR1C performance and match high-intensity activity (r=0.53). Large correlations were found between YYIR1C and match sprinting (r=0.42) and high-intensity metabolic power (r=0.46) distances. Match total distance was largely associated with YYIR1C (r=0.30). The results of this study showed that YYIR1C may be considered a valid and reliable field test for assessing intermittent high-intensity endurance in young male soccer players. Due to the relevance of aerobic fitness in youth soccer, future studies testing the sensitiveness of YYIR1C are necessary.


#6 A previous hamstring injury affects kicking mechanics in soccer players
Reference: J Sports Med Phys Fitness. 2018 Jan 10. doi: 10.23736/S0022-4707.18.07852-0. [Epub ahead of print]
Authors: Navandar A, Veiga S, Torres G, Chorro D, Navarro E
Summary: Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury. 45 professional players (males: n=19, previously injured players=4, age=21.16 ± 2.00 years; females: n=19, previously injured players=10, age=22.15 ± 4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases. A shorter backswing (20.20 ± 3.49% vs 25.64 ± 4.57%), and differences in knee flexion angle (58 ± 10o vs 72 ± 14o) and hip flexion velocity (8 ± 0rad/s vs 10 ± 2rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50 ± 0.84m/s vs 4.10 ± 0.45m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern. Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.


#7 Physical Fitness Performance of Young Professional Soccer Players Does not Change During Several Training Seasons in A Spanish Elite Reserve Team: A Club Study, 1996-2013
Reference: J Strength Cond Res. 2018 Jan 5. doi: 10.1519/JSC.0000000000002426. [Epub ahead of print]
Authors: Los Arcos A, Martins J
Summary: The purpose of the study was to assess the changes in physical fitness performance in young professional soccer players during several training seasons in a Spanish elite reserve team. Physical test values (i.e. vertical jump test, straight line sprint test, and discontinuous and progressive submaximal running test) of 97 young professional soccer players that belonged for at least two consecutive seasons to the reserve team of a Spanish professional team from 1996 to 2013 were analyzed. A distinction was made between the soccer players that were promoted to the Spanish 1/2 Divisions (n = 38) (PFL) and those that were not (n = 59) (non-PFL) (until the end of the 2016/2017 season). Players were also classified according to their playing positions. Independently of the competitive level reached and the playing position, the variability of the fitness performance was limited (coefficient of variation <6%) and the players did not improve their fitness values [ZERO WIDTH SPACE][ZERO WIDTH SPACE](ES ≤ small) from the first to the last season in which they were enrolled in the team (after 2-4 seasons). During the last stage of training in an elite soccer academy, young professional soccer players achieve a very similar physical fitness performance when their soccer competence is evaluated, and other soccer performance factors are those which make them stand out for selection.


#8 Investigating Effects of Sex Differences and Prior Concussions on Symptom Reporting and Cognition Among Adolescent Soccer Players
Reference: Am J Sports Med. 2018 Jan 1:363546517749588. doi: 10.1177/0363546517749588. [Epub ahead of print]
Authors: Brooks BL, Silverberg N, Maxwell B, Mannix R, Zafonte R, Berkner PD, Iverson GL
Summary: There has been increasing concern regarding the possible effect of multiple concussions on the developing brain, especially for adolescent females. Hypothesis/Purpose: The objectives were to determine if there are differences in cognitive functioning, symptom reporting, and/or sex effects from prior concussions. In a very large sample of youth soccer players, it was hypothesized that (1) there would be no differences in cognitive test performance between those with and without prior concussions, (2) baseline preseason symptoms would be better predicted by noninjury factors than concussion history, and (3) males and females with prior concussions would not have differences in cognition or symptoms. Participants included 9314 youth soccer players (mean = 14.8 years, SD = 1.2) who completed preseason baseline cognitive testing, symptom reporting, and a health/injury history questionnaire from the ImPACT battery (Immediate Post-concussion Assessment and Cognitive Testing). On the basis of injury history, athletes were grouped by number of prior concussions: 0 (boys, n = 4012; girls, n = 3963), 1 (boys, n = 527; girls, n = 457), 2 (boys, n = 130; girls, n = 97), or ≥3 (boys, n = 73; girls, n = 55). The primary measures were the 4 primary cognitive scores and the total symptom ratings from ImPACT. Primary outcomes were assessed across injury groups, controlling for age, sex, learning disability, attention-deficit/hyperactivity disorder (ADHD), treatment for headaches/migraines, substance abuse, and mental health problems. Cognitive test performance was not associated with concussion history but was associated with sex, age, learning disability, ADHD, and prior mental health problems. Greater symptom reporting was more strongly associated with psychiatric problems, older age, learning disability, substance abuse, headaches, being female, and ADHD than with a history of multiple concussions. Boys and girls did not differ on cognitive scores or symptom reporting based on a history of concussion. In this very large sample of youth soccer players with prior concussion, there was no evidence of negative effects on cognition, very weak evidence of negative effects on symptom reporting, and no evidence of sex × concussion differences in cognition or symptom reporting.


#9 Breast Injuries in Female Collegiate Basketball, Soccer, Softball and Volleyball Athletes: Prevalence, Type and Impact on Sports Participation
Reference: Eur J Breast Health. 2018 Jan 1;14(1):46-50. doi: 10.5152/ejbh.2017.3748. eCollection 2018 Jan.
Authors: Smith LJ, Eichelberger TD, Kane EJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5758063/pdf/ejbh-14-1-46.pdf
Summary: In 2015-2016, over 214,000 female athletes competed at the collegiate level in the United States (U.S.). The National Collegiate Athletic Association (NCAA) collects injury data; however, breast-related injuries do not have a specific reporting category. The exact sequelae of breast injury are unknown; however, a relationship between breast injury and fat necrosis, which mimics breast carcinoma, is documented outside of sports participation. Breast injuries related to motor vehicle collisions, seatbelt trauma, and blunt trauma have been reported. For these reasons, it is important to investigate female breast injuries in collegiate sports. The objectives of this study are to report the prevalence of self-reported breast injuries in female collegiate athletes, explore injury types and treatments, and investigate breast injury reporting and impact on sports participation. A cross-sectional study of female collegiate athletes at four U.S. universities participating in basketball, soccer, softball, or volleyball. Main outcome measure was a questionnaire regarding breast injuries during sports participation. Almost half of the 194 participants (47.9%) reported a breast injury during their collegiate career, less than 10% reported their injury to health personnel with 2.1% receiving treatment. Breast injuries reported by breast injuries reported by sport include softball (59.5%), basketball (48.8%), soccer (46.7%), and volleyball (34.6%). The long-term effects and sequelae of breast injuries reported by female collegiate athletes during sport play are unknown. Nearly 50% of participants had a breast injury during sports activities. Although 18.2% indicated that breast injury affected sports participation, only 9.6% of the injuries were reported to medical personnel with 2.1% receiving treatment.



American Football
#1 Can Functional Movement Assessment Predict Football Head Impact Biomechanics?
Reference: Med Sci Sports Exerc. 2017 Dec 30. doi: 10.1249/MSS.0000000000001538. [Epub ahead of print]
Authors: Ford JM, Campbell KR, Ford CB, Boyd KE, Padua DA, Mihalik JP.
Summary: The purpose was to determine functional movement assessments' ability to predict head impact biomechanics in college football players, and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance. Participants (N = 44, mass = 109.0 ± 20.8 kg, age = 20.0 ± 1.3 years) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test, and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75); moderate (50 to 75); and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors); moderate (6-7 errors); and poor (> 7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We employed random intercepts general linear mixed models to analyze our data. There were no effects of preseason movement assessment group on the two HIT System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R=0.006) or the LESS (F1,36 < 0.01 p = 0.988, R<0.001) assessments. Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.


#2 "But He's a Star Football Player!": How Social Status Influences Mock Jurors' Perceptions in a Sexual Assault Case
Reference: J Interpers Violence. 2017 Jun 1:886260517713715. doi: 10.1177/0886260517713715. [Epub ahead of print]
Authors: Pica E, Sheahan C, Pozzulo J
Summary: There have been several recent, high-profile cases in the media that have shed light on the perceived leniency in sentencing defendants in sexual assault cases. In a number of these cases, the defendant was well known within their community (e.g., Brock Turner; People v. Turner) or nationally (e.g., Ghomeshi; R v. Ghomeshi). The purpose of this study was to examine how the social status of the defendant (low vs. high), victim social status (low vs. high), victim gender (male vs. female), and the reason the victim was unconscious during the assault (consuming alcohol vs. consuming cold medicine) influenced mock jurors' decisions in a sexual assault case. Mock jurors ( N = 489) read a mock trial transcript depicting an alleged sexual assault. Mock jurors were asked to render a dichotomous verdict, continuous guilt rating, and rate their perceptions of the victim and defendant. There was no influence of the variables on mock jurors' dichotomous verdicts; however, social status influenced guilt ratings. There also was a combined influence of the defendant's social status and the reason the victim was unconscious such that when the defendant was described as low status, and the victim was unconscious due to alcohol consumption, the defendant received higher guilt ratings compared with when the victim was unconscious due to cold medicine. Moreover, the victim was perceived as having more control over the situation when the defendant was the star quarterback (i.e., high status), the victim was female, and she was unconscious due to alcohol consumption compared with cold medicine. These results suggest that victims may be blamed based on their perceived social status and other factors that may have influenced their control over the sexual assault, such as alcohol consumption.


#3 The Evolving Treatment Patterns of NCAA Division I Football Players by Orthopaedic Team Physicians Over the Past Decade, 2008-2016
Reference: Sports Health. 2018 Jan 1:1941738117745488. doi: 10.1177/1941738117745488. [Epub ahead of print]
Authors: Carver TJ, Schrock JB, Kraeutler MJ, McCarty EC
Summary: Previous studies have analyzed the treatment patterns used to manage injuries in National Collegiate Athletic Association (NCAA) Division I football players. The hypothesis is that Treatment patterns used to manage injuries in NCAA Division I football players will have changed over the study period.  The head orthopaedic team physicians for all 128 NCAA Division I football teams were asked to complete a survey containing questions regarding experience as team physician, medical coverage of the team, reimbursement issues, and treatment preferences for some of the most common injuries occurring in football players. Responses from the current survey were compared with responses from the same survey sent to NCAA Division I team physicians in 2008. Responses were received from 111 (111/119, 93%) NCAA Division I orthopaedic team physicians in 2008 and 115 (115/128, 90%) orthopaedic team physicians between April 2016 and April 2017. The proportion of team physicians who prefer a patellar tendon autograft for primary anterior cruciate ligament reconstruction (ACLR) increased from 67% in 2008 to 83% in 2016 ( P < 0.001). The proportion of team physicians who perform anterior shoulder stabilization arthroscopically increased from 69% in 2008 to 93% in 2016 ( P < 0.0001). Of team physicians who perform surgery for grade III posterior cruciate ligament (PCL) injuries, the proportion who use the arthroscopic single-bundle technique increased from 49% in 2008 to 83% in 2016 ( P < 0.0001). The proportion of team physicians who use Toradol injections prior to a game to help with nagging injuries decreased from 62% in 2008 to 26% in 2016 ( P < 0.0001). Orthopaedic physicians changed their injury treatment preferences for NCAA Division I football players over the study period. In particular, physicians have changed their preferred techniques for ACLR, anterior shoulder stabilization, and PCL reconstruction. Physicians have also become more conservative with pregame Toradol injections.

Tue

16

Jan

2018

Latest research in football - week 1 - 2018

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 Physiological and Physical Responses According to the Game Surface in a Soccer Simulation Protocol
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-22. doi: 10.1123/ijspp.2017-0570. [Epub ahead of print]
Authors: Lopez-Fernandez J, Sanchez-Sanchez J, Garcia-Unanue J, Felipe JL, Colino-Acevedo E, Gallardo L
Summary: Recent studies have shown that soccer player's responses are similar on natural grass (NG) and artificial turf (AT), but they did not control the mechanical properties of these surfaces. This work aimed to analyse the influence of the game surface on amateur soccer player's physical and physiological responses using a soccer simulation protocol (SSP). Sixteen amateur players performed three bouts of the SSP on AT and NG. The mechanical properties of both surfaces were recorded. The order of surfaces was randomly established for each participant. Physiological responses of players were assessed before and after the six-repeated sprints test existing at the midpoint of each bout. Fatigue (% Best; % Diff) and general variables (total time; best time, mean time; maximum speed) for both the repeated sprint test and the agility tests (nonlinear actions at maximum speed) incorporated into the SSP were also analysed. The two surfaces displayed different mechanical properties. Physical responses were found similar for both surfaces (p>0.05) before and after the repeated sprint test. There were no surface differences in sprint times or fatigue variables for the repeated sprint test (p>0.05). The agility test was faster on AT than on NG in bout 1 (average speed [+1.17 Km/h; p=0.037]; agility test cut time [-0.31 s; p=0.027] and best time [-0.52 s; p=0.042]). The differences in the mechanical properties of the two surfaces are not sufficient to cause differences in the physiological and physical responses of soccer players, although they may affect turns and cuts.


#2 Investigating the influence of intra-individual changes in perceived stress symptoms on injury risk in soccer
Reference: Scand J Med Sci Sports. 2017 Dec 28. doi: 10.1111/sms.13048. [Epub ahead of print]
Authors: Clement D, Ivarsson A, Tranaeus U, Johnson U, Stenling A
Summary: Research has shown that high levels of stress and stress responsivity can increase the risk of injuries. However, most of the research that has supported this notion has focused on between-person relationships, ignoring the relationships at the within-person level. As a result, the objective of this study was to investigate if within-person changes in perceived stress symptoms over a one-month time period could predict injury rates during the subsequent three months. A prospective design with two measurement points (Time 1 - at the beginning of the season and Time 2 - one month into the season) was utilized. A total of 121 competitive soccer players (85 males and 36 females; Mage = 18.39, SD = 3.08) from Sweden and the United States completed the Kessler Psychological Distress Scale (KPDS) and a demographic sheet at Time 1. The KPDS was also completed at Time 2 and all acute injuries that occurred during the subsequent three-month period were recorded. A Bayesian latent change scores model was used to determine if within-person changes in stress symptoms could predict the risk of injury. Results revealed that there was a credible positive effect of changes in stress symptoms on injury rates, indicating that an increase in reported stress symptoms was related to an increased risk for injury. This finding highlights the importance of creating caring and supportive sporting environments and relationships and teaching stress management techniques, especially during the earlier portion of competitive seasons, to possibly reduce the occurrence of injuries.


#3 Soccer helps build strong bones during growth: a systematic review and meta-analysis
Reference: Eur J Pediatr. 2017 Dec 28. doi: 10.1007/s00431-017-3060-3. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente A, Gonzalez-Aguero A, Gomez-Bruton A, Gomez-Cabello A, Vicente-Rodriguez G, Casajus JA
Summary: The aim of this study was to analyze the effects of soccer practice on bone in male and female children and adolescents. MEDLINE, PubMed, SPORTDiscus and Web of Science databases were searched for scientific articles published up to and including October 2016. Twenty-seven studies were included in this systematic review (13 in the meta-analysis). The meta-analysis was performed by using OpenMeta[Analyst] software. It is well documented that soccer practice during childhood provides positive effects on bone mineral content (BMC) and density (BMD) compared to sedentary behaviors and other sports, such as tennis, weightlifting, or swimming. Furthermore, soccer players present higher BMC and BMD in most weight-bearing sites such as the whole body, lumbar spine, hip, and legs. Moreover, bone differences were minimized between groups during prepuberty. Therefore, the maturity status should be considered when evaluating bone. According to meta-analysis results, soccer practice was positively associated with whole-body BMD either in males (mean difference 0.061; 95%CI, 0.042-0.079) or in females (mean difference 0.063; 95%CI, 0.026-0.099). Soccer may be considered a sport that positively affects bone mass during growth. Pubertal soccer players presented increased bone mass compared to controls or other athletes; however, these bone differences are minimized during the prepubertal stage. What is known: • It has been described that childhood and adolescence are important periods for bone mass and structure. • Previous studies have demonstrated that soccer participation improves bone mass in male and female children and adolescents. What is new: • The differences between soccer players and controls are more marked during puberty than prepuberty. • Weight-bearing sites such as lumbar spine, hip, femoral neck, trochanter, intertrochanteric region and both legs are particularly sensitive to soccer actions.


#4 Assessing Differences in Cardiorespiratory Fitness With Respect to Maturity Status in Highly Trained Youth Soccer Players
Reference: Pediatr Exerc Sci. 2017 Dec 23:1-13. doi: 10.1123/pes.2017-0185. [Epub ahead of print]
Authors: Doncaster G, Iga J, Unnithan V
Summary: The purpose of the study was to examine differences in measures of cardiorespiratory fitness and determinants of running economy with respect to maturity status in a group of highly trained youth soccer players. A total of 21 highly trained youth soccer players participated in this study. On separate visits, players' peak oxygen uptake (VO2peak), running economy at 3 different speeds [8 km·h-1, 80% gaseous exchange threshold (GET), and 95% GET], and pulmonary oxygen uptake (VO2) kinetics were determined. Players also performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Players were categorized as either "pre-PHV" (peak height velocity) or "mid-PHV" group using the measure of maturity offset. Independent t tests and Cohen's d effect sizes were then used to assess differences between groups. The mid-PHV group was significantly taller, heavier, and advanced in maturity status. Absolute measures of VO2peak were greater in the mid-PHV group; however, when expressed relative to body mass, fat-free mass, and theoretically derived exponents, VO2peak values were similar between groups. Pre-PHV group presented a significantly reduced VO2 response, during relative submaximal running speeds, when theoretically derived exponents were used, or expressed as %VO2peak. VO2 kinetics (tau) were faster during a low (standing) to moderate (95% GET) transition in the pre-PHV group. Yo-Yo IR1 performance was similar between groups. Although measures of VO2peak and Yo-Yo IR1 performance are shown to be similar between groups, those categorized as pre-PHV group display a superior running economy at relative submaximal running speeds and faster taus during a low to moderate exercise transition than their more mature counterparts.


#5 Reliability, Validity and Sensitivity of a Novel Smartphone-Based Eccentric Hamstring Strength Test in Professional Football Players
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-19. doi: 10.1123/ijspp.2017-0336. [Epub ahead of print]
Authors: Lee JWY, Cai MJ, Yung PSH, Chan KM
Summary: This study aims to evaluate the test-retest reliability, sensitivity and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players. Twenty-five healthy male professional football players have performed CUHK Nordic break-point test, hamstring fatigue protocol and isokinetic hamstring strength test. CUHK Nordic break-point test is based on a Nordic hamstring exercise. The Nordic break-point angle was defined as the maximum point where the participants could no longer support the weight of their body against gravity. The criterion for the sensitivity test was the pre-sprinting and post-sprinting difference of the Nordic break-point angle with a hamstring fatigue protocol. The hamstring fatigue protocol consists of 12 repetitions of the 30m sprint with 30 seconds recovery between each sprint. Hamstring peak torque of the isokinetic hamstring strength test was used as the criterion for validity. A high test-retest reliability (ICC = 0.94, 95% CI = 0.82 - 0.98) was found in the Nordic break-point angle measurements. The Nordic break-point angle significantly correlated with isokinetic hamstring peak torques at eccentric action of 30 °/s (r = 0.88, r2 = 0.77, p < 0.001). The minimal detectable difference was 8.03 °. The sensitivity of the measure was good enough that a significance difference (ES = 0.70, p < 0.001) was found between pre-sprinting and post-sprinting value. The CUHK Nordic break-point test is a simple, portable, quick smartphone based method to provide reliable and accurate eccentric hamstring strength measures among male professional football players.


#6 Electrocardiographic patterns and long-term training-induced time changes in 2484 elite football players
Reference: Arch Cardiovasc Dis. 2017 Dec 21. pii: S1875-2136(17)30233-4. doi: 10.1016/j.acvd.2017.10.005. [Epub ahead of print]
Authors: Huttin O, Selton-Suty C, Venner C, Vilain JB, Rochecongar P, Aliot E
Summary: High-level physical training induces cardiac structural and functional changes, including 12-lead electrocardiogram modifications. The purpose of this cross-sectional longitudinal study was to establish a quantitative electrocardiographic profile in highly trained football players. Initial and serial annual electrocardiogram monitoring over subsequent years allowed us to investigate the long-term effects of exercise on cardiac conduction and electrophysiological remodelling. Between 2005 and 2015, serial evaluations, including 12-lead electrocardiograms, were performed in 2484 elite male football players from the French Professional Football League. A total of 6247 electrocardiograms were performed (mean 2.5±1.8 electrocardiograms/player). Heart rate (beats/min), atrioventricular delay (PR, ms), intraventricular conduction delay (QRS, ms), corrected QT delay (QTc) and electrical left ventricular hypertrophy (LVH) (Sokolow-Lyon index, mm) were measured, and the fixed effect of time was evaluated using panel data analysis (β [95% confidence interval] change between two visits). According to European Society of Cardiology and Seattle criteria, 15% of the electrocardiogram intervals were considered abnormal. We observed 17% sinus bradycardia<50 beats/min (mean heart rate 60±11 beats/min), 8% first-degree atrioventricular block>200ms (mean PR 170±27ms), 1.5% QRS>120ms (mean QRS 87±19ms) and 3% prolonged QT interval (mean QTc using Bazett's formula [QTcB] 395±42ms). Electrical LVH (mean Sokolow-Lyon index 34±10mm) was noted in 37% of players. Over time, electrocardiogram changes were noted, with a significant remodelling trend in terms of decreased heart rate (-0.41 [-0.55 to -0.26] beats/min), QRS duration (-2.4 [-2.7 to -2.1] ms) and QTcB delay (-1.2 [-1.9 to -0.5] ms) (all P<0.001). This study describes usual electrocardiographic training-induced changes in a large series of football players over the follow-up timeframe. The most frequent outliers were electrical LVH and sinus bradycardia. These results have important implications for optimizing electrocardiogram interval measurements in initial screening and during follow-up of football players, with potential cost-effective implications.


#7 A Multinational Cluster Randomised Controlled Trial to Assess the Efficacy of '11+ Kids': A Warm-Up Programme to Prevent Injuries in Children's Football
Reference: Sports Med. 2017 Dec 22. doi: 10.1007/s40279-017-0834-8. [Epub ahead of print]
Authors: Rossler R, Junge A, Bizzini M, Verhagen E, Chomiak J, Aus der Funten K, Meyer T, Dvorak J, Lichtenstein E, Beaudouin F, Faude O
Summary: The objective of this study was to assess the efficacy of a newly developed warm-up programme ('11+ Kids') regarding its potential to reduce injuries in children's football. Children's football teams (under 9 years, under 11 years, and under 13 years age groups) from Switzerland, Germany, the Czech Republic and the Netherlands were invited. Clubs were randomised to an intervention group and a control group, and followed for one season. The intervention group replaced their usual warm-up by '11+ Kids', while the control group warmed up as usual. The primary outcome was the overall risk of football-related injuries. Secondary outcomes were the risks of severe and lower extremity injuries. We calculated hazard ratios using extended Cox models, and performed a compliance analysis. In total, 292,749 h of football exposure of 3895 players were recorded. The mean age of players was 10.8 (standard deviation 1.4) years. During the study period, 374 (intervention group = 139; control group = 235) injuries occurred. The overall injury rate in the intervention group was reduced by 48% compared with the control group (hazard ratio 0.52; 95% confidence interval 0.32-0.86). Severe (74% reduction, hazard ratio 0.26; 95% confidence interval 0.10-0.64) and lower extremity injuries (55% reduction, hazard ratio 0.45; 95% confidence interval 0.24-0.84) were also reduced. Injury incidence decreased with increasing compliance. '11+ Kids' is efficacious in reducing injuries in children's football. We observed considerable effects for overall, severe and lower extremity injuries. The programme should be performed at least once per week to profit from an injury preventive effect. However, two sessions per week can be recommended to further increase the protective benefit.


#8 Crowd medical services in the English Football League: remodelling the team for the 21st century using a realist approach
Reference: BMJ Open. 2017 Dec 21;7(12):e018619. doi: 10.1136/bmjopen-2017-018619.
Authors: Leary A, Kemp A, Greenwood P, Hart N, Agnew J, Barrett J, Punshon G
Summary: The objective was to evaluate the new model of providing care based on demand. This included reconfiguration of the workforce to manage workforce supply challenges and meet demand without compromising the quality of care. Currently the Sports Ground Safety Authority recommends the provision of crowd medical cover at English Football League stadia. The guidance on provision of services has focused on extreme circumstances such as the Hillsborough disaster in 1989, while the majority of demand on present-day services is from patients with minor injuries, exacerbations of injuries and pre-existing conditions. A new model of care was introduced in the 2009/2010 season to better meet demand. A realist approach was taken. Data on each episode of care were collected over 14 consecutive football league seasons at Millwall FC divided into two periods, preimplementation of changes and postimplementation of changes. Data on workforce retention and volunteer satisfaction were also collected. The data were obtained from one professional football league team (Millwall FC) located in London, UK. The primary outcome was to examine the demand for crowd medical services. The secondary outcome was to remodel the service to meet these demands. In total, 981 episodes of care were recorded over the evaluation period of 14 years. The groups presenting, demographic and type of presentation did not change over the evaluation. First aiders were involved in 87.7% of episodes of care, nurses in 44.4% and doctors 17.8%. There was a downward trend in referrals to hospital. Workforce feedback was positive. The new workforce model has met increased service demands while reducing the number of referrals to acute care. It involves the first aid workforce in more complex care and key decision-making and provides a flexible registered healthcare professional team to optimise the skill mix of the team.



Australian Football
#1 The Quantification of Within Week Session Intensity, Duration and Intensity Distribution Across a Season in Australian Football Using the Session RPE Method
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-21. doi: 10.1123/ijspp.2017-0626. [Epub ahead of print]
Authors: Juhari F, Ritchie DM, O'Connor F, Pitchford N, Weston M, Thornton HR, Bartlett JDB
Summary: Team-sports training requires the daily manipulation of intensity, duration and frequency with pre-season focusing on meeting the demands of in-season competition and in-season on maintaining fitness. To provide information about daily training in Australian Football (AF), this study aimed to quantify session intensity, duration, and intensity distribution across different stages of an entire season. Intensity (session Ratings of Perceived Exertion [s-RPE]; CR-10 scale) and duration were collected from forty-five professional male AF for every training session and game. Each s-RPE was categorized into the corresponding intensity zone; Low (<4.0 AU), Moderate (≥4.0 and <7.0), and High (≥7.0) to categorize session intensity. Linear mixed models were constructed to estimate session duration, intensity and distribution between the 3 pre-season and 4 in-season periods. Effects were assessed using linear mixed models, and magnitude-based inferences. The distribution of the mean session intensity across the season was 29% low-, 57% moderate- and 14% high-intensity. While 96% of games were high-intensity, 44% and 49% of skills training sessions were low- and moderate-intensity, respectively. Running had the highest proportion of high-intensity training sessions (27%). Pre-season displayed higher training session intensity (ES = 0.29-0.91) and duration (ES = 0.33-1.44), while in-season game intensity (ES = 0.31-0.51) and duration (ES = 0.51-0.82) were higher. By using a cost-effective monitoring tool, this study provides information about the intensity, duration and intensity distribution of all training types across different phases of a season, thus allowing a greater understanding of the training and competition demands of Australian Footballers.



American Football
#1 Catastrophic Eye Injury in a Football Player
Reference: Phys Sportsmed. 1982 Oct;10(10):71-72. doi: 10.1080/00913847.1982.11947341.
Authors: Heinrichs EH, Willcockson JR
Summary: In brief Although catastrophic eye injuries are rare in collegiate football, this varsity defensive tackle sustained a giant inferior retinal tear with a partially detached retina when another player's thumb went through his face mask. The retina was surgically repaired, and the player's vision in that eye is 20/20 with a contact lens. He continues to play football as an offensive tackle.


#2 Fatalities and Catastrophic Injuries in Football
Reference: Phys Sportsmed. 1982 Oct;10(10):135-140. doi: 10.1080/00913847.1982.11947346.
Authors: Mueller FO, Blyth CS
Summary: In brief Football fatality and catastrophic injury data for 1976 through 1981 are compared with earlier data. The purpose is to analyze the data in regard to rule and equipment changes that have taken place in football since 1976 and to demonstrate the reduction in fatalities and catastrophic injuries. Fatality data for 1981 show five high school and two college fatalities. In 1981 there were five permanent spinal cord injuries in high schools and one in college.


#3 Mouth Protectors in Junior Football Players
Reference: Phys Sportsmed. 1982 Sep;10(9):41-48. doi: 10.1080/00913847.1982.11947318.
Authors: Godwin WC, Craig RG, Koran A, Lang BR, Powers JM
Summary: In brief This study tested Sta-Guard and Proform mouth protectors that were worn by 280 football players aged 9 to 12 years. Laboratory studies were also conducted to test tensile and tear strength, dynamic modulus and resilience, and hardness. The players received new mouth guards every two weeks for 12 weeks and reported any problems with gagging, taste, speech, feel, and durability. Ninety percent of the boys preferred the Sta-Guard mouth protector, stating that it was softer, more resilient, and more comfortable than the Proform mouth guard.


#4 The Association of Vitamin D Status in Lower Extremity Muscle Strains and Core Muscle Injuries at the National Football League Combine
Reference: Arthroscopy. 2017 Dec 19. pii: S0749-8063(17)31282-3. doi: 10.1016/j.arthro.2017.10.005. [Epub ahead of print]
Authors: Rebolledo BJ, Bernard JA, Werner BC, Finlay AK, Nwachukwu BU, Dare DM, Warren RF, Rodeo SA
Summary: The purpose of the study was to evaluate the association between serum vitamin D level and the prevalence of lower extremity muscle strains and core muscle injuries in elite level athletes at the National Football League (NFL) combine. During the 2015 NFL combine, all athletes with available serum vitamin D levels were included for study. Baseline data were collected, including age, race, body mass index, position, injury history specific to lower extremity muscle strain or core muscle injury, and Functional Movement Screen scores. Serum 25-hydroxyvitamin D was collected and defined as normal (≥32 ng/mL), insufficient (20-31 ng/mL), and deficient (<20 ng/mL). Univariate regression analysis was used to examine the association of vitamin D level and injury history. Subsequent multivariate regression analysis was used to examine this relation with adjustment for collected baseline data variables. The study population included 214 athletes, including 78% African American athletes and 51% skilled position players. Inadequate vitamin D was present in 59%, including 10% with deficient levels. Lower extremity muscle strain or core muscle injury was present in 50% of athletes, which was associated with lower vitamin D levels (P = .03). Athletes with a positive injury history also showed significantly lower vitamin D levels as compared with uninjured athletes (P = .03). African American/black race (P < .001) and injury history (P < .001) was associated with lower vitamin D. Vitamin D groups showed no differences in age (P = .9), body mass index (P = .9), or Functional Movement Screen testing (P = .2). Univariate analysis of inadequate vitamin D levels showed a 1.86 higher odds of lower extremity strain or core muscle injury (P = .03), and 3.61 higher odds of hamstring injury (P < .001). Multivariate analysis did not reach an independent association of low vitamin D with injury history (P = .07). Inadequate vitamin D levels are a widespread finding in athletes at the NFL combine. Players with a history of lower extremity muscle strain and core muscle injury had a higher prevalence of inadequate vitamin D.

Mon

15

Jan

2018

Football is...(#54)

Couple of reasons to warm-up

Mon

15

Jan

2018

Football is...(#53)

Positional roles with and without ball = different high-intensity profiles

Fri

12

Jan

2018

Football is...(#52)

Depending on the level of play and duration of break, detraining occurs

Sun

07

Jan

2018

Latest research in football - week 52 - 2017

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 Unique Rectus Femoris Injury in an Adolescent Professional Soccer Player: A Case Report
Reference: JBJS Case Connect. 2014 Oct/Dec/Nov;4(4):e115. doi: 10.2106/JBJS.CC.M.00290.
Authors: Huri G, Dubin JM, Ozgonen K, Kaya D, Doral MN
Summary: A sixteen-year-old professional soccer player presented with persistent pain in the right thigh of two years' duration and the inability to return to play. Evaluation revealed a chronic rupture of the rectus femoris muscle. Because physiotherapy and rehabilitation failed to help, a surgical repair was performed. He returned to his previous activity level within nine months after surgery. Rupture of the proximal part of the rectus femoris should be acknowledged in the differential diagnosis, especially when presenting with persistent pain in the anterior aspect of the thigh lasting more than one year. Delayed repair might be recognized as a reasonable option for chronic rupture of the proximal part of the rectus femoris.


#2 Power and endurance in Hong Kong professional football players
Reference: Asia Pac J Sports Med Arthrosc Rehabil Technol. 2016 Jun 10;5:1-5. doi: 10.1016/j.asmart.2016.05.001. eCollection 2016 Jul.
Authors: Chan HC, Fong DT, Lee JW, Yau QK, Yung PS, Chan KM
Summary: The purpose of this study was to investigate the power and endurance characteristics of Hong Kong professional football players. Training recommendations can be deduced based on the comparison between Hong Kong and international football players. Eighty-eight Hong Kong professional football players (height, 177.2 ± 6.4 cm; weight, 70.6 ± 7.6 kg; age, 25.6 ± 5.0 years) in the first division league participated in a battery of tests, which included: (1) height, (2) weight, (3) countermovement jump, (4) 30-m sprinting, and (5) Yo-Yo Intermittent Recovery Test Level 2. Compared with the test results of the first division players in other countries as reported in the literature (Norway, France, and Scandinavian countries), Hong Kong players were shorter in height (0.1-2.1%), lighter in weight (5.5-8.3%), fair in vertical jump height (-4.8-17%), slower in acceleration (4.2-5.1%) and maximum speed (3-14.2%), and had poorer aerobic and anaerobic endurance (22.9%). The present study suggests that Hong Kong football players (or players with similar physique and ability) need to improve their power and endurance.


#3 Halftime Rewarm-up With Intermittent Exercise Improves the Subsequent Exercise Performance of Soccer Referees
Reference: J Strength Cond Res. 2018 Jan;32(1):211-216. doi: 10.1519/JSC.0000000000002197.
Authors: Yanaoka T, Yamagami J, Kidokoro T, Kashiwabara K, Miyashita M
Summary: This study investigated the effect of halftime rewarm-up (RW) with intermittent exercise on the subsequent exercise performance of soccer referees, determined by the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1). Using a randomized cross-over design, 10 male referees were required to complete 2 trials. The trials consisted of the Loughborough Intermittent Shuttle Test, halftime, and Yo-Yo IR1 periods. During halftime, participants either rested on a chair (Control) or performed a halftime RW exercise for 15 minutes. The halftime RW protocol comprised 2.15 minutes of seated rest, followed by 2.15 minutes of running at 70% of the maximum heart rate (HRmax)-this cycle of recovery and running was repeated for a total of 13 minutes. The halftime RW protocol started at 1 minute after the commencement of the halftime period and concluded 1 minute before its end. The Yo-Yo IR1 performance, blood glucose, free fatty acids (FFAs), triglycerides (TGs), creatine kinase (CK), and lactate concentrations, the rating of perceived exertion, mean HR, and HRmax were analyzed. The Yo-Yo IR1 performance was higher in the halftime RW trial than in the control trial (3,095 ± 326 vs. 2,904 ± 421 m, P ≤ 0.05). The mean HR and HRmax, blood glucose, FFA, TG, CK, and lactate concentrations did not differ between the trials. The rating of perceived exertion during the halftime RW, but not after the Yo-Yo IR1 period, was higher than that in the control trial. In conclusion, this study showed that halftime RW with intermittent exercise improves the subsequent exercise performance.


#4 Defining the Process of a Cardiovascular Risk Assessment Program: Lessons Learnt From Cardiac Assessment of Elite Soccer Players in the United Kingdom
Reference: Clin J Sport Med. 2017 Dec 14. doi: 10.1097/JSM.0000000000000534. [Epub ahead of print]
Authors: Speers C, Seth AN, Patel KC, Rakhit DJ, Gillett MJ
Summary: Retrospectively analyze the cardiac assessment process for elite soccer players, and provide team physicians with a systematic guide to managing longitudinal cardiac risk. Cardiac assessments incorporating clinical examination, 12-lead ECG, echocardiography, and health questionnaire. Soccer players at 5 professional clubs in England, the United Kingdom. Data was retrospectively collected, inspected, and analyzed to determine their clinical management and subsequent follow-up. Over 2 years, 265 soccer players, aged 13 to 37 years with 66% of white European ethnicity, were included in the cohort. Eleven percent had "not-normal" assessments, of these assessments, 83% were considered gray screens, falling into three broad categories: structural cardiac features (including valvular abnormalities), functional cardiac features, and electrocardiogram changes. After cardiology consultation, all assessments were grouped into low, enhanced and high-risk categories for ongoing longitudinal risk management. Overall clear-cut pathology was identified in 2%. Cardiovascular assessment is a vital tool in identifying athletes at risk of sudden cardiac death to mitigate their risk through surveillance, intervention, or participation restriction. The decision whether a player is fit to play or not requires a robust risk assessment followed by input from a multidisciplinary team that includes both the team physician and cardiologist. This educational article proposes a clinical management pathway to aid clinicians with this process.


#5 Rehabilitation of Injured Soccer Players
Reference: Phys Sportsmed. 1979 Aug;7(8):58-67. doi: 10.1080/00913847.1979.11948469.
Author: Smodlaka VN.
Summary: Treatment of soccer injuries revolves around preventing pain, edema, and reinjury, and rehabilitation is aimed at restoring the players' high levels of physical fitness.


#6 Self-controlled video feedback on tactical skills for soccer teams results in more active involvement of players
Reference: Hum Mov Sci. 2017 Dec 15;57:194-204. doi: 10.1016/j.humov.2017.12.005. [Epub ahead of print]
Authors: van Maarseveen MJJ, Oudejans RRD, Savelsbergh GJP
Summary: Many studies have shown that self-controlled feedback is beneficial for learning motor tasks, and that learners prefer to receive feedback after supposedly good trials. However, to date all studies conducted on self-controlled learning have used individual tasks and mainly relatively simple skills. Therefore, the aim of this study was to examine self-controlled feedback on tactical skills in small-sided soccer games. Highly talented youth soccer players were assigned to a self-control or yoked group and received video feedback on their offensive performance in 3 vs. 2 small-sided games. The results showed that the self-control group requested feedback mostly after good trials, that is, after they scored a goal. In addition, the perceived performance of the self-control group was higher on feedback than on no-feedback trials. Analyses of the conversations around the video feedback revealed that the players and coach discussed good and poor elements of performance and how to improve it. Although the coach had a major role in these conversations, the players of the self-control group spoke more and showed more initiative compared to the yoked group. The results revealed no significant beneficial effect of self-controlled feedback on performance as judged by the coach. Overall, the findings suggest that in such a complex situation as small-sided soccer games, self-controlled feedback is used both to confirm correct performance elements and to determine and correct errors, and that self-controlled learning stimulates the involvement of the learner in the learning process.


#7 May Heading in Soccer Result in Traumatic Brain Injury? A Review of Literature
Reference: Med Arch. 2017 Oct;71(5):356-359. doi: 10.5455/medarh.2017.71.356-359.
Authors: Bunc G, Ravnik J, Velnar T
Summary: Globally, soccer is the most popular team sport, unifying many fans all around the world. The epidemiological studies so far have confirmed that head playing and hitting the ball with head may cause minor head injuries, which exert their effects in a cumulative way. Literature search for this review was conducted and data about traumatic brain injury collected from various sources. The consequences of head injury are evident as chronic changes in cognition, including disturbances in concentration and slowing of mental and physical agility. Various recommendations have been issued for the prevention of chronic negative cumulative effects of soccer ball head playing. In addition, the professional soccer players are also exposed to more intense craniocerebral trauma, such as concussions and contusions. These patients require treatment of skilled sports physicians, neurologists and neurosurgeons and some may need long to return to the sport scene again.


#8 The Neuromuscular Determinants of Unilateral Jump Performance in Soccer Players are Direction-Specific
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-28. doi: 10.1123/ijspp.2017-0589. [Epub ahead of print]
Authors: Murtagh C, Nulty C, Vanrenterghem J, O'Boyle A, Morgans R, Drust B, Erskine R
Summary: The purpose was to investigate differences in neuromuscular factors between elite and non-elite players, and to establish which factors underpin direction-specific unilateral jump performance. Elite (n=23; age, 18.1 ± 1.0 yrs; BMI, 23.1 ± 1.8 kg/m2) and non-elite (n=20; age, 22.3 ± 2.7 yrs; BMI, 23.8 ± 1.8 kg/m2) soccer players performed three unilateral countermovement jumps (CMJs) on a force platform in the vertical, horizontal-forward and medial directions. Knee extension isometric maximum voluntary contraction (iMVC) torque was assessed using isokinetic dynamometry. Vastus lateralis fascicle length and angle of pennation (AoP), and quadriceps femoris muscle volume (Mvol) and physiological cross sectional area (PCSA) were assessed using ultrasonography. Vastus lateralis activation was assessed via  torque (365.7±66.6 vs. 320.1±62.6 N·m; P=0.045), Mvol (2853±508 vs. 2429±232 cm3, P=0.001) and PCSA (227±42 vs. 193±25 cm2, P=0.003) than non-elite. In both cohorts, unilateral vertical and unilateral medial CMJ performance correlated with Mvol and PCSA (r≥0.310 P≤0.043). In elite soccer players, unilateral vertical and unilateral medial CMJ performance correlated with upward phase vastus lateralis activation, and AoP (r≥0.478, P≤0.028). Unilateral horizontal-forward CMJ peak vertical power did not correlate with any measure of muscle size or activation but correlated inversely with AoP (r=-0.413; P=0.037). Whilst larger and stronger quadriceps differentiated elite from non-elite players, relationships between neuromuscular factors and unilateral jump performance were shown to be direction-specific. These findings support a notion that improving direction-specific muscular power in soccer requires improving a distinct neuromuscular profile.


#9 Relationships Between the External and Internal Training Load in Professional Soccer: What Can We Learn From Machine Learning?
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-18. doi: 10.1123/ijspp.2017-0299. [Epub ahead of print]
Authors: Jaspers A, Beeck TO, Brink MS, Frencken WGP, Staes F, Davis JJ, Helsen WF
Summary: Machine learning may contribute to understanding the relationship between the external load and internal load in professional soccer. Therefore, the relationship between external load indicators and the rating of perceived exertion (RPE) was examined using machine learning techniques on a group and individual level. Training data were collected from 38 professional soccer players over two seasons. The external load was measured using global positioning system technology and accelerometry. The internal load was obtained using the RPE. Predictive models were constructed using two machine learning techniques, artificial neural networks (ANNs) and least absolute shrinkage and selection operator (LASSO), and one naive baseline method. The predictions were based on a large set of external load indicators. Using each technique, one group model involving all players and one individual model for each player was constructed. These models' performance on predicting the reported RPE values for future training sessions was compared to the naive baseline's performance. Both the ANN and LASSO models outperformed the baseline. Additionally, the LASSO model made more accurate predictions for the RPE than the ANN model. Furthermore, decelerations were identified as important external load indicators. Regardless of the applied machine learning technique, the group models resulted in equivalent or better predictions for the reported RPE values than the individual models. Machine learning techniques may have added value in predicting the RPE for future sessions to optimize training design and evaluation. Additionally, these techniques may be used in conjunction with expert knowledge to select key external load indicators for load monitoring.



Australian Football
#1 Physical characteristics of players within the Australian Football League participation pathways: a systematic review
Reference: Sports Med Open. 2017 Dec 19;3(1):46. doi: 10.1186/s40798-017-0109-9.
Authors: Haycraft JAZ, Kovalchik S, Pyne DB, Robertson S
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-017-0109-9?site=sportsmedicine-open.springeropen.com
Summary: Australian football (AF) players require endurance, strength, speed, and agility to be successful. Tests assessing physical characteristics are commonly used for talent identification; however, their ability to differentiate between players across the Australian Football League's (AFL) participation pathway remains unclear. The objective of this review was to quantify the physical characteristics of male AF players across the AFL participation pathway. A search of databases was undertaken. Studies examining tests of physical performance were included, with 27 meeting the inclusion/exclusion criteria. Study appraisal was conducted using a checklist of selection criteria. The 20-m sprint time was the most reported test, followed by vertical jump (VJ), AFL planned agility, and 20-m multi-stage fitness test (MSFT). The fastest times for 20-m sprint were for Elite AFL players (range 2.94-3.13 s), with local-level players the slowest (3.22-4.06 s). State Junior Under (U) 18s (58-66 cm) had higher jumps than senior players, with the lowest jumps reported for Local U10s (mean 31 cm). No elite-level data were reported for the AFL planned agility or 20-m MSFT. AFL planned agility times were only reported for talent pathway levels, with large performance variability evident across all levels (8.17-9.12 s). Only mean 20-m MSFT scores were reported from Local U10s to National Draft Camp (6.10-13.50 shuttles). Talent pathway players exhibit similar mean test scores irrespective of the physical test, with the exception of 20-m sprint and VJ. Physical tests can discriminate between local participation level players but are less useful within the AFL talent pathway.



American Football
#1 Motor function in former professional football players with history of multiple concussions
Reference: J Neurotrauma. 2017 Dec 19. doi: 10.1089/neu.2017.5290. [Epub ahead of print]
Authors: Tarazi A, Tator C, Wennberg R, Ebraheem A, Green RE, Colella B, Saverino C, Khodadadi M, Misquitta K, Tartaglia MC
Summary: The objective of this study was to assess the incidence of motor impairment in former professional Canadian Football League (ex-CFL) players with multiple concussions. We investigated motor symptoms and signs in 45 ex-CFL players with multiple concussions and 25 age-and education matched healthy controls with no history of concussion. Neurological assessment included items from the SCAT3 (Sport Concussion Assessment Tool 3) and the Unified Parkinson's Disease Rating Scale part III (UPDRS-Part III). A performance-based measurement of manual motor function was undertaken using the Grooved Pegboard test. Cognition was measured with patient-reported outcomes for memory, executive and behavioral symptoms as well as performance-based measures of memory and executive function. Symptoms of anxiety and depression were measured using the Personality Assessment Inventory. There was no significant difference between the ex-CFL players and controls on the UPDRS-Part III scores, and neither group reported clinically significant motor complaints. Ex-CFL players did not perform differently from control subjects on the Grooved Pegboard test. In contrast, with regard to cognitive and mood testing, players were more symptomatic: The ex-CFL players reported significantly more memory (77.8% vs. 16%, respectively, p<0.001), executive (53.3% vs. 8%, respectively, p<0.001), and behavioral symptoms (66.7% vs. 20%, respectively, p<0.001). No significant differences were found when comparing ex-CFL players and controls in performance on memory and executive tests. In summary, in a group of retired CFL players who self-reported declines in memory, executive and behavioral symptoms, no motor symptoms were reported and no motor signs were detected.


#2 Epidemiology of Injuries Sustained as a Result of Intentional Player Contact in High School Football, Ice Hockey, and Lacrosse: 2005-2006 Through 2015-2016
Reference: Orthop J Sports Med. 2017 Dec 12;5(12):2325967117740887. doi: 10.1177/2325967117740887. eCollection 2017 Dec.
Authors: Bartley JH, Murray MF, Kraeutler MJ, Pierpoint LA, Welton KL, McCarty EC, Comstock RD
Summary: Lacrosse and ice hockey are quickly growing in popularity, while football remains the most popular sport among high school student-athletes. Injuries remain a concern, given the physical nature of these contact sports. The purpose was to describe the rates and patterns of injuries sustained as a result of intentional player contact in United States high school boys' football, ice hockey, and lacrosse. We conducted a secondary analysis of High School RIO (Reporting Information Online) data, including exposure and injury data collected from a large sample of high schools in the United States from 2005-2006 through 2015-2016. Data were analyzed to calculate rates, assess patterns, and evaluate potential risk factors for player-to-player contact injuries. A total of 34,532 injuries in boys' football, ice hockey, and lacrosse occurred during 9,078,902 athlete-exposures (AEs), for a rate of 3.80 injuries per 1000 AEs in the 3 contact sports of interest. The risk of injuries was found to be greater in competition compared with practice for all 3 sports, with the largest difference in ice hockey (rate ratio, 8.28) and the smallest difference in lacrosse (rate ratio, 3.72). In all 3 contact sports, the most commonly injured body site in competition and practice caused by both tackling/checking and being tackled/checked was the head/face. However, a significantly greater proportion of concussions sustained in football were the result of tackling compared with being tackled (28.2% vs 24.1%, respectively). In addition, a significantly greater proportion of concussions were sustained in competition compared with practice for all 3 sports. This study is the first to collectively compare injury rates and injury patterns sustained from intentional player-to-player contact in boys' high school football, ice hockey, and lacrosse. Notably, there was a relatively high risk of injuries and concussions during football practices.


#3 White Matter Changes Related to Subconcussive Impact Frequency during a Single Season of High School Football
Reference: AJNR Am J Neuroradiol. 2017 Dec 21. doi: 10.3174/ajnr.A5489. [Epub ahead of print]
Authors: Kuzminski SJ, Clark MD, Fraser MA, Haswell CC, Morey RA, Liu C, Choudhury KR, Guskiewicz KM, Petrella JR
Summary: The effect of exposing the developing brain of a high school football player to subconcussive impacts during a single season is unknown. The purpose of this pilot study was to use diffusion tensor imaging to assess white matter changes during a single high school football season, and to correlate these changes with impacts measured by helmet accelerometer data and neurocognitive test scores collected during the same period. Seventeen male athletes (mean age, 16 ± 0.73 years) underwent MR imaging before and after the season. Changes in fractional anisotropy across the white matter skeleton were assessed with Tract-Based Spatial Statistics and ROI analysis. The mean number of impacts over a 10-g threshold sustained was 414 ± 291. Voxelwise analysis failed to show significant changes in fractional anisotropy across the season or a correlation with impact frequency, after correcting for multiple comparisons. ROI analysis showed significant (P < .05, corrected) decreases in fractional anisotropy in the fornix-stria terminalis and cingulum hippocampus, which were related to impact frequency. The effects were strongest in the fornix-stria terminalis, where decreases in fractional anisotropy correlated with worsening visual memory. Our findings suggest that subclinical neurotrauma related to participation in American football may result in white matter injury and that alterations in white matter tracts within the limbic system may be detectable after only 1 season of play at the high school level.


#4 Determination of priority and other hazardous substances in football fields of synthetic turf by gas chromatography-mass spectrometry: A health and environmental concern
Reference: Chemosphere. 2017 Dec 11;195:201-211. doi: 10.1016/j.chemosphere.2017.12.063. [Epub ahead of print]
Authors: Celeiro M, Dagnac T, Llompart M
Summary: Due to the high concern generated in the last years about the safety of recycled tire rubber used for recreational sports surfaces, this study aims at evaluating the presence of forty organic compounds including polycyclic aromatic hydrocarbons (PAHs), phthalates, adipates, vulcanisation additives and antioxidants in recycled tire crumb of synthetic turf football fields. Ultrasound Assisted Extraction (UAE) was successfully employed to extract the target compounds from the crumb rubber, and analysis was performed by gas chromatography-mass spectrometry (GC-MS). The transfer of the target chemicals from the crumb rubber to the runoff water and to the air above the rubber surface has also been evaluated employing solid-phase microextraction (SPME). Samples from fifteen football fields were analysed, and the results revealed the presence of 24 of the 40 target compounds, including 14 of the 16 EPA PAHs, with total concentrations up to 50 μg g-1. Heavy metals such as Cd, Cr and Pb were also found. A partial transfer of organic compounds to the air and runoff water was also demonstrated. The analysis of rain water collected directly from the football field, showed the presence of a high number of the target compounds at concentrations reaching above 100 μg L-1. The environmental risk arising from the burning of crumb rubber tires has been assessed, as well, analysing the crumb rubber, and the air and water in contact with this material, showing a substantial increase both of the number and concentration of the hazardous chemicals.


#5 Emergency Removal of Football Helmets
Reference: Phys Sportsmed. 1994 Sep;22(9):57-59. doi: 10.1080/00913847.1994.11947694.
Authors: Patel MN, Rund DA, Howe WB
Summary: In brief when a football player has a brief suspected head or neck injury, when and how to remove the football helmet become critical issues. Protocols differ; however, the National Collegiate Athletic Association guidelines, which state that the helmet should only be removed on the field under very special circumstances, are appropriate. An understanding of the technologically advanced design and tight fit of modern football helmets will help guide medical personnel through each step of the helmet removal process.


#6 Flexibility as a Predictor of Knee Injuries in College Football Players
Reference: Phys Sportsmed. 1982 Jul;10(7):93-97. doi: 10.1080/00913847.1982.11947274.
Authors: Moretz JA, Walters R, Smith L.
Summary: In brief The ligamentous laxity testing scores and knee injuries of football players from three colleges were compared and statistically analyzed. Since no correlation was found between laxity test scores and knee injuries, the tests have no apparent predictive value.

Fri

29

Dec

2017

Latest research in football - week 51 - 2017

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 What Performance Analysts Need to Know About Research Trends in Association Football (2012-2016): A Systematic Review
Reference: Sports Med. 2017 Dec 14. doi: 10.1007/s40279-017-0836-6. [Epub ahead of print]
Authors: Sarmento H, Clemente FM, Araujo D, Davids K, McRobert A, Figueiredo A
Summary: Evolving patterns of match analysis research need to be systematically reviewed regularly since this area of work is burgeoning rapidly and studies can offer new insights to performance analysts if theoretically and coherently organized. The purpose of this paper was to conduct a systematic review of published articles on match analysis in adult male football, identify and organize common research topics, and synthesize the emerging patterns of work between 2012 and 2016, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The Web of Science database was searched for relevant published studies using the following keywords: 'football' and 'soccer', each one associated with the terms 'match analysis', 'performance analysis', 'notational analysis', 'game analysis', 'tactical analysis' and 'patterns of play'. Of 483 studies initially identified, 77 were fully reviewed and their outcome measures extracted and analyzed. Results showed that research mainly focused on (1) performance at set pieces, i.e. corner kicks, free kicks, penalty kicks; (2) collective system behaviours, captured by established variables such as team centroid (geometrical centre of a set of players) and team dispersion (quantification of how far players are apart), as well as tendencies for team communication (establishing networks based on passing sequences), sequential patterns (predicting future passing sequences), and group outcomes (relationships between match-related statistics and final match scores); and (3) activity profile of players, i.e. playing roles, effects of fatigue, substitutions during matches, and the effects of environmental constraints on performance, such as heat and altitude. From the previous review, novel variables were identified that require new measurement techniques. It is evident that the complexity engendered during performance in competitive soccer requires an integrated approach that considers multiple aspects. A challenge for researchers is to align these new measures with the needs of the coaches through a more integrated relationship between coaches and researchers, to produce practical and usable information that improves player performance and coach activity.


#2 Sleep/Wake Behaviours in Elite Athletes from Three Different Football Codes
Reference: J Sports Sci Med. 2017 Dec 1;16(4):604-605. eCollection 2017 Dec.
Authors: Miller DJ, Sargent C, Vincent GE, Roach GD, Halson SL, Lastella M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5721193/pdf/jssm-16-604.pdf


#3 Do Red and Blue Uniforms Matter in Football and Handball Penalties?
Reference: J Sports Sci Med. 2017 Dec 1;16(4):565-573. eCollection 2017 Dec.
Authors: Krenn B, Pernhaupt N, Handsteiner M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5721188/pdf/jssm-16-565.pdf
Summary: Past research has revealed ambiguous results on the impact of red uniforms in sports competition. The current study was aimed at analyzing the role of red and blue uniforms in football and handball penalties. Two experiments were conducted using a within subjects design, where participants rated uniform color-manipulated video clips. In the first study, participants (n = 39) watched footage of football players kicking a penalty, whereas in the second study (n = 118) videos of handball penalty takers, handball goalkeepers and football goalkeepers preparing themselves to score/save a penalty were shown. Participants rated player's/goalkeeper's level of confidence and the expected position of the ball crossing the goal line in the first experiment and additionally the probability of scoring the penalty against the goalkeepers in the second experiment. The videos stopped at the point where the ball was leaving the foot and hand respectively. Results did not show any beneficial impact of red uniforms. Rather, football players wearing blue were rated to kick the ball higher. The study contradicts any positive effect of red versus blue uniforms in the context of football and handball penalties, which emphasizes the need of searching for potential moderators of color's impact on human behavior.


#4 How Can Governmental Positive Power Decrease Violence in Crime-Oriented Arenas? The Case of English Football
Reference: Int J Offender Ther Comp Criminol. 2017 Jan 1:306624X17694375. doi: 10.1177/0306624X17694375. [Epub ahead of print]
Authors: Guy S, Muchtar O, Ronel N
Summary: This article will survey the dramatic change English football had undergone since the end of the last century. The authors will closely explore the implementation of the Taylor Report recommendations, to convince that which power and management techniques were used to decrease violence in public areas that were previously considered dangerous and crime-oriented. It will be argued that disciplinarian techniques were practiced, much like those described in Foucault's Discipline and Punish, while this very power has proven to be positive and revitalizing. It will be therefore concluded that power is at its most effective when operated via techniques of discipline and social inclusion. These arguments correspond with the positive criminology theory whose popularity within the discipline is gradually increasing.


#5 Eccentric hamstring strength deficit and poor hamstring-to-quadriceps ratio are risk factors for hamstring strain injury in football: A prospective study of 146 professional players
Reference: J Sci Med Sport. 2017 Dec 5. pii: S1440-2440(17)31822-4. doi: 10.1016/j.jsams.2017.11.017. [Epub ahead of print]
Authors: Lee JWY, Mok KM, Chan HCK, Yung PSH, Chan KM
Summary: The purpose of this study was to investigate whether preseason isokinetic strength measures were predictive of future HSI among professional football players. A total of 169 professional players participated in a preseason isokinetic strength screening, followed by a 10-month competitive season. Testing protocol included the concentric performance of both knee flexion and extension at 60degs-1 and 240degs-1 and the eccentric performance of the knee flexor at 30degs-1. Strength deficits, bilateral differences, and hamstring to quadriceps strength ratios were computed. Univariate and multivariate logistic regressions were used to identify potential risk factors of HSI. Receiver operating characteristic (ROC) curves were used to investigate the sensitivity and specificity of the strength measures. Forty-one acute HSIs were sustained, and 12% (n=5) reoccurred within the study period. In the multivariate analysis, we have shown an association between the injury risk and eccentric hamstring peak torque below 2.4Nmkg-1 (OR=5.59; 95% CI, 2.20-12.92); concentric H/Q ratio below 50.5% (OR=3.14; 95% CI, 1.37-2.22); players with previous injury of HSI (OR=3.57; 95% CI, 3.13-8.62). ROC analysis displayed an area under curve (AUC) of 0.77, indicating fair combined sensitivity and specificity of the overall predicting model. Professional football players with significant lower isokinetic hamstring strength, lower hamstring-to-quadriceps strength ratio, and a previous injury of HSI were linked to an increased risk of acute HSI.


#6 Operative Fixation of an Anterior Inferior Iliac Spine Apophyseal Avulsion Fracture Nonunion in an Adolescent Soccer Player: A Case Report
Reference: JBJS Case Connect. 2017 Apr-Jun;7(2):e29. doi: 10.2106/JBJS.CC.16.00167.
Authors: Carr JB 2nd, Conte E, Rajadhyaksha EA, Laroche KA, Gwathmey FW, Carson EW
Summary: A 14-year-old male competitive soccer player presented with a history of recurrent right hip pain for 18 months. He was diagnosed with an anterior inferior iliac spine (AIIS) apophyseal avulsion fracture nonunion with subspinal impingement, which was confirmed by radiographs, computed tomography, and magnetic resonance imaging. The patient underwent surgical fixation and subspinal decompression. He returned to competitive soccer 5 months postoperatively. AIIS apophyseal avulsion fractures occur in adolescent athletes and generally respond to nonoperative treatment. When such management is unsuccessful, surgical fixation can lead to resolution of pain with return of full function.


#7 Effect of Boards in Small-Sided Street Soccer Games on Movement Pattern and Physiological Response in Recreationally Active Young Men
Reference: J Strength Cond Res. 2017 Dec 11. doi: 10.1519/JSC.0000000000002401. [Epub ahead of print]
Authors: Randers MB, Brix J, Hagman M, Nielsen JJ, Krustrup P.
Summary: The present study investigated whether street soccer might be proposed as an alternative to recreational small-sided games on grass as a health-enhancing activity, and specifically the effects of the boards surrounding the pitch. Eleven recreationally active young males (28.4±4.2 (±SD) yrs, 19.9±4.2% body fat, 47.7±6.0 mlminkg), after familiarization, completed one to two sessions of 20x13-m 3v3 street soccer games with boards (WB) and one to two sessions without boards (WOB) in a randomized order. Movement pattern was measured using GPS and heart rate recordings, blood sampling and RPE scales were used to evaluate exercise intensity and physiological strain. Total number of accelerations (19%) and Player Load (18%) were higher (p < 0.05) in WB than in WOB, whereas total distance covered (12%), high-speed running (59%) and peak speed (11%) were lower (p < 0.05) in WB than in WOB. Moreover, HRmean was higher in WB than in WOB (85.7±5.4 vs. 81.3±8.2%HRmax, p = 0.012, ES = 0.64), whereas time with HR>90%HRmax did not differ between WB and WOB (42±34 vs. 32±30%, p = 0.243, ES = 0.32). Plasma ammonia increased more in WB than in WOB, with no differences found in mean and peak blood lactate. RPE was higher after WB than after WOB (7.1±1.0 vs. 5.5±1.2, p < 0.001, ES = 1.39). In conclusion, intensity was sufficiently high in both game formats to expect short- and long-term health improvements as a result of regular participation. Boards affected movement pattern and physiological demands, producing higher number of accelerations, Player Load, average heart rate, plasma ammonia, and rating of perceived exertion, but lower total distance, number of intense runs and peak speed.


#8 Surgical treatment of rectus femoris injury in soccer playing athletes: report of two cases
Reference: Rev Bras Ortop. 2017 Jan 17;52(6):743-747. doi: 10.1016/j.rboe.2017.01.001. eCollection 2017 Nov-Dec.
Authors: Shimba LG, Latorre GC, Pochini AC, Astur DC, Andreoli CV
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5720843/pdf/main.pdf
Summary: Muscle injury is the most common injury during sport practice. It represents 31% of all lesions in soccer, 16% in track and field, 10.4% in rugby, 17.7% in basketball, and between 22% and 46% in American football. The cicatrization with the formation of fibrotic tissue can compromise the muscle function, resulting in a challenging problem for orthopedics. Although conservative treatment presents adequate functional results in the majority of the athletes who have muscle injury, the consequences of treatment failure can be dramatic, possibly compromising the return to sport practice. The biarticular muscles with prevalence of type II muscle fibers, which are submitted to excentric contraction, present higher lesion risk. The quadriceps femoris is one example. The femoris rectus is the quadriceps femoris muscle most frequently involved in stretching injuries. The rupture occurs in the acceleration phase of running, jump, ball kicking, or in contraction against resistance. Although the conservative treatment shows good results, it is common that the patient has lower muscle strength, difficulty in return to sports, and a permanent and visible gap. Surgical treatment can be an option for a more efficient return to sports.


#9 Isokinetic knee muscle strength profile in Brazilian male soccer, futsal and beach soccer players: A cross-sectional study
Reference: Int J Sports Phys Ther. 2017 Dec;12(7):1103-1110.
Authros: de Lira CAB, Mascarin NC, Vargas VZ, Vancini RL, Andrade MS
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717486/pdf/ijspt-12-1103.pdf
Summary: Anterior cruciate ligament injury is higher in soccer athletes as compared to athletes of other sports. Risk factors for anterior cruciate ligament injury include low knee hamstring/quadriceps strength ratio and bilateral strength deficits. The purpose was to investigate isokinetic thigh muscles strength, hamstring/quadriceps strength ratio, and bilateral strength comparisons in athletes who participate in professional soccer, futsal, and beach soccer. Brazilian professional soccer (n=70), futsal (n=30), and beach soccer (n=12) players were isokinetically assessed to examine strength of knee extensors and flexors at 60 degrees/second in concentric mode, to measure peak torque of dominant and non-dominant limbs. In the dominant limb, for extensors muscles, futsal players presented significantly lower peak torque values (223.9 ± 33.4 Nm) than soccer (250.9 ± 43.0 Nm; p=0.02) and beach soccer players (253.1 ± 32.4 Nm; p=0.03). Peak torque for extensor muscles in the non-dominant limb was significantly lower in futsal (224.0 ± 35.8 Nm) than in beach soccer players (256.8 ± 39.8 Nm; p=0.03). Hamstring/quadriceps strength ratio for dominant limbs for futsal (57.6 ± 10.1%), soccer (53.5 ± 8.8%), and beach soccer (56.3 ± 8.4%) players presented no significant differences between groups; however, the mean values were lower than recommended values found in the literature. There were no strength deficits for any of the evaluated groups when compared bilaterally. Futsal athletes presented lower values for quadriceps strength than soccer and beach soccer athletes. Futsal, soccer, and beach soccer players presented no strength asymmetries, but they presented with strength imbalance in hamstring/quadriceps strength ratio.


#10 Collegiate male soccer players exhibit between-limb symmetry in body composition muscle strength and range of motion
Reference: Int J Sports Phys Ther. 2017 Dec;12(7):1087-1094.
Authors: DeLang MD, Kondratek M, DiPace LJ, Hew-Butler T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717484/pdf/ijspt-12-1087.pdf
Summary: Functional and structural asymmetries attributed to limb dominance are equivocal in soccer players. Previous authors hypothesize the existence of between-limb asymmetry secondary to the repetitive unilateral nature of kicking. However, symmetry is often present, particularly in measures of muscle strength. The purpose of the present study was to determine if lateral dominance is accompanied by corresponding between-limb asymmetries in a comprehensive assessment of body composition, muscle strength, and range of motion in healthy soccer players. 17 healthy male NCAA Division One collegiate soccer players participated (age 19.6 ± 1.5 years; BMI 23.9 ± 1.4 kg/m2). Footedness was attained via participant self-report. Lower limb muscle strength (hand held dynamometry), range of motion (goniometry), and body composition (dual energy x-ray absorptiometry scan) were measured. Lower-leg symmetry was analyzed comparing the dominant versus non-dominant limb using paired t-tests. Comparisons revealed no statistically different differences in outcomes, indicating remarkable symmetry in all measures of body composition, muscle strength, and range of motion (p>0.05) between the dominant and non-dominant lower limbs. The authors speculate the prevalence of running versus kicking, the longitudinal effects of playing careers, and/or functional compensation attenuates the expected asymmetries in healthy male collegiate soccer players.


#11 Injuries in Japanese Junior Soccer Players During Games and Practices
Reference: J Athl Train. 2017 Dec 11. doi: 10.4085/1062-6050-52.12.23. [Epub ahead of print]
Authors: Kuzuhara K, Shibata M, Uchida R
Summary: Soccer is the most popular junior sport in the world. In junior sports, injury analysis and injury-prevention measures for players, especially those under 12 years of age, are urgently needed. The purpose was to prospectively study the incidence, sites, types, and mechanisms of injuries in elementary school-aged junior soccer players during games and practices. Eighty-nine players in 5 community-based club teams of junior soccer (U-12, age range =11-12 years; U-11, age range =10-11 years; U-10, age ≤10 years). Data on all game and practice injuries for the 2013-2014 season were collected using an injury report form. Injury rates were calculated according to injury site, type, and mechanism. The overall injury rate was 2.59/1000 athlete-hours (AHs). The game injury rate (GIR; 6.43/1000 AHs) was higher than the practice injury rate (PIR; 1.49/1000 AHs; P < .05). The most common anatomical areas of injury during games and practices were the lower limbs (62.5% and 4.02/1000 AHs versus 38.5% and 0.57/1000 AHs, respectively). Contusions (27.6%, n = 8) were the most frequent type of overall injuries. Most game injuries resulted from body contact (43.8%, 2.81/1000 AHs), wherease most practice injuries resulted from other types of contact (53.8%, 0.83/1000 AHs). The GIRs were higher than the PIRs in Japanese junior soccer players. A lower overall PIR suggested that players in the U-12 age group practiced under appropriate conditions. However, the higher GIR in this age category needs to be decreased.


#12 Aerodynamic effects of dimples on soccer ball surfaces
Reference: Heliyon. 2017 Oct 31;3(10):e00432. doi: 10.1016/j.heliyon.2017.e00432. eCollection 2017 Oct.
Authors: Hong S, Asai T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5714554/pdf/main.pdf
Summary: Recently, the shape and design of the panel on the official ball used in the FIFA World Cup was considerably different from that of a conventional soccer ball (having 32 pentagonal and hexagonal panels). Depending on the number of different panels and their orientation, the aerodynamic force experienced by a ball is believed to change, which in turn changes the ball trajectory. However, not much is known about the impact of the surface forms of a ball on its aerodynamics. Therefore, in the present study, 10 different types of soccer balls were produced and their aerodynamic properties were studied by wind tunnel experiments. The results confirmed that the aerodynamic force acting on the ball varied considerably depending on the existence of dimples on the ball surface. In addition, the 4 types of soccer balls, which had different kinds of roughness, revealed that even balls having the same number and shapes of panels experienced greatly varying aerodynamic forces depending on the surface form of the balls.


Australian Football
#1 Physical demands and technical performance in Australian Football League Women's (AFLW) competition match-play
Reference: J Sci Med Sport. 2017 Dec 5. pii: S1440-2440(17)31823-6. doi: 10.1016/j.jsams.2017.11.018. [Epub ahead of print]
Authors: Clarke AC, Ryan S, Couvalias G, Dascombe BJ, Coutts AJ, Kempton T
Summary: The purpose was to compare positional differences in the physical and technical demands of Australian Football League Women's (AFLW) match-play. A secondary aim was to examine the time course changes in activity profiles during AFLW match-play. Global positioning system data were collected from 26 players (6 positional groups) from the same club during seven AFLW matches. Absolute and relative physical performance data were categorised into total distance, high-speed running (>14.4kmh-1, HSR), very high-speed running (>18.0kmh-1, VHSR), and sprinting distance (>20.0kmh-1, Sprint). Technical performance data was obtained from a commercial statistics provider. A mixed model analysis was used to examine differences between positional groups and playing quarters. Absolute measures of running performance did not differ between position groups. Relative total distance was moderately greater (ES=∼0.80, p<0.05) for midfielders, small backs and small forwards (125-128mmin-1) than tall backs and tall forwards (102-107mmin-1). Relative HSR distance was greater (ES=∼0.73) for midfielders and small backs (∼28mmin-1) than tall backs (17mmin-1). Analysis of technical performance indicators showed: midfielders and small forwards had the most inside 50s; tall backs had the highest number of rebound 50s; tall forwards scored more goals; while midfielders made more tackles (p<0.05). All relative running performance measures were reduced in the fourth quarter when compared to the first and second quarters (ES=0.32-0.77). These data can be used as benchmarks for temporal analysis of AFLW match demands and assist in developing specific training strategies.


#2 Oculomotor cognitive control abnormalities in Australian rules football players with a history of concussion
Reference: J Neurotrauma. 2017 Dec 11. doi: 10.1089/neu.2017.5204. [Epub ahead of print]
Authors: Clough M, Mutimer S, Wright DK, Tsang A, Costello D, Gardner A, Stanwell P, Mychasiuk R, Sun M, Brady RD, McDonald SJ, Webster KM, Johnstone M, Fielding J, Semple B, Agoston DV, White OB, Frayne R, O'Brien TJ, Shultz SR
Summary: This study used oculomotor, cognitive, and multimodal magnetic resonance imaging (MRI) measures to assess for neurological abnormalities in current asymptomatic amateur Australian rules footballers (i.e., Australia's most participated collision sport) with a history of sports-related concussion (SRC). Participants were 15 male amateur Australian rules football players with a history of SRC greater than 6 months previously, and 15 sex-, age- and education-matched athlete control subjects that had no history of neurotrauma or participation in collision sports. Participants completed a clinical interview, neuropsychological measures and oculomotor measures of cognitive control. MRI investigation involved structural imaging, as well as diffusion tensor imaging and resting state functional MRI sequences. Despite no group differences on conventional neuropsychological tests and multimodal MRI measures, Australian rules football players with a history of SRC performed significantly worse on an oculomotor switch task: a measure of cognitive control that interleaves the response of looking towards a target (i.e., a prosaccade) with the response of looking away from a target (i.e., an antisaccade). Specifically, Australian footballers performed significantly shorter latency prosaccades and found changing from an antisaccade trial to a prosaccade trial (switch cost) significantly more difficult than control subjects. Poorer switch cost was related to poorer performance on a number of neuropsychological measures of inhibitory control. Further, when comparing performance on the cognitively more demanding switch task with performance on simpler, antisaccade/prosaccades tasks which require a single response, Australian footballers demonstrated a susceptibility to increased cognitive load, compared to the control group who were unaffected. These initial results suggest that current asymptomatic amateur Australian rules football players with a history of SRC may have persisting, subtle, cognitive changes, which are demonstrable on oculomotor cognitive measures. Future studies are required in order to further elucidate the full nature and clinical relevance of these findings.


American Football
#1 Game Schedules and Rate of Concussions in the National Football League
Reference: Orthop J Sports Med. 2017 Nov 28;5(11):2325967117740862. doi: 10.1177/2325967117740862. eCollection 2017 Nov.
Authors: Teramoto M, Cushman DM, Cross CL, Curtiss HM, Willick SE
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5714093/pdf/10.1177_2325967117740862.pdf
Summary: Concussion prevention in the National Football League (NFL) is an important priority for player safety. The NFL now has modified game schedules, and one concern is that unconventional game schedules, such as a shortened rest period due to playing on a Thursday rather than during the weekend, may lead to an increased risk of injuries. The hypothesis is that unconventional game schedules in the NFL are associated with an increased rate of concussion. This study analyzed concussions and game schedules over the NFL regular seasons from 2012 to 2015 (4 years). Documented numbers of concussions, identified by use of the online database PBS Frontline Concussion Watch, were summarized by regular-season weeks. Association of days of rest and game location (home, away, or overseas) with the rate of concussion was examined by use of the χ2 test. Logistic regression analysis was performed to examine the relationships of days of rest and home/away games to the risk of repeated concussions, with adjustment for player position. A total of 582 concussions were analyzed in this study. A significantly greater number of concussions occurred in the second half of the season (P < .01). No significant association was found between the rate of concussion and the days of rest, game location, or timing of the bye week by the team or the opponent (P > .05). Game schedules were not significantly associated with the occurrence of repeat concussions (P > .05). Unconventional game schedules in the NFL, including playing on Thursday and playing overseas, do not seem to put players at increased risk of concussions.


#2 Posterior Cruciate Ligament Injuries of the Knee at the National Football League Combine: An Imaging and Epidemiology Study
Reference: Arthroscopy. 2017 Dec 7. pii: S0749-8063(17)31163-5. doi: 10.1016/j.arthro.2017.08.304. [Epub ahead of print]
Authors: Logan CA, Beaulieu-Jones BR, Sanchez G, Chahla J, Kennedy NI, Cinque ME, LaPrade RF, Whalen JM, Vopat BG, Price MD, Provencher MT
Summary: The purpose was to determine the epidemiology by player position, examination, imaging findings, and associated injuries of posterior cruciate ligament (PCL) injuries in players participating in the National Football League (NFL) Combine. All PCL injuries identified at the NFL Combine (2009-2015) were reviewed. Data were obtained from the database organized by the NFL medical personnel for the compilation of the medical and physical performance examination results of NFL Draftees participating in the NFL Combine from 2009 to 2015. Inclusion criteria were any player with clinical findings or a previous surgery consistent with a PCL injury who participated in the NFL Combine. Of the 2,285 players who participated in the NFL Combine between 2009 and 2015, 69 (3%) had evidence of a PCL injury, of which 11 players (15.9%) were managed surgically. On physical examination, 35 players (52%) had a grade II or III posterior drawer. Concomitant injuries were present frequently and included medial collateral ligament (MCL; 42%), anterior cruciate ligament (ACL; 11.6%), and chondral injuries (31.8%), especially in the lateral tibiofemoral compartment. Three percent of the players at the NFL Combine presented with a PCL injury, with a significant amount being either running backs (14/69, 20.2%) or offensive linemen (14/69, 20.2%). Approximately half of the players with a PCL tear had a residual grade II or III posterior drawer after sustaining a PCL injury. Concomitant injuries were present frequently and included MCL (42%), ACL (11.6%), and chondral injuries (31.8%), especially in the lateral tibiofemoral compartment. For those players with clinical concern for PCL ligamentous laxity, there should be a complete comprehensive workup that includes plain and PCL stress view radiographs, and magnetic resonance imaging.


#3 Symptomatic Focal Knee Chondral Injuries in National Football League Combine Players Are Associated With Poorer Performance and Less Volume of Play
Reference: Arthroscopy. 2017 Dec 7. pii: S0749-8063(17)31159-3. doi: 10.1016/j.arthro.2017.08.300. [Epub ahead of print]
Authors: Provencher MT, Chahla J, Cinque ME, Sanchez G, Kennedy NI, Haber DB, Tisosky AJ, Beaulieu-Jones BR, Price MD, Whalen JM, Moatshe G, LaPrade RF
Summary: The purpose was to (1) describe the magnetic resonance imaging (MRI) characteristics of knee chondral injuries identified at the National Football League (NFL) Combine and (2) assess in-game performance of prospective NFL players with previously untreated knee chondral injuries and compare it with matched controls. All players with knee chondral injuries identified at the NFL Combine (2009-2015) were retrospectively reviewed. Players with prior knee surgery were excluded. A knee MRI for each player was reviewed; location, modified International Cartilage Repair Society (ICRS) grade (I-IV), and associated compartment subchondral edema were documented. Position, respective NFL Draft pick selection number, games started, played, snap percentage, and position-specific performance metrics during the first 2 NFL seasons were recorded for the injury and injury-free control group composed of players with (1) no prior knee injury, (2) no significant missed time prior to the NFL (≤2 total missed games in college), (3) no history of knee surgery, and (4) drafted in the respective NFL Draft following the NFL Combine. Of the 2,285 players reviewed, 101 (4.4%) had an injury without prior knee surgery. The patella (63.4%) and trochlea (34%) were most commonly affected. Defensive linemen were at highest risk for unrecognized injuries (odds ratio 1.8, P = .015). Players with previously untreated injuries, compared with controls, were picked later (mean pick: 125.8) and played (mean: 23) and started (mean: 10.4) fewer games during the initial 2 NFL seasons (P < .001 for all). Particularly, subchondral bone edema and full-thickness cartilage injuries were associated with fewer games played (P = .003). The patellofemoral joint was most commonly affected in NFL Combine participants. Previously untreated knee articular injuries in players at the NFL Combine are associated with poorer early NFL performance in comparison to uninjured players. Subchondral bone edema and full-thickness cartilage injury on MRI were associated with fewer games played during the initial NFL career.

Thu

21

Dec

2017

Football is...(#51)

Cognitive tasks in football training

Wed

20

Dec

2017

Latest research in football - week 50 - 2017

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 the Nordic Hamstring exercise on sprint capacity in male football players: a randomized controlled trial
Reference: J Sports Sci. 2017 Dec 1:1-10. doi: 10.1080/02640414.2017.1409609. [Epub ahead of print]
Authors: Ishoi L, Holmich P, Aagaard P, Thorborg K, Bandholm T, Serner A
Summary: This assessor-blinded, randomized controlled superiority trial investigated the efficacy of the 10-week Nordic Hamstring exercise (NHE) protocol on sprint performance in football players. Thirty-five amateur male players (age: 17-26 years) were randomized to a do-as-usual control group (CG; n = 17) or to 10-weeks of supervised strength training using the NHE in-season (IG; n = 18). A repeated-sprint test, consisting of 4 × 6 10 m sprints, with 15 s recovery period between sprints and 180 s between sets, was conducted to evaluate total sprint time as the primary outcome. Secondary outcomes were best 10 m sprint time (10mST) and sprint time during the last sprint (L10mST). Additionally, peak eccentric hamstring strength (ECC-PHS) and eccentric hamstring strength capacity (ECC-CAPHS) were measured during the NHE. Ten players were lost to follow-up, thus 25 players were analyzed (CG n = 14; IG n = 11). Between-group differences in mean changes were observed in favor of the IG for sprint performance outcomes; TST (-0.649 s, p = 0.056, d = 0.38), 10mST (-0.047 s, p = 0.005, d = 0.64) and L10mST (-0.052 s, p = 0.094, d = 0.59), and for strength outcomes; ECC-PHS (62.3 N, p = 0.006, d = 0.92), and ECC-CAPHS (951 N, p = 0.005, d = 0.95). In conclusion, the NHE showed small-to-medium improvements in sprint performance and large increases in peak eccentric hamstring strength and capacity.


#2 Vertical and Horizontal Jump Capacity in International Cerebral Palsy Football Players
Reference: Int J Sports Physiol Perform. 2017 Nov 28:1-23. doi: 10.1123/ijspp.2017-0321. [Epub ahead of print]
Authors: Reina R, Iturricastillo A, Sabido R, Campayo-Piernas M, Yanci J
Summary: The aims of the present study were to evaluate the reliability and validity of vertical and horizontal jump tests in football players with cerebral palsy (FPCP), and to analyze the jump performance differences between current IFCPF functional classes (i.e. FT5-FT8). One hundred and thirty-two international para-footballers (25.8 ± 6.7 years; 70.0 ± 9.1 kg; 175.7 ± 7.3 cm; 22.8 ± 2.8 kg·m-2; 10.7 ± 7.5 years training experience) participated in the study. The participants were classified according to the IFCPF Classification Rules (i.e. FT5-FT8), and a group of 39 players without CP was included in the study as a control group (CG). Football players' vertical and horizontal jump performance was assessed. All the tests showed good to excellent relative intra-session reliability scores, both in FPCP and in the CG (ICC=.78-.97, SEM<10.5%). Significant between-group differences (p<.001) were obtained in the counter-movement jump (CMJ), standing broad jump (SBJ), four bounds for distance (4B), triple hop for distance dominant leg (THd) and non-dominant leg (THnd). The CG performed higher/farther jumps with regard to all the FPCP classes, obtaining significant differences and moderate to large effect sizes (.85< ES <5.54, p<.01). Players in FT8 class (less severe impairments) had significantly higher scores in all the jump tests compared to players in the lower classes (ES=moderate to large, p<.01). the vertical and horizontal jump tests performed in this study could be applied to the classification procedures and protocols for cerebral palsy football players.


#3 Prognostic factors for specific lower extremity and spinal musculoskeletal injuries identified through medical screening and training load monitoring in professional football (soccer): a systematic review
Reference: BMJ Open Sport Exerc Med. 2017 Sep 21;3(1):e000263. doi: 10.1136/bmjsem-2017-000263. eCollection 2017.
Authors: Hughes T, Sergeant JC, Parkes MJ, Callaghan MJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5623323/pdf/bmjsem-2017-000263.pdf
Summary: Medical screening and load monitoring procedures are commonly used in professional football to assess factors perceived to be associated with injury. The objectives were to identify prognostic factors (PFs) and models for lower extremity and spinal musculoskeletal injuries in professional/elite football players from medical screening and training load monitoring processes. The MEDLINE, AMED, EMBASE, CINAHL Plus, SPORTDiscus and PubMed electronic bibliographic databases were searched (from inception to January 2017). Prospective and retrospective cohort studies of lower extremity and spinal musculoskeletal injury incidence in professional/elite football players aged between 16 and 40 years were included. The Quality in Prognostic Studies appraisal tool and the modified Grading of Recommendations Assessment, Development and Evaluation synthesis approach was used to assess the quality of the evidence. Fourteen studies were included. 16 specific lower extremity injury outcomes were identified. No spinal injury outcomes were identified. Meta-analysis was not possible due to heterogeneity and study quality. All evidence related to PFs and specific lower extremity injury outcomes was of very low to low quality. On the few occasions where multiple studies could be used to compare PFs and outcomes, only two factors demonstrated consensus. A history of previous hamstring injuries (HSI) and increasing age may be prognostic for future HSI in male players. The assumed ability of medical screening tests to predict specific musculoskeletal injuries is not supported by the current evidence. Screening procedures should currently be considered as benchmarks of function or performance only. The prognostic value of load monitoring modalities is unknown.


#4 Data concerning the effect of plyometric training on jump performance in soccer players: A meta-analysis
Reference: Data Brief. 2017 Sep 30;15:324-334. doi: 10.1016/j.dib.2017.09.054. eCollection 2017 Dec.
Authors: Slimani M, Paravlic A, Bragazzi NL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5712054/pdf/main.pdf
Summary: Plyometric training (PT) enhances soccer performance, particularly vertical jump. However, the effectiveness of PT depends on various factors. A systematic search of the research literature was conducted for randomized controlled trials (RCTs) studying the effects of PT on countermovement jump (CMJ) height in soccer players. Ten studies were obtained through manual and electronic journal searches (up to April 2017). Significant differences were observed when compared: (1) PT group vs. control group (ES=0.85; 95% CI 0.47-1.23; I2=68.71%; p<0.001), (2) male vs. female soccer players (Q=4.52; p=0.033), (3) amateur vs. high-level players (Q=6.56; p=0.010), (4) single session volume (<120 jumps vs. ≥120 jumps; Q=6.12, p=0.013), (5) rest between repetitions (5 s vs. 10 s vs. 15 s vs. 30 s; Q=19.10, p<0.001), (6) rest between sets (30 s vs. 60 s vs. 90 s vs. 120 s vs. 240 s; Q=19.83, p=0.001) and (7) and overall training volume (low: <1600 jumps vs. high: ≥1600 jumps; Q=5.08, p=0.024). PT is an effective form of training to improve vertical jump performance (i.e., CMJ) in soccer players. The benefits of PT on CMJ performance are greater for interventions of longer rest interval between repetitions (30 s) and sets (240 s) with higher volume of more than 120 jumps per session and 1600 jumps in total. Gender and competitive level differences should be considered when planning PT programs in soccer players.


#5 Soccer (Football Association) and chronic traumatic encephalopathy: A short review and recommendation
Reference: Dement Neuropsychol. 2017 Jul-Sep;11(3):218-220. doi: 10.1590/1980-57642016dn11-030002 in English, Portuguese
Authors: Nitrini R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5674664/pdf/1980-5764-dn-11-03-0218.pdf
Summary: Chronic traumatic encephalopathy (CTE) was initially described in boxers, but in recent years it has been reported in other settings, particularly in contact sports and military personnel. Soccer (football association) had previously been (and still is) considered relatively safe when compared to other sports, such as American football. However, a few cases of professional soccer players with CTE have been reported in the last few years. It is still unknown how frequent this condition is in soccer players, and the role played by heading the ball remains elusive. Other traumas to the head, face and neck caused by contact with another player's head, arm or other body parts are among the most frequent in soccer. In spite of the lack of more in-depth knowledge, there is reasonable evidence for recommending severe punishment (red card and suspension for several matches) for players causing avoidable trauma to another player's head.


#6 The Reliability and Validity of A Submaximal Warm-Up Test for Monitoring Training Status in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Nov 27. doi: 10.1519/JSC.0000000000002335. [Epub ahead of print]
Authors: Rabbani A, Kargarfard M, Twist C
Summary: Two studies were conducted to assess the reliability and validity of a submaximal warm-up test (SWT) in professional soccer players. For the reliability study, 12 male players performed SWT over three trials, with one week between trials. For the validity study, 14 players of the same team performed SWT and 30-15 Intermittent Fitness Test (30-15IFT) 7 days apart. Week-to-week reliability in selected heart rate (HR) responses [exercise HR (HRex), HR recovery (HRR) expressed as the number of beats recovered within 1 min (HRR60s) and expressed as the mean HR during 1 min (HRpost1)], were determined using intraclass correlation coefficient (ICC) and typical error of measurement expressed as coefficient of variation (CV). The relationships between HR measures derived from SWT and the maximal speed reached at the 30-15IFT (VIFT) were used to assess validity. The range for ICC and CV values were 0.83 to 0.95 and 1.4 to 7.0% in all HR measures, respectively, with the HRex as the most reliable HR measure of SWT. Inverse large (r = -0.50, 90% confidence limits, CL (-0.78; -0.06)) and very large (r = -0.76, CL, -0.90; -0.45) relationships were observed between HRex and HRpost1 with VIFT in relative (expressed as the % of maximal HR) measures, respectively. SWT is a reliable and valid submaximal test to monitor high-intensity intermittent running fitness in professional soccer players. In addition, the test's short duration (5-min) and simplicity mean that it can be used regularly to assess training status in high-level soccer players.


#7 The FIFA 11+ injury prevention program for soccer players: a systematic review
Reference: BMC Sports Sci Med Rehabil. 2017 Nov 28;9:18. doi: 10.1186/s13102-017-0083-z. eCollection 2017.
Authors: Sadigursky D, Braid JA, De Lira DNL, Machado BAB, Carneiro RJF, Colavolpe PO
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5704377/pdf/13102_2017_Article_83.pdf
Summary: Soccer is one of the most widely played sports in the world. However, soccer players have an increased risk of lower limb injury. These injuries may be caused by both modifiable and non-modifiable factors, justifying the adoption of an injury prevention program such as the Fédération Internationale de Football Association (FIFA) 11+. The purpose of this study was to evaluate the efficacy of the FIFA 11+ injury prevention program for soccer players. This meta-analysis was based on the PRISMA 2015 protocol. A search using the keywords "FIFA," "injury prevention," and "football" found 183 articles in the PubMed, MEDLINE, LILACS, SciELO, and ScienceDirect databases. Of these, 6 studies were selected, all of which were randomized clinical trials. The sample consisted of 6,344 players, comprising 3,307 (52%) in the intervention group and 3,037 (48%) in the control group. The FIFA 11+ program reduced injuries in soccer players by 30%, with an estimated relative risk of 0.70 (95% confidence interval, 0.52-0.93, p = 0.01). In the intervention group, 779 (24%) players had injuries, while in the control group, 1,219 (40%) players had injuries. However, this pattern was not homogeneous throughout the studies because of clinical and methodological differences in the samples. This study showed no publication bias. The FIFA 11+ warm-up program reduced the risk of injury in soccer players by 30%.


#8 Sprint and jump performance in elite male soccer players following a 10-week Nordic Hamstring exercise Protocol: a randomised pilot study
Reference: BMC Res Notes. 2017 Dec 4;10(1):669. doi: 10.1186/s13104-017-2986-x.
Authors: Krommes K, Petersen J, Nielsen MB, Aagaard P, Holmich P, Thorborg K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5716363/pdf/13104_2017_Article_2986.pdf
Summary: The preseason Nordic Hamstring Protocol (NHP) reduces hamstring strain injuries in football players. Despite persisting injury rates, elite clubs are reluctant to apply the NHP often over concerns of negative impacts on performance. This pilot study investigated if sprint or jump-performance outcomes tended to increase or decrease following implementation of the NHP in elite male soccer-players. Nineteen male soccer players from the Danish 1st division were randomised to perform NHP (27 sessions) during pre-season, or to control group (CG). Sprint performance (30 m with 5 and 10 m split times) and countermovement jump (CMJ height) was measured before the mid-seasonal break and again after 10 weeks of performing the NHP at the end of pre-season. Dropouts were due to transfers and injuries unrelated to performing NHP (NHP = 0, CG = 5). Sprint performance on the short split distances improved for most players in the NHP (6 out of 9 improved, median changes for 5 m split: - 0.068 s; 10 m split: - 0.078 s), but not CG (2 out of 5 improved, median changes for 5 m split: + 0.1 s; 10 m split: CG: + 0.11 s), but both groups had small declines at 30 m sprint (NHP: 7 out of 9 declined, median changes: + 0.116 s; CG: 4 out of 5 declined, median changes: + 0.159 s). CMJ height mostly improved in both groups (NHP: 6 out of 9 improved, median changes: + 2.1 cm; CG: 4 out of 8 improved, median changes: + 0.55 cm). Performing the NHP in elite soccer players did therefore not seem to negatively affect sprint and vertical jump performance outcomes in the present study, while in fact showing some promise for the more explosive characteristics such as the short 5 and 10 m split-times and maximal CMJ height, which all are highly relevant performance parameters in elite football.


#9 Analysis of the acceleration profile according to initial speed and positional role in elite professional male soccer players
Reference: J Sports Med Phys Fitness. 2017 Dec 1. doi: 10.23736/S0022-4707.17.08003-3. [Epub ahead of print]
Authors: de Hoyo M, Sanudo B, Suarez-Arrones L, Carrasco L, Joel T, Dominguez-Cobo S, Nunez FJ
Summary: The aim of the current study was to analyse the acceleration profile in elite professional soccer players according to their initial speed but also considering players' position. Players' accelerations profiles were analysed using a relative acceleration profile according to the initial speed (S1, from 0 to 7 km/h; S2, from 7.1 to 14.3 km/h; and S3, ≥14.4 km/h) and the maximum acceleration. Within-group analyses showed that Center Backs (CB) performed more high intensity accelerations (likely) when they started in S1 than S2 (ES: 0.50). Strikers (S) and Wide Midfielders (W-MD) achieved more accelerations (likely to almost certain) starting in S3 than S1 (ES: 0.80 and 0.59, respectively) and S2 (ES: 0.67 and 1.09, respectively). Full Backs (FB) completed more accelerations (almost certain) starting in S1 and S3 than S2 (ES: 1.39 and 1.36, respectively). Finally, Midfielders (MD) executed a greater number of high intensity accelerations (likely to almost certain) when they started in S1 than S2 (ES: 0.83) and S3 (ES: 0.66), and in S3 than S2 (ES: 4.72). Between-group analyses showed that S, W-MD, and FB performed a greater total number of high intensity accelerations (very likely to almost certain) than CB (ES: 1.94, 1.57, and 1.51, respectively) and MD (ES: 1.23, 0.92; and 0.81, respectively). Furthermore, MD performed substantially greater total number of high intensity accelerations (likely) than CB (ES: 0.56). Results suggest that CB achieved more high-intensity accelerations starting in low and moderate speed, S and W-MD in high speed, and FB combined low and high speed.


#10 Anthropometric and physiological characteristics of male Soccer players according to their competitive level, playing position and age group: a systematic review
Reference: J Sports Med Phys Fitness. 2017 Dec 1. doi: 10.23736/S0022-4707.17.07950-6. [Epub ahead of print]
Authors: Slimani M, Nikolaidis PT
Summary: The aim of the present systematic review was to profile soccer players' anthropometric, physiological, and physical attributes relative to different competitive levels, playing positions and age groups. The systematic search was conducted using different databases and according to the Population/Intervention or Exposure/Comparison/Outcome(s) [PICO] criteria. The present review shows that the somatotype characteristics, percentage (%) of body fat, maximal oxygen uptake (VO2max), repeatedsprint ability (RSA), running speed, strength, and muscular power of the lower limbs were the most powerful discriminators between male soccer players of different competitive levels, playing positions, and age groups. Specifically, higher VO2max, muscle strength, muscular power (vertical jump height), running speed (1030 m) and agility, and lower % of body fat were identified in elite soccer players (higherlevel) compared to all other competitive levels (i.e., lowerlevel: subelite, amateur, recreational). As for the competitive level differences, higher VO2max, mean anaerobic power, RSA and sprint performances (5 to 20 m), and lower % of body fat and lower limbs' explosive capabilities (countermovement jump (CMJ) and squat jump (SJ)) were found in outfielders (forwards, midfielders, and defenders) as compared to goalkeepers, from a very youth age (8 years old). Concerning age related performance, it appears that physical performance increased significantly with age. These data, together with the fact that each position, age category, and playing level has a different physiological background in male soccer players, demonstrate that training programs should be individualized to each position, playing level and age category, as is already done with goalkeepers.


American Football
#1 Characterization of American Football Injuries in Children and Adolescents
Reference: J Pediatr Orthop. 2017 Nov 16. doi: 10.1097/BPO.0000000000001101. [Epub ahead of print]
Authors: Smith PJ, Hollins AM, Sawyer JR, Spence DD, Outlaw S, Kelly DM
Summary: As a collision sport, football carries a significant risk of injury, as indicated by the large number of pediatric football-related injuries seen in emergency departments. There is little information in the medical literature focusing on the age-related injury patterns of this sport. Our purpose was to evaluate the types of football-related injuries that occur in children and adolescents and assess which patient characteristics, if any, affect injury pattern. Retrospective chart review was performed of football-related injuries treated at a level 1 pediatric referral hospital emergency department and surrounding urgent care clinics between January 2010 and January 2014. Patients with e-codes for tackle football selected from the electronic medical record were divided into 4 age groups: younger than 8 years old, 8 to 11, 12 to 14, and 15 to 18 years. Data collected included diagnosis codes, procedure codes, and hospital admission status. Review identified 1494 patients with 1664 football-related injuries, including 596 appendicular skeleton fractures, 310 sprains, 335 contusions, 170 closed head injuries, 62 dislocations, 9 spinal cord injuries, and 14 solid organ injuries. There were 646 (43.2%) athletes with upper extremity injuries and 487 (32.6%) with injuries to the lower extremity. Hospital admissions were required in 109 (7.3%) patients. Fracture was the most common injury in all four patient age groups, but occurred at a lower rate in the 15 to 18 years old age group. The rate of soft tissue injury was higher in the 15 to 18 years old age group. The rate of closed head injury, which included concussions, was highest in the younger than 8 years old age group. Age does influence the rates of certain football-related injuries in children and adolescents. Fractures decrease with increasing age, while the rate of soft tissue trauma increases with increasing age. Younger patients (younger than 8 y old) trended toward higher rates of closed head injury compared with other age groups. Awareness of these variations in injury patterns based on age could result in age-specific changes in equipment, training, and safety rules.


#2 Positional Differences in Running and Non-Running Activities During Elite American Football Training
Reference: J Strength Cond Res. 2017 Nov 22. doi: 10.1519/JSC.0000000000002294. [Epub ahead of print]
Authors: Ward PA, Ramsden S, Coutts AJ, Hulton AT, Drust B
Summary: The aim of this investigation was to describe differences in training loads between position groups within professional American football. Integrated micro technology data was collected on 63 NFL football players during an American football training camp. Five key metrics (total distance, high speed distance, Player Load, Player Load per Minute, and Total Inertial Movement Analysis (IMA)) served to quantify both running and non-running activities. Players were classified into position groups (DB, DL, LB, OL, QB, RB, TE, and WR). Training sessions were identified by their relationship to the upcoming match (e.g., -4, -3, -2). Running and non-running activities varied between position groups relative to the training day. Differences in total distance were between DB and WR were observed to be unclear between the three training days (Game Day (GD) -4: 74 ± 392 m; GD -3: -122 ± 348; GD - 2: -222 ± 371 m). However, moderate to large differences were observed between these two positions and the other positional groups. A similar relationship was observed in Player Load and Player Load per Minute, with the DB and WR groups performing greater amounts of load compared to other positional groups. Differences in High Speed Distance varied across positional groups, indicating different outputs based on ergonomic demands. The OL and DL groups ran less but engaged in a higher amount of non-running activities (Total IMA) with differences ranging from moderate to large across the three training days. Total IMA differences between offensive and defensive linemen were unclear on GD -4 (-4 ± 9) and GD -2 (-2 ± 8) and likely moderate on GD -3 (-9 ± 9). Positional differences with regard to running and non-running activities highlight the existence of position specific training within a training micro-cycle. Additionally, Total IMA provides a useful metric for quantifying sport specific movements within the game of American football.


#3 Motion-preserving, 2-stage transoral and posterior treatment of an unstable Jefferson fracture in a professional football player
Reference: J Neurosurg Spine. 2017 Dec 1:1-5. doi: 10.3171/2017.6.SPINE17274. [Epub ahead of print]
Authors: Rodts GE Jr, Baum GR, Stewart FG, Heller JG
Summary: The authors report the case of a patient who suffered a Jefferson fracture during a professional football game. The C-1 (atlas) fracture was widely displaced anteriorly, but the transverse ligament was intact. In an effort to enable a return to play and avoid intersegmental (C1-2) fusion, the patient underwent a transoral approach for open reduction and internal fixation of the fracture. The associated posterior ring fracture displacement widened after this procedure, and a subsequent posterior arthrodesis and fixation of the fracture site was performed 6 months later when the fracture failed to heal with rigid collar immobilization. The approach maintained the normal range of motion at the atlantoaxial and atlantooccipital joints, which would have been sacrificed by an atlantoaxial or occipitocervical fusion, as is traditionally performed. Ultimately, the patient decided not to return to the football field, but this approach could avoid the more significant loss of motion associated with atlantoaxial or occipitocervical fusion for unstable Jefferson fractures.


Australian Football
#1 How do professional Australian Football League (AFL) players utilise social media during periods of injury? A mixed methods analysis
Reference: J Sci Med Sport. 2017 Nov 7. pii: S1440-2440(17)31747-4. doi: 10.1016/j.jsams.2017.10.034. [Epub ahead of print]
Authors: Nankervis B, Ferguson L, Gosling C, Storr M, Ilic D, Young M, Maloney S
Summary: The objective of this study was to explore how social media is used by a population of injured professional athletes, by comparing the content and frequency of posts on social media, pre and post-injury. Professional Australian Football League (AFL) players, injured during the 2015 season, were included in the study. Publicly accessible social media profiles for these players were identified on Twitter and Instagram. All posts published on verified profiles, from four weeks prior to injury until return to play, were extracted. Thematic analysis was used to investigate the content of these posts, while univariate and multivariate linear regression was used to investigate the frequency of posts during this time period. Two reoccurring themes were identified exclusively post-injury; 'supporting team from the sideline' and 'sharing information about injury and rehabilitation'. The frequency of total posts did not differ significantly pre and post-injury, but the frequency of injury related posts increased in the immediate post-injury phase, then decreased between 4-8 weeks and 8-12 weeks post-injury. The frequency of injury related posts was higher with more severe injuries. The findings of this study suggest that injured players use social media to seek social support from their followers, especially in the immediate post-injury period and after sustaining a severe injury. The role of social media in injury rehabilitation may warrant further investigation, to determine if it could be used to facilitate return to play.

Mon

18

Dec

2017

Football is...(#50)

Static stretching in warm-ups...take care of applied tension, time under tension and number of reps

Thu

14

Dec

2017

Football is...(#49)

Eccentric strength to improve functional H:Q ratio

Wed

13

Dec

2017

Latest research in football - week 49 - 2017

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 Injury and illness epidemiology in soccer - effects of global geographical differences - a call for standardized and consistent research studies
Reference: Biol Sport. 2017 Sep;34(3):249-254. doi: 10.5114/biolsport.2017.66002. Epub 2017 Feb 19.
Authors: Eirale C, Gillogly S, Singh G, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5676321/pdf/JBS-34-66002.pdf
Summary: Soccer is the most popular sport in the world. While injuries and illnesses can affect the players' health and performance, they can also have a major economic impact on teams. Moreover, several studies have shown the favourable association between higher player availability and team success. Therefore, injury prevention could directly impact clubs' financial balance and teams' performance via increased player availability. To be able to develop effective methods of injury prevention, it is vital to first determine the scope and the degree of the problem: the mechanisms and types of injuries, their frequency and severity, etc. According to the most widely known prevention model, systematic injury surveillance is the first and most fundamental step towards injury prevention. Since epidemiological studies have shown that injuries and illnesses in soccer players differ from region to region, it is important to establish a specific injuries and illness database in order to guide specific preventive actions. Since Asia is the largest continent, with the highest number of soccer players, and in the light of the long-term research on injuries performed in UEFA clubs, the authors of the present article present the AFC surveillance. Some methodological issues related to this prospective design study are discussed. The definition of injury and illness and the methods to track players' exposure are described along with the potential challenges related to such a vast scale study. This article is also a call for action to have consistent and standardized epidemiological studies on soccer injuries and illnesses, with the aim to improve their prevention.


#2 Blood pressure, heart rate and perceived enjoyment after small-sided soccer games and repeated sprint in untrained healthy adolescents
Reference: Biol Sport. 2017 Sep;34(3):219-225. doi: 10.5114/biolsport.2017.65997. Epub 2017 Feb 19.
Authors: Hammami A, Kasmi S, Farinatti P, Fgiri T, Chamari K, Bouhlel E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5676316/pdf/JBS-34-65997.pdf
Summary: The purpose of this study was to examine systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), rating of perceived exertion (RPE) and perceived enjoyment responses to a repeated-sprint training session (RST) compared to a small-sided soccer game session (SSG) in untrained adolescents. Twelve healthy post-pubertal adolescent males (age 15.8±0.6 years, body mass 59.1±3.7 kg, height 1.7±0.1m) performed RST and SSG sessions in a randomized and counterbalanced order. Blood pressure and HR were measured at rest and at 10, 20 and 30 minutes after interventions, and RPE and enjoyment were assessed. RST and SSG elicited similar exercise HR (74.0% vs. 73.7% of HR peak during RST and SSG respectively, P>0.05). There was no significant change in SBP or DBP after the 2 interventions (all P>0.05, ES<0.5) with a trend to a decrease in SBP after SSG at 30 min after intervention (moderate effect, ES=0.6). Pearson's correlation analysis revealed a significant and large correlation between baseline BP values and magnitude of decline after both RST and SSG. Heart rate during recovery was higher compared with baseline at all times after both sessions (all P<0.05), with HR values significantly lower after SSG versus RST at 30 min after interventions (82.3±3.2 versus 92.4±3.2 beats/min, respectively, P=0.04). RPE was significantly lower (P=0.02, ES=1.1) after SSG than after RST, without significant differences in enjoyment. In conclusion, repeated sprint and small-sided games elicited similar exercise intensity without a significant difference in perceived enjoyment. Post-exercise hypotension after the two forms of training may depend on resting BP of subjects.


#3 Immediate Effects of Ankle Balance Taping with Kinesiology Tape for Amateur Soccer Players with Lateral Ankle Sprain: A Randomized Cross-Over Design
Reference: Med Sci Monit. 2017 Nov 21;23:5534-5541.
Authors: Kim MK, Shin YJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5706382/pdf/medscimonit-23-5534.pdf
Summary: The objective of this study was to investigate the immediate effect on gait function when ankle balance taping is applied to amateur soccer players with lateral ankle sprain. A cross-over randomized design was used. Twenty-two soccer players with an ankle sprain underwent 3 interventions in a random order. Subjects were randomly assigned to ankle balance taping, placebo taping, and no taping groups. The assessment was performed using the GAITRite portable walkway system, which records the location and timing of each footfall during ambulation. Significant differences were found in the velocity, step length, stride length, and H-H base support among the 3 different taping methods (p<0.05). The ankle balance taping group showed significantly greater velocity, step length, and stride length in comparison to the placebo and no taping group. The ankle balance taping group showed a statistically significant decrease (p<0.05) in the H-H base support compared to the placebo and no taping groups, and the placebo group showed significantly greater velocity in comparison to the no taping group (p<0.05). We conclude that ankle balance taping that uses kinesiology tape instantly increased the walking ability of amateur soccer players with lateral ankle sprain. Therefore, ankle balance taping is a useful alternative to prevent and treat ankle sprain of soccer players.


#4 Does Maturity Status Affect The Relationship Between Anaerobic Speed Reserve And Multiple Sprints Sets Performance in Young Soccer Players?
Reference: J Strength Cond Res. 2017 Nov 29. doi: 10.1519/JSC.0000000000002266. [Epub ahead of print]
Authors: Selmi MA, Al-Haddabi B, Yahmed MH, Sassi RH
Summary: The purpose of this study is to examine the relationship between repeated-sprint sets (RSS) performance indices and anaerobic speed reserve (ASR) in young soccer players of different maturity status. One hundred and seventy nine young male soccer players (11.1 to 17.8 years) classified as pre- (n=50), circum- (n=60), or post- (n=69) peak height velocity (PHV) performed multi-stage shuttle run test (MRST) to measure maximal aerobic speed (MAS), 30-m sprint with 10-m splits to estimate maximal anaerobic speed (MAnS), and RSS test. ASR was calculated as the difference between MAS and MAnS. The RSS indices, MAS, MAnS and ASR were significantly different in the three maturity groups (p< 0.001; ES =0.12-0.64). Correlations between RSS performance indices and ASR varied considerably depending on maturity status. Very large correlations between ASR and RSS indices expressed as sum sprint time (SST) and best sprint time (BST) were found for pre- and circum-PHV groups (r=-0.76, -0.79 and r=-0.82, -0.86, respectively). In the post-PHV group, ASR was moderately associated with both SST (r=-0.45) and BST (r=-0.46). To sum up, these results highlighted that the ASR is more related to factors of RSS performance in pre- and circum-PHV male soccer players compared with post-PHV ones. These findings could help coaches and strength and conditioning professionals to better understand how the relationship between ASR and RSS evolve across the maturity and may be considered, therefore, useful in youth soccer selection/training process.


#5 Aerobic Fitness in Top-Class Soccer Referees
Reference: J Strength Cond Res. 2017 Nov 16. doi: 10.1519/JSC.0000000000002264. [Epub ahead of print]
Authors: Castagna C, Bizzini M, Araujo Povoas SC, Schenk K, Busser G, DʼOttavio S
Summary: The aim of this study was to examine the aerobic fitness status of top-class male soccer officials using a cross-sectional design and known population group constructs. Fifty-two field referees (FRs, age 38.4 ± 3.3 years; height 181 ± 5.6 cm; body mass 76.8 ± 6.8 kg; body mass index [BMI] 23.4 ± 1.7 kg·m; body fat 20.4 ± 3.6%; and international refereeing experience 5 ± 3.5 years) and 104 assistant referees (ARs, age 37.8 ± 4.1 years; height 176.9 ± 7.5 cm; body mass 72.1 ± 7.4 kg; BMI 23 ± 1.6 kg·m; body fat 19.2 ± 3.6%; and international refereeing experience 7 ± 3.8 years) from 53 National Football Associations worldwide, and candidates of the preliminary open-list developed by the FIFA Refereeing Department for the 2014 World Cup Final Tournament, were tested for aerobic fitness in laboratory conditions with a progressive speed treadmill test to exhaustion. Large (+8.54%, d = 0.8) and small (+3.1%, d = 0.3) differences in absolute (L·min) and relative (ml·kg·min) V[Combining Dot Above]O2max were found between FR and AR, respectively. Trivial differences (d = 0.07) were shown in running economy (RE) (6 minutes at 8 km·h) between AR and FR. Using the scaling notation (b = 0.64), medium and significant differences were found between match officials for V[Combining Dot Above]O2max and RE (FR > AR; d = 0.6 and 0.67, respectively). Using receiver operating characteristic curve statistics, cutoff values of 3.93 L·min and 50.6 ml·kg·min were detected in absolute and relative V[Combining Dot Above]O2max for the FR and the AR (FR > AR), respectively. The FR showed superior aerobic fitness compared with AR. Training prescription should consider intensities at anaerobic threshold speed (14 km·h, 91% heart rate max) when aerobic fitness development is the aim in elite officials.


#6 Skill not athleticism predicts individual variation in match performance of soccer players
Reference: Proc Biol Sci. 2017 Dec 13;284(1868). pii: 20170953. doi: 10.1098/rspb.2017.0953.
Authors: Wilson RS, David GK, Murphy SC, Angilletta MJ Jr, Niehaus AC, Hunter AH, Smith MD
Summary: Just as evolutionary biologists endeavour to link phenotypes to fitness, sport scientists try to identify traits that determine athlete success. Both disciplines would benefit from collaboration, and to illustrate this, we used an analytical approach common to evolutionary biology to isolate the phenotypes that promote success in soccer, a complex activity of humans played in nearly every modern society. Using path analysis, we quantified the relationships among morphology, balance, skill, athleticism and performance of soccer players. We focused on performance in two complex motor activities: a simple game of soccer tennis (1 on 1), and a standard soccer match (11 on 11). In both contests, players with greater skill and balance were more likely to perform better. However, maximal athletic ability was not associated with success in a game. A social network analysis revealed that skill also predicted movement. The relationships between phenotypes and success during individual and team sports have potential implications for how selection acts on these phenotypes, in humans and other species, and thus should ultimately interest evolutionary biologists. Hence, we propose a field of evolutionary sports science that lies at the nexus of evolutionary biology and sports science. This would allow biologists to take advantage of the staggering quantity of data on performance in sporting events to answer evolutionary questions that are more difficult to answer for other species. In return, sports scientists could benefit from the theoretical framework developed to study natural selection in non-human species.


#7 Effects of lower extremity injuries on aerobic exercise capacity, anaerobic power, and knee isokinetic muscular function in high school soccer players
Reference: J Phys Ther Sci. 2017 Oct;29(10):1715-1719. doi: 10.1589/jpts.29.1715. Epub 2017 Oct 21.
Authors: Ko KJ, Ha GC, Kim DW, Kang SJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5683996/pdf/jpts-29-1715.pdf
Summary: The study investigated the effects of lower extremity injuries on aerobic exercise capacity, anaerobic power, and knee isokinetic muscular function in high school soccer players. The study assessed U High School soccer players (n=40) in S area, South Korea, divided into 2 groups: a lower extremity injury group (n=16) comprising those with knee and ankle injuries and a control group (n=24) without injury. Aerobic exercise capacity, anaerobic power, and knee isokinetic muscular function were compared and analyzed. Regarding the aerobic exercise capacity test, significant differences were observed in maximal oxygen uptake and anaerobic threshold between both groups. For the anaerobic power test, no significant difference was observed in peak power and average power between the groups; however, a significant difference in fatigue index was noted. Regarding the knee isokinetic muscular test, no significant difference was noted in knee flexion, extension, and flexion/extension ratio between both groups. Lower extremity injury was associated with reduced aerobic exercise capacity and a higher fatigue index with respect to anaerobic exercise capacity. Therefore, it seems necessary to establish post-injury training programs that improve aerobic and anaerobic exercise capacity for soccer players who experience lower extremity injury.


#8 Seasonal Training Load and Wellness Monitoring in a Professional Soccer Goalkeeper
Reference: Int J Sports Physiol Perform. 2017 Nov 28:1-13. doi: 10.1123/ijspp.2017-0472. [Epub ahead of print]
Authors: Malone JJ, Jaspers A, Helsen WF, Merks B, Frencken WG, Brink MS
Summary: The purpose of this investigation was to: (a) quantify the training load practices of a professional soccer GK, and (b) investigate the relationship between the training load observed and the subsequent self-reported wellness response. One male goalkeeper playing for a team in the top league of the Netherlands participated in this case study. Training load data were collected across a full season using a global positioning system (GPS) device and session rating of perceived exertion (session-RPE). Data was assessed in relation to the number of days to a match (MD- and MD+). In addition, self-reported wellness was assessed using a questionnaire. Duration, total distance, average speed, PlayerLoadTM and load (derived from session-RPE) were highest on MD. The lowest values for duration, total distance and PlayerLoadTM were observed on MD-1 and MD+1. Total wellness scores were highest on MD and MD-3 and were lowest on MD+1 and MD-4. Small to moderate correlations between training load measures (duration, total distance covered, high deceleration efforts and load) and the self-reported wellness scores were found. This exploratory case-study provides novel data about the physical load undertaken by a goalkeeper during one competitive season. The data suggest there are small to moderate relationships between training load indicators and self-reported wellness. This weak relation indicates that the association is not meaningful. This may be due to the lack of position-specific training load parameters we can currently measure in the applied context.


#9 Irisin levels correlate with bone mineral density in soccer players
Reference: J Biol Regul Homeost Agents. 2017 Oct-Dec,;31(4 suppl 1):21-28.
Authors: Colaianni G, Notarnicola A, Sanesi L, Brunetti G, Lippo L, Celi M, Moretti L, Pesce V, Vicenti G, Moretti B, Colucci S, Grano M
Summary: Irisin, a novel myokine produced in response to physical exercise by skeletal muscle, displays anabolic effect on bone and can improve the bone-loss-induced osteoporosis in hind limb suspended mice. It is well known that muscles positively impact the skeleton and in different sports, including soccer, total body bone mineral density (TB-BMD) is elevated. Therefore, we have investigated the correlation between irisin serum levels and total and bone sub-regional BMD in soccer players never studied before. In this study, Caucasian football players of Bari team have been enrolled. Their sera were collected to measure by ELISA kit irisin levels and by dual-energy X-ray absorptiometry (DEXA) analysis measurements of BMD (g • cm−2) in the whole body and different bone sub-regions (head, arms, legs, ribs, dorsal vertebrae, lumbar vertebrae, pelvis) were performed. The BMC (g) was measured in the whole body. By means of Pearson’s (R) and Cohen’s (d) coefficient we investigated the linear association between the irisin serum levels and BMD. In soccer players, we have found a positive correlation between irisin and TB-BMD as demonstrated by the values of Pearson and Cohen’s (d) coefficient. Furthermore, linear association was detected between irisin and BMD of different bone-site such as right arm, lumbar vertebrae and head. A positive trend was also observed analyzing circulating levels of irisin and bone mineral content as well as total Z-score. In conclusion, we have demonstrated the correlation between irisin and total or bone sub-regional BMD in soccer players for the first time, an additional systemic effect of the “sport-hormone” defined myokine.


#10 Prognostic factors for specific lower extremity and spinal musculoskeletal injuries identified through medical screening and training load monitoring in professional football (soccer): a systematic review
Reference: BMJ Open Sport Exerc Med. 2017 Sep 21;3(1):e000263. doi: 10.1136/bmjsem-2017-000263. eCollection 2017.
Authors: Hughes T, Sergeant JC, Parkes MJ, Callaghan MJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5623323/pdf/bmjsem-2017-000263.pdf
Summary: Medical screening and load monitoring procedures are commonly used in professional football to assess factors perceived to be associated with injury. The aim was to identify prognostic factors (PFs) and models for lower extremity and spinal musculoskeletal injuries in professional/elite football players from medical screening and training load monitoring processes. The MEDLINE, AMED, EMBASE, CINAHL Plus, SPORTDiscus and PubMed electronic bibliographic databases were searched (from inception to January 2017). Prospective and retrospective cohort studies of lower extremity and spinal musculoskeletal injury incidence in professional/elite football players aged between 16 and 40 years were included. The Quality in Prognostic Studies appraisal tool and the modified Grading of Recommendations Assessment, Development and Evaluation synthesis approach was used to assess the quality of the evidence. Fourteen studies were included. 16 specific lower extremity injury outcomes were identified. No spinal injury outcomes were identified. Meta-analysis was not possible due to heterogeneity and study quality. All evidence related to PFs and specific lower extremity injury outcomes was of very low to low quality. On the few occasions where multiple studies could be used to compare PFs and outcomes, only two factors demonstrated consensus. A history of previous hamstring injuries (HSI) and increasing age may be prognostic for future HSI in male players. The assumed ability of medical screening tests to predict specific musculoskeletal injuries is not supported by the current evidence. Screening procedures should currently be considered as benchmarks of function or performance only. The prognostic value of load monitoring modalities is unknown.


#11 Effects of Plyometric and Directional Training on Speed and Jump Performance in Elite Youth Soccer Players
Reference: J Strength Cond Res. 2017 Nov 22. doi: 10.1519/JSC.0000000000002371. [Epub ahead of print]
Authors: Beato M, Bianchi M, Coratella G, Merlini M, Drust B
Summary: Soccer players perform approximately 1350 activities (every 4-6 s), such as accelerations/decelerations, and changes of direction (COD) during matches. It is well established that COD and plyometric training have a positive impact on fitness parameters in football players. This study analyzed the effect of a complex COD and plyometric protocol (CODJ-G) compared to an isolated COD protocol (COD-G) training on elite football players.A randomized pre-post parallel group trial was used in this study. Twenty-one youth players were enrolled in this study (mean ± SDs; age 17 ± 0.8 years, weight 70.1 ± 6.4 kg, height 177.4 ± 6.2 cm). Players were randomized into two different groups: CODJ-G (n = 11) and COD-G (n = 10), training frequency of 2 times a week over 6 weeks. Sprint 10, 30 and 40 m, long jump, triple hop jump, as well as 505 COD test were considered. Exercise-induced within-group changes in performance for both CODJ-G and COD-G: long jump (effect size (ES) = 0.32 and ES = 0.26, respectively), sprint 10 m (ES = -0.51 and ES = -0.22 respectively), after 6 weeks of training. Moreover, CODJ-G reported substantially better results (between-group changes) in long jump test (ES = 0.32). In conclusion, this study showed that short-term protocols (CODJ-G and COD-G) are important and able to give meaningful improvements on power and speed parameters in a specific soccer population. CODJ-G showed a larger effect in sprint and jump parameters compared to COD-G after the training protocol. This study offers important implications for designing COD and jumps training in elite soccer.

Tue

12

Dec

2017

Football is...(#48)

Upper-body stability to withstand opposition players' challenges

Mon

11

Dec

2017

Latest research in football - week 48 - 2017

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 Movement pattern and physiological response in recreational small-sided football - effect of number of players with a fixed pitch size
Reference: J Sports Sci. 2017 Nov 13:1-8. doi: 10.1080/02640414.2017.1402552. [Epub ahead of print]
Authors: Randers MB, Orntoft C, Hagman M, Nielsen JJ, Krustrup P
Summary: Recreational soccer is an effective health-promoting activity, but it is unclear how different game formats influence internal and external load. Thus, to be able to advise how to maximise the outcome of recreational football, we examined movement pattern and physiological response in 11 untrained men (32.6 ± 6.7 yrs, 23.3 ± 4.9 fat%, 43.4 ± 5.3 ml·min-1·kg-1) during three football sessions comprising 4 × 12 min of 3v3, 5v5 or 7v7 with a constant pitch size of 20 × 40 m. Movement pattern, heart rate (HR), blood lactate and RPE were measured during and after the 12-min periods. Greater (P < 0.05) total distance and high-speed distance was covered during 3v3 than 5v5 (14 and 30%) and 7v7 (15 and 75%). Mean HR was higher in 3v3 (85.7 ± 5.7%HRmax) and 5v5 (84.2 ± 5.1%HRmax) than in 7v7 (80.7 ± 4.6%HRmax, P < 0.05) and percentage time >90%HR was higher in 3v3 (43 ± 18%, P < 0.05) than in 5v5 (28 ± 21%) and 7v7 (18 ± 14%). Blood lactate was higher in 3v3 (7.4 ± 2.7 mmol·l-1) than in 7v7 (4.5 ± 2.2 mmol·l-1, P < 0.001) but not in 5v5 (6.1 ± 2.1 mmol·l-1, P = 0.061). RPE was higher in 3v3 (6.7 ± 2.3, P < 0.01) than in 5v5 (5.2 ± 2.2) and 7v7 (4.3 ± 2.3). In conclusion, higher external and internal load was found with fewer players, when the pitch size is fixed.


#2 Body fat percentage comparisons between four methods in young football players: are they comparable?
Reference: Nutr Hosp. 2017 Oct 24;34(5):1119-1124. doi: 10.20960/nh.760.
Authors: Lozano Berges G, Matute Llorente A, Gomez Bruton A, Gonzalez Aguero A, Vicente Rodriguez G, Casajus JA
Download link: revista.nutricionhospitalaria.net/index.php/nh/article/download/760/664
Summary: Dual X-ray absorptiometry (DXA), air displacement plethysmography (ADP), bioelectrical impedance analysis (BIA) and anthropometry are four body composition methods that have been frequently used for the assessment of body fat percentage (%BF) in athletes. However, the agreement between these methods has not been studied yet in adolescent football players. The aim of this study was to compare %BF calculated by DXA, ADP, BIA and anthropometry in 92 participants. Sixty-four males (13.4 ± 0.6 years of age) and 28 females (13.4 ± 0.6 years) participated in this study. %BF was measured with four methods: DXA, ADP, BIA, and anthropometry. ADP %BF was calculated by using Siri's equation. The equation proposed by Slaughter et al. was used to calculate %BF by anthropometry. Paired t-test was used to compare %BF means. The heteroscedasticity was calculated by Bland-Altman analyses. Both in males and females, DXA, ADP, BIA and Slaughter et al. equation demonstrated significant %BF differences when compared to each other (p < 0.05); 95% limits of agreements ranged from 5.13 to 15.09% points. Only BIA showed heteroscedasticity compared to the other methods in both genders (p < 0.05). Although DXA, ADP, BIA, and anthropometry have been used in the scientific literature in order to assess %BF in adolescent football players, these results demonstrate that these body composition methods are not interchangeable in this population.


#3 Adoption and use of an injury prevention exercise programme in female football: a qualitative study among coaches
Reference: Scand J Med Sci Sports. 2017 Nov 11. doi: 10.1111/sms.13012. [Epub ahead of print]
Authors: Lindblom H, Carlfjord S, Hagglund M
Summary: This study focuses on an injury prevention exercise programme (IPEP), Knee Control, which has been shown to reduce the incidence of acute knee injury in female adolescent football players. The aim was to explore the factors influencing coaches' adoption and use of Knee Control within female football in Sweden. This was a qualitative study involving interviews with 20 strategically selected coaches for female football teams, predominantly adolescent teams. The semi-structured interview guide was influenced by the Health Belief Model, and an ecological perspective was adopted during the interviews. Interviews were analysed with qualitative content analysis. The results illustrate the different influences that interact on adoption and use of Knee Control by coaches. The coaches described themselves as crucial for Knee Control adoption and use, but external facilitators and barriers such as resources for training, social support from other coaches, clubs and football associations and player buy-in were also described as important. Knee Control characteristics, such as how well the programme fit the team, also influenced use of Knee Control. Many coaches modified the programme to improve player buy-in and Knee Control fit. Such modifications may risk compromising the preventive effect but may increase feasibility, i.e. the ease of using Knee Control, and thereby long-term use. These findings may guide the design and delivery of future IPEPs, and improve use of Knee Control, for example by expanding the programme to fit different target groups and supporting coaches and players in the use of Knee Control.


#4 Measurement properties and feasibility of the Loughborough soccer passing test: A systematic review
Reference: J Sports Sci. 2017 Nov 24:1-13. doi: 10.1080/02640414.2017.1409611. [Epub ahead of print]
Authors: Wen D, Robertson S, Hu G, Song B, Chen H
Summary: The purpose of this paper was to systematically review the literature and examine the research methodological quality, measurement properties and feasibility of the Loughborough Soccer Passing Test (LSPT). Databases were searched up to June 2017. Twenty five studies fulfilled the eligibility criteria. The main methodological limitations of the studies were the small sample size and the lack of information on participants and eligibility criteria. Results showed that test-retest reliability of the LSPT was moderate to excellent. Good discriminative validity was found between playing levels and ages. The LSPT was positively correlated with sprint, dribbling, and agility test; however, a weak correlation was established with in-game performance. Test responsiveness (an ability to detect change over time) to some external interventions was observed in studies. Adjusted Cronbach's alpha (α = 0.67), smallest worthwhile change (SWC = 0.8-3.8) and minimal detectable change (MDC50 = 1.9-11.3) were calculated based on available data. The findings indicate that the LSPT has acceptable test-retest reliability and discriminative validity. However, it may not be a feasible and effective way to interpret the intra-individual change of skill performance in practice. Future work should be undertaken to establish additional measurement properties of the LSPT, and to improve its practical feasibility.


#5 Neural bases of ingroup altruistic motivation in soccer fans
Reference: Sci Rep. 2017 Nov 23;7(1):16122. doi: 10.1038/s41598-017-15385-7.
Authors: Bortolini T, Bado P, Hoefle S, Engel A, Zahn R, de Oliveira Souza R, Dreher JC, Moll J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5700961/pdf/41598_2017_Article_15385.pdf
Summary: Humans have a strong need to belong to social groups and a natural inclination to benefit ingroup members. Although the psychological mechanisms behind human prosociality have extensively been studied, the specific neural systems bridging group belongingness and altruistic motivation remain to be identified. Here, we used soccer fandom as an ecological framing of group membership to investigate the neural mechanisms underlying ingroup altruistic behaviour in male fans using event-related functional magnetic resonance. We designed an effort measure based on handgrip strength to assess the motivation to earn money (i) for oneself, (ii) for anonymous ingroup fans, or (iii) for a neutral group of anonymous non-fans. While overlapping valuation signals in the medial orbitofrontal cortex (mOFC) were observed for the three conditions, the subgenual cingulate cortex (SCC) exhibited increased functional connectivity with the mOFC as well as stronger hemodynamic responses for ingroup versus outgroup decisions. These findings indicate a key role for the SCC, a region previously implicated in altruistic decisions and group affiliation, in dovetailing altruistic motivations with neural valuation systems in real-life ingroup behaviour.


#6 Novel mathematical model to estimate ball impact force in soccer
Reference: Sports Biomech. 2017 Nov 22:1-17. doi: 10.1080/14763141.2017.1364415. [Epub ahead of print]
Authors: Iga T, Nunome H, Sano S, Sato N, Ikegami Y
Summary: The purpose was to assess ball impact force during soccer kicking is important to quantify from both performance and chronic injury prevention perspectives. We aimed to verify the appropriateness of previous models used to estimate ball impact force and to propose an improved model to better capture the time history of ball impact force. A soccer ball was fired directly onto a force platform (10 kHz) at five realistic kicking ball velocities and ball behaviour was captured by a high-speed camera (5,000 Hz). The time history of ball impact force was estimated using three existing models and two new models. A new mathematical model that took into account a rapid change in ball surface area and heterogeneous ball deformation showed a distinctive advantage to estimate the peak forces and its occurrence times and to reproduce time history of ball impact forces more precisely, thereby reinforcing the possible mechanics of 'footballer's ankle'. Ball impact time was also systematically shortened when ball velocity increases in contrast to practical understanding for producing faster ball velocity, however, the aspect of ball contact time must be considered carefully from practical point of view.


#7 Somatotrope Pituitary Function in Professional Soccer Players
Reference: Exp Clin Endocrinol Diabetes. 2017 Nov 17. doi: 10.1055/s-0043-119876. [Epub ahead of print]
Authors: Roser P, Wehrhahn T, Krogmann H, Riedel N, Marshall RP, Gille J, Flitsch J, Aberle J
Summary: Soccer is associated with repetitive head trauma, which, as it is known from sports like football and boxing, can result in hypopituitarism. Gonadotropins and GH are the most common pituitary hormones to become deficient. GH deficiency is associated with an increased risk of cardiovascular mortality and has negative influence on body mass index, visceral fat mass, insulin resistance and sensitivity, bone mineral density and inflammatory markers. Therefore the aim of this study was to evaluate the somatotrope pituitary function in professional soccer players. This clinical study included 15 male, professional soccer players with at least 10 years of professional training. Basal hormonal parameters of the pituitary axis were obtained from the participants. To assess GH-IGF-I axis, glucagon stimulation tests were used. Rise in growth hormone during glucagon test was analyzed and the prevalence of newly diagnosed hormone deficiencies was evaluated. Mean age of all participants was 31±10 years. None of the 15 soccer players had GH deficiency. Mean rising factor of GH after stimulation with glucagon was 100 in all participants. We did not find signs of ACTH, TSH or LH/FSH deficiency in any player. In this small collective of soccer players we did not find playing soccer to be a risk factor for the development of GH-deficiency. According to our data screening for somatotrope deficiency is not necessary. Further investigations in larger cohorts are needed.


#8 Correction to: Tanner-Whitehouse Skeletal Ages in Male Youth Soccer Players: TW2 or TW3?
Reference: Sports Med. 2017 Nov 21. doi: 10.1007/s40279-017-0827-7. [Epub ahead of print]
Authors: Malina RM, Coelho-E-Silva MJ, Figueiredo AJ, Philippaerts RM, Hirose N, Reyes MEP, Gilli G, Benso A, Vaeyens R, Deprez D, Guglielmo LGA, Buranarugsa R
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-017-0827-7.pdf
Summary: An Online First version of this article was made available online at https://link.springer.com/article/10.1007%2Fs40279-017-0799-7 on 29 October 2017. Errors were subsequently identified in the article, and the following corrections should be noted.


#9 The functional movement screen (FMSTM) in elite young soccer players between 14 and 20 years: Composite score, individual test scores and asymmetries
Reference: Int J Sports Phys Ther. 2017 Nov;12(6):977-985.
Authors: Marques VB, Medeiros TM, de Souza Stigger F, Nakamura FY, Baroni BM
Summary: The Functional Movement Screen (FMS™) is a widely used seven-test battery used by practitioners working in sport medicine. The FMS™ composite score (sum of seven tests) in soccer athletes from different competitive levels has been well explored in literature, but the specific movement deficits presented by young high competitive level players remains unclear. The aim of the present study was to provide a detailed description of the performance of elite young soccer players (age 14-20 years) on the FMS™ testing battery. One-hundred and three young soccer players (14-20 years) from a premier league club were assessed by two experienced raters using the FMS™ testing battery. FMS™ composite score, individual-test scores and asymmetries were considered for analysis, and comparisons between age categories were performed. FMS™ composite scores ranged from 9 to 16 points (median=13 points). 82% of the athletes had a composite score ≤14 points, and 91% were classified into the "Fail" group (score 0 or 1 in at least one test). Almost half of athletes (48%) had poor performance (i.e., individual score < 2) in "deep squat" test. Most of athletes in the younger categories (under-15 and under-16) had poor performance in the "trunk stability push-up" test (70%) and in the "rotary stability" test (74%). Asymmetry in at least one of five unilateral FMS™ tests was found in 65% of athletes. High-performance young soccer players have important functional deficits, especially in tasks involving deep squat and trunk stability, as well as high prevalence of asymmetry between right and left body side.


#10 Vision in high-level football officials
Reference: PLoS One. 2017 Nov 21;12(11):e0188463. doi: 10.1371/journal.pone.0188463. eCollection 2017.
Authors: Baptista AMG, Serra PM, McAlinden C, Barrett BT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5697857/pdf/pone.0188463.pdf
Summary: Officiating in football depends, at least to some extent, upon adequate visual function. However, there is no vision standard for football officiating and the nature of the relationship between officiating performance and level of vision is unknown. As a first step in characterising this relationship, we report on the clinically-measured vision and on the perceived level of vision in elite-level, Portuguese football officials. Seventy-one referees (R) and assistant referees (AR) participated in the study, representing 92% of the total population of elite level football officials in Portugal in the 2013/2014 season. Nine of the 22 Rs (40.9%) and ten of the 49 ARs (20.4%) were international-level. Information about visual history was also gathered. Perceived vision was assessed using the preference-values-assigned-to-global-visual-status (PVVS) and the Quality-of-Vision (QoV) questionnaire. Standard clinical vision measures (including visual acuity, contrast sensitivity and stereopsis) were gathered in a subset (n = 44, 62%) of the participants. Data were analysed according to the type (R/AR) and level (international/national) of official, and Bonferroni corrections were applied to reduce the risk of type I errors. Adopting criterion for statistical significance of p<0.01, PVVS scores did not differ between R and AR (p = 0.88), or between national- and international-level officials (p = 0.66). Similarly, QoV scores did not differ between R and AR in frequency (p = 0.50), severity (p = 0.71) or bothersomeness (p = 0.81) of symptoms, or between international-level vs national-level officials for frequency (p = 0.03) or bothersomeness (p = 0.07) of symptoms. However, international-level officials reported less severe symptoms than their national-level counterparts (p<0.01). Overall, 18.3% of officials had either never had an eye examination or if they had, it was more than 3 years previously. Regarding refractive correction, 4.2% had undergone refractive surgery and 23.9% wear contact lenses when officiating. Clinical vision measures in the football officials were similar to published normative values for young, adult populations and similar between R and AR. Clinically-measured vision did not differ according to officiating level. Visual acuity measured with and without a pinhole disc indicated that around one quarter of participants may be capable of better vision when officiating, as evidenced by better acuity (≥1 line of letters) using the pinhole. Amongst the clinical visual tests we used, we did not find evidence for above-average performance in elite-level football officials. Although the impact of uncorrected mild to moderate refractive error upon officiating performance is unknown, with a greater uptake of eye examinations, visual acuity may be improved in around a quarter of officials.


#11 Monitoring the effect of football match congestion on hamstring strength and lower limb flexibility: Potential for secondary injury prevention?
Reference: Phys Ther Sport. 2017 Sep 15;29:14-18. doi: 10.1016/j.ptsp.2017.09.001. [Epub ahead of print]
Authors: Wollin M, Thorborg K, Pizzari T
Summary: The purpose was to investigate the effect of competitive football match congestion on hamstring strength and lower limb flexibility. Fifteen male elite youth football players from the national football association centre of excellence were included (age = 15.81 ±0.65 years, height = 171.95 ±6.89 cm, weight = 65.93 ±7.53 kg). Hamstring strength and pain, ankle dorsiflexion, hip extension, knee extension and flexion range of motion were used as main outcome measures. Hamstring strength was highest at baseline and significantly reduced at 24 (p = 0.001, mean difference -0.19 Nm/Kg, CI95 -0.28, -0.1) and 48 h post-match 1 (p = 0.002, mean difference -0.16 Nm/Kg, CI95 -0.25, -0.07). Strength recovered by match day 2 before significantly reducing again 24 h post-match 2 (p = 0.012, mean difference -0.17 Nm/Kg, CI95 -0.29, -0.04). Pain was lowest at baseline and increased in the post-match periods (p < 0.05) with standardised effect sizes ranging from 0.07 to 0.42. Passive knee flexion range decreased post-match (p < 0.01) with mean differences of 1.5°-2.7°. The other flexibility measures remained unaffected by match play. Isometric hamstring strength and pain can be considered for inclusion in-season to monitor player's post-match hamstring recovery characteristics during congested match fixtures.


#12 Alcohol intoxication at Swedish football matches: A study using biological sampling to assess blood alcohol concentration levels among spectators
Reference: PLoS One. 2017 Nov 20;12(11):e0188284. doi: 10.1371/journal.pone.0188284. eCollection 2017.
Authors: Durbeej N, Elgan TH, Jalling C, Gripenberg J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5695776/pdf/pone.0188284.pdf
Summary: Alcohol use and alcohol-related problems, including accidents, vandalism and violence, at sporting events are of increased concern in Sweden and other countries. The relationship between alcohol use and violence has been established and can be explained by the level of intoxication. Given the occurrence of alcohol use and alcohol-related problems at sporting events, research has assessed intoxication levels measured through biological sampling among spectators. This cross-sectional study aimed to assess the level of alcohol intoxication among spectators at football matches in the Swedish Premier Football League. Spectators were randomly selected and invited to participate in the study. Alcohol intoxication was measured with a breath analyser for Blood Alcohol Concentration levels, and data on gender, age, and recent alcohol use were gathered through a face-to-face interview. Blood Alcohol Concentration samples from 4420 spectators were collected. Almost half (46.8%) had a positive Blood Alcohol Concentration level, with a mean value of 0.063%, while 8.9% had a Blood Alcohol Concentration level ≥ 0.1%, with a mean value of 0.135%. Factors that predicted a higher Blood Alcohol Concentration level included male gender (p = 0.005), lower age (p < 0.001), attending a local derby (p < 0.001), alcohol use prior to having entered the arena (p < 0.001), attending a weekend match (p < 0.001), and being a spectator at supporter sections (p < 0.001). About half of all spectators at football matches in the Swedish Premier Football League drink alcohol in conjunction with the match. Approximately one tenth have a high level of alcohol intoxication.


#13 Longitudinal improvement in Balance Error Scoring System scores among NCAA Division-I football athletes
Reference: J Neurotrauma. 2017 Nov 17. doi: 10.1089/neu.2017.5072. [Epub ahead of print]
Authors: Mathiasen RE, Hogrefe CP, Harland KK, Peterson A, Smoot K
Summary: The Balance Error Scoring System (BESS) is a commonly used concussion assessment tool. Recent studies have questioned the stability and reliability of baseline BESS scores. The purpose of this longitudinal prospective cohort study is to examine differences in yearly baseline BESS scores in athletes participating on an NCAA Division-I football team. NCAA Division-I freshman football athletes were videotaped performing the BESS test at matriculation and following one year of participation in the football program. Twenty-three athletes were enrolled in year one of the study, and twenty-five athletes were enrolled in year two. Those athletes enrolled in year one were again videotaped following year two of the study. The paired t-test was used to assess for change in score over time for the firm surface, foam surface, and the cumulative BESS score. Additionally, inter- and intra-rater reliability values were calculated. Cumulative errors on the BESS significantly decreased from a mean of 20.3 at baseline to 16.8 after one year of participation. The mean number of errors following the second year of participation was 15.0. Inter-rater reliability for the cumulative score ranged from 0.65 to 0.75. Intra-rater reliability was 0.81. Following one year of participation, there is a statistically and clinically significant improvement in BESS scores in an NCAA Division-I football program. While additional improvement in the BESS scores was noted following the second year of participation, it did not reach statistical significance. Football athletes should undergo baseline BESS testing at least yearly if the BESS is to optimally useful as a diagnostic test for concussion.

Fri

08

Dec

2017

Football ist...(#47)

Crosses into the penalty box = ↑ chances of winning

Wed

06

Dec

2017

Football is...(#46)

Training according to players' positions.

Wed

29

Nov

2017

Latest research in football - week 47 - 2017

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 Z-scores-based methods and their application to biological monitoring: an example in professional soccer players
Reference: Biostatistics. 2017 Nov 15. doi: 10.1093/biostatistics/kxx044. [Epub ahead of print]
Authors: Sauliere G, Dedecker J, Marquet LA, Rochcongar P, Toussaint JF, Berthelot G
Summary: The clinical and biological follow-up of individuals, such as the biological passport for athletes, is typically based on the individual and longitudinal monitoring of hematological or urine markers. These follow-ups aim to identify abnormal behavior by comparing the individual's biological samples to an established baseline. These comparisons may be done via different ways, but each of them requires an appropriate extra population to compute the significance levels, which is a non-trivial issue. Moreover, it is not necessarily relevant to compare the measures of a biomarker of a professional athlete to that of a reference population (even restricted to other athletes), and a reasonable alternative is to detect the abnormal values by considering only the other measurements of the same athlete. Here we propose a simple adaptive statistic based on maxima of Z-scores that does not rely on the use of an extra population. We show that, in the Gaussian framework, it is a practical and relevant method for detecting abnormal values in a series of observations from the same individual. The distribution of this statistic does not depend on the individual parameters under the null hypothesis, and its quantiles can be computed using Monte Carlo simulations. The proposed method is tested on the 3-year follow-up of ferritin, serum iron, erythrocytes, hemoglobin, and hematocrit markers in 2577 elite male soccer players. For instance, if we consider the abnormal values for the hematocrit at a 5% level, we found that 5.57% of the selected cohort had at least one abnormal value (which is not significantly different from the expected false-discovery rate). The approach is a starting point for more elaborate models that would produce a refined individual baseline. The method can be extended to the Gaussian linear model, in order to include additional variables such as the age or exposure to altitude. The method could also be applied to other domains, such as the clinical patient follow-up in monitoring abnormal values of biological markers.


#2 Effects of detraining on breathing pattern and ventilatory efficiency in young soccer players
Reference: J Sports Med Phys Fitness. 2017 Nov 17. doi: 10.23736/S0022-4707.17.07619-8. [Epub ahead of print]
Authors: Alvero Cruz JR, Ronconi M, Garcia Romero J, Naranjo Orellana J
Summary: This study investigated the effects of detraining on breathing pattern. The aim of this study was to evaluate the effect of a sixweek detraining period on breathing patterns and ventilatory efficiency. Fourteen young soccer players were evaluated at the end of a competitive season and after a sixweek detraining period. Assessment of respiratory efficiency was based on VE/VCO2 slope changes below 70% of exercise intensity. All participants underwent twice an incremental graded exercise test up to exhaustion. No differences in breathing frequency and inspiratory time/ total time ratio (Ti/Ttot) were found after detraining (p>.05). Differences in tidal volume (VT), VT/Ti quotient and VE were significant (p<.05) at between 40 to 100% of exercise intensity. The VE/VCO2 slope did not change (p>.05) during a postdetraining maximal incremental test. A sixweek detraining period causes changes in inspiratory flow but does not affect the inspiratory time/total respiratory cycle time ratio. The overall ventilatory efficiency of the respiratory system remains constant and is not affected by detraining.


#3 Acoustic Analysis of Soccer Fans in Acute Phonotrauma After the Match
Reference: J Voice. 2017 Nov 13. pii: S0892-1997(17)30294-1. doi: 10.1016/j.jvoice.2017.10.004. [Epub ahead of print]
Authors: Pinarbasli MO, Kaya E, Ozudogru E, Gurbuz MK, Colak E, Aksoy MA, Birdane L, Guney FO
Summary: Acute phonotrauma is the result of sound production by shouting or straining one's voice. In this study, we aimed to investigate the acute changes in the vocal folds and voices of soccer fans who voluntarily applied to our clinic after the soccer match where they engaged in acute phonotrauma. There are no other studies in the literature conducted on a similar sample group. Videolaryngostroboscopic (VLS) examination, acoustic voice analysis, and Voice Handicap Index (VHI) questionnaire were performed on 29 voluntary soccer fans included to the study before the match and at the first hour after the match. The values obtained were compared statistically with each other and with 29 control groups without voice pathology. The jitter, shimmer, and normalized noise energy values measured after the match increased significantly statistically compared with the pre-match level, but harmonic noise ratio value decreased significantly (P < 0.05). VHI scores increased significantly after the match according to the pre-match scores (P < 0.05). In the VLS examinations, there was no difference in the images before and after the match. It has been concluded that people who are using their voices loudly and intensely by shouting during the match are exposed to sound changes after the match, and if this situation becomes persistent, it may cause permanent voice pathologies. It is thought that VHI and acoustic voice analysis should be done together with VLS for diagnosis and follow-up of voice changes for which the VLS examination alone is not sufficient.


#4 Sex Differences in Aerobic Fitness in Top-Class Soccer Referees
Reference: J Strength Cond Res. 2017 Nov 14. doi: 10.1519/JSC.0000000000002292. [Epub ahead of print]
Authors: Castagna C, Bizzini M, DʼOttavio S, Araujo Povoas SC
Summary: The aim of this study was to assess the aerobic-fitness differences between male and female top-class soccer field referees (FRs). This with the purpose to provide cutoff values useful for training prescription in female FRs. Forty female top-class FRs (age 34.18 ± 3.50 years and 5 ± 3.9 years international refereeing experience) and 52 male FRs (age 38.4 ± 3.3 years and 5 ± 3.5 years international refereeing experience) candidates in the preliminary open list developed by the FIFA Refereeing Department for the 2014 and 2015 World Cup Tournaments, participated in the study. The FRs were tested for aerobic fitness under laboratory conditions with a progressive speed treadmill test until exhaustion. Female FRs showed to possess, on average, lower (large effect) levels of aerobic fitness and performance compared with their male counterparts. The female FRs' V[Combining Dot Above]O2max (48.1 ± 4.4 ml·kg·min) was 7% (large effect) lower than the male FRs (51.9 ml·kg·min). Peak treadmill speed was 11% lower (large effect) in female FRs (16.27 ± 0.94 vs. 14.64 ± 0.96 km·h). The receiver operating characteristic curve analysis enabled cutoff values (47.8 ml·kg·min for V[Combining Dot Above]O2max) that may be used as preliminary cues to guide physiological selection and training prescription in female FRs aiming to officiate male-soccer matches. Only 2.5% of the female FRs showed V[Combining Dot Above]O2max higher than the mean values of male FRs when using the scaled notation (0.68). Female FRs aiming to officiate male competitions should consider training intensities at anaerobic threshold speed (13 km·h, 95% heart rate max) when developing aerobic fitness. Given the very large sex differences in aerobic performance, strength/power training should be proposed to perspective female top-class FRs.


#5 Return to Play After Hip Arthroscopic Surgery for Femoroacetabular Impingement in Professional Soccer Players
Reference: Am J Sports Med. 2017 Nov 1:363546517738741. doi: 10.1177/0363546517738741. [Epub ahead of print]
Authors: Locks R, Utsunomiya H, Briggs KK, McNamara S, Chahla J, Philippon MJ
Summary: Arthroscopic hip surgery has been shown to be effective in returning professional athletes back to play at a high level of performance in different sports. Limited information exists regarding professional soccer players and their return to play. The purpose of the study was to determine the rate and time to return to sport for professional soccer players after hip arthroscopic surgery for the treatment of femoroacetabular impingement (FAI) and to identify possible risk factors associated with a delay in returning to play. Professional soccer players who underwent hip arthroscopic surgery for FAI by a single surgeon between 2005 and 2015 were evaluated. Data retrieved from www.mlssoccer.com , www.fifa.com , www.transfermarkt.co.uk , and www.wikipedia.org included information on each player's professional career, participation on the national team, length of professional career before surgery, number of appearances (games) before surgery, time between surgery and first appearance in a professional game, and number of appearances after surgery. Other data were obtained from the patient's medical records. Twenty-four professional soccer players (26 hips) were included. The mean age at surgery was 25.0 ± 4.0 years (range, 19-32 years). A total of 96% of patients were able to return to play at the professional level. The mean time between surgery and the first professional game played was 9.2 months (range, 1.9-24.0 months). On average, players played in 70 games after surgery (range, 0-224). National team players were able to return to play significantly earlier than the rest of the players (median, 5.7 months vs 11.6 months, respectively; P = .018). Severe chondral damage and microfracture did not interfere with return to play. The arthroscopic management of FAI in symptomatic professional soccer players allowed 96% of them to return to play. Players with national team experience were able to return to play earlier than those without it. Severe chondral damage and microfracture did not interfere with return to play.


#6 Effects of an Interpersonal Style Intervention for Coaches on Young Soccer Players' Motivational Processes
Reference: J Hum Kinet. 2017 Oct 20;59:107-120. doi: 10.1515/hukin-2017-0151. eCollection 2017 Oct.
Authors: Pulido JJ, Sanchez-Oliva D, Leo FM, Matos S, Garcia-Calvo T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680690/pdf/hukin-59-107.pdf
Summary: The main goal of the study was to assess the effects of an intervention programme developed with soccer coaches, based on promoting strategies to optimise the satisfaction of the basic psychological needs of athletes. Eight soccer coaches, aged between 19 and 50 years (M = 32.5; SD = 14.34), participated in the study. They were selected intentionally (without academic or federative training) and divided equally into a control and an experimental group by random peer selection. Also, 109 soccer players, aged between 11 and 15 years (M = 13.78; SD = 1.38), divided into a control group (CG; n = 56) and an experimental group (EG; n = 53), participated in the experiment. The training programme (12 hours) was aimed to develop methodological and motivational strategies to promote autonomy, competence and relatedness need satisfaction among the players. The results showed that the participants in the EG decreased competence and relatedness control, while significantly increased (post-intervention) competence and relatedness needs satisfaction. Moreover, values for the EG did not decrease for autonomy, competence frustration and amotivation, while they increased for the sport commitment. Also, intrinsic motivation decreased in both groups (greater decrease in the CG). In conclusion, we can affirm the effectiveness of the training programme to create an environment of "bright side" motivation, and reduce thwarting styles, needs frustration and low self-determination levels.


#7 Mental Strategies Predict Performance and Satisfaction with Performance among Soccer Players
Reference: J Hum Kinet. 2017 Oct 20;59:79-90. doi: 10.1515/hukin-2017-0149. eCollection 2017 Oct.
Authors: Kruk M, Blecharz J, Boberska M, Zarychta K, Luszczynska A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680688/pdf/hukin-59-079.pdf
Summary: This study investigated the changes in mental strategies across the season and their effects on performance and satisfaction with individual performance. Data were collected three times: at the pre-season at Time 1 (T1; baseline), in the mid-season at Time 2 (T2; two-month follow-up), and at the end-of-season at Time 3 (T3; nine-month follow-up) among male soccer players (N = 97) aged 16-27. Athletes completed the questionnaires assessing the use of nine psychological strategies in competition and the level of satisfaction with individual performance. Endurance performance was measured objectively with a 300 m run. A high level of relaxation (T1) explained better 300 m run performance (T3) and a high level of self-talk explained a higher satisfaction with individual performance (T3). A rare use of distractibility and emotional control (T1) predicted a higher level of satisfaction with individual performance (T3). No predictive role of other psychological strategies was found. The use of emotional control, relaxation, and distractibility increased over the season, whereas the use of imagery and negative thinking declined. Besides the roles of self-talk, imagery, relaxation and goal-setting, the effects of distractibility and emotional control should be taken into account when considering athletes' mental training programs.


#8 Low perceptual sensitivity to altered video speed in viewing a soccer match
Reference: Sci Rep. 2017 Nov 13;7(1):15379. doi: 10.1038/s41598-017-15619-8.
Authors: de'Sperati C, Baud Bovy G
Download link: https://www.nature.com/articles/s41598-017-15619-8.pdf
Summary: When watching videos, our sense of reality is continuously challenged. How much can a fundamental dimension of experience such as visual flow be modified before breaking the perception of real time? Here we found a remarkable indifference to speed manipulations applied to a popular video content, a soccer match. In a condition that mimicked real-life TV watching, none of 100 naïve observers spontaneously noticed speed alterations up/down to 12%, even when asked to report motion anomalies, and showed very low sensitivity to video speed changes (Just Noticeable Difference, JND = 18%). When tested with a constant-stimuli speed discrimination task, JND was still high, though much reduced (9%). The presence of the original voice-over with compensation for pitch did not affect perceptual performance. Thus, our results document a rather broad tolerance to speed manipulations in video viewing, even under attentive scrutiny. This finding may have important implications. For example, it can validate video compression strategies based on sub-threshold temporal squeezing. This way, a soccer match can last only 80 min and still be perceived as natural. More generally, knowing the boundaries of natural speed perception may help to optimize the flow of artificial visual stimuli which increasingly surround us.


#9 A prospective investigation to evaluate risk factors for lower extremity injury risk in male youth soccer players
Reference: Scand J Med Sci Sports. 2017 Nov 11. doi: 10.1111/sms.13013. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: There is an inherent risk of injury in male youth football; however, pertinent risk factors for injury have yet to be examined. This study used a prospective cohort design with 357 elite male youth football players (aged 10-18 years) assessed during the pre-season period and then monitored during the season recording all non-contact lower extremity injuries. Screening tests included: single leg hop for distance (SLHD); 75% of maximum hop and stick (75%Hop); single leg countermovement jump (SLCMJ); and the tuck jump assessment (TJ). Players were divided into sub-groups based on chronological age. SLCMJ peak landing vertical ground reaction force (pVGRF) asymmetry was the most prominent risk factor (U11-U12's, OR 0.90, p = 0.04; and U15-U16's, OR 0.91, p < 0.001). Maturational offset (OR 0.58, p = 0.04), lower right leg SLCMJ pVGRF relative to body weight (OR 0.36, p = 0.03) and advanced chronological age (OR 3.62, p = 0.04) were also significantly associated with heightened injury risk in the U13-U14's, U15-U16's and U18's respectively. Univariate analyses showed combinations of anthropometric and movement screening risk factors were associated with heightened risk of lower extremity injury; however, there was variability across the different chronological age groups. Greater SLCMJ pVGRF asymmetry, lower right leg SLCMJ pVGRF %BW, later maturation and advanced chronological age are potential risk factors for injury in elite male youth football players, although the strength of these relationships were often low to moderate. In addition, risk factors are likely to change at different stages of development.


#10 Kinematic analysis of pressing situations in female collegiate football games: New insight into ACL injury causation
Reference: Scand J Med Sci Sports. 2017 Nov 16. doi: 10.1111/sms.13018. [Epub ahead of print]
Authors: Sasaki S, Koga H, Krosshaug T, Kaneko S, Fukubayashi T
Summary: The most common events during which anterior cruciate ligament (ACL) injuries occur in football are pressing situations. This study aimed to describe the knee and hip joint kinematics during pressing situations in football games in order to identify kinematic patterns in actions with a high risk for ACL injuries. We filmed 5 female collegiate football matches and identified 66 pressing situations. Five situations with a large distance between the trunk and foot placements in the sagittal plane were analysed using a model-based image-matching technique. The mean knee flexion angle at initial contact (IC) was 13° (range, 8°-28°), and increased by 11° (95% confidence interval [CI], 3°-14°) at 40 ms after IC. As for knee adduction and rotation angles, the knee positions were close to neutral at IC, and only minor knee angular changes occurred later in the sequences. The mean hip flexion was 25° (range, 8°-43°) at IC, and increased by 22° (95% CI, 11°-32°) after 100 ms. The hip was also externally rotated by 7° (range, -19° to 3°) at IC, and gradually rotated internally, reaching 10° of internal rotation (range, -5° to 27°) at 100 ms after IC. This study suggests that the observed knee valgus, internal hip and knee rotation, and static hip flexion previously reported in non-contact ACL injury events are unique to injury situations. In contrast, neither rapid knee valgus nor increased internal rotation was seen in non-injury pressing manoeuvres.


#11 The prognostic value of physiological and physical characteristics in youth soccer: A systematic review
Reference: Eur J Sport Sci. 2017 Nov 21:1-13. doi: 10.1080/17461391.2017.1386719. [Epub ahead of print]
Authors: Murr D, Raabe J, Honer O
Download link: http://www.tandfonline.com/doi/abs/10.1080/17461391.2017.1386719?needAccess=true#aHR0cDovL3d3dy50YW5kZm9ubGluZS5jb20vZG9pL3BkZi8xMC4xMDgwLzE3NDYxMzkxLjIwMTcuMTM4NjcxOT9uZWVkQWNjZXNzPXRydWVAQEAw
Summary: Talent identification and selection in soccer is typically based on subjective evaluations of experienced coaches. Recently, there has been a trend to complement these subjective assessments with objective tests. However, there is currently no comprehensive overview of the prognostic relevance of objective measurements in youth soccer. Therefore, the primary purpose of the current study was to systematically review published empirical studies related to the prognostic relevance of physiological (e.g. endurance and speed) and physical characteristics (i.e. height and weight). Of 6876 initially identified studies, nine articles were included. In those studies, endurance (nine studies), change of direction (seven), height (seven), and weight (seven) received the most meaningful consideration within the literature. In regard to physiological predictors, between 16 and 29 effect sizes were tested for endurance, sprint, and change of direction, and about half of them were found to be significant with small to moderate effects (0.37 ≤ Mdn(d) ≤ 0.57). In addition, while only investigated in two studies all tested effect sizes for repeated sprint ability were found to be significant. Despite their frequent consideration in the literature, low numbers of significant effect sizes (≤ 26%) and magnitude (0.23 ≤ Mdn(d) ≤ 0.29) were found for the physical predictors height and weight. Overall, results appear to be dependent on the respective study design and, in particular, moderator variables (i.e. soccer development stage, performance level T1/T2, prognostic period, and sample size). Consequently, additional research seems warranted to more comprehensively investigate the predictive relevance of the individual characteristics using more homogeneous study designs.



American Football
#1 Associations between BMI Change and Cardiometabolic Risk in Retired Football Players
Reference: Med Sci Sports Exerc. 2017 Nov 14. doi: 10.1249/MSS.0000000000001492. [Epub ahead of print]
Authors: Trexler ET, Smith-Ryan AE, DeFreese JD, Marshall SW, Guskiewicz KM, Kerr ZY
Summary: Elevated rates of cardiometabolic diseases have been observed in former American football players. The current study sought to determine if change in body mass index (ΔBMI) following retirement influences the prevalence of coronary heart disease (CHD), diabetes, or high blood pressure (HBP) in former professional football players. Retired professional football players (n=3,729) were sent a survey with questions regarding health status, playing history, and demographic information. Self-reported BMI at the time of retirement was subtracted from current self-reported BMI to calculate ΔBMI. Prevalence of CHD, diabetes, and HBP were determined by asking participants if they had ever been diagnosed by a healthcare professional. Binomial regression with a Poisson residual and robust variance estimation was used to compute crude prevalence ratios (PRs) and 95% confidence intervals (CI) for each outcome. Adjusted PRs were calculated by adjusting for BMI at the time of retirement, age, years of football experience, race, exercise habits, alcohol use, steroid history, smoking history, and playing position. Complete data were available for 2,062 respondents. Prevalence of CHD increased 25-31% for each 5-point increase in ΔBMI following retirement (Crude PR: 1.25; 95%CI: 1.03-1.52; p=0.026; Adjusted PR: 1.31; 95%CI: 1.11-1.55; p=0.001). Diabetes prevalence increased 69-88% for each 5-point ΔBMI increase (Crude: 1.88; 95%CI: 1.45-2.44; p<0.001; Adjusted: 1.69; 95%CI: 1.32-2.15; p<0.001). A 5-point increase in ΔBMI was associated with a 35-40% increase in HBP prevalence (Crude: 1.40; 95%CI: 1.27-1.53; p<0.001; Adjusted: 1.35; 95%CI: 1.24-1.47; p<0.001). After controlling for relevant covariates, post-retirement ΔBMI was positively and independently associated with prevalence of CHD, diabetes, and HBP. Post-retirement interventions using diet and/or exercise to influence body composition may improve long-term health in retired football players.


#2 Calling Injury Timeouts for the Medical Evaluation of Concussion: Determinants of Collegiate Football Officials' Behavior
Reference: J Athl Train. 2017 Nov 8. doi: 10.4085/1062-6050-52.11.17. [Epub ahead of print]
Authors: Kroshus E, Parsons J, Hainline B
Summary: Sports officials can play an important role in concussion safety by calling injury timeouts so that athletic trainers can evaluate athletes with possible concussions. Understanding the determinants of whether officials call an injury timeout when they suspect a concussion has important implications for the design of interventions that better support officials in this role. The objective of the study was to assess the knowledge of US collegiate football officials about concussion symptoms and to determine the associations between knowledge, perceived injunctive norms, and self-efficacy and calling injury timeouts for suspected concussions in athletes. 3074 US collegiate football officials contacted, 1324 (43% response rate) participated.  Concussion knowledge, injunctive norms (belief about what others would want them to do), and behavioral self-efficacy (confidence in their ability to call injury timeouts for suspected concussions in athletes during challenging game-day conditions) were used as outcome measures. Officials reported calling approximately 1 injury timeout for a suspected concussion every 4 games during the 2015 season. Structural equation modeling indicated that officials with more concussion-symptom knowledge had greater behavioral self-efficacy. Independent of an official's symptom knowledge, injunctive norms that were more supportive of calling an injury timeout were associated with greater self-efficacy. Concussion education for officials is important because when officials are aware of concussion symptoms, they are more confident in calling injury timeouts. Beyond increasing symptom knowledge, fostering sports environments that encourage concussion safety in all stakeholder groups can support officials in calling injury timeouts. Athletic trainers can help create sports environments that support proactive concussion identification by educating stakeholders, including officials, about the importance of concussion safety. When officials believe that other stakeholders support concussion safety, they are more likely to call injury timeouts if they suspect a concussion has occurred.


#3 Postmortem Autopsy-Confirmation of Antemortem [F-18]FDDNP-PET Scans in a Football Player With Chronic Traumatic Encephalopathy
Reference: Neurosurgery. 2017 Nov 10. doi: 10.1093/neuros/nyx536. [Epub ahead of print]
Authors: Omalu B, Small GW, Bailes J, Ercoli LM, Merrill DA, Wong KP, Huang SC, Satyamurthy N, Hammers JL, Lee J, Fitzsimmons RP, Barrio JR
Summary: Currently, only presumptive diagnosis of chronic traumatic encephalopathy (CTE) can be made in living patients. We present a modality that may be instrumental to the definitive diagnosis of CTE in living patients based on brain autopsy confirmation of [F-18]FDDNP-PET findings in an American football player with CTE. [F-18]FDDNP-PET imaging was performed 52 mo before the subject's death. Relative distribution volume parametric images and binding values were determined for cortical and subcortical regions of interest. Upon death, the brain was examined to identify the topographic distribution of neurodegenerative changes. Correlation between neuropathology and [F-18]FDDNP-PET binding patterns was performed using Spearman rank-order correlation. Mood, behavioral, motor, and cognitive changes were consistent with chronic traumatic myeloencephalopathy with a 22-yr lifetime risk exposure to American football. There were tau, amyloid, and TDP-43 neuropathological substrates in the brain with a differential topographically selective distribution. [F-18]FDDNP-PET binding levels correlated with brain tau deposition (rs = 0.59, P = .02), with highest relative distribution volumes in the parasagittal and paraventricular regions of the brain and the brain stem. No correlation with amyloid or TDP-43 deposition was observed. [F-18]FDDNP-PET signals may be consistent with neuropathological patterns of tau deposition in CTE, involving areas that receive the maximal shearing, angular-rotational acceleration-deceleration forces in American football players, consistent with distinctive and differential topographic vulnerability and selectivity of CTE beyond brain cortices, also involving midbrain and limbic areas. Future studies are warranted to determine whether differential and selective [F-18]FDDNP-PET may be useful in establishing a diagnosis of CTE in at-risk patients.


#4 Intracranial Ischemic Infarct Due to Blunt Force Trauma in a High School Football Player
Reference: Cureus. 2017 Sep 7;9(9):e1659. doi: 10.7759/cureus.1659.
Authors: Esianor BI, Haider AS, Engelhardt MI, Osumah T, Vayalumkal S, Thakur R, Leonard D, Haithcock J, Layton KF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5675602/pdf/cureus-0009-00000001659.pdf
Summary: Ischemic stroke is an uncommon cause of death among teenagers and young adults; however, the etiologies differ when compared to ischemic strokes in older individuals. Large-vessel atherosclerosis and small-vessel disease causing ischemic stroke are rare for the teenage population, while cervicocerebral arterial dissections account for up to 20% of ischemic strokes. Here, we present the case of a 16-year-old male who developed internal carotid artery dissection (ICAD) after a head injury and subsequently developed ischemic stroke and seizures.


#6 Posterolateral Corner Injuries of the Knee at the National Football League Combine: An Imaging and Outcomes Analysis
Reference: Arthroscopy. 2017 Nov 13. pii: S0749-8063(17)31162-3. doi: 10.1016/j.arthro.2017.08.303. [Epub ahead of print]
Authors: Chahla J, Kennedy NI, Cinque ME, Sanchez G, Logan C, Vopat BG, Beaulieu-Jones B, Price M, Whalen J, LaPrade RF, Provencher MT
Summary: (1) To determine the epidemiology, examination findings, imaging findings, and associated injuries of posterolateral corner (PLC) injuries in players participating in the National Football League (NFL) Combine and (2) to evaluate the impact of PLC injuries on performance compared with matched controls. All PLC injuries identified at the NFL Combine between 2009 and 2015 were reviewed. The inclusion criteria were any player who had clinical findings or a previous surgical procedure consistent with a PLC injury and who participated in medical and performance testing at the NFL Combine. PLC injuries were identified by evaluating the side-to-side difference in lateral-compartment laxity with varus stress and reviewing magnetic resonance imaging studies. NFL performance outcomes (draft position and number of games played or started within the first 2 years) were compared with matched controls. Of the 2,285 players assessed at the NFL Combine, 16 (0.7%) were identified with a history of a grade II or III PLC tear and surgical management whereas 7 additional players (0.3%) had a PLC injury diagnosed on clinical examination, for 23 total PLC injuries (1%). On examination, 13 of 22 knees (59%) were shown to be stable; however, most of those managed surgically had significantly improved stability (13 of 15 stable) versus none of those managed nonsurgically (0 of 7 stable). Surgically managed PLC-injured athletes started significantly fewer games than controls (5.3 vs 10.5, P = .03); the mean draft position for players with surgically treated PLC injuries was 139.7 versus controls' mean draft position of 111.3. Of the 16 athletes treated operatively, 2 reported a PLC injury recurrence; both were managed nonoperatively. A small percentage of players at the NFL Combine had evidence of a previous PLC injury (1%), with 0.4% having residual varus asymmetry on clinical examination. A worse overall mean draft position for isolated PLC-injured athletes versus controls was found: 132.8 versus 111.3 (P = .02). It is recommended that the use of varus stress radiographs be considered for NFL Combine athletes to objectively determine their grade of injury. LEVEL OF EVIDENCE: Level IV, retrospective case series.


Australian Football
#1 Phases of match-play in professional Australian Football: Descriptive analysis and reliability assessment
Reference: J Sci Med Sport. 2017 Oct 23. pii: S1440-2440(17)31671-7. doi: 10.1016/j.jsams.2017.10.021. [Epub ahead of print]
Authors: Rennie MJ, Watsford ML, Spurrs RW, Kelly SJ, Pine MJ
Summary: The purpose was to examine the frequency and time spent in the phases of Australian Football (AF) match-play and to assess the intra-assessor reliability of coding these phases of match-play. Video footage of 10 random quarters of AF match-play were coded by a single researcher. Phases of offence, defence, contested play, umpire stoppage, set shot and goal reset were coded using a set of operational definitions. Descriptive statistics were provided for all phases of match-play. Following a 6-month washout period, intra-coder reliability was assessed using typical error of measurement (TEM) and intra-class correlation coefficients (ICC). A quarter of AF match-play involved 128±20 different phases of match-play. The highest proportion of match-play involved contested play (25%), followed by offence (18%), defence (18%) and umpire stoppages (18%). The mean duration of offence, defence, contested play, umpire stoppage, set shot and goal reset were 14, 14, 10, 11, 28 and 47s, respectively. No differences were found between the two coding assessments (p>0.05). ICCs for coding the phases of play demonstrated very high reliability (r=0.902-0.992). TEM of the total time spent in each phase of play represented moderate to good reliability (TEM=1.8-9.3%). Coding of offence, defence and contested play tended to display slightly poorer TEMs than umpire stoppages, set shots and goal resets (TEM=8.1 vs 4.5%). Researchers can reliably code the phases of AF match-play which may permit the analysis of specific elements of competition.


#2 Eight Week Return to Play following Latarjet Shoulder Reconstruction in an Australian Football Player: A Case Report
Reference: J Sport Rehabil. 2017 Nov 15:1-28. doi: 10.1123/jsr.2017-0194. [Epub ahead of print]
Authors: Murphy M, Stockden M, Withers K, Breidahl W, Charlesworth J
Summary: Anterior shoulder dislocations are a common injury in many sports resulting in extended time lost from play with an extremely high recurrence rate in young athletes playing high risk sport. Latarjet shoulder reconstruction is a common surgical procedure used to prevent subsequent dislocation with an expected rehabilitation timeframe of between four to six months before return to play. A 21-year-old male Australian football player experienced two left sided shoulder dislocations before undergoing a left Latarjet shoulder reconstruction. He was assessed clinically and with magnetic resonance imaging which revealed significant tearing of the anterior labrum. We theorized maximal glenohumeral stability occurs after bony healing of the coracoid onto the glenoid at six weeks. The patient then underwent an eight-week structured and graduated rehabilitation program aimed at preventing loss of shoulder range of motion, muscle and functional capacity and returned to play at eight weeks post injury with no complications or recurrence at twelve month follow-up. This is the first time an eight-week rehabilitation following Latarjet shoulder reconstruction has been reported. In athletes with anterior glenohumeral dislocation who require accelerated return to play, a Latarjet reconstruction with an eight-week rehabilitation protocol can be considered.

Mon

27

Nov

2017

Football is...(#45)

Coach feedback to influence intensity

Fri

24

Nov

2017

Football is ...(#44)

Inter-player, inter-team and inter-line = team's tactical orientation

Thu

23

Nov

2017

Football is ...(#43)

End of warm-up = ballistic stretching with SSC activity

Wed

22

Nov

2017

Latest research in football - week 46 - 2017

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 Hamstring Injuries in Professional Soccer Players: Extent of MRI-Detected Edema and the Time to Return to Play
Reference: Sports Health. 2017 Nov 1:1941738117741471. doi: 10.1177/1941738117741471. [Epub ahead of print]
Authors: Crema MD, Godoy IRB, Abdalla RJ, de Aquino JS, Ingham SJM, Skaf AY
Summary: Discrepancies exist in the literature regarding the association of the extent of injuries assessed on magnetic resonance imaging (MRI) with recovery times. Thr hypothesis was that MRI-detected edema in grade 1 hamstring injuries does not affect the return to play (RTP). Grade 1 hamstring injuries from 22 professional soccer players were retrospectively reviewed. The extent of edema-like changes on fluid-sensitive sequences from 1.5-T MRI were evaluated using craniocaudal length, percentage of cross-sectional area, and volume. The time needed to RTP was the outcome. Negative binomial regression analysis tested the measurements of MRI-detected edema-like changes as prognostic factors. The mean craniocaudal length was 7.6 cm (SD, 4.9 cm; range, 0.9-19.1 cm), the mean percentage of cross-sectional area was 23.6% (SD, 20%; range, 4.4%-89.6%), and the mean volume was 33.1 cm3 (SD, 42.6 cm3; range, 1.1-161.3 cm3). The mean time needed to RTP was 13.6 days (SD, 8.9 days; range, 3-32 days). None of the parameters of extent was associated with RTP. The extent of MRI edema in hamstring injuries does not have prognostic value.


#2 Hip Strength as a Predictor of Ankle Sprains in Male Soccer Players: A Prospective Study
Reference: J Athl Train. 2017 Nov 8. doi: 10.4085/1062-6050-52.11.18. [Epub ahead of print]
Authors: Powers CM, Ghoddosi N, Straub RK, Khayambashi K
Summary: Diminished hip-abductor strength has been suggested to increase the risk of noncontact lateral ankle sprains. The purpose was to determine prospectively whether baseline hip-abductor strength predicts future noncontact lateral ankle sprains in competitive male soccer players. Two hundred ten competitive male soccer players participated in this study.  Before the start of the sport season, isometric hip-abductor strength was measured bilaterally using a handheld dynamometer. Any previous history of ankle sprains, body mass index, age, height, and weight was documented. During the sport season (30 weeks), ankle injury status was recorded by team medical providers. Injured athletes were further classified based on the mechanism of injury. Only data from injured athletes who sustained noncontact lateral ankle sprains were used for analysis. Postseason, logistic regression was used to determine whether baseline hip strength predicted future noncontact lateral ankle sprains. A receiver operating characteristic curve was constructed for hip strength to determine the cutoff value for distinguishing between high-risk and low-risk outcomes. A total of 25 noncontact lateral ankle sprains were confirmed, for an overall annual incidence of 11.9%. Baseline hip-abductor strength was lower in injured players than in uninjured players (P = .008). Logistic regression indicated that impaired hip-abductor strength increased the future injury risk (odds ratio = 1.10 [95% confidence interval = 1.02, 1.18], P = .010). The strength cutoff to define high risk was ≤33.8% body weight, as determined by receiver operating characteristic curve analysis. For athletes classified as high risk, the probability of injury increased from 11.9% to 26.7%. Reduced isometric hip-abductor strength predisposed competitive male soccer players to noncontact lateral ankle sprains.


#3 Nonsurgical Management of an Anterior Cruciate Ligament-Deficient Knee in a Women's Soccer Player: A Validation Clinical Case Report
Reference: J Athl Train. 2017 Nov 8. doi: 10.4085/1062-6050.52.11.21. [Epub ahead of print]
Authors: Gray CE, Hummel C, Lazenby T
Summary: A collegiate women's soccer player sustained an isolated anterior cruciate ligament (ACL) tear and expressed a desire to continue her season without surgical intervention. Using the results of a randomized controlled trial and published clinical guidelines, the clinicians classified the patient as an ACL-deficient coper. The patient completed her soccer season without incident, consistent with the findings of the established clinical guidelines. However, 6 months later, she sustained a meniscal tear, which was not unexpected given that 22% of ACL-deficient copers in the randomized controlled trial incurred a meniscal tear within 24 months of ACL injury.


#4 Risk Factors for Lower Extremity Overuse Injuries in Female Youth Soccer Players
Reference: Orthop J Sports Med. 2017 Oct 23;5(10):2325967117733963. doi: 10.1177/2325967117733963. eCollection 2017 Oct.
Authors: O'Kane JW, Neradilek M, Polissar N, Sabado L, Tencer A, Schiff MA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5656111/pdf/10.1177_2325967117733963.pdf
Summary: Youth soccer injuries are common and of increasing concern, with sport specialization occurring at younger ages. Limited research is available regarding overuse injuries and risk factors in young female athletes. The purpose was to identify the number and rate of overuse injuries in female soccer players (ages 12-15 years), describe the anatomic location and type of injury, and evaluate contributing risk factors. A total of 351 female youth soccer players, ages 12 to 15 years, from Washington State were evaluated from 2008 to 2012. Players with lower extremity overuse injuries were identified through weekly emails and were interviewed by telephone to obtain data on injury type and body region. We evaluated the association between overuse injuries and preseason risk factors, including joint hypermobility, hip and knee muscle strength, and jump biomechanics, using Poisson regression to estimate relative risk (RR) and 95% CIs. The incidence rate for first-time lower extremity overuse injuries was 1.7 per 1000 athlete-exposure hours (AEH; 95% CI, 1.4-2.2), and that for repeat injuries was 3.4 per 1000 AEH (95% CI, 2.1-5.6). Knee injuries accounted for 47% of overuse injuries. Increased valgus was associated with a 3.2-fold increased risk (95% CI, 1.52-6.71) for knee injury. A 1-standard deviation (SD) increase in hamstring strength was associated with a 35% decreased risk (RR, 0.65; 95% CI, 0.46-0.91) for overuse knee injuries, and a 1-SD increase in quadriceps strength was associated with a 30% decreased risk (RR, 0.70; 95% CI, 0.50-0.98). A 1-SD increase in hip flexor strength was associated with a 28% decreased risk (RR, 0.72; 95% CI, 0.51-1.00) for overuse knee injuries, and a 1-SD increase in external rotation strength was associated with a 35% decreased risk (RR, 0.65; 95% CI, 0.46-0.91). Playing on more than 1 soccer team was associated with a 2.5-fold increased risk (95% CI, 1.08-5.35) for overuse knee injuries, and participating in other physical activities was associated with a 61% decreased risk (odds ratio, 0.39; 95% CI, 0.15-0.81). In this study, lower extremity overuse injuries in female youth soccer players affected primarily the knee. Lower knee separation distance, decreased lower extremity strength, and playing on more than 1 soccer team increased injury risk.


#5 Comparison of body fat percentage of male soccer players of different competitive levels, playing positions and age groups: a meta-analysis
Reference: J Sports Med Phys Fitness. 2017 Nov 7. doi: 10.23736/S0022-4707.17.07941-5. [Epub ahead of print]
Authors: Slimani M, Znazen H, Hammami A, Bragazzi NL
Summary: The aim of the present meta-analysis was to compare the body fat percentage (%) between male soccer players of different competitive levels, playing positions and age groups. The systematic search was conducted using different databases and according to the Population/Intervention or Exposure/Comparison/Outcome(s) [PICO] criteria. Higher % values of body fat in lower-level soccer players than higher-level counterparts (ES=0.18, 95% CI -0.86 to -0.14, p=0.006) were noted. Higher body fat % values in goalkeepers than defenders (ES=0.21, 95% CI -1.17 to -0.34, p<0.001), midfielders (ES=0.26, 95% CI -1.50 to -0.45, p<0.001) and forwards (ES=0.18, 95% CI -1.26 to -0.53, p<0.001) were observed. There was no significant association between % of body fat and age (p=0.86). In conclusion, body fat % clearly distinguished higher- from lower-level soccer players. These findings also imply that body fat % differ as a function of positional role in soccer and that sports scientists, coaches, and strength and conditioning professionals need to be aware of the specific positional requirements in soccer in terms of body fat. However, due to some limitations of the present meta-analysis (high statistically significant heterogeneity and evidence of publication bias), further studies are urgently needed in the field.


#6 Muscle injury rate in professional football is higher in matches played within 5 days since the previous match: a 14-year prospective study with more than 130000 match observations
Reference: Br J Sports Med. 2017 Nov 3. pii: bjsports-2016-097399. doi: 10.1136/bjsports-2016-097399. [Epub ahead of print]
Authors: Bengtsson H, Ekstrand J, Walden M, Hägglund M
Summary: The association between match congestion and injury rates in professional football has yielded conflicting results. The aim was to analyse associations between match congestion on an individual player level and injury rates during professional football matches. Data from a prospective cohort study of professional football with 133 170 match observations were analysed with Poisson regressions. Associations between short-term match congestion, defined as number of days between two match exposures (≤3, 4, 5, 6 and 7-10 days) and injury rates were analysed. To analyse the influence of long-term match congestion, defined as individual match exposure hours in the 30 days preceding a match, observations were categorised into three groups (low, ≤4.5; medium, >4.5 to ≤7.5; and high, >7.5 hours). No differences in total match injury rates were found between the reference category (≤3 days) and the other categories of short-term congestion. Muscle injury rates were significantly lower in matches preceded by 6 (rate ratio (RR) 0.79; 95% CI 0.65 to 0.95) or 7-10 days (RR 0.81; 95% CI 0.71 to 0.93) compared with ≤3 days since the last match exposure. No differences in total and muscle injury rates between the three long-term match congestion groups were found. In this study of male professional football players, there were no match congestion-related differences in total match injury rates, but muscle injury rates during matches were lower when players were given at least 6 days between their match exposures.


#7 Change in knee flexor torque after fatiguing exercise identifies previous hamstring injury in football players
Reference: Scand J Med Sci Sports. 2017 Nov 8. doi: 10.1111/sms.13007. [Epub ahead of print]
Authors: Lord C, Ma'ayah F, Blazevich AJ
Summary: Muscular fatigue and inter-limb strength asymmetry are factors known to influence hamstring injury risk, however limb-specific exacerbation of knee flexor (hamstrings) torque production after fatiguing exercise has previously been ignored. To investigate changes in muscular force production before and after sport-specific (repeated-sprint) and non-specific (knee extension-flexion) fatiguing exercise, and explore the sensitivity and specificity of isokinetic endurance (i.e. muscle-specific) and single-leg vertical jump (i.e. whole limb) tests to identify previous hamstring injury. 20 Western Australia State League footballers with previous unilateral hamstring injury and 20 players without participated. Peak concentric knee extensor and flexor (180°∙s-1 ) torques were assessed throughout an isokinetic endurance test, which was then repeated alongside a single-leg vertical jump test (SLVJ) before and after maximal repeated-sprint exercise. Greater reductions in isokinetic knee flexor torque (-16%) and the concentric hamstring:quadriceps peak torque ratio (-15%) were observed after repeated-sprint running only in the injured (kicking) leg and only in the previously injured subjects. Changes in (1) peak knee flexor torque after repeated-sprint exercise, and (2) the decline in knee flexor torque during the isokinetic endurance test measured after repeated-sprint exercise, correctly identified the injured legs (N=20) within the cohort (N=80) with 100% specificity and sensitivity. Decreases in peak knee flexor torque and knee flexor torque during an isokinetic endurance test after repeated-sprint exercise identified previous hamstring injury with 100% accuracy. Changes in knee flexor torque, but not SLVJ, should be tested to determine its prospective ability to predict hamstring injury in competitive football players.


#8 Effects of special exercise programs on functional movement screen scores and injury prevention in preprofessional young football players
Reference: J Exerc Rehabil. 2017 Oct 30;13(5):535-540. doi: 10.12965/jer.1735068.534. eCollection 2017 Oct.
Authors: Dinc E, Kilinc BE, Bulat M, Erten YT, Bayraktar B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5667599/pdf/jer-13-5-535.pdf
Summary: To increase movement capacity and to reduce injury risk in young soccer players by implementing a special functional exercise program based on functional movement screen (FMS) and correctives. 67 young male athletes 14-19 years of age from a Super League Football Club Academy participated in the study. Functional movement patterns were evaluated with FMS assessment protocol. Deep squat, hurdle step, inline lunge, shoulder mobility, active straight leg raise, trunk stability push-up, and rotatory stability were examined in FMS. Considering the FMS scores the number of intervention and control groups were defined as 24 and 43, respectively. Intervention program was composed of 1 hr twice a week sessions in total of 12 weeks with 4 weeks of mobility, 4 weeks of stability, and 4 weeks of integration exercises. At the end of 12-week intervention and control groups were re-evaluated with FMS protocol. Contact and noncontact sports injuries recorded during one season. In intervention group there was statistically significant difference in increase in total FMS scores (P<0.01), deep squat (P≤0.001), hurdle step (P<0.05), inline lunge (P<0.01), and trunk stability push-up (P<0.01). In control group total FMS, deep squat, and trunk stability push-up scores increased with a statistical difference (P<0.01, P<0.05, P≤0.01, respectively). The incidence of noncontact injury in control group was higher than intervention group (P<0.05). Periodic movement screening and proper corrections with functional training is valuable in order to create better movement capacity to build better physical performance and more effective injury prevention.


#9 Heads Up: The Presentation of Schizoaffective Disorder in an Elite College Soccer Player with Prior Concussion
Reference: Harv Rev Psychiatry. 2017 Nov/Dec;25(6):302-310. doi: 10.1097/HRP.0000000000000147.
Authors: Adelsky SJ, Ducharme S, Wilner EK, Yudkoff B, Lejeune S.


American Football
#1 Is Big Truly Bad? Aortic Dilation in Former National Football League Players
Reference: Circ Cardiovasc Imaging. 2017 Nov;10(11). pii: e007157. doi: 10.1161/CIRCIMAGING.117.007157.
Authors: Churchill TW, Baggish AL


#2 Ascending Aortic Dimensions in Former National Football League Athletes
Reference: Circ Cardiovasc Imaging. 2017 Nov;10(11). pii: e006852. doi: 10.1161/CIRCIMAGING.117.006852.
Autors: Gentry JL 3rd, Carruthers D, Joshi PH, Maroules CD, Ayers CR, de Lemos JA, Aagaard P, Hachamovitch R, Desai MY, Roselli EE, Dunn RE, Alexander K, Lincoln AE, Tucker AM, Phelan DM
Summary: Ascending aortic dimensions are slightly larger in young competitive athletes compared with sedentary controls, but rarely >40 mm. Whether this finding translates to aortic enlargement in older, former athletes is unknown. This cross-sectional study involved a sample of 206 former National Football League (NFL) athletes compared with 759 male subjects from the DHS-2 (Dallas Heart Study-2; mean age of 57.1 and 53.6 years, respectively, P<0.0001; body surface area of 2.4 and 2.1 m2, respectively, P<0.0001). Midascending aortic dimensions were obtained from computed tomographic scans performed as part of a NFL screening protocol or as part of the DHS. Compared with a population-based control group, former NFL athletes had significantly larger ascending aortic diameters (38±5 versus 34±4 mm; P<0.0001). A significantly higher proportion of former NFL athletes had an aorta of >40 mm (29.6% versus 8.6%; P<0.0001). After adjusting for age, race, body surface area, systolic blood pressure, history of hypertension, current smoking, diabetes mellitus, and lipid profile, the former NFL athletes still had significantly larger ascending aortas (P<0.0001). Former NFL athletes were twice as likely to have an aorta >40 mm after adjusting for the same parameters. Ascending aortic dimensions were significantly larger in a sample of former NFL athletes after adjusting for their size, age, race, and cardiac risk factors. Whether this translates to an increased risk is unknown and requires further evaluation.


#3 Total And Segmental Body Composition Examination In Collegiate Football Players Using Multifrequency Bia And Dxa
Reference: J Strength Cond Res. 2017 Nov 6. doi: 10.1519/JSC.0000000000002320. [Epub ahead of print]
Authors: Raymond CJ, Dengel DR, Bosch TA
Summary: The current study examined the influence of player position on the agreement between multi-frequency bioelectrical impedance analysis (MfBIA) and dual X-ray absorptiometry (DXA) when assessing total and segmental percent body fat (BF%), fat mass (FM), and fat-free mass (FFM) in NCAA Division I collegiate football athletes. Forty-four male collegiate athletes (age=19±1 yrs; height=1.9±1.0 m; weight=106.4±18.8 kg) participated. Player positions included: offensive linemen (OL; n=7), tight ends (TE; n=4), wide receivers (WR; n=9), defensive linemen (DL; n=6), defensive backs (DB; n=8), linebackers (LB; n=6), and running backs (RB; n=4). Total and segmental body composition measured using MfBIA were compared with values obtained using DXA. Compared to DXA, MfBIA underestimated BF% (3.0±3.8%), total FM (2.5±4.3 kg), arm FM (0.4±0.8 kg), arm FFM (1.4±0.9 kg), leg FM (2.8±2.0 kg), and leg FFM (5.4±2.4 kg) (all p<0.001; arm FM p=0.002) and overestimated total FFM (-2.4±4.5 kg) (p<0.001). Limits of agreement (LOAs) were: ±7.39% (BF%), ±8.50 kg (total FM), ±1.50 kg (arm FM), ±1.83 kg (arm FFM), ±3.83 kg (leg FM), ±4.62 kg (leg FFM), and ±8.83 kg (total FFM). No significant differences were observed between devices for trunk FM (-0.3±3.0 kg; p = 0.565) and trunk FFM (0.4±2.4 kg; p=0.278), with LOAs of ±5.92 kg and ±4.69 kg, respectively. Player position significantly affected all between-device mean body composition measurement differences (adjusted p<0.05), with OL demonstrating the greatest effect on each variable. Therefore, MfBIA does not appear accurate in examining between-player body composition in college football players.


#4 Calling Injury Timeouts for the Medical Evaluation of Concussion: Determinants of Collegiate Football Officials' Behavior
Reference: J Athl Train. 2017 Nov 8. doi: 10.4085/1062-6050-52.11.XX. [Epub ahead of print]
Authors: Kroshus E, Parsons J, Hainline B
Summary: Sports officials can play an important role in concussion safety by calling injury timeouts so that athletic trainers can evaluate athletes with possible concussions. Understanding the determinants of whether officials call an injury timeout when they suspect a concussion has important implications for the design of interventions that better support officials in this role. The objective was to assess the knowledge of US collegiate football officials about concussion symptoms and to determine the associations between knowledge, perceived injunctive norms, and self-efficacy and calling injury timeouts for suspected concussions in athletes. Of the 3074 US collegiate football officials contacted, 1324 (43% response rate) participated. Concussion knowledge, injunctive norms (belief about what others would want them to do), and behavioral self-efficacy (confidence in their ability to call injury timeouts for suspected concussions in athletes during challenging game-day conditions) was used as outcome measures. Officials reported calling approximately 1 injury timeout for a suspected concussion every 4 games during the 2015 season. Structural equation modeling indicated that officials with more concussion-symptom knowledge had greater behavioral self-efficacy. Independent of an official's symptom knowledge, injunctive norms that were more supportive of calling an injury timeout were associated with greater self-efficacy. Concussion education for officials is important because when officials are aware of concussion symptoms, they are more confident in calling injury timeouts. Beyond increasing symptom knowledge, fostering sports environments that encourage concussion safety in all stakeholder groups can support officials in calling injury timeouts. Athletic trainers can help create sports environments that support proactive concussion identification by educating stakeholders, including officials, about the importance of concussion safety. When officials believe that other stakeholders support concussion safety, they are more likely to call injury timeouts if they suspect a concussion has occurred.


#5 Effects of Intravenous Cold Saline on Hyperthermic Athletes Representative of Large Football Players and Small Endurance Runners
Reference: Clin J Sport Med. 2017 Oct 27. doi: 10.1097/JSM.0000000000000505. [Epub ahead of print]
Authors: Morrison KE, Desai N, McGuigan C, Lennon M, Godek SF
Summary: The purpose was to evaluate the cooling effects of intravenous (IV) cold normal (0.9%) saline on hyperthermic athletes. Twelve male participants who were representative of a collegiate cross-country (6) and American football (6) population. Participants underwent body composition analysis using a BodPod. They were placed in an environmentally controlled chamber and brought to a Tc of 39.5°C with dynamic exercise. When temperatures were reached, they were treated with either 2 L of cold saline (CS) (4°C) or intravenous room temperature (22°C) saline (RS) over a ∼30-minute period. Tre was measured with a rectal temperature probe every minute during the treatment period. Total ΔTre (ending Tre - starting Tre) and cooling rate (total change in Tre/time) were measured for each condition, and body composition variables calculated included body surface area (BSA), BSA-to-mass ratio (BSA/mass), lean body mass, and body fat percentage (%BF) (P < 0.05). Statistically significant differences were found in the total ΔTre and cooling rate between the CS and RS trials. The cooling rate for the CS trials was significantly correlated to mass, BSA, BSA/mass, and %BF. In hyperthermic athletes, core temperature was reduced more effectively using chilled saline during IV infusion. Body composition had a significant impact on overall cooling revealing that the smaller and leaner participants cooled at a greater rate. When indicated, CS infusion could be considered for cooling hyperthermic individuals when other methods are not available.


#6 Meniscectomy and Resultant Articular Cartilage Lesions of the Knee Among Prospective National Football League Players: An Imaging and Performance Analysis
Reference: Am J Sports Med. 2017 Nov 1:363546517737991. doi: 10.1177/0363546517737991. [Epub ahead of print]
Authors: Chahla J, Cinque ME, Godin JA, Sanchez G, Lebus GF, Whalen JM, Price MD, Kennedy NI, Moatshe G, LaPrade RF, Provencher MT
Summary: The effect of prior meniscectomy and the resulting reduction in meniscal tissue on a potential National Football League (NFL) player's articular cartilage status and performance remain poorly elucidated. Purpose/Hypothesis: (1) To determine the epidemiology, imaging characteristics, and associated articular cartilage pathology of the knee among players with a previous meniscectomy who were participating in the NFL Combine and (2) to evaluate the effect of these injuries on performance as compared with matched controls. The hypothesis was that players with less meniscal tissue would have worse cartilage status and inferior performance metrics in their first 2 NFL seasons. All athletes with a history of a meniscectomy and magnetic resonance imaging scan of the knee who participated in the NFL Combine (2009-2015) were identified. Medical records and imaging were analyzed, and surgical history, games missed in college, position played, and draft position were documented. The conditions of the meniscus and cartilage were graded with modified ISAKOS scores (International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine) and ICRS scores (International Cartilage Repair Society), respectively. Players with a previous meniscectomy of at least 10% of total medial or lateral meniscal volume excised (ISAKOS meniscus grade ≤8) and matched controls without a significant pre-Combine injury were similarly evaluated and compared by position of play through analysis of draft position, number of games played and started, and how many eligible plays they participated in (snap percentage) within the first 2 NFL seasons. Of the 2285 players who participated in the NFL Combine (2009-2015), 287 players (322 knees) had a prior meniscectomy (206 lateral, 81 medial). Among these players, 247 (85%) had a total of 249 chondral lesions, most commonly on the lateral femoral condyle (111 lesions, 45%). There was a significant inverse correlation found between the ISAKOS medial and lateral meniscus grade and the corresponding compartment chondral lesion grade ( P = .001). A poorer meniscus score was also associated with worse chondral pathology, especially in the lateral compartment. After controlling for position of play, the injury-free control group had a significantly greater number of total games played and games started and higher snap percentage versus those with a prior meniscectomy of at least 10% volume (ISAKOS meniscus grade ≤8). Players with severe chondral lesions (ICRS grade 4) in the medial and lateral compartments had significantly worse performance metrics when compared with matched controls. Previous meniscectomy of at least 10% of total medial or lateral meniscus volume in prospective NFL players was significantly correlated with larger and more severe chondral lesions. Chondral and meniscal defects of the knee were found to result in a significant decrease in objective performance measures during a player's initial NFL career versus matched controls. Given these findings, players with a prior meniscectomy with evidence of chondral damage should be evaluated carefully for their overall functional levels; however, additional work is needed to fully clarify the effect of prior knee meniscal surgery on overall NFL performance.


#7 CranioSacral Therapy, Brain Injury, and American Football: Time for a Convergence
Reference: J Altern Complement Med. 2017 Nov 7. doi: 10.1089/acm.2017.0264. [Epub ahead of print]
Authors: Leskowitz E


#8 Correction to: Impact Performance of Modern Football Helmets
Reference: Ann Biomed Eng. 2017 Oct 25. doi: 10.1007/s10439-017-1948-8. [Epub ahead of print]
Authors: Viano DC, Withnall C, Halstead D
Summary: This erratum is to correct headings listing the impact location and speed in Figs. 5 and 6. The following provides corrected Figs. 5 and 6. The data is unchanged. The authors apologize for any inconvenience this might have caused.


#9 Clinical and Radiologic Outcomes After Scaphoid Fracture: Injury and Treatment Patterns in National Football League Combine Athletes Between 2009 and 2014
Reference: Arthroscopy. 2017 Nov 1. pii: S0749-8063(17)31071-X. doi: 10.1016/j.arthro.2017.08.259. [Epub ahead of print]
Authors: Moatshe G, Godin JA, Chahla J, Cinque ME, Kennedy NI, Sanchez G, Beaulieu-Jones BR, LaPrade RF, Provencher MT
Summary: The purpose was to report on the clinical and radiologic outcomes and complications after surgical treatment in National Football League (NFL) Combine athletes with a history of a scaphoid fracture. The medical records of 2,285 athletes participating in the NFL Combine from 2009 to 2015 were evaluated for a history of scaphoid, hand, or wrist injury. Clinical outcomes, including grip strength, pinch test, range of motion, and presence of pain and stiffness, were recorded. Imaging studies were evaluated for the percentage of healing, fixation treatment type, hardware complications, radiographic deformity, and presence of osteoarthritis. Of the 2,285 athletes evaluated, 56 presented with a history of a scaphoid fracture. Most fractures were in the middle and proximal aspects of the scaphoid. Of the scaphoid fractures, 76% (43 players) were treated with screw fixation. Of the athletes, 36 (72%) had normal range of motion of the affected wrist, 52 (93%) reported no pain, and 44 (83%) reported no stiffness in the affected wrist. The grip strength and pinch strength were 91% and 96%, respectively, of the uninjured side. The fracture was healed in 75% of the cases; however, 34% had degenerative changes. Hardware complications were found in 15% of the athletes. Good clinical outcomes can be achieved after scaphoid fractures in prospective NFL athletes. However, the rates of nonunion (25%), degenerative changes (34%), and hardware complications (15%) in this study suggest the need for close postoperative radiographic follow-up in this population of patients because their athletic demands may lead to higher rates of the aforementioned complications.



Australian Football
#1 Weak Relationships between Stint Duration, Physical and Skilled Match Performance in Australian Football
Reference: Front Physiol. 2017 Oct 23;8:820. doi: 10.3389/fphys.2017.00820. eCollection 2017.
Authors: Corbett DM, Sweeting AJ, Robertson S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5660114/pdf/fphys-08-00820.pdf
Summary: Australian Rules football comprises physical and skilled performance for more than 90 min of play. The cognitive and physiological fatigue experienced by participants during a match may reduce performance. Consequently, the length of time an athlete is on the field before being interchanged (known as a stint), is a key tactic which could maximize the skill and physical output of the Australian Rules athlete. This study developed two methods to quantify the relationship between athlete time on field, skilled and physical output. Professional male athletes (n = 39) from a single elite Australian Rules football club participated, with physical output quantified via player tracking systems across 22 competitive matches. Skilled output was calculated as the sum of involvements performed by each athlete, collected from a commercial statistics company. A random intercept and slope model was built to identify how a team and individuals respond to physical outputs and stint lengths. Stint duration (mins), high intensity running (speeds >14.4 km · hr-1) per minute, meterage per minute and very high intensity running (speeds >25 km·hr-1) per minute had some relationship with skilled involvements. However, none of these relationships were strong, and the direction of influence for each player was varied. Three conditional inference trees were computed to identify the extent to which combinations of physical parameters altered the anticipated skilled output of players. Meterage per minute, player, round number and duration were all related to player involvement. All methods had an average error of 10 to 11 involvements, per player per match. Therefore, other factors aside from physical parameters extracted from wearable technologies may be needed to explain skilled output within Australian Rules football matches.


Gaelic Football
#1 The Influence Of Team Rating On Running Performance In Elite Gaelic Football
Reference: J Strength Cond Res. 2017 Nov 6. doi: 10.1519/JSC.0000000000002316. [Epub ahead of print]
Authors: Mangan S, Malone S, Ryan M, Gahan JM, Warne J, Martin D, O'Neill C, Burns C, Collins K.
Summary: It is currently unknown how team rating influences running performance in Gaelic football. GPS technologies were used to quantify match-running performance within 5 elite Gaelic football teams over a period of 5 years (2012-2016). In total 780 player data sets were collected over 95 matches. Running performance variables included total distance, high-speed distance (≥17 km h) and the percentage of high-speed distance. Team ratings were determined objectively using the Elo Ratings System for Gaelic football. Reference team rating had trivial effects on total distance (p = 0.011, partial η2 = 0.008) and high-speed distance (p = 0.011, partial η2 = 0.008). Opposition team rating had small effects on total distance (p = 0.005, partial η2 = 0.016) and high-speed distance (p = 0.001, partial η2 = 0.020). Top tier teams cover greater total distances and high-speed distance than lower tier teams. Players cover considerably less total distance and high-speed distance against tier 3 and tier 4 teams. Tier 1 players ran a significantly higher percentage of distance at high-speed, than players who played for tier 2 teams (p = 0.020). The competitive advantage of top tier Gaelic football teams is closely linked with their ability to demonstrate a higher physical intensity than lower tier teams.

Tue

21

Nov

2017

Football is...(#42)

Couple of reasons to monitor load

Fri

17

Nov

2017

Football is...(#41)

Individual injury history = possibility to tailor specific program

Wed

15

Nov

2017

Football is...(#40)

Recovery runs in training = improvement in defensive positioning

Wed

15

Nov

2017

Latest research in football - week 45 - 2017

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 Prospective evaluation of injuries occurred during a professional soccer championship in 206 in Sao Paulo
Reference: BrazilActa Ortop Bras. 2017 Sep-Oct;25(5):212-215. doi: 10.1590/1413-785220172505167238.
Authors: Arliani GG, Lara PHS, Astur DC, Pedrinelli A, Pagura JR, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608742/pdf/1413-7852-aob-25-05-00212.pdf
Summary: The aim of the study was to identify the incidence of injuries, their main characteristics, and the way they were managed throughout 2016 in two major series of a professional soccer championship in São Paulo, Brazil. This prospective study used an electronic questionnaire previously developed by the Medical Committee of the Paulista Soccer Federation which was sent to the team doctors after each match. Two hundred and fifty-nine injuries occurred during 361 matches, and the incidence of injury per 1000 hours of game play was 21.32. Strikers were the most affected by injury; the most frequent diagnosis was muscle injury and the legs were predominantly affected. Most of the injuries occurred in the last 15 minutes of the first half and only 7.7% required surgical treatment. Muscle injuries were the most frequent, with most occurring in forwards and in the legs. Approximately half of the injuries occurred after contact and the vast majority was treated without surgery. MRI was the most requested exam and most injuries were classified as moderate (8 to 28 lost play days).


#2 Does decrease in hip range of motion interfere in frontal plane leg alignment in teenage soccer players?
Reference: Eur J Orthop Surg Traumatol. 2017 Oct 27. doi: 10.1007/s00590-017-2066-x. [Epub ahead of print]
Authors: Scaramussa K, de Castro JV, Ellera Gomes JL
Summary: This study determines cross-sectional changes in transverse plane hip range of motion (ROM) in teenager soccer athletes and non-athletes and correlates these measures with changes in frontal plane leg alignment (varus-valgus alignment). Participants were recruited from a major professional soccer club and two local state-run schools in southern Brazil. A total of 396 male participants aged 9-18 years were assessed, 183 soccer players (athlete group; mean age, 13.3 ± 2.7 years) and 213 students (non-athlete group; mean age 14.4 ± 2.5 years). Hip internal rotation (IR) and external rotation (ER) and frontal plane leg alignment were measured in all participants. Changes in transverse plane hip ROM and frontal plane leg alignment were determined. Mean IR was 20.7° ± 5.8° in athletes versus 32.8° ± 2.9° in non-athletes, and mean ER was 36.5° ± 7.4° in athletes versus 46.7° ± 4.8° in non-athletes. Overall, IR was decreased in the athlete group compared to the non-athlete group (P < 0.001). Mean IR and ER were significantly lower in older athletes (P < 0.001), while only ER was significantly lower in older non-athletes (P < 0.001). Varus leg alignment was prevalent at all ages in the athlete group (71.0%, P = 0.153). In the non-athlete group, the occurrence of varus leg alignment was higher in older participants (P = 0.001). Lower mean IR was correlated with more severe varus leg alignment in the athlete group (rs = 0.19; P = 0.009). We found a lower hip ROM, particularly in IR, in teenager soccer players according to the enhancement age group from the sample. But varus alignment of the leg was also prevalent in this group and comes before hip abnormalities started to be detected.


#3 Examination of the external and internal load indicators' association with overuse injuries in professional soccer players
Reference: J Sci Med Sport. 2017 Oct 13. pii: S1440-2440(17)31655-9. doi: 10.1016/j.jsams.2017.10.005. [Epub ahead of print]
Authors: Jaspers A, Kuyvenhoven JP, Staes F, Frencken WGP, Helsen WF, Brink MS
Summary: Research in professional soccer focusing on the relevance of external and internal load indicators for injury prevention is scarce. This study examined the relationship between load indicators and overuse injuries. Data were collected from 35 professional male soccer players over two seasons. Following load indicators were examined: total distance covered (TD), distance covered at high speed (THSR; >20kmh-1), number of accelerations (ACCeff; >1ms-2), number of decelerations (DECeff; <-1ms-2), and rating of perceived exertion (RPE) multiplied by duration. Cumulative 1-, 2-, 3-, 4-weekly loads and acute:chronic workload ratios (ACWR) were calculated and split into low, medium and high groups. Only overuse injuries were included in the analysis to focus on their specific relationship with the load indicators. Generalized estimating equations were applied to analyse the relationship between load indicators and overuse injuries in the subsequent week. In total, 64 overuse injuries were registered. For cumulative loads, results indicated an increased injury risk for higher 2- to 4-weekly loads as indicated by TD, DECeff, and RPE multiplied by duration. For ACWR, a high ratio for THSR (>1.18) resulted in a higher injury risk. In contrast, a lower injury risk was found when comparing medium ratios for ACCeff (0.87-1.12), DECeff (0.86-1.12), and RPE x duration (0.85-1.12) to low ratios. Findings demonstrate that mainly external load indicators are associated with increased or decreased injury risk. The monitoring of various load indicators is recommended for injury prevention in professional soccer.


#4 Individualisation of speed thresholds does not enhance the dose-response determination in football training
Reference: J Sports Sci. 2017 Nov 3:1-10. doi: 10.1080/02640414.2017.1398894. [Epub ahead of print]
Authors: Scott D, Lovell R
Summary: This study examined the utility of a range of approaches used to develop player-dependent speed zones in time-motion analysis (TMA), in determining the dose-response (internal load) of daily football training. Daily external (10 Hz GPS) and internal load (heart rate metrics, ratings of perceived exertion [RPE], wellness ratings) measures were tracked for 22 International women's football players during a 21-day training camp. High-speed (HSR) and very high speed running (VHSR) were determined according to arbitrary speed thresholds, as well as using a range of different individualization approaches that included the velocities corresponding to the heart rate deflection point, maximal aerobic speed, YYIR1 performance, and maximal sprint speed (MSS). Within-player correlations between the TMA approaches versus internal load measures quantified the dose-response to training. Correlations between HSR and VHSR vs. RPE were large (r = 0.53-0.67), with the exception of VHSR for the MSS technique (moderate; r = 0.44). HSR was very-largely associated with heart rate indices (r = 0.72-0.78), again with the exception of MSS (large; r = 0.60-0.67). Using a range of different fitness characteristics to individualise speed thresholds did not enhance the dose-response determination to daily fluctuations in external load, and was worsened with MSS per se.


#5 Comprehensive profile of hip, knee and ankle ranges of motion in professional football players
Reference: J Sports Med Phys Fitness. 2017 Oct 31. doi: 10.23736/S0022-4707.17.07910-5. [Epub ahead of print]
Authors: Lopez-Valenciano A, Ayala F, Vera-Garcia FJ, de Ste Croix M, Hernández-Sanchez S, Ruiz-Perez I, Cejudo A, Santonja F
Summary: Limited ranges of motion (ROM) have been considered as a primary risk factor for some football injuries, but only a few studies have analysed differences in lower extremity joints. The main purposes were (a) to describe the lower extremity ROM profile in professional football players; and (b) to examine differences between goalkeepers and outfield players. 82 professional male football players from 4 teams were measured in the 2013 pre-season. Measures of passive hip (flexion with knee flexed [PHFKF] and extended [PHFKE], extension [PHE], abduction [PHA], external [PHER] and internal [PHIR] rotation), knee (flexion [PKF]) and ankle (dorsiflexion with knee flexed [ADFKF] and extended [ADFKE]) ROMs were taken. Magnitude-based inferences exploring differences between player position and limb were made. 46% of all participants showed restricted PHFKE and/or around 30% showed restricted ADFKF ROM values. Contrarily, most players reported normal PHFKF, PHE, PHIR and PHER as well as PKF ROM scores with percentage values close to 100%. Bilateral meaningful differences for PHA, PHIR and PHER were found in approximately 30% of outfield players and goalkeepers. Statistical analysis found trivial differences between players for PHFKE, PHE, PHIR, PHER, ADFKE and ADFKF. However, moderate differences between players were found for PHFKF, PHA and PKF, with goalkeepers demonstrating higher values than outfield players. The findings of this study reinforce the necessity of prescribing exercises aimed at improving PHFKE and ADFKF ROM within everyday football training routines. In addition, as some bilateral deficits were observed, unilateral training should be considered where appropriate.


#6 An evaluation of the impact of FIFA World Cup on soccer emergency department injuries among Montreal adolescents
Reference: J Paediatr Child Health. 2017 Nov 10. doi: 10.1111/jpc.13784. [Epub ahead of print]
Authors: Keays G, Friedman D, Beaudin M, Gagnon I
Summary: The 'trickle-down effect', or how major sports events have a positive impact on sports participation, has been the subject of many studies, but none produced conclusive results. We took a different approach and rather than look at sports participation, we used injuries as a proxy and see if injuries increased, or remained the same, after the International Federation of Association Football World Cup. Using a retrospective cohort design, we looked at the injuries suffered by males and females (13-16 years old) while playing team sports in Montreal, that occurred in May to July, from 1999 to 2014. Information reported by the Canadian Hospitals Injury Reporting Prevention Program (CHIRPP) was limited to the two CHIRPP centres in Montreal: the Montreal Children's Hospital and Hopital Sainte-Justine. In females, no significant trends were noticed. In males who played non-organised soccer, the percent changes between FIFA World Cup (WC) (June) and pre-FIFA WC (May) was always highest during FIFA WC years: 17.2% more injuries in years when FIFA WC was held compared to 1.3% less injuries during non-FIFA WC years. In non-organised soccer, male players suffered less strains/sprains (11.9% vs. 30.1%; P = 0.015), suffered more severe injuries (59.7% vs. 43.1%; P = 0.049) and more of their injuries were the results of direct contact with another player (26.8% vs. 13.3%; P = 0.028) during FIFA WC. FIFA WC seems to have an impact on the injuries of teenage boys when playing non-organised soccer. The impact was short-lived, only lasting during the FIFA WC event.


#7 A soccer player with an unstable knee
Reference: Ned Tijdschr Geneeskd. 2017;161(0):D1524. [Article in Dutch]
Authors: Janssen D, Koc B, Jansen E
Summary: A 19-year-old soccer player presented with instability of his left knee after a rotation trauma. Congenital absence of the anterior cruciate ligament was suspected because of leg length discrepancy and specific MRI findings. He regained stability after an anterior cruciate reconstruction.


#8 An audit of injuries in six english professional soccer academies
Reference: J Sports Sci. 2017 Nov 10:1-7. doi: 10.1080/02640414.2017.1402535. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: Regulations now state that professional academies in the United Kingdom are required to substantially increase the volume of soccer training. This study assessed the current injury occurrence, providing an update to reports published prior to the introduction of the Elite Player Performance Plan (EPPP). 608 soccer players aged 11-18 years from six professional soccer clubs were prospectively monitored, recording injuries during the 2014-2015 season. An injury rate of 1.32 injuries per player/season was indicated with a mean time loss of 21.9 days per injury. The greatest time loss per injury was in the U14s-U15s, and the highest rate of severe injuries in the U15s. Strains and sprains were the most common injury type, with the knee and ankle the most frequently injured anatomical sites. Seasonal variation indicated two peaks in injury incidence, occurring in September and January. In comparison to a published audit prior to the inception of the EPPP, this study indicates that academy soccer players are three-times more likely to experience an injury. Given that time loss and injury severity also increased during periods that typically follow rapid growth, these players should be considered an important group for training load monitoring and injury prevention strategies.


#9 Match-derived relative pitch area changes the physical and team tactical performance of elite soccer players in small-sided soccer games
Reference: J Sports Sci. 2017 Nov 10:1-7. doi: 10.1080/02640414.2017.1403412. [Epub ahead of print]
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Small-sided games (SSGs) are used in training sessions to prepare for full-sized matches. For the same number of players, smaller pitch sizes result in decreased physical performance and shorter interpersonal distances. A relative pitch area derived from the full-sized match results in larger pitch sizes and this may increase the fit between SSGs and full-sized matches. This study aimed to investigate SSGs with a traditional small pitch and a match-derived relative pitch area in youth elite soccer players. Four age categories (under-13, under-15, under-17 and under-19) played 4 vs. 4 plus goalkeepers on a small (40x30m, 120m2 relative pitch area) and large pitch (68x47m, 320m2 relative pitch area). The number of games per age category ranged 15-30. Positional data (LPM-system) were collected to determine physical (total distance covered, high intensity distance and number of sprints) and team tactical (inter-team distance, LPW-ratio, surface area, stretch indices, goalkeeper-defender distance) performance measures and tactical variability. On a large pitch, physical performance significantly increased, inter-team and intra-team distances were significantly larger and tactical variability of intra-team distance measures significantly increased. The match-derived relative pitch area is an important training manipulation and leads to changes in physical and tactical performance 4 vs. 4 plus goalkeepers.


#10 Etiology and Recovery of Neuromuscular Fatigue following Competitive Soccer Match-Play
Reference: Front Physiol. 2017 Oct 25;8:831. doi: 10.3389/fphys.2017.00831. eCollection 2017.
Authors: Brownstein CG, Dent JP, Parker P, Hicks KM, Howatson G, Goodall S, Thomas K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5661001/pdf/fphys-08-00831.pdf
Summary: Previous research into the etiology of neuromuscular fatigue following competitive soccer match-play has primarily focused on peripheral perturbations, with limited research assessing central nervous system function in the days post-match. The aim of the present study was to examine the contribution and time-course of recovery of central and peripheral factors toward neuromuscular fatigue following competitive soccer match-play. Sixteen male semi-professional soccer players completed a 90-min soccer match. Pre-, post- and at 24, 48, and 72 h participants completed a battery of neuromuscular, physical, and perceptual tests. Maximal voluntary contraction force (MVC) and twitch responses to electrical (femoral nerve) and transcranial magnetic stimulation (TMS) of the motor cortex during isometric knee-extension and at rest were measured to assess central nervous system (voluntary activation, VA) and muscle contractile (potentiated twitch force, Qtw, pot) function. Electromyography responses of the rectus femoris to single- and paired-pulse TMS were used to assess corticospinal excitability and short-interval intracortical inhibition (SICI), respectively. Fatigue and perceptions of muscle soreness were assessed via visual analog scales, and physical function was assessed through measures of jump (countermovement jump height and reactive strength index) and sprint performance. Competitive match-play elicited significant post-match declines in MVC force (-14%, P < 0.001) that persisted for 48 h (-4%, P = 0.01), before recovering by 72 h post-exercise. VA (motor point stimulation) was reduced immediately post-match (-8%, P < 0.001), and remained depressed at 24 h (-5%, P = 0.01) before recovering by 48 h post-exercise. Qtw,pot was reduced post-match (-14%, P < 0.001), remained depressed at 24 h (-6%, P = 0.01), before recovering by 48 h post-exercise. No changes were evident in corticospinal excitability or SICI. Jump performance took 48 h to recover, while perceptions of fatigue persisted at 72 h. Conclusion: Competitive soccer match-play elicits substantial impairments in central nervous system and muscle function, requiring up to 48 h to resolve. The results of the study could have important implications for fixture scheduling, the optimal management of the training process, squad rotation during congested competitive schedules, and the implementation of appropriate recovery interventions.



American Football
#1 Effects of Career Duration, Concussion History, and Playing Position on White Matter Microstructure and Functional Neural Recruitment in Former College and Professional Football Athletes
Reference: Radiology. 2017 Oct 31:170539. doi: 10.1148/radiol.2017170539. [Epub ahead of print]
Authors: Clark MD, Varangis EML, Champagne AA, Giovanello KS, Shi F, Kerr ZY, Smith JK, Guskiewicz KM
Summary: The purpose was to better understand the relationship between exposure to concussive and subconcussive head impacts, white matter integrity, and functional task-related neural activity in former U.S. football athletes. Materials and Methods Between 2011 and 2013, 61 cognitively unimpaired former collegiate and professional football players (age range, 52-65 years) provided informed consent to participate in this cross-sectional study. Participants were stratified across three crossed factors: career duration, concussion history, and primary playing position. Fractional anisotropy (FA) and blood oxygen level-dependent (BOLD) percent signal change (PSC) were measured with diffusion-weighted and task-related functional magnetic resonance imaging, respectively. Analyses of variance of FA and BOLD PSC were used to determine main or interaction effects of the three factors. Results A significant interaction between career duration and concussion history was observed; former college players with more than three concussions had lower FA in a broadly distributed area of white matter compared with those with zero to one concussion (t29 = 2.774; adjusted P = .037), and the opposite was observed for former professional players (t29 = 3.883; adjusted P = .001). A separate interaction between concussion history and position was observed: Nonspeed players with more than three concussions had lower FA in frontal white matter compared with those with zero to one concussion (t25 = 3.861; adjusted P = .002). Analysis of working memory-task BOLD PSC revealed a similar interaction between concussion history and position (all adjusted P < .004). Overall, former players with lower FA tended to have lower BOLD PSC across three levels of a working memory task. Conclusion Career duration and primary playing position seem to modify the effects of concussion history on white matter structure and neural recruitment. The differences in brain structure and function were observed in the absence of clinical impairment, which suggested that multimodal imaging may provide early markers of onset of traumatic neurodegenerative disease. © RSNA, 2017 Online supplemental material is available for this article.


#2 White matter alterations over the course of two consecutive high-school football seasons and the effect of a jugular compression collar: A preliminary longitudinal diffusion tensor imaging study
Reference: Hum Brain Mapp. 2017 Oct 28. doi: 10.1002/hbm.23859. [Epub ahead of print]
Authors: Yuan W, Barber Foss KD, Thomas S, DiCesare CA, Dudley JA, Kitchen K, Gadd B, Leach JL, Smith D, Altaye M, Gubanich P, Galloway RT, McCrory P, Bailes JE, Mannix R, Meehan WP 3rd, Myer GD
Summary: The cumulative effects of repetitive subclinical head impacts during sports may result in chronic white matter (WM) changes and possibly, neurodegenerative sequelae. In this pilot study, we investigated the longitudinal WM changes over the course of two consecutive high-school football seasons and explored the long-term effects of a jugular vein compression collar on these WM alterations. Diffusion tensor imaging data were prospectively collected both pre- and postseason in the two consecutive seasons. Participants were assigned into either collar or noncollar groups. Tract-based spatial statistics (TBSS) approach and region of interest-based approach were used to quantify changes in WM diffusion properties. Despite comparable exposure to repetitive head impacts, significant reductions in mean, axial, and/or radial diffusivity were identified in Season 1 in multiple WM regions in the noncollar group but not in the collar group. After an 8- to 9-month long off-season, these changes observed in the noncollar group partially and significantly reversed but also remained significantly different from the baseline. In Season 2, trend level WM alterations in the noncollar group were found but located in spatially different regions than Season 1. Last, the WM integrity in the collar group remained unchanged throughout the four time points. In conclusion, we quantitatively assessed the WM structural changes and partial reversal over the course of two consecutive high-school football seasons. In addition, the mitigated WM alterations in athletes in the collar group might indicate potential effect of the collar in ameliorating the changes against repetitive head impacts.


#3 Postural Control and Head Impact Exposure in Youth Football Players: Comparison of the Balance Error Scoring System and a Force Plate Protocol
Reference: J Appl Biomech. 2017 Nov 1:1-25. doi: 10.1123/jab.2017-0066. [Epub ahead of print]
Authors: Campolettano ET, Brolinson G, Rowson S
Summary: Postural control testing is often used by clinicians and athletic trainers to assess the health of athletes during recovery from a concussion. Characterization of postural control as a clinical tool for use with youth athletes is limited though. The objective of this study was to compare performance on the Balance Error Scoring System (BESS) and a force plate protocol at the beginning and end of a season of football within a cohort of 34 healthy youth football players (average age of 9.9 ± 0.6 years). A secondary aim was to investigate if changes in measures of balance from the postseason to the preseason were correlated with head impact exposure. Players completed testing at the beginning and end of the youth football season. There were no significant differences between BESS scores before the season and after the season (p = 0.54). Performance on the BESS was not associated with any of the center of pressure (COP) metrics considered in this study. No correlation was observed between measures of balance and head impact exposure for the season. Further research is required to determine the viability of postural control testing with this population.



Australian Football
#1 Brief Education Intervention Increases Nutrition Knowledge and Confidence of Coaches of Junior Australian Football Teams
Reference: Int J Sport Nutr Exerc Metab. 2017 Nov 1:1-21. doi: 10.1123/ijsnem.2017-0170. [Epub ahead of print]
Authors: Belski R, Donaldson A, Staley K, Skiadopoulos A, Randle E, O'Halloran P, Kappelides P, Teakel S, Stanley S, Nicholson M
Summary: This study evaluated the impact of a brief (20-minute) nutrition education intervention embedded in an existing mandatory coach education course for coaches of junior (8-12 year old) Australian football teams. Two hundred and eighty-four coaches (68% of 415 coaching course participants) completed a pre-session questionnaire and 110 (27% of coaching course participants) completed an identical post-session questionnaire. The responses to the pre- and post-session surveys were matched for 78 coaches. Coaches' ratings of their own understanding of the nutritional needs of young athletes (6.81, 8.95, p<0.001), the importance of young athletes adhering to a healthy diet (9.09, 9.67, p=001), their confidence in their own nutrition knowledge (7.24, 8.64, p<0.001) and their confidence in advising young athletes on nutrition and hydration practices (6.85, 8.62, p<0.001), all improved significantly following the education session. Nearly all coaches (>95%) provided a correct response to six of the 15 nutrition and hydration knowledge questions included in the pre-session questionnaire. Even with this high level of pre-session knowledge, there was a significant improvement in the coaches' nutrition and hydration knowledge after the education session across five of the 15 items, compared to before the education session. The results of this study suggest that a simple, short nutrition education intervention, embedded in an existing coach education course, can positively influence the nutrition knowledge and self-efficacy of community-level, volunteer coaches of junior sports participants.

Tue

14

Nov

2017

Football is...(#39)

Repeated sprint work to rest ratio of 1:6 = match demands

 

Mon

13

Nov

2017

Football is...(#38)

SSG with small player numbers = training offensive actions

Fri

10

Nov

2017

Football is...(#37)

Benefits utilizing split blocks with SSG.

Mon

06

Nov

2017

Latest research in football - week 44 - 2017

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

Following studies were retrieved for this week:

#1 Acute and Residual Soccer Match-Related Fatigue: A Systematic Review and Meta-analysis
Reference: Sports Med. 2017 Nov 2. doi: 10.1007/s40279-017-0798-8. [Epub ahead of print]
Authors: Silva JR, Rumpf MC, Hertzog M, Castagna C, Farooq A, Girard O, Hader K

Full-test read: https://link.springer.com/epdf/10.1007/s40279-017-0798-8?author_access_token=zbISRhwR-ZwDDBJWZlZU2ve4RwlQNchNByi7wbcMAY6y_aUGySQg-494DXIFKoAvCj28IZ0ACKLvu-zVIZ24ZvxHDXDQPWW5XYROP3K5FxHmshJUT8sivfZ9eIVXRiV7RKW_u49GjOmZWnm-Wy6ung%3D%3D
Summary: Understanding soccer players' match-related fatigue and recovery profiles likely helps with developing conditioning programs that increase team performance and reduce injuries and illnesses. In order to improve match recovery (the return-to-play process and ergogenic interventions) it is also pivotal to determine if match simulation protocols and actual match-play lead to similar responses. The objectives were (1) To thoroughly describe the development of fatigue during actual soccer match play and its recovery time course in terms of physiological, neuromuscular, technical, biochemical and perceptual responses, and (2) to determine similarities of recovery responses between actual competition (11 vs. 11) and match simulations. A first screening phase consisted of a systematic search on PubMed (MEDLINE) and SportDiscus databases until March 2016. Inclusion criteria were: longitudinal study with soccer players; match or validated protocol; duration > 45 min; and published in English. A total of 77 eligible studies (n = 1105) were used to compute 1196 effect sizes (ES). Half-time assessments revealed small to large alterations in immunological parameters (e.g. leukocytes, ES = 1.9), a moderate decrement in insulin concentration (ES = - 0.9) and a small to moderate impairment in lower-limb muscle function (ES = - 0.5 to - 0.7) and physical performance measures (e.g. linear sprint, ES = - 0.3 to - 1.0). All the systematically analyzed fatigue-related markers were substantially altered at post-match. Hamstrings force production capacity (ES = - 0.7), physical performance (2-4%, ES = 0.3-0.5), creatine kinase (CK, ES = 0.4), well-being (ES = 0.2-0.4) and delayed onset muscle soreness (DOMS, ES = 0.6-1.3) remained substantially impaired at G + 72 h. Compared to simulation protocols, 11 vs. 11 match format (CK, ES = 1.8) induced a greater magnitude of change in muscle damage (i.e. CK, ES = 1.8 vs. 0.7), inflammatory (IL-6, ES = 2.6 vs. 1.1) and immunological markers and DOMS (ES = 1.5 vs. 0.7) than simulation protocols at post-assessments. Neuromuscular performances at post-match did not differ between protocols. While some parameters are fully recovered (e.g. hormonal and technical), our systematic review shows that a period of 72 h post-match play is not long enough to completely restore homeostatic balance (e.g. muscle damage, physical and well-being status). The extent of the recovery period post-soccer game cannot consist of a 'one size fits all approach'. Additionally, the 'real match' (11 vs. 11 format) likely induces greater magnitudes of perceptual (DOMS) and biochemical alterations (e.g. muscle damage), while neuromuscular alterations were essentially similar. Overall, coaches must adjust the structure and content of the training sessions during the 72-h post-match intervention to effectively manage the training load within this time-frame.

#2 Head impact locations in US high school boys' and girls' soccer concussions, 2012/13-2015/16
Reference: J Neurotrauma. 2017 Nov 1. doi: 10.1089/neu.2017.5319. [Epub ahead of print]
Authors: Kerr Z, Campbell KR, Fraser MA, Currie DW, Pierpoint LA, Kamimski T, Mihalik J
Summary: This study describes concussions and concussion-related outcomes sustained by high school soccer players by head impact location, sex, and injury mechanism. Data were obtained for the 2012/13-2015/16 school years from the National High School Sports-Related Injury Surveillance System, High School RIO™. This Internet-based sports injury surveillance system captures data reported by athletic trainers from an annual average of 162 US high schools. Data were analyzed to describe circumstances of soccer concussion (e.g., symptomology, symptom resolution and return-to-play time) by impact location [i.e., front- (face included), back-, side-, and top-of-the-head] and sex. Most concussions were from front-of-the-head impacts (boys: 30.5%; girls: 34.0%). Overall, 4.1±2.2 and 4.6±2.3 symptoms were reported in boys and girls, respectively. In boys, symptom frequency was not associated with head impact location (P=0.66); an association was found in girls (p=0.02), with the highest symptom frequency reported in top-of-the-head impacts (5.4±2.2). Head impact location was not associated with symptom resolution time (boys P=0.21; girls P=0.19) or return-to-play time (boys P=0.18; girls P=0.07). Heading was associated with 28.0% and 26.5% of concussions in boys and girls, respectively. Most player-player contact concussions during heading occurred from side-of-the-head impacts (boys: 49.4%; girls: 43.2%); most heading-related ball contact concussions occurred from front-of-the-head (boys: 41.4%; girls: 42.6%) and top-of-the-head (boys: 34.5%; girls: 36.9%) impacts. Head impact location was generally independent of symptom resolution time, return-to-play time, and recurrence among high school soccer concussions. However, impact location may be associated with reported symptom frequency. Further, many of these clinical concussion descriptors were associated with sex.


#3 Acute Effects Of Active, Ballistic, Passive And Proprioceptive Neuromuscular Facilitation Streching On Sprint And Vertical Jump Performance In Trained Young Soccer Players
Reference: J Strength Cond Res. 2017 Oct 27. doi: 10.1519/JSC.0000000000002298. [Epub ahead of print]
Authors: de Paula Oliveira L, Palucci Vieira LH, Aquino R, Vieira Manechini JP, Pereira Santiago PR, Puggina EF.
Summary: The aim of the present study was to compare the acute effects of active (AC), ballistic (BA), passive (PA), proprioceptive neuromuscular facilitation stretching (PNF) methods on performance in vertical jumping, sit and reach, and sprinting in young soccer players. Twelve trained soccer players (17.67 ± 0.87 years) participated in the study. The jump height (H), peak power (PP), and relative power (RP) in the squat jump (SJ) and countermovement jump (CMJ), the range of motion (ROM), the rate of perceived exertion (RPE), and time (s) in 10-20-30 m sprints were evaluated. Significant differences (p <0.05) in H were found in the comparisons between the PA and control condition (CO) for the SJ. For the CMJ, differences in H were observed between the PA and CO, and PNF with CO and BA, and in the PP between the PNF and CO, AC, and BA, as well as in the RP between the PNF and BA. Significant increases in ROM were found in the AC, BA, PA, and PNF, compared to the CO. In relation to RPE, higher scores were reported in the PA and PNF conditions compared to the AC and BA. No significant differences were found in 10-20-30 m sprints. Therefore, the AC and BA methods can be used prior to vertical jump and sprint activities, with the aim of increasing flexibility. However, the PA and PNF methods should be avoided, due to subsequent negative effects on vertical jump performance.


#4 Fractures in German elite male soccer
Reference: J Sports Med Phys Fitness. 2017 Oct 27. doi: 10.23736/S0022-4707.17.07901-4. [Epub ahead of print]
Authors: Schiffner E, Latz D, Grassmann JP, Schek A, Scholz A, Windolf J, Jungbluth P, Schneppendahl J
Summary: Aim of this retrospective cohort study was to identify fracture epidemiology and off times after different types of fractures in German male elite soccer players from the first division Bundesliga based on information from the public media. Exposure and fracture data over 7.5 consecutive seasons (2009/10 -1.Half 2016/17) were collected from two media based register (transfermarkt.de® and kicker.de®). 357 fractures from 290 different players were recorded with an incidences of 0.19/1000 h of exposure (95% 0.14 - 0.24). Most fractures in German elite soccer players involved the lower extremities (35.3%), the head/face (30.3%) and the upper extremities (24.9%). The median off time after a fracture in German elite male professional soccer in 7.5 Season was 51.1 days (range 0-144). The number of fractures per 100 players per season decreased between 2009 and 2016. There was no significant difference in overall fracture incidence when comparing players at different position (p=0.11). Goalkeepers have a significantly (p<0.02) higher likelihood of suffering hand and finger fractures and they are significantly (p<0.03) less prone of suffering foot fractures, cranial and maxillofacial fractures (p<0.04) compared to outfield players. This study can confirm that male professional soccer teams experience 1-2 fractures per season in German elite soccer. The incidence of fractures in elite German soccer players decreased between 2009 and 2016. The most fractures occur in the lower extremities and there is no difference in overall fracture risk for players at different playing positions. The information from our study might be of a great importance to medical practitioners, soccer coaches and soccer manager.


#5 Exercise to rest ratios in RSA training in women's soccer
Reference: J Sports Med Phys Fitness. 2017 Oct 27. doi: 10.23736/S0022-4707.17.07741-6. [Epub ahead of print]
Authors: Ruscello B, Esposito M, Partipilo F, DI Cicco D, Filetti C, Pantanella L, D'Ottavio S
Summary: The purpose was to investigate the applicability of three different exercise to rest ratios in RSA training in women's soccer players, applying those ones already adopted in male adult and young players, when performing three different sprinting modes (straight, shuttle and sprinting with changing of direction). 15 trained female soccer players (height: 1.65 ± 0.06 m; weight: 59.3 ± 9.0 kg; BMI 21.6 ± 2.7 kg·m-2; age: 23.3±5.9 years) participated to the study. In order to compare the different values of the time recorded, an Index of Fatigue was used. Recovery times among trials in the sets were administered according to the 1:5, 1:3; 1:2 exercise to rest ratio, respectively. Blood lactate concentrations at the end of each set (3') were analyzed. Significant differences among trials within each set (Repeated Measures Anova; p<0.05) were found, as evidence of fatigue over time, with an average decay of performance of about 5% but no significant differences were found in IF%, among the three different sprinting modalities when applying the investigated exercise to rest ratios (Factorial Anova; between; p>0.05). Significant differences were found in blood lactate concentrations (p<0.05). The results of this study confirm that the exercise to rest ratios considered in this study might be suitable to design effective testing protocols and training sessions aimed at the development of the RSA in women's soccer players, keeping the performances in the speed domain (IF% < ⊕7-8%) but inducing the fatigue processes sought with this kind of training method.


#6 Influence of different types of compression garments on exercise-induced muscle damage markers after a soccer match
Reference: Res Sports Med. 2017 Oct 30:1-16. doi: 10.1080/15438627.2017.1393755. [Epub ahead of print]
Authors: Marques-Jimenez D, Calleja-Gonzalez J, Arratibel-Imaz I, Delextrat A, Uriarte F, Terrados N
Summary: There is not enough evidence of positive effects of compression therapy on the recovery of soccer players after matches. Therefore, the objective was to evaluate the influence of different types of compression garments in reducing exercise-induced muscle damage (EIMD) during recovery after a friendly soccer match. Eighteen semi-professional soccer players (24 ± 4.07 years, 177 ± 5 cm; 71.8 ± 6.28 kg and 22.73 ± 1.81 BMI) participated in this study. A two-stage crossover design was chosen. Participants acted as controls in one match and were assigned to an experimental group (compression stockings group, full-leg compression group, shorts group) in the other match. Participants in experimental groups played the match wearing the assigned compression garments, which were also worn in the 3 days post-match, for 7 h each day. Results showed a positive, but not significant, effect of compression garments on attenuating EIMD biomarkers response, and inflammatory and perceptual responses suggest that compression may improve physiological and psychological recovery.


#7 Tanner-Whitehouse Skeletal Ages in Male Youth Soccer Players: TW2 or TW3?
Reference: Sports Med. 2017 Oct 29. doi: 10.1007/s40279-017-0799-7. [Epub ahead of print]
Authors: Malina RM, Coelho-E-Silva MJ, Figueiredo AJ, Philippaerts RM, Hirose N, Pena Reyes ME, Gilli G, Benso A, Vaeyens R, Deprez D, Guglielmo LF, Buranarugsa R
Summary: The Tanner-Whitehouse radius-ulna-short bone protocol (TW2 RUS) for the assessment of skeletal age (SA) is widely used to estimate the biological (skeletal) maturity status of children and adolescents. The scale for converting TW RUS ratings to an SA has been revised (TW3 RUS) and has implications for studies of youth athletes in age-group sports. The aim of this study was to compare TW2 and TW3 RUS SAs in an international sample of male youth soccer players and to compare distributions of players by maturity status defined by each SA protocol. SA assessments with the TW RUS method were collated for 1831 male soccer players aged 11-17 years from eight countries. RUS scores were converted to TW2 and TW3 SAs using the appropriate tables. SAs were related to chronological age (CA) in individual athletes and compared by CA groups. The difference of SA minus CA with TW2 SA and with TW3 SA was used to classify players as late, average, or early maturing with each method. Concordance of maturity classifications was evaluated with Cohen's Kappa coefficients. For the same RUS score, TW3 SAs were systematically and substantially reduced compared with TW2 SAs; mean differences by CA group ranged from - 0.97 to - 1.16 years. Kappa coefficients indicated at best fair concordance of TW2 and TW3 maturity classifications. Across the age range, 42% of players classified as average with TW2 SA were classified as late with TW3 SA, and 64% of players classified as early with TW2 SA were classified as average with TW3 SA. TW3 SAs were systematically lower than corresponding TW2 SAs in male youth soccer players. The differences between scales have major implications for the classification of players by maturity status, which is central to some talent development programs.


#8 Orthopedic injuries in soccer – an analysis of professional championship tournament in Brazil
Reference:  Acta Ortop Bras. 2017 Sep-Oct;25(5):216-219. doi: 10.1590/1413-785220172505171247.
Authors: Souza RFR, Mainine S, Souza FFR, Zanon EM, Nishimi AY, Dobashi ET, Fernandes FA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608743/pdf/1413-7852-aob-25-05-00216.pdf
Summary: The purpose was to analyze the incidence of orthopedic injuries which occurred during a professional soccer championship in São Paulo, Brazil in 2010. This assessment collected data from the pre-season until the final stage of the championship. We analyzed 227 professional players from eight of the top teams in this championship. Data were obtained for 71.02% of all games. The athletes were all male with a mean age of 23.1 years; the average number of injuries was 1.6 per athlete, with muscle injuries and sprains resulting from indirect origin predominating in the legs. Injuries were more frequent in forwards and outside backs, and players generally returned to play within one week of treatment.

Fri

03

Nov

2017

Football is...(#36)

Throw-ins could = ball possession or goal scoring opportunity

Sun

29

Oct

2017

Latest research in football - week 43 - 2017

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

Following studies were retrieved for this week:

#1 Is there a correlation between coaches' leadership styles and injuries in elite football teams? A study of 36 elite teams in 17 countries
Reference: Br J Sports Med. 2017 Oct 22. pii: bjsports-2017-098001. doi: 10.1136/bjsports-2017-098001. [Epub ahead of print]
Authors: Ekstrand J, Lundqvist D, Lagerback L, Vouillamoz M, Papadimitiou N, Karlsson J
Summary: Do coaches' leadership styles affect injury rates and the availability of players in professional football? Certain types of leadership behaviour may cause stress and have a negative impact on players' health and well-being. The aim of the study was to investigate the transformational leadership styles of head coaches in elite men's football and to evaluate the correlation between leadership styles, injury rates and players' availability. Medical staff from 36 elite football clubs in 17 European countries produced 77 reports at four postseason meetings with a view to assessing their perception of the type of leadership exhibited by the head coaches of their respective teams using the Global Transformational Leadership scale. At the same time, they also recorded details of individual players' exposure to football and time-loss injuries. There was a negative correlation between the overall level of transformational leadership and the incidence of severe injuries (rho=-0.248; n=77; p=0.030); high levels of transformational leadership were associated with smaller numbers of severe injuries. Global Transformational Leadership only explained 6% of variation in the incidence of severe injuries (r2=0.062). The incidence of severe injuries was lower at clubs where coaches communicated a clear and positive vision, supported staff members and gave players encouragement and recognition. Players' attendance rates at training were higher in teams where coaches gave encouragement and recognition to staff members, encouraged innovative thinking, fostered trust and cooperation and acted as role models. There is an association between injury rates and players' availability and the leadership style of the head coach.


#2 Sex and age differences in head acceleration during purposeful soccer heading
Reference: Res Sports Med. 2017 Oct 25:1-11. doi: 10.1080/15438627.2017.1393756. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Rose WC, Glutting JJ, Kaminski TW
Summary: Differences in head-neck segment mass, purposeful heading technique, and cervical strength and stiffness may contribute to differences in head accelerations across sex and age. The purpose of this study was to compare head acceleration across sex and age (youth [12-14 years old], high school and collegiate) during purposeful soccer heading. One-hundred soccer players (42 male, 58 female, 17.1 ± 3.5 years, 168.5 ± 20.3 cm, 61.5 ± 13.7 kg) completed 12 controlled soccer headers at an initial ball velocity of 11.2 m/s. Linear and rotational accelerations were measured using a triaxial accelerometer and gyroscope and were transformed to the head centre-of-mass. A MANOVA revealed a significant multivariate main effect for sex (Pillai's Trace = .165, F(2,91) = 11.868, p < .001), but not for age (Pillai's Trace = .033, F(4,182) = 0.646, p = .630). Peak linear and rotational accelerations were higher in females (40.9 ± 13.3 g; 3279 ± 1065 rad/s2) than males (27.6 ± 8.5 g, 2219 ± 823 rad/s2). These data suggest that under controlled soccer heading conditions, females may be exposed to higher head accelerations than males.


#3 Multifactorial examination of sex-differences in head injuries and concussions among collegiate soccer players: NCAA ISS, 2004-2009
Reference: Inj Epidemiol. 2017 Oct 25;4(1):28. doi: 10.1186/s40621-017-0127-6.
Authors: Chandran A, Barron MJ, Westerman BJ, DiPietro L
Summary: While head injuries and concussions are major concerns among soccer players, the multifactorial nature of head injury observations in this group remains relatively undefined. We aim to extend previous analyses and examine sex-differences in the incidence of head injuries, odds of head injuries within an injured sample, and severity of head injuries, among collegiate soccer players between 2004 and 2009. Data collected within the National Collegiate Athletic Association (NCAA) Injury Surveillance System (ISS) between the years of 2004 and 2009, were analyzed in this study. Unadjusted rate ratios (RR), compared incidence rates between categories of sex, injury mechanism, setting and competition level. We also examined sex-differences in head injury incidence rates, across categories of the other covariates. Multivariable logistic regression and negative binomial regression modeling tested the relation between sex and head injury corollaries, while controlling for contact, setting, and competition level. Between 2004 and 2009, head injuries accounted for approximately 11% of all soccer-related injuries reported within the NCAA-ISS. The rate of head injuries among women was higher than among men (RR = 1.23, 95% CI = [1.08, 1.41]). The rate of head injuries due to player-to-player contact was comparable between women and men (RR = 0.95, 95% CI = [0.81, 1.11]). Whereas, the rate of injury due to contact with apparatus (ball/goal) was nearly 2.5 times higher (RR = 2.46, 95% CI = [1.76, 3.44]) and the rate due to contact with a playing surface was over two times higher (RR = 2.29, 95% CI = [1.34, 3.91]) in women than in men. In our multifactorial models, we also observed that the association between sex and head injury corollaries varied by injury mechanism. Sex-differences in the incidence, odds (given an injury), and severity (concussion diagnosis, time-loss) of head injuries varied by injury mechanism (player-to-player contact vs. all other mechanisms) in this sample.


#4 Leg Stiffness in Female Soccer Players: Intersession Reliability and the Fatiguing Effects of Soccer-Specific Exercise
Reference: J Strength Cond Res. 2017 Nov;31(11):3052-3058. doi: 10.1519/JSC.0000000000001715.
Authors: De Ste Croix MBA, Hughes JD, Lloyd RS, Oliver JL, Read PJ
Summary: Low levels of leg stiffness and reduced leg stiffness when fatigue is present compromise physical performance and increase injury risk. The purpose of this study was to (a) determine the reliability of leg stiffness measures obtained from contact mat data and (b) explore age-related differences in leg stiffness after exposure to a soccer-specific fatigue protocol in young female soccer players. Thirty-seven uninjured female youth soccer players divided into 3 subgroups based on chronological age (under 13 [U13], under 15 [U15], and under 17 [U17] year-olds) volunteered to participate in the study. After baseline data collection, during which relative leg stiffness, contact time, and flight time were collected, participants completed an age-appropriate soccer-specific fatigue protocol (SAFT). Upon completion of the fatigue protocol, subjects were immediately retested. Intersession reliability was acceptable and could be considered capable of detecting worthwhile changes in performance. Results showed that leg stiffness decreased in the U13 year-olds, was maintained in the U15 age group, and increased in the U17 players. Contact times and flight times did not change in the U13 and U15 year-olds, but significantly decreased and increased, respectively, in the U17 age group. The data suggest that age-related changes in the neuromuscular control of leg stiffness are present in youth female soccer players. Practitioners should be aware of these discrepancies in neuromuscular responses to soccer-specific fatigue, and should tailor training programs to meet the needs of individuals, which may subsequently enhance performance and reduce injury risk.


#5 Biomechanical Differences of Multidirectional Jump Landings Among Female Basketball and Soccer Players
Reference: J Strength Cond Res. 2017 Nov;31(11):3034-3045. doi: 10.1519/JSC.0000000000001785.
Authors: Taylor JB, Ford KR, Schmitz RJ, Ross SE, Ackerman TA, Shultz SJ
Summary: Anterior cruciate ligament (ACL) injury prevention programs are less successful in basketball than soccer and may be due to distinct movement strategies that these athletes develop from sport-specific training. The purpose of this study was to identify biomechanical differences between female basketball and soccer players during multidirectional jump landings. Lower extremity biomechanics of 89 female athletes who played competitive basketball (n = 40) or soccer (n = 49) at the middle- or high-school level were analyzed with 3-dimensional motion analysis during a drop vertical jump, double- (SAG-DL) and single-leg forward jump (SAG-SL), and double- (FRONT-DL) and single-leg (FRONT-SL) lateral jump. Basketball players landed with either less hip or knee, or both hip and knee excursion during all tasks (p ≤ 0.05) except for the SAGSL task, basketball players landed with greater peak hip flexion angles (p = 0.04). The FRONT-SL task elicited the most distinct sport-specific differences, including decreased hip adduction (p < 0.001) angles, increased hip internal rotation (p = 0.003), and increased relative knee external rotation (p = 0.001) excursions in basketball players. In addition, the FRONT-SL task elicited greater forces in knee abduction (p = 0.003) and lesser forces in hip adduction (p = 0.001) and knee external rotation (p < 0.001) in basketball players. Joint energetics were different during the FRONT-DL task, as basketball players exhibited less sagittal plane energy absorption at the hip (p < 0.001) and greater hip (p < 0.001) and knee (p = 0.001) joint stiffness. Sport-specific movement strategies were identified during all jump landing tasks, such that soccer players exhibited a more protective landing strategy than basketball players, justifying future efforts toward sport-specific ACL injury prevention programs.


#6 Head Impact Exposure in Youth Soccer and Variation by Age and Sex
Reference: Clin J Sport Med. 2017 Oct 20. doi: 10.1097/JSM.0000000000000497. [Epub ahead of print]
Authors: Chrisman SPD, Ebel BE, Stein E, Lowry SJ, Rivara FP
Summary: The purpose was to examine variation in head impact exposure (HIE) by age and sex in youth soccer. Youth soccer athletes (11-14 years old) in local clubs participated in this study.  Head impact exposure measured using adhesive-mounted accelerometers during 1 month of soccer. Forty-six youth athletes (54% female) participated. No athlete reported a concussion during the study. More males than females had at least 1 head impact ≥15 g (P = 0.02). Of those who sustained a head impact above the 15-g threshold (57%), females sustained HIE of greater magnitude than males (median 47.4 g vs 33.3 g, P = 0.04). Eighty-five percent of athletes on U14 teams had at least 1 head impact ≥15 g compared with 15% of athletes on U12 teams (P < 0.001). Poisson regression stratified by sex and controlling for team-suggested age effects were significant only for females (P = 0.02). There was significant variation in HIE by team. There were no decrements in concussion symptoms, health-related quality of life, or neuropsychological testing after 1 month of soccer play. There is significant variation in HIE in youth soccer, which seems to be influenced by age and sex. Further studies are needed to better understand potential significance for injury prevention.


#7 Combined visual and dribbling performance in young soccer players of different expertise
Reference: Res Sports Med. 2017 Oct 23:1-8. doi: 10.1080/15438627.2017.1393751. [Epub ahead of print]
Authors: Bekris E, Gissis I, Ispyrlidis I, Mylonis E, Axeti G
Summary: We aimed to evaluate dribbling performance in terms of technique and visual skills assessment of both young experienced (EX, n = 24) and novice (NO, n = 24) soccer players. Both groups performed two dribbling tests with four levels of difficulty in visual signals (A1-A4 and B1-B4; B - half distance of A; 1 - no visual signal; 4 - signal with the shorter flashing time). All players performed slower when visual signals were added to the testing process (~2.5 s; p < 0.01). EX completed all tests faster than NO (~3 s, p < 0.01). The average number of visual mistakes was significantly lower for EX than NO in all tests (p < 0.01). These results demonstrated the importance of evaluating dribbling along with visual stimuli in young soccer EX and NO players.


#8 Positional synchronization affects physical and physiological responses to preseason in professional football (soccer)
Reference: Res Sports Med. 2017 Oct 23:1-13. doi: 10.1080/15438627.2017.1393754. [Epub ahead of print]
Authors: Folgado H, Goncalves B, Sampaio J
Summary: This study aimed to identify changes in tactical, physical and physiological performances in large-sided games during the preseason of elite footballers. Thirty professional football players participated in several GK+8vs.8+GK large-sided games across the first four weeks of the season. Players were monitored by GPS units and heart rate monitors to quantify physical, physiological and tactical performances. The variables were compared according to the preseason period, players' positioning and professional experience. The training situation promoted similar physiological responses during the first and the last training period. However, players were revealed to have higher levels of positional synchronization during the last preseason period, indicating an improved tactical performance. Tactical variables seem to reflect the improvement of players' performance during the preseason, measured in large-sided games situation, while affecting both physical and physiological demands. These results highlight the potential of positioning derived variables, concurrently to physical and physiological variables, for football training optimization.


American Football
#1 Risk and Causes of Death among Former National Football League Players (1986-2012)
Reference: Med Sci Sports Exerc. 2017 Oct 26. doi: 10.1249/MSS.0000000000001466. [Epub ahead of print]
Authors: Lincoln AE, Vogel RA, Allen TW, Dunn RE, Alexander K, Kaufman ND, Tucker AM
Summary: Previous research identified decreased overall and cardiovascular mortality for National Football League (NFL) players from the 1959-1988 era. The present study explored the mortality risk among recent NFL players who played in an era of heavier linemen and nearly year-round physical conditioning. This cohort study included 9778 former NFL players with at least one year in the NFL whose last season was between 1986 and 2012. Players' pension fund records were matched to the National Death Index (NDI) to determine vital status, date of death, and cause of death. Standardized mortality ratios (SMRs) compared player mortality through 2014 with US men of the same age, race, and calendar year. Cox proportional hazards models assessed the effect of player characteristics on overall and cardiovascular mortality. Two percent (n=227) of players were deceased with a median age at death of 38 years (range: 23-61). The most common major causes of death were diseases of the heart (n=47, 21%), violence (n=39, 17%), and transportation injuries (n=34, 15%). Risk of death was significantly lower than the general population for overall mortality (SMR 0.46, 95% CI 0.40-0.52), cardiovascular disease (SMR 0.65, 95% CI 0.50-0.84), and other major causes. Players with playing-time BMI>35 kg/m had significantly higher cardiovascular disease mortality (SMR 2.20, 95% CI 1.32-3.44) than the general population and higher overall mortality risk (SRR 3.84, 95% CI 2.66-5.54) than players with BMI<30 kg/m. Consistent with an earlier NFL cohort and other elite athlete populations, the overall and cardiovascular mortality risk of this NFL cohort was significantly lower than the general US male population, likely attributable to a healthy worker effect and less smoking.However, players with the highest playing-time BMI exhibited elevated cardiovascular mortality risk.


#2 Acute changes in plasma total Tau levels are independent of subconcussive head impacts in college football players
Reference: J Neurotrauma. 2017 Oct 26. doi: 10.1089/neu.2017.5376. [Epub ahead of print]
Authors: Kawata K, Rubin LH, Wesley L, Lee J, Sim T, Takahagi M, Bellamy A, Tierney R, Langford D
Summary: Athletes in contact sports sustain repetitive subconcussive head impacts in a brief window, yet neurophysiological sequelae from repetitive subconcussion remain unclear. This prospective longitudinal study examined a relationship between changes in plasma Tau protein levels and subconcussive impact kinematic data in 23 Division-I collegiate football players during a series of pre-season practices. Plasma measures for Tau and S100β proteins, symptom scores, and near point of convergence were obtained at preseason baseline and pre-post practices. During each practice, impact frequency and linear and rotational head accelerations were recorded via an accelerometer-embedded mouth guard. There were significant elevations in plasma Tau levels at all post-practice time points compared to those of pre-practice and baseline levels. However, the highest degree of elevation in plasma Tau was observed after the first practice, for which players sustained the lowest number of hits and magnitudes for these hits. Subconcussive impact exposure during practice (e.g., head impact frequency and magnitude) did not predict increased plasma Tau levels. Concussion history and years of football experience were also unrelated to changes in plasma Tau levels. Increases in plasma Tau levels were associated with increases in S100β levels only after the first practice. There were no significant aassociations between changes in Tau levels, symptom scores, or near point of convergence. These data suggest that the changes in levels of circulating Tau protein were independent from subconcussive head impact exposure, pointing to the possibility that other factors may have played roles in changes in plasma Tau levels.


#3 Why Professional Football Players Chose Not to Reveal Their Concussion Symptoms During a Practice or Game
Reference: Clin J Sport Med. 2017 Oct 20. doi: 10.1097/JSM.0000000000000495. [Epub ahead of print]
Authors: Delaney JS, Caron JG, Correa JA, Bloom GA
Summary: The purpose was to determine why professional football players in Canada decided not to seek medical attention during a game or practice when they believed they had suffered a concussion. Four hundred fifty-four male professional football players participated in this study. Reasons athletes did not seek medical attention for a presumed concussion during the previous season, how often this occurred and how important these reasons were in the decision process were used as outcome measured. One hundred six of the 454 respondents (23.4%) believed they had suffered a concussion during their previous football season and 87 of the 106 (82.1%) did not seek medical attention for a concussion at least once during that season. The response "Did not feel the concussion was serious/severe and felt you could still continue to play with little danger to yourself" was the most commonly listed reason (49/106) for not seeking medical attention for a presumed concussion. Many players answered that they did not seek medical attention because they did not want to be removed from a game (42/106) and/or they did not want to risk missing future games (41/106) by being diagnosed with a concussion. Some professional football players who believed they had suffered a concussion chose not to seek medical attention at the time of injury. Players seemed educated about the concussion evaluation process and possible treatment guidelines, but this knowledge did not necessarily translate into safe and appropriate behavior at the time of injury.



Gaelic Football
#1 Lower limb injuries in men's elite Gaelic football: A prospective investigation among division one teams from 2008 to 2015
Reference: J Sci Med Sport. 2017 Sep 6. pii: S1440-2440(17)31028-9. doi: 10.1016/j.jsams.2017.08.023. [Epub ahead of print]
Authors: Roe M, Murphy JC, Gissane C, Blake C
Summary: The purpose was to prospectively investigate incidence and associated time-loss of lower limb injuries in elite Gaelic football. Additionally, to identify sub-groups of elite players at increased risk of sustaining a lower limb injury. Team physiotherapists provided exposure and injury on a weekly basis to the National Gaelic Athletic Association (GAA) Injury Surveillance Database. Injury was defined using a time-loss criterion. Fifteen different teams participated throughout the 8-year study providing 36 team datasets from 2008 to 2015. Lower limb injuries (n=1239) accounted for 83.5% (95% CI 82.0-85.0) and 77.6% (95% CI 75.8-79.4) of training and match-play injuries, respectively. Injury incidence was 4.5 (95% CI 3.7-5.2) and 38.4 (95% CI 34.3-42.60) per 1000 training and match-play hours, respectively. One-in-four (25.0%, 95% CI 22.4-27.0) lower limb injuries were recurrent. Non-contact injuries accounted for 80.9% (95% CI 79.2-82.6) of cases. The median team rate was 30 (IQR 24-43) lower limb injuries per season resulting in 840.8 (95% CI 773.3-908.2) time-loss days. Previously injured players had a 2.5-times (OR 95% CI 2.2-2.8) greater risk of sustaining a lower limb injury. Overall, 56.8% of players with a previous lower limb injury sustained another. Incidence was higher for forward players and those aged >25years. Lower limb injuries are the most common injury among elite division one Gaelic football teams. Injury risk management should become an ongoing component of a player's development programme and consider injury history, age, and playing position.

Sun

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Football is...(#35)

Preparing the players with football specific movements.

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2017

Football is...(#34)

Time motion analysis to design training sessions.

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2017

Latest research in football - week 42 - 2017

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 Repeated-Sprint Ability in Division I Collegiate Male Soccer Players: Positional Differences and Relationships with Performance Tests
Reference: J Strength Cond Res. 2017 Oct 16. doi: 10.1519/JSC.0000000000001948. [Epub ahead of print]
Autors: Lockie RG, Moreno MR, Orjalo AJ, Stage AA, Liu TM, Birmingham-Babauta SA, Hurley JM, Torne IA, Beiley MD, Risso FG, Davis DL, Lazar A, Stokes JJ, Giuliano DV.
Summary: Repeated-sprint ability (RSA) in essential for soccer. Important considerations when assessing RSA is whether there are differences between positions (defenders, midfielders, forwards), and what physiological characteristics may contribute to RSA. This has not been assessed in collegiate male players. Eighteen Division I male field players from one school performed several performance tests. The RSA test involved 7 x 30-m sprints completed on 20-s cycles. Measurements included total time (TT), and performance decrement (percent change in time from the first to last sprint; PD). Subjects also completed tests of lower-body power (vertical [VJ] and standing broad [SBJ] jump); linear (30-m sprint; 0-5, 0-10, 0-30 m intervals) and change-of-direction (505) speed; and soccer-specific endurance (Yo-Yo Intermittent Recovery Test Level 2; YYIRT2). A one-way ANOVA (p < 0.05) determined between-position differences, and effect sizes were calculated. Pearson's correlations (p < 0.05) calculated relationships between RSA TT and PD with the other tests. There were no significant between-position differences for any test. There were large effects for the faster right-leg 505 and greater YYIRT2 distance for midfielders compared to defenders and forwards. Nonetheless, no between-position differences in RSA TT and PD were documented. There were relationships between RSA TT and the VJ (r = -0.59), SBJ (r = -0.61), 0-10 m (r = 0.64) and 0-30 m (r = 0.83) sprint intervals. There were no significant correlations for RSA PD. Male field players from one collegiate soccer team can demonstrate similar RSA across different positions. Greater lower-body power and sprinting speed could augment RSA.


#2 Pre-season dietary intake of professional soccer players
Reference: Nutr Health. 2017 Jan 1:260106017737014. doi: 10.1177/0260106017737014. [Epub ahead of print]
Authors: Raizel R, Godois ADM, Coqueiro AY, Voltarelli FA, Fett CA, Tirapegui J, Ravagnani FCP, Coelho-Ravagnani CF
Summary: Despite the well-documented importance of nutrition in optimizing performance and health, the dietary intake of soccer players has attracted little attention. We aimed to assess the pre-season dietary intake of professional soccer players and its adequacy in macro and micronutrients. The pre-season dietary intake of 19 male athletes was assessed using a semi-structured 3-day food record. To determine dietary adequacy and excess, energy and macronutrient intake were compared with the Brazilian dietary reference values for athletes, and micronutrients were compared with the Estimated Average Requirement - EAR (minimum recommendation) and Tolerable Upper Intake Level - UL (maximum recommendation). Mean daily energy intake (40.74±12.81 kcal/kg) was adequate. However, there was a low carbohydrate intake (5.44±1.86 g/kg/day) and a high amount of protein and fat (1.91±0.75 and 1.27±0.50 g/kg/day, respectively). Sodium intake (3141.77±939.76 mg/day) was higher than UL (2300 mg/day), while the majority of players showed daily intake of vitamin A (74%), vitamin D (100%), folate (58%), calcium and magnesium (68%) below the EAR (625, 10 and 320 µg/day, 800 and 330 mg/day, respectively). The dietary intake of professional soccer players was adequate in energy, but inadequate in macro and micronutrients, which suggests the need to improve nutritional practices to sustain the physical demands of soccer during pre-season.


#3 Head and neck size and neck strength predict linear and rotational acceleration during purposeful soccer heading
Reference: Sports Biomech. 2017 Oct 16:1-15. doi: 10.1080/14763141.2017.1360385. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Arbogast KB, Rose WC, Glutting JJ, Kaminski TW
Summary: There is increasing societal concern about the long-term effects of repeated impacts from soccer heading, but there is little information about ways to reduce head impact severity. The purpose of this study was to identify factors that contribute to head acceleration during soccer heading. One-hundred soccer players completed 12 controlled soccer headers. Peak linear (PLA) and rotational (PRA) accelerations were measured using a triaxial accelerometer and gyroscope. Head acceleration contributing factors were grouped into 3 categories: size (head mass, neck girth), strength (sternocleidomastoid, upper trapezius) and technique [kinematics (trunk, head-to-trunk range-of-motion), sternocleidomastoid and upper trapezius activity]. Multiple regression analyses indicated size variables explained 22.1% of the variance in PLA and 23.3% of the variance in PRA; strength variables explained 13.3% of the variance in PLA and 17.2% of the variance in PRA; technique variables did not significantly predict PLA or PRA. These findings suggest that head and neck size and neck strength predict PLA and PRA. Anthropometric and neck strength measurements should be considered when determining an athlete's readiness to begin soccer heading.


#4 Difference in kick motion of adolescent soccer players in presence and absence of low back pain
Reference: Gait Posture. 2017 Oct 7;59:89-92. doi: 10.1016/j.gaitpost.2017.10.012. [Epub ahead of print]
Authors: Tojima M, Torii S
Summary: Many adolescent soccer players experience low back pain (LBP). However, there are no reports studying the kick motion of adolescent soccer players experiencing LBP. This study aimed to clarify the kick motion of adolescent soccer players in the presence and absence of LBP. We recruited 42 adolescent soccer players and divided them into two groups according to the presence of LBP (LBP group, n=22) and absence of LBP (NBP group, n=20). We measured real-time kick motion using a three-dimensional motion analysis system. We placed 65 spherical markers on each anatomical landmark and calculated the angle of the lumbar spine, center of mass (COM) of the whole body, and displacement of the support foot. We used an unpaired t-test to compare the data between the groups. Compared with the NBP group, the LBP group showed a lateral shift in COM, which increased the duration of kick motion. The presence of LBP affected the posterior positioning of the support foot and restricted the player's lumbar spine from bending laterally. A lateral shift in COM and larger rotation of the lumbar spine could stress the lumbar spine during kick motion. Therefore, coaches and athletic trainers should pay attention to soccer players' lumbar spine rotation and the COM shift during kick motion. This would be important for preventing LBP in adolescent soccer players.


#5 Hamstring muscle injuries in elite football: translating research into practice
Reference: Br J Sports Med. 2017 Oct 19. pii: bjsports-2017-097573. doi: 10.1136/bjsports-2017-097573. [Epub ahead of print]
Authors: Buckthorpe M, Gimpel M, Wright S, Sturdy T, Stride M


#6 A social network analysis of the goal scoring passing networks of the 2016 European Football Championships
Reference: Hum Mov Sci. 2017 Oct 16. pii: S0167-9457(17)30539-0. doi: 10.1016/j.humov.2017.10.001. [Epub ahead of print]
Authors: Mclean S, Salmon PM, Gorman AD, Stevens NJ, Solomon C
Summary: In the current study, social network analysis (SNA) and notational analysis (NA) methods were applied to examine the goal scoring passing networks (GSPN) for all goals scored at the 2016 European Football Championships. The aim of the study was to determine the GSPN characteristics for the overall tournament, between the group and knock out stages, and for the successful and unsuccessful teams. The study also used degree centrality (DC) metrics as a novel method to determine the relative contributions of the pitch locations involved in the GSPN. To determine changes in GSPN characteristics as a function of changing score line, the analysis considered the match status of the game when goals were scored. There were significant differences for SNA metrics as a function of match status, and for the DC metrics in the comparison of the different pitch locations. There were no differences in the SNA metrics for the GSPN between teams in the group and knock out stages, or between the successful and unsuccessful teams. The results indicate that the GSPN had low values for network density, cohesion, connections, and duration. The networks were direct in terms of pitch zones utilised, where 85% of the GSPN included passes that were played within zones or progressed through the zones towards the goal. SNA and NA metrics were significantly different as a function of changing match status. The current study adds to the previous research on goal scoring in football, and demonstrates a novel method to determine the prominent pitch zones involved in the GSPN. These results have implications for match analysis and the coaching process.


#7 "Football is a boys' game": children's perceptions about barriers for physical activity during recess time
Reference: Int J Qual Stud Health Well-being. 2017;12(sup2):1379338. doi: 10.1080/17482631.2017.1379338.
Authors: Martinez-Andres M, Bartolome-Gutierrez R, Rodriguez-Martin B, Pardo-Guijarro MJ, Martinez-Vizcaino V
Summary: The aim of the study was to know the factors that influence boys and girls' perceptions for performing physical activity during playground recess from their own perspective. Ninety-eight schoolchildren aged 8-11 years from five schools from Cuenca (Spain) participated in 22 focus groups and carried out 98 drawings following the socioecological model as a theoretical framework. A content analysis of the transcripts from the focus groups and drawings was carried out by three researchers. Results showed that, in spite of boys and girls identified same barriers, there were gender differences in their perceptions. Gender socialization was the key as central category and helped to understand these differences. Boys preferred play football and this sport had a monopoly on the recess space. Weather was a barrier for boys. Girls and boys, who did not play football, were relegated to peripheral areas and lack of materials was a barrier for them. Teachers were a barrier for all children who did not play football. Thus, in order to promote recess physical activity, researchers, teachers and educational policy makers should take into account gender socialization and promote inclusive non-curricular physical activity in schools.


#8 Effectiveness of above real-time training on decision-making in elite football: A dose-response investigation
Reference: Prog Brain Res. 2017;234:101-116. doi: 10.1016/bs.pbr.2017.08.007. Epub 2017 Sep 22.
Authors: Farahani JJ, Javadi AH, O'Neill BV, Walsh V
Summary: We examined the effects of video-based training in elite footballers' decision-making by presenting videos with training and testing scenarios at above real-time speeds. We also examined different training protocols to establish how much training is beneficial. We found that above real-time training improved accuracy and response time in football decision-making. In terms of scheduling, we found that the benefits were short lasting and did not last beyond 2 weeks.


#9 Elite professional soccer players’ experience of injury prevention
Reference: Cogent Medicine
Authors: Kristiansen JB, Larsson I.
Download link: https://www.cogentoa.com/article/10.1080/2331205X.2017.1389257.pdf
Summary: Injuries are common in professional soccer and might interfere with the ability of the team and the individual player to perform. Several studies have shown the benefits of exercise as a means to prevent injuries in soccer, but research is needed to substantiate, how injury prevention strategies are best implemented. The purpose of this study was to describe and interpret soccer players’ experience of injury prevention. A hermeneutic phenomenological approach was used as described by van Manen. Eight professional Danish soccer players were interviewed with open-ended interviews. The players’ lived experience of injury prevention across all the interviews were shown as the interaction between three overreaching themes: (1) being a part of a performance environment, (2) the need for an individual approach and (3) strong personal ambitions. Interaction between the three themes empowered the players to engage in injury prevention. Professional soccer players’ experience of injury prevention can be interpreted within the four components of the empowerment model: (1) impact, (2) competence, (3) meaningfulness and (4) choice. The presence of the four components empowered the players to engage in injury prevention in the soccer club.



Australian Football
#1 SCAT3 changes from baseline and associations with X2 Patch measured head acceleration in amateur Australian football players
Reference: J Sci Med Sport. 2017 Oct 6. pii: S1440-2440(17)31637-7. doi: 10.1016/j.jsams.2017.09.591. [Epub ahead of print]
Authors: Willmott C, McIntosh AS, Howard T, Mitra B, Dimech-Betancourt B, Donovan J, Rosenfeld JV
Summary: The purpose was to investigate changes from baseline on SCAT3 as a result of football game exposure, and association with X2 Patch measured head acceleration events in amateur Australian footballers. Peak linear acceleration (PLA) of the head (>10 g) was measured by wearable head acceleration sensor X2 Biosystems X-Patch in male (n=34) and female (n=19) Australian footballers. SCAT3 was administered at baseline (B) and post-game (PG). 1394 head acceleration events (HEA) >10 g were measured. Mean and median HEA PLA were recorded as 15.2 g (SD=9.2, range=10.0-115.8) and 12.4 g (IQR=11.0-15.6) respectively. No significant difference in median HEA PLA (g) was detected across gender (p=0.55), however, more HEAs were recorded in males (p=0.03). A greater number (p=0.004) and severity (p<0.001) of symptoms were reported PG than at B. No significant association between number of HEA or median PLA, and SCAT3 change scores (p>0.05 for all), was identified for either gender. Increase in symptom severity post game was not associated with X2 measured HEA. Males sustained more HEA, however HEA PLA magnitude did not differ across gender. Further work on the validation of head acceleration sensors is required and their role in sports concussion research and medical management.


#2 The Influence of Physical Qualities on Activity Profiles of Female Australian Football Match-Play
Reference: Int J Sports Physiol Perform. 2017 Oct 16:1-20. doi: 10.1123/ijspp.2016-0723. [Epub ahead of print]
Authors: Black GM, Gabbett TJ, Johnston RD, Cole MH, Naughton G, Dawson B
Summary: The rapid transition of female Australian football players from amateur to semi-elite competitions has the potential for athletes to be underprepared for match-play. To gain an understanding the match demands of female football, the aims of this study were three-fold: (1) to highlight the physical qualities that discriminate selected and non-selected female Australian Football players, (2) to investigate activity profiles of female Australian Football players, and (3) to gain an understanding of the influence of physical qualities on running performance in female Australian Football match-play. Twenty-two female Australian football (AF) state academy players (mean ± SD age, 23.2 ± 4.5 years) and 27 non-selected players (mean ± SD age, 23.4 ± 4.9 years) participated in this study. The Yo-Yo Intermittent Recovery Test (Level 1), countermovement jump and 30m sprint tests were completed prior to the competitive season. During 14 matches, players wore global positioning system (GPS) units to describe the running demands of female AF match-play. Selected players were faster over 30 metres (ES=0.57; p=0.04) and covered greater distances on the Yo-Yo IR1 test (ES=1.09; p<0.001). Selected midfielders spent greater time on the field and covered greater total distances (ES=0.73-0.85; p<0.009). No differences were reported in relative distances covered between selected and non-selected players (p=0.08). Players who were faster over 5 metres (r= -0.612), and 30-metres (r= -0.807) and performed better on the Yo-Yo IR1 (r=0.489) covered greater high-speed distances during match-play. Selected female AF players were faster and had greater intermittent running ability than players not selected to a State academy program. An emphasis should be placed on the development of physical fitness in this playing group to ensure optimal preparation for the national competition.



American football
#1 High-magnitude head impact exposure in youth football
Reference: J Neurosurg Pediatr. 2017 Oct 17:1-9. doi: 10.3171/2017.5.PEDS17185. [Epub ahead of print]
Authors: Campolettano ET, Gellner RA, Rowson S
Summary: Even in the absence of a clinically diagnosed concussion, research suggests that neurocognitive changes may develop in football players as a result of frequent head impacts that occur during football games and practices. The objectives of this study were to determine the specific situations in which high-magnitude impacts (accelerations exceeding 40 g) occur in youth football games and practices and to assess how representative practice activities are of games with regard to high-magnitude head impact exposure. METHODS A total of 45 players (mean age 10.7 ± 1.1 years) on 2 youth teams (Juniors [mean age 9.9 ± 0.6 years; mean body mass 38.9 ± 9.9 kg] and Seniors [mean age 11.9 ± 0.6 years; mean body mass 51.4 ± 11.8 kg]) wore helmets instrumented with accelerometer arrays to record head impact accelerations for all practices and games. Video recordings from practices and games were used to verify all high-magnitude head impacts, identify specific impact characteristics, and determine the amount of time spent in each activity. RESULTS A total of 7590 impacts were recorded, of which 571 resulted in high-magnitude head impact accelerations exceeding 40 g (8%). Impacts were characterized based on the position played by the team member who received the impact, the part of the field where the impact occurred, whether the impact occurred during a game or practice play, and the cause of the impact. High-magnitude impacts occurred most frequently in the open field in both games (59.4%) and practices (67.5%). "Back" position players experienced a greater proportion of high-magnitude head impacts than players at other positions. The 2 teams in this study structured their practice sessions similarly with respect to time spent in each drill, but impact rates differed for each drill between the teams. CONCLUSIONS High-magnitude head impact exposure in games and practice drills was quantified and used as the basis for comparison of exposure in the 2 settings. In this cohort, game impact rates exceeded those for practice. Back players, who were often positioned in the open field, were shown to experience elevated levels of head impact exposure relative to players at other positions. The analysis also suggests that practice intensity, which may be influenced by coaching style, may also affect high-magnitude head impact exposure. Future studies should investigate this aspect as a factor affecting head impact exposure.


#2 Examination of Risk for Sleep Disordered Breathing among College Football Players
Reference: J Sport Rehabil. 2017 Oct 16:1-24. doi: 10.1123/jsr.2017-0127. [Epub ahead of print]
Authors: Peck B, Renzi T, Peach H, Gaultney J, Marino JS
Summary: Professional football linemen are at risk for sleep disordered breathing (SDB) compared to other types of athletes. It is currently unknown whether collegiate football linemen display a similar risk profile. The objectives were 1) Determine for the first time whether collegiate football linemen show risk for SDB, and 2) Test the hypothesis that SDB risk is higher in collegiate football linemen compared to an athletic comparison group. Male football linemen (n = 21) and track (n = 22) Division I athletes between the ages of 18 and 22 participated in this study.  Participants completed the Multivariable Apnea Prediction (MAP) Index and Epworth Sleepiness Scale (ESS) surveys, validated measures of symptoms of sleep apnea and daytime sleepiness, respectively. Neck and waist circumferences, blood pressure, Mallampati Index (MMPI) and Tonsil Size were determined, followed by body composition assessment using DEXA. Scores from surveys, anthropometric data, MMPI and body composition were used in the statistical analysis. Survey data demonstrated a deficiency in sleep quality and efficiency, coinciding with increased self-reported symptoms of apnea (MAP index=0.79) in college linemen relative to track athletes. Neck circumference (45cm), waist circumference (107.07cm), body mass index (36.64kg/m2) and body fat % (30.19%), all of which exceeded the clinical predictors of risk for obstructive sleep apnea, were significantly greater in linemen compared to track athletes. MAP variables were significantly correlated with MMPI, neck circumference, body fat %, body mass index, and systolic blood pressure (r ≥ .31, p < 0.05), indicating that college football linemen are at increased risk for SDB. Risk factors for SDB recognized in professional football linemen are also present at the collegiate level. Screening may minimize present or future risk for SDB, as well as the downstream risk of SDB-associated metabolic and cardiovascular disease.



Mon

23

Oct

2017

Football is...(#33)

Short and long shots + different angles = complexity of goal defending

Mon

23

Oct

2017

Football is...(#32)

utilizing both feet - not only for running!

Fri

20

Oct

2017

Football is...(#31)

Dribbling can also be used to improve aerobic endurance.

Thu

19

Oct

2017

Small-sided games website update

The Small-sided training part on the website was updated with some research.

 

If you want to know everything about small-sided games you should read the updated section and click HERE.

Wed

18

Oct

2017

Football is...(#30)

Training one-touch play for promising goal scoring opportunities.

Wed

18

Oct

2017

Football is...(#29)

The core connects arms and legs - train it use it.

Mon

16

Oct

2017

Football is...(#28)

Skillful players have a good first touch.

Mon

16

Oct

2017

Latest research in football - week 41 - 2017

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 Unloaded vs. Loaded Plyometrics on Speed and Power Performance of Elite Young Soccer Players
Reference: Front Physiol. 2017 Sep 26;8:742. doi: 10.3389/fphys.2017.00742. eCollection 2017.
Authors: Kobal R, Pereira LA, Zanetti V, Ramirez-Campillo R, Loturco I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5623051/pdf/fphys-08-00742.pdf
Summary: The purpose of this study was to investigate the effects of loaded and unloaded plyometric training strategies on speed and power performance of elite young soccer players. Twenty-three under-17 male soccer players (age: 15.9 ± 1.2 years, height: 178.3 ± 8.1 cm, body-mass (BM): 68.1 ± 9.3 kg) from the same club took part in this study. The athletes were pair-matched in two training groups: loaded vertical and horizontal jumps using an haltere type handheld with a load of 8% of the athletes' body mass (LJ; n = 12) and unloaded vertical and horizontal plyometrics (UJ; n = 11). Sprinting speeds at 5-, 10-, and 20-m, mean propulsive power (MPP) relative to the players' BM in the jump squat exercise, and performance in the squat jump (SJ) and countermovement jump (CMJ) were assessed pre- and post-training period. During the experimental period, soccer players performed 12 plyometric training sessions across a 6-week preseason period. Magnitude based inferences and standardized differences were used for statistical analysis. A very likely increase in the vertical jumps was observed for the LJ group (99/01/00 and 98/02/00 for SJ and CMJ, respectively). In the UJ group a likely increase was observed for both vertical jumps (83/16/01 and 90/10/00, for SJ and CMJ, respectively). An almost certainly decrease in the sprinting velocities along the 20-m course were found in the LJ group (00/00/100 for all split distances tested). Meanwhile, in the UJ likely to very likely decreases were observed for all sprinting velocities tested (03/18/79, 01/13/86, and 00/04/96, for velocities in 5-, 10-, and 20-m, respectively). No meaningful differences were observed for the MPP in either training group (11/85/04 and 37/55/08 for LJ and UJ, respectively). In summary, under-17 professional soccer players increased jumping ability after a 6-week preseason training program, using loaded or unloaded jumps. Despite these positive adaptations, both plyometric strategies failed to produce worthwhile improvements in maximal speed and power performances, which is possible related to the interference of concurrent training effects. New training strategies should be developed to ensure adequate balance between power and endurance loads throughout short (and high-volume) soccer preseasons.


#2 Soccer-based promotion of voluntary medical male circumcision: A mixed-methods feasibility study with secondary students in Uganda
Reference: PLoS One. 2017 Oct 9;12(10):e0185929. doi: 10.1371/journal.pone.0185929. eCollection 2017.
Authors: Miiro G, DeCelles J, Rutakumwa R, Nakiyingi-Miiro J, Muzira P, Ssembajjwe W, Musoke S, Gibson LJ, Hershow RB, Francis S, Torondel B, Ross DA, Weiss HA
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0185929&type=printable
Summary: The Ugandan government is committed to scaling-up proven HIV prevention strategies including safe male circumcision, and innovative strategies are needed to increase circumcision uptake. The aim of this study was to assess the acceptability and feasibility of implementing a soccer-based intervention ("Make The Cut") among schoolboys in a peri-urban district of Uganda. The intervention was led by trained, recently circumcised "coaches" who facilitated a 60-minute session delivered in schools, including an interactive penalty shoot-out game using metaphors for HIV prevention, sharing of the coaches' circumcision story, group discussion and ongoing engagement from the coach to facilitate linkage to male circumcision. The study took place in four secondary schools in Entebbe sub-district, Uganda. Acceptability of safe male circumcision was assessed through a cross-sectional quantitative survey. The feasibility of implementing the intervention was assessed by piloting the intervention in one school, modifying it, and implementing the modified version in a second school. Perceptions of the intervention were assessed with in-depth interviews with participants. Of the 210 boys in the cross-sectional survey, 59% reported being circumcised. Findings showed high levels of knowledge and generally favourable perceptions of circumcision. The initial implementation of Make The Cut resulted in 6/58 uncircumcised boys (10.3%) becoming circumcised. Changes made included increasing engagement with parents and improved liaison with schools regarding the timing of the intervention. Following this, uptake improved to 18/69 (26.1%) in the second school. In-depth interviews highlighted the important role of family and peer support and the coach in facilitating the decision to circumcise. This study showed that the modified Make The Cut intervention may be effective to increase uptake of safe male circumcision in this population. However, the intervention is time-intensive, and further work is needed to assess the cost-effectiveness of the intervention conducted at scale.


#3 The Effects of Foam Rolling as a Recovery Tool in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Oct 7. doi: 10.1519/JSC.0000000000002277. [Epub ahead of print]
Authors: Rey E, Padron-Cabo A, Costa PB, Barcala-Furelos R
Summary: Foam rolling (FR) is a common strategy used after training and competition by players. However, no previous studies have assessed the effectiveness of FR as recovery tool in sports populations. The aim of this study was to examine the effectiveness of FR (20 minutes of foam rolling exercises on quadriceps, hamstrings, adductors, gluteals, and gastrocnemius) and passive recovery (20 minutes sit on a bench) interventions performed immediately after a training session on Total Quality Recovery (TQR), perceived muscle soreness, jump performance, agility, sprint, and flexibility 24 hours after the training. During 2 experimental sessions, 18 professional soccer players (age 26.6 ± 3.3 years; height: 180.2 ± 4.5 cm; body mass: 75.8 ± 4.7 kg) participated in a randomized fully controlled trial design. The first session was designed to collect the pre-test values of each variable. After baseline measurements, the players performed a standardized soccer training. At the end of training unit, all the players were randomly assigned to the FR recovery group and the passive recovery group. A second experimental session was carried out to obtain the posttest values. Results from the between-group analyses showed that FR had a large effect on the recovery in agility (Effect Sizes [ES]= 1.06), TQR (ES= 1.08), and perceived muscle soreness (ES= 1.02) in comparison to passive recovery group at 24 h post-training. Thus, it is recommended soccer coaches and physical trainers working with high-level players use a structured recovery session lasting from 15 to 20 min based on FR exercises that could be implemented at the end of a training session to enhance recovery between training loads.


#4 Injury prevention in male youth soccer: Current practices and perceptions of practitioners working at elite English academies
Reference: J Sports Sci. 2017 Oct 11:1-9. doi: 10.1080/02640414.2017.1389515. [Epub ahead of print]
Authors: Read PJ, Jimenez P, Oliver JL, Lloyd RS
Summary: Forty-one practitioners inclusive of physiotherapists, sports scientists and strength and conditioning coaches from the academies of elite soccer clubs in the United Kingdom completed an on-line questionnaire which examined their: (1) background information; (2) perceptions of injury occurrence and risk factors; (3) screening and return to play; and (4) approach to designing and delivering injury prevention programmes with a response rate of 55% (41/75). Contact injuries were the most common mechanism reported and players between 13-16 years of age were perceived to be at the greatest risk. Pertinent risk factors included: reduced lower limb and eccentric hamstring strength, proprioception, muscle imbalances, and under developed foundational movement skills. Joint range of motion, jump tests, the functional movement screen, overhead and single leg squats were the most utilised screening methods. Training modalities rated in order of importance included: resistance training, flexibility development, agility, plyometrics and balance training. Training frequency was most commonly once or twice per week, during warm-ups, independent sessions or a combination of both. Injury prevention strategies in this cohort appear to be logical; however, the classification of injury occurrence and application of screening tools to identify "at risk" players do not align with existing research. The frequency and type of training used may also be insufficient to elicit an appropriate stimulus to address pertinent risk factors based on current recommendations.


#5 The physical response to a simulated period of soccer-specific fixture congestion
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002257. [Epub ahead of print]
Authors: Page RM, Marrin K, Brogden CM, Greig M
Summary: The aim of this study was to assess the physiological, perceptual, and mechanical measures associated with the completion of a simulated period of short-term soccer-specific fixture congestion. Ten male semi-professional soccer players completed three trials of a treadmill-based match simulation, with 48 hours intervening each trial. A repeated measures general linear model identified significantly (P= 0.02) lower knee flexor peak torque (PT) recorded at 300 degs[BULLET OPERATOR]s in the second (141.27 ± 28.51 Nm) and third trials (139.12 ± 26.23 Nm) when compared to the first (154.17 ± 35.25 Nm). Similarly, muscle soreness (MS) and PT data recorded at 60 degs[BULLET OPERATOR]s were significantly (P< 0.05) different in the third trial (MS= 42 ± 25 a.u; PT60= 131.10 ± 35.38 Nm) when compared to the first (MS= 29 ± 29 a.u; PT60= 145.61 ± 42.86 Nm). Significant (P= 0.003) differences were also observed for mean Bicep Femoris electromyography (EMGmean) between the third trial (T0-15= 126.36 ± 15.57 µV; T75-90= 52.18 ± 17.19 µV) and corresponding time points in the first trial (T0-15= 98.20 ± 23.49 µV; T75-90= 99.97 ± 39.81 µV). Cumulative increases in perceived exertion, heart rate, oxygen consumption, blood lactate concentrations, EMGmean, and PlayerLoad were recorded across each trial. MS and PT were also significantly different post-trial. There were however no significant main effects or interactions for the salivary Immunoglobulin A, and the medial-lateral PlayerLoad metrics. These data suggest a biomechanical and muscular emphasis with residual fatigue, with implications for injury risk and the development of recovery strategies.


#6 Steroid hormones and psychological responses to soccer matches: Insights from a systematic review and meta-analysis
Reference: PLoS One. 2017 Oct 12;12(10):e0186100. doi: 10.1371/journal.pone.0186100. eCollection 2017.
Authors: Slimani M, Baker JS, Cheour F, Taylor L, Bragazzi NL
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0186100&type=printable
Summary: The present systematic review and meta-analysis aimed to assess the perturbations in hormonal and psychological homeostasis in response to soccer match-play. These perturbations were explored according to match outcome (i.e., win versus loss), gender, type of contest (i.e., competitive versus non-competitive fixtures) and competitive level (i.e., novice versus high-level). The review was conducted according to the Population/Intervention or Exposure/Comparison/Outcome(s) (PICO) criteria and the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Match outcome, type of contest and competitive levels were moderator variables in the examined steroid hormones responses to a soccer match-play. Different testosterone responses were seen between match winners (increase) and losers (decrease) when compared to pre-game or baseline values (p <0.05), whilst no changes could be detected for cortisol relative to match outcome in female soccer players. Males (Δ% = 6.26; ES = 0.28) demonstrated a marginally lower increase in testosterone levels when compared to females (Δ% = 49.16; ES = 1.00), though not statistically significant. Females (Δ% = 162.7; ES = 0.98) did not demonstrate elevated cortisol match response compared to males (Δ% = 34.60; ES = 1.20). Male novice soccer match-play increased cortisol levels compared to high-level soccer match-play (Q = 18.08, p<0.001). Competitive soccer matches increased cortisol levels compared to non-competitive fixtures (i.e., collegiate tournament). Additionally, competitive levels moderate the relationship between a soccer match and testosterone levels (p <0.001), regardless of gender differences. From the presented systematic review and meta-analysis it appears (1) cortisol changes are associated with cognitive anxiety in starter female soccer players, while (2) testosterone changes are associated with changes in mood state in females and social connectedness in male soccer players. This apparent psycho-physiological relationship may proffer the opportunity for targeted intervention(s) by practitioners to favorably influence performance and/or recovery agendas. Further mechanistic and/or applied evidence is required in this regard in addition to further data sets from females.


#7 Effects of Plyometric Training on Components of Physical Fitness in Prepuberal Male Soccer Athletes: The Role of Surface Instability
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002262. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Sammoud S, Bouguezzi R, Mkaouer B, Hachana Y, Granacher U
Summary: Previous studies contrasted the effects of plyometric training (PT) conducted on stable vs. unstable surfaces on components of physical fitness in child and adolescent soccer players. Depending on the training modality (stable vs. unstable), specific performance improvements were found for jump (stable PT) and balance performances (unstable PT). In an attempt to combine the effects of both training modalities, this study examined the effects of PT on stable surfaces compared with combined PT on stable and unstable surfaces on components of physical fitness in prepuberal male soccer athletes. Thirty-three boys were randomly assigned to either a PT on stable surfaces (PTS; n = 17; age = 12.1 ± 0.5 years; height = 151.6 ± 5.7 cm; body mass = 39.2 ± 6.5 kg; and maturity offset = -2.3 ± 0.5 years) or a combined PT on stable and unstable surfaces (PTC; n = 16; age = 12.2 ± 0.6 years; height = 154.6 ± 8.1 cm; body mass = 38.7 ± 5.0 kg; and maturity offset = -2.2 ± 0.6 years). Both intervention groups conducted 4 soccer-specific training sessions per week combined with either 2 PTS or PTC sessions. Before and after 8 weeks of training, proxies of muscle power (e.g., countermovement jump [CMJ], standing long jump [SLJ]), muscle strength (e.g., reactive strength index [RSI]), speed (e.g., 20-m sprint test), agility (e.g., modified Illinois change of direction test [MICODT]), static balance (e.g., stable stork balance test [SSBT]), and dynamic balance (unstable stork balance test [USBT]) were tested. An analysis of covariance model was used to test between-group differences (PTS vs. PTC) at posttest using baseline outcomes as covariates. No significant between-group differences at posttest were observed for CMJ (p > 0.05, d = 0.41), SLJ (p > 0.05, d = 0.36), RSI (p > 0.05, d = 0.57), 20-m sprint test (p > 0.05, d = 0.06), MICODT (p > 0.05, d = 0.23), and SSBT (p > 0.05, d = 0.20). However, statistically significant between-group differences at posttest were noted for the USBT (p < 0.01, d = 1.49) in favor of the PTC group. For most physical fitness tests (except RSI), significant pre-to-post improvements were observed for both groups (p < 0.01, d = 0.55-3.96). Eight weeks of PTS or PTC resulted in similar performance improvements in components of physical fitness except for dynamic balance. From a performance-enhancing perspective, PTC is recommended for pediatric strength and conditioning coaches because it produced comparable training effects as PTS on proxies of muscle power, muscle strength, speed, agility, static balance, and additional effects on dynamic balance.


American Football
#1 Heart Rate Variability and Training Load Among National Collegiate Athletic Association Division 1 College Football Players Throughout Spring Camp
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002241. [Epub ahead of print]
Authors: Flatt AA, Esco MR, Allen JR, Robinson JB, Earley RL, Fedewa MV, Bragg A, Keith CM, Wingo JE
Summary: The purpose of this study was to determine whether recovery of cardiac-autonomic activity to baseline occurs between consecutive-day training sessions among positional groups of a collegiate football team during Spring camp. A secondary aim was to evaluate relationships between chronic (i.e., 4-week) heart rate variability (HRV) and training load parameters. Baseline HRV (lnRMSSD_BL) was compared with HRV after ∼20 hours of recovery before next-day training (lnRMSSDpost20) among positional groups composed of SKILL (n = 11), MID-SKILL (n = 9), and LINEMEN (n = 5) with a linear mixed model and effect sizes (ES). Pearson and partial correlations were used to quantify relationships between chronic mean and coefficient of variation (CV) of lnRMSSD (lnRMSSD_chronic and lnRMSSDcv, respectively) with the mean and CV of PlayerLoad (PL_chronic and PL_cv, respectively). A position × time interaction was observed for lnRMSSD (p = 0.01). lnRMSSD_BL was higher than lnRMSSDpost20 for LINEMEN (p < 0.01; ES = large), whereas differences for SKILL and MID-SKILL were not statistically different (p > 0.05). Players with greater body mass experienced larger reductions in lnRMSSD (r = -0.62, p < 0.01). Longitudinally, lnRMSSDcv was significantly related to body mass (r = 0.48) and PL_chronic (r = -0.60). After adjusting for body mass, lnRMSSDcv and PL_chronic remained significantly related (r = -0.43). The ∼20-hour recovery time between training sessions on consecutive days may not be adequate for restoration of cardiac-parasympathetic activity to baseline among LINEMEN. Players with a lower chronic training load throughout camp experienced greater fluctuation in lnRMSSD (i.e., lnRMSSDcv) and vice versa. Thus, a capacity for greater chronic workloads may be protective against perturbations in cardiac-autonomic homeostasis among American college football players.


#2 Longitudinal Changes in Body Composition throughout Successive Seasonal Phases among Canadian University Football Players
Reference: J Strength Cond Res. 2017 Oct 7. doi: 10.1519/JSC.0000000000002011. [Epub ahead of print]
Authors: Kim J, Delisle-Houde P, Reid RE, Andersen RE.
Summary: The purpose of this study was to assess changes in body composition during seasonal phases of the training year among Canadian Inter-University Sport (CIS) football players. Forty university football players were assessed for anthropometry, total body composition, regional body composition and central adiposity over a 7-month period including the summer-off-season and the in-season. Baseline testing occurred in April, prior to the summer-off-season, and follow-ups were completed prior to training camp, at the beginning of August, and following the in-season, at the beginning of November. Linemen had the greatest tissue percent fat (25.98 ± 6.56%) at baseline, significantly (p < 0.01) greater than big skill (18.69 ± 3.97%) and followed by skill (14.35 ± 3.39%) who were significantly (p < 0.01) leaner than both other groups. Skill players significantly increased fat mass (0.98 ± 0.30 kg, p < 0.05) and waist-to-hip ratio (WHR; 0.02 ± 0.01, p ≤ 0.05) during the in-season, and linemen increased visceral fat mass from April to November (0.20 ± 0.06 kg, p ≤ 0.01). All players significantly (-1.26 ± 0.30 kg, p = 0.001) decreased lean mass during the in-season. All groups significantly increased bone mineral content during the summer-off-season (p < 0.05). There was also a significant time × summer training location interaction (p < 0.05) for fat mass with athletes who remained on campus during summer months gaining the least amount of adiposity. Body composition and central adiposity appear to change differentially among positional groups across the annual training season.


#3 Age at First Exposure to Repetitive Head Impacts Is Associated with Smaller Thalamic Volumes in Former Professional American Football Players
Reference: J Neurotrauma. 2017 Oct 7. doi: 10.1089/neu.2017.5145. [Epub ahead of print]
Authors: Schultz V, Stern RA, Tripodis Y, Stamm JM, Wrobel P, Lepage C, Weir I, Guenette JP, Chua A, Alosco ML, Baugh CM, Fritts NG, Martin B, Chaisson C, Coleman MJ, Lin AP, Pasternak O, Shenton ME, Koerte IK
Summary: Thalamic atrophy has been associated with exposure to repetitive head impacts (RHI) in professional fighters. The aim of this study is to investigate whether or not age at first exposure (AFE) to RHI is associated with thalamic volume in symptomatic former National Football League (NFL) players at risk for chronic traumatic encephalopathy (CTE). Eighty-six symptomatic former NFL players (mean age=54.9±7.9 years) were included. T1-weighted data were acquired on a 3T MRI and thalamic volumes were derived using FreeSurfer. Mood and behavior, psychomotor speed, and visual and verbal memory were assessed. The association between thalamic volume and AFE to playing football, and to number of years playing were calculated. Decreased thalamic volume was associated with more years of play (left: p=0.03; right: p=0.03). Younger AFE was associated with decreased right thalamic volume (p=0.014). This association remained significant after adjusting for total years of play. Decreased left thalamic volume was associated with worse visual memory (p=0.014), whereas increased right thalamic volume was associated with fewer mood and behavior symptoms (p=0.003). In our sample of symptomatic former NFL players at risk for CTE, total years of play, and AFE were associated with decreased thalamic volume. The effect of AFE on right thalamic volume was almost twice as strong as the effect of total years of play. Our findings confirm previous reports of an association between thalamic volume and exposure to RHI. They further suggest that younger AFE may result in smaller thalamic volume later in life.


#4 Anthropometrics and maturity status: A preliminary study of youth football head impact biomechanics
Reference: Int J Psychophysiol. 2017 Oct 3. pii: S0167-8760(17)30580-9. doi: 10.1016/j.ijpsycho.2017.09.022. [Epub ahead of print]
Authors: Yeargin SW, Kingsley P, Mensch JM, Mihalik JP, Monsma EV
Summary: There is a paucity of head impact biomechanics research focusing on youth athletes. Little is known about how youth subconcussive head impact tolerances are related to physical size and maturation. The objective was to examine the effects of age, anthropometric and maturational status variability on head impact biomechanics. Thirty-four male recreational youth football players, 8 to 13yrs participated in this study. Categorized by CDC standards, independent variables were: age, height, mass, BMI, and estimated peak height velocity (PHV). Participants wore a designated head impact sensor (xPatch) on their mastoid process during practices and games. Main outcome measures were Linear acceleration (g) and rotational acceleration (rad/s2). Boys in the older age category had a greater linear (F=17.72; P<0.001) and rotational acceleration (F=10.74; P<0.001) than those in the younger category. Post-PHV boys had higher linear (F=9.09, P=0.002) and rotational (F=5.57, P=0.018) accelerations than those who were pre-PHV. Rotational, but not linear acceleration differed by height category with lowest impacts found for the tallest category, whereas both linear and rotational accelerations by mass differences favored average and heavy categories. BMI overweight boys, had the greatest linear (F=5.25; P=0.011) and rotational acceleration (F=4.13; P=0.260) means. Post-PHV boys who were older, taller and had longer legs, but who were not heavier, had higher impacts perhaps due to the type of impacts sustained. Taller boys' heads are above their peers possibly encouraging hits in the torso region resulting in lower impact accelerations. Obese boys did not have sequential results compared to boys in the other BMI categories probably due to league rules, player position, and lack of momentum produced.

Mon

16

Oct

2017

Football is...(#27)

SSG = Technical + Tactical + Physical Training

Fri

13

Oct

2017

Football is...(#26)

Numerical (dis)advantages can be crucial.

Thu

12

Oct

2017

Football is...(#25)

Testing players intermittent running capacity - a suggestion.

Wed

11

Oct

2017

Latest research in football - week 40 - 2017

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 Professional football players at risk for non-acute groin injuries during the first half of the season: A prospective cohort study in The Netherlands
Reference: J Back Musculoskelet Rehabil. 2017 Sep 15. doi: 10.3233/BMR-150427. [Epub ahead of print]
Authors: Gouttebarge V, Veenstra E, Goedegebuure S, Frings-Dresen M, Kuijer P
Summary: The purpose was to study the incidence, diagnostics, treatment, anatomical region and return to play of non-acute groin injuries among professional footballers in the Netherlands. Medical staff members of all Dutch professional football clubs, recording prospectively injury occurrence of all professional footballers in their clubs, were asked to fill in an injury form about time-loss (⩾ 8 days) non-acute groin injury over the 2012-2013 season. A cohort of 410 players from 12 professional football clubs were included (response rate = 44%). The season incidence of non-acute groin injuries was nearly 7% (29 non-acute groin injuries). In 82% of all cases, the player suffered from non-acute groin injury in the first half of the season. The average time to return to play was 35 days, ranging from 8 to 84 days. The adductors were the most affected anatomical regions (82%), with the most frequent diagnosis being overuse of the adductors (36%), followed by adductor tendinopathy (18%). In addition to medical history and physical examination, ultrasound (50%) and MRI (32%) were the diagnostic methods most frequently mentioned. As well as physical therapy, treatment consisted mostly of manual therapy (96%) and dry needling (61%). A professional club with a squad of 25 players can expect on average two non-acute groin injuries per season with an average time-loss of 35 days. Players are more at risk in the first half of the season. In Dutch professional football, ultrasound is commonly used to diagnose non-acute groin injury, while manual therapy is the most commonly applied treatment.


#2 Osteitis pubis in professional football players: MRI findings and correlation with clinical outcome
Reference: Eur J Radiol. 2017 Sep;94:46-52. doi: 10.1016/j.ejrad.2017.07.009. Epub 2017 Jul 19.
Authors: Gaudino F, Spira D, Bangert Y, Ott H, Beomonte Zobel B, Kauczor HU, Weber MA
Summary: Osteitis pubis (OP), a common pathology in elite athletes, is an aseptic inflammatory process of the pubic symphysis bone, and may involve surrounding soft tissues, tendons and muscles. OP is typically characterized by (often recurring) groin pain and is an important cause of time-off from sports activity in athletes. Aim of this retrospective study was to analyze magnetic resonance imaging (MRI) findings in professional football players with clinical diagnosis of OP and to correlate MRI findings with clinical outcome. All professional football players (23 males, 1 female; mean age: 21±3.7years; range: 16-30 years) with groin pain and clinical diagnosis of OP, who underwent pelvic MRI in our institution were retrospectively analyzed. The MR images were analyzed regarding the presence of bone marrow edema and its extension, whether fluid in the symphysis pubis or periarticular soft tissue edema with a rim-like periosteal distribution or edema in the muscles located around the symphyseal joint were present, whether degenerative changes of the symphysis pubis and of signs of symphyseal instability were encountered. A quantitative measurement of the signal intensity in bone marrow edema on 3T STIR sequences was performed, normalizing these values to the mean signal intensity values in the ipsilateral iliopsoas muscle. All patients were classified according to a 3-point grading scale. For each patient, both the symptoms 18 months after the initial MRI examination, the duration of time off from playing football and the kind of treatment applied were evaluated. Among all professional athletes, in 20/24 (83.3%) MRI showed signs of OP with bone marrow edema at the pubic bone. 12 of these patients showed complete clinical recovery without any symptoms after 18 months, while in 8 patients partial recovery with persistence of groin pain during higher sports activity was observed. Patients with edema in periarticular soft tissues or in the muscles around the symphyseal joint on MRI at the beginning of symptoms presented significantly more often with a partial recovery after returning to high sports activity (p=0.042 and p=0.036, respectively). A partial recovery was also significantly associated with higher normalized mean signal intensity values in bone marrow edema on STIR sequences at the beginning of symptoms (mean=4.77±1.63 in the group with partial recovery vs. mean=2.86±0.45 in the group with complete recovery; p=0.0019). No significant association was noticed between MRI findings and time of abstinence from high sports activity, as well as between the 3-point grading scale and the time off from high sport activity and recovery at 18 months. Edema in periarticular soft tissues, edema with extension to the muscles located around the symphyseal joint, as well as higher normalized signal intensity values in bone marrow edema on STIR sequences in the pubic bones at the beginning of groin pain are the most reliable MRI findings of a poor clinical long-term outcome of OP in professional football players and should be regarded as negative prognostic factors.


#3 Applying graphs and complex networks to football metric interpretation
Reference: Hum Mov Sci. 2017 Sep 20. pii: S0167-9457(17)30628-0. doi: 10.1016/j.humov.2017.08.022. [Epub ahead of print]
Authors: Arriaza-Ardiles E, Martin-Gonzalez JM, Zuniga MD, Sanchez-Flores J, de Saa Y, Garcia-Manso JM
Summary: This work presents a methodology for analysing the interactions between players in a football team, from the point of view of graph theory and complex networks. We model the complex network of passing interactions between players of a same team in 32 official matches of the Liga de Fútbol Profesional (Spain), using a passing/reception graph. This methodology allows us to understand the play structure of the team, by analysing the offensive phases of game-play. We utilise two different strategies for characterising the contribution of the players to the team: the clustering coefficient, and centrality metrics (closeness and betweenness). We show the application of this methodology by analyzing the performance of a professional Spanish team according to these metrics and the distribution of passing/reception in the field. Keeping in mind the dynamic nature of collective sports, in the future we will incorporate metrics which allows us to analyse the performance of the team also according to the circumstances of game-play and to different contextual variables such as, the utilisation of the field space, the time, and the ball, according to specific tactical situations.


#4 Mental Fatigue and Spatial References Impair Soccer Players' Physical and Tactical Performances
Reference: Front Psychol. 2017 Sep 21;8:1645. doi: 10.3389/fpsyg.2017.01645. eCollection 2017.
Authors: Coutinho D, Gonçalves B, Travassos B, Wong DP, Coutts AJ, Sampaio JE
Summary: This study examined the effects of mental fatigue and additional corridor and pitch sector lines on players' physical and tactical performances during soccer small-sided games. Twelve youth players performed four Gk+6vs6+Gk small-sided games. Prior to the game, one team performed a motor coordination task to induce mental fatigue, while the other one performed a control task. A repeated measures design allowed to compare players' performances across four conditions: (a) with mental fatigue against opponents without mental fatigue in a normal pitch (MEN), (b) with mental fatigue on a pitch with additional reference lines (#MEN); (c) without mental fatigue against mentally fatigued opponents on a normal pitch (CTR); and (d) without mental fatigue on a pitch with reference lines (#CTR). Player's physical performance was assessed by the distance covered per minute and the number of accelerations and decelerations (0.5-3.0 m/s2; > -3.0 m/s2). Positional data was used to determine individual (spatial exploration index, time synchronized in longitudinal and lateral directions) and team-related variables (length, width, speed of dispersion and contraction). Unclear effects were found for the physical activity measures in most of the conditions. There was a small decrease in time spent laterally synchronized and a moderate decrease in the contraction speed when MEN compared to the CTR. Also, there was a small decrease in the time spent longitudinally synchronized during the #MEN condition compared to MEN. The results showed that mental fatigue affects the ability to use environmental information and players' positioning, while the additional reference lines may have enhanced the use of less relevant information to guide their actions during the #MEN condition. Overall, coaches could manipulate the mental fatigue and reference lines to induce variability and adaptation in young soccer players' behavior.


#5 Exercise physiology and nutritional perspectives of elite soccer refereeing
Reference: Scand J Med Sci Sports. 2017 Oct 5. doi: 10.1111/sms.12989. [Epub ahead of print]
Authors: Schenk K, Bizzini M, Gatterer H
Summary: Referees are an integral part of soccer and their performance is fundamental for regular match flow, irrespective of the competition level or age classes. So far, scientific interest was mainly limited to aspects of exercise physiology and match performance of soccer referees, whereas recommendations for nutrition were adopted from active professional soccer. In contrast to elite soccer players most referees are non-professional and engaged in different occupations. Furthermore, elite referees and soccer players differ in regard to age, body composition, aerobic capacity and training load. Thus, referees' caloric needs and recommended daily carbohydrate intake may generally be lower compared to active soccer players, with higher intakes limited to periods of increased training load and match days or for referees engaged in physical demanding occupations. With respect to fluid intake, pre-match and in-match hydration strategies generally valid in sports are recommended also for referees to avoid cognitive and physical performance loss, especially when officiating in extreme climates and altitude. In contrast to elite soccer, professional assistance concerning nutrition and training is rarely available for national elite referees of most countries. Therefore, special attention on education about adequate nutrition and fluid intake, about the dietary prevention of deficiencies (iron in female referees, vitamin D irrespective of sex and age) and basic precautions for travels abroad is warranted. In conclusion, the simple adoption of nutritional considerations from active soccer for referees may not be appropriate. Recommendations should respect gender differences, population specific physical characteristics and demands just as well as individual characteristics and special needs.


#6 A rare case of localised pigmented villonodular synovitis in the knee of a 24-year-old female soccer player: diagnosis, management and summary of tenosynovial giant cell tumours
Reference: BMJ Case Rep. 2017 Oct 4;2017. pii: bcr-2017-219549. doi: 10.1136/bcr-2017-219549.
Authors: Falster C, Stockmann Poulsen S, Joergensen U
Summary: Localised pigmented villonodular synovitis (PVNS) of the knee is a rare diagnosis, with clinical signs and symptoms mimicking meniscal damage or other common knee injuries.We report the case of a 24-year-old female soccer player, seeking treatment after 7 months of persisting knee pain. Additionally, we present an overview of tenosynovial giant cell tumours.On examination, the patient was found to have tenderness in the medial joint space of the knee. MRI revealed a heterogeneous formation in the central part of the knee. The formation was completely enucleated arthroscopically, histological analyses confirmed the diagnosis of localised PVNS. The patient was subsequently free of symptoms with no signs of recurrence on MRI and had resumed soccer practice at the 1-year follow-up appointment.


#7 Genetic Variants and Hamstring Injury in Soccer: an Association and Validation Study
Reference: Med Sci Sports Exerc. 2017 Oct 2. doi: 10.1249/MSS.0000000000001434. [Epub ahead of print]
Authors: Larruskain J, Celorrio D, Barrio I, Odriozola A, Gil SM, Fernandez-Lopez JR, Nozal R, Ortuzar I, Lekue JA, Aznar JM.
Summary: The purpose was to investigate the association of candidate single nucleotide polymorphisms (SNPs) with non-contact hamstring muscle injuries in elite soccer players, and to create and validate a model to assess the risk of hamstring injury. 107 elite male outfield players were prospectively followed for 6 seasons. Players were genotyped for 37 SNPs previously investigated in relation to musculoskeletal injuries. The association of SNPs, previous injury, age, level of play, position and anthropometric data with 129 hamstring injuries (413 observations) was investigated in the discovery phase (2010-2015), and a multivariable Cox-frailty model was created using forward selection. The model's discriminative ability was tested in the validation phase (2015-2016, 31 injuries, 98 observations) using Harrell's C index. Five SNPs were found to be significantly associated with hamstring injury in a multivariable model, MMP3 (Matrix metalloproteinase-3) rs679620 (A vs. G, hazard ratio (HR)=2.06, 95% confidence interval (CI)=1.51-2.81), TNC (Tenascin-C) rs2104772 (A vs. T, HR=1.65, 95% CI=1.17-2.32), IL6 (Interleukin-6) rs1800795 (GG vs. GC+CC, HR=1.68, 95% CI=1.11-2.53), NOS3 (Nitric oxide synthase-3) rs1799983 (G vs. T, HR=1.35, 95% CI=1.01-1.79), and HIF1A (Hypoxia-inducible factor-1α) rs11549465 (CC vs. CT, HR=2.08, 95% CI=1.00-4.29). Age also entered the model (≥24 vs. <24 years, HR=2.10, 95% CI=1.29-3.42). The model showed acceptable discrimination in the discovery phase (C index=0.74), but not in the validation phase (C index=0.52). Genetic variants appear to be involved in the etiology of hamstring injuries, but were not found to have predictive value by themselves. Further research, increasing the number of genetic variants and including environmental factors in complex multifactorial risk models is necessary.


#8 Prevalence of femoroacetabular impingement morphology in asymptomatic youth soccer players: magnetic resonance imaging study with clinical correlation
Reference: Rev Bras Ortop. 2017 Jun 24;52(Suppl 1):14-20. doi: 10.1016/j.rboe.2017.06.005. eCollection 2017.
Authors: Yepez AK, Abreu M, Germani B, Galia CR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620002/pdf/main.pdf
Summary: The purpose was to determine the prevalence of femoroacetabular impingement morphology (FAIM), cam- or pincer-type, by magnetic resonance imaging (MRI) in asymptomatic adolescent soccer players, and to evaluate the possible correlation between alterations on MRI and clinical examination findings. A cross-sectional study was conducted to determine the prevalence of FAIM in asymptomatic youth soccer players aged 13-18 years. A total of 112 hips in 56 players (mean age 15.3 years) were evaluated by MRI. Images were examined by two musculoskeletal radiologists for signs of FAIM. Cam-type (impingement) deformity was diagnosed by alpha angle ≥55° or head-neck offset <7 mm. Pincer-type (impingement) deformity was diagnosed by center-edge angle (CEA) ≥35° or acetabular index ≤0°. Other MRI changes, characteristic of FAIM, were observed. Clinical examination was performed to determine the range of motion (ROM) of the hips. In addition, specific tests for anterolateral and posteroinferior impingement were performed. The prevalence of MRI findings consistent with FAIM among this young population was 84.8% (95/112). The alpha angle was ≥55° in 77.7% (87/112) of hips, while the CEA was altered in 10.7% (12/112) of hips. Qualitative MRI findings consistent with FAIM were highly prevalent, and included loss of sphericity of the femoral head (77%), osseous bump (44%), femoral neck edema (21%), and acetabular osteitis (9%). The anterior impingement test was positive in 15% of the hips evaluated. Youth soccer players have a high prevalence of FAIM as diagnosed by MRI. There is no correlation between physical examination findings and MRI evidence of FAIM in this population.


#9 In-Season High-Intensity Interval Training Improves Conditioning In High School Soccer Players
Reference: Int J Exerc Sci. 2017 Sep 1;10(5):713-720. eCollection 2017.
Authors: Howard N, Stavrianeas S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5609662/pdf/ijes-10-05-713.pdf
Summary: Soccer is characterized by high aerobic demands interspersed with frequent bursts of anaerobic activity. High-intensity interval training (HIIT) is considered a viable alternative to traditional endurance conditioning and offers the additional time-saving benefits of anaerobic training. We hypothesized that HIIT will compare favorably to traditional (aerobic-based) soccer conditioning over the course of a high school soccer season. Junior varsity soccer players were split into control (CON, n=16) and experimental (HIIT, n=16) groups for the 10-week study. The HIIT group performed 4-6 "all-out" sprints lasting 30s each, with 4.5 minute recovery, 3 times a week. The CON group performed endurance running for the same duration. The groups did not differ in any other aspect of their training. Participants completed the Yo-Yo intermittent recovery test level 1 (IR1), a 40-yard dash, vertical jump, Illinois agility test, and a sit-and-reach test, in two different testing sessions (pre/post season). Both HIIT and CON groups exhibited significant increase in IR1 test performance with time (741.6±307.6m vs. 1067.6±356.8m, p<.001 and 733.2±318.8m vs. 1165.2±252.8m, p<0.001 respectively), with no difference between groups. The CON group demonstrated a significant difference in the 40-yard dash over time (5.48±0.36s vs. 5.21±0.16s, p<0.004). While there was a difference in vertical jump between the pre and post tests for the HIIT group (42.20±7.04cm vs. 47.87±750cm respectively, p<0.019), no such effect was observed in the CON group. In contrast, there were differences in the agility test only for the CON group over time (16.67±0.76s vs. 16.15±0.49s, p<0.001). There were no differences in the flexibility test between groups. Our results indicate that HIIT offers similar endurance improvements to more traditional soccer training.

#10 Maturation-related adaptations in running speed in response to sprint training in youth soccer players
Reference: J Sci Med Sport. 2017 Sep 21. pii: S1440-2440(17)31058-7. doi: 10.1016/j.jsams.2017.09.012. [Epub ahead of print]
Authors: Moran J, Parry DA, Lewis I, Collison J, Rumpf MC, Sandercock GRH
Summary: This study investigated the effects of a previously recommended dose of sprint training (ST) in young male soccer players of differing maturity status. Male soccer players from two professional academies were divided into Pre-PHV (Training: n=12; Control: n=13) and Mid-PHV (Training: n=7; Control=10) groups. The training groups completed 16 sprints of 20m with 90s recovery, once per week. Between-group effect sizes (ES) were substantially larger in Pre-PHV (10m [1.54, CI: 0.74-2.23]; 20m [1.49, CI: 0.75-2.23]; 5-10-5 [0.92, CI: 0.23-1.61]) than in Mid-PHV (10m [-0.00, CI: -0.81 to 0.81]; 20m [-0.12, CI: -0.93 to 0.69]; 5-10-5 [-0.41, CI: -1.22 to 0.41]). Within-group effects demonstrated a similar, though less accentuated, trend which revealed ST to be effective in both Pre-PHV (10m [0.44, CI: -0.24 to 1.12]; 20m [0.45, CI: -0.23 to 1.13]; 5-10-5 [0.69, CI: 0.00-1.38]) and Mid-PHV (10m [0.51, CI: -0.38 to 1.40]; 20m [0.33, CI: -0.56 to 1.21]; 5-10-5 [0.43, CI: -0.46 to 1.32]). ST, in the amount of 16 sprints over 20m with a 90s rest, may be more effective in Pre-PHV youths than in Mid-PHV youths.


American Football
#1 National Football League Skilled and Unskilled Positions Vary in Opportunity and Yield in Return to Play After an Anterior Cruciate Ligament Injury
Reference: Orthop J Sports Med. 2017 Sep 21;5(9):2325967117729334. doi: 10.1177/2325967117729334. eCollection 2017 Sep.
Authors: Yang J, Hodax JD, Machan JT, Secrist ES, Durand WM, Owens BD, Eltorai AEM, Dodson CC
Summary: Anterior cruciate ligament (ACL) injuries pose a significant risk to the careers of players in the National Football League (NFL). The relationships between draft round and position on return to play (RTP) among NFL players are not well understood, and the ability to return to preinjury performance levels remains unknown for most positions. The purpose was to test for differences in RTP rates and changes in performance after an ACL injury by position and draft round. We hypothesized that skilled positions would return at a lower rate compared to unskilled positions. We further hypothesized that early draft-round status would relate to a greater rate of RTP and that skilled positions and a lower draft round would correlate with decreased performance for players who return to sport. Utilizing a previously established database of publicly available information regarding ACL tears among NFL players, athletes with ACL tears occurring between the 2010 and 2013 seasons were identified. Generalized linear models and Kaplan-Meier time-to-event models were used to test the study hypotheses. The overall RTP rate was 61.7%, with skilled players and unskilled players returning at rates of 64.1% and 60.4%, respectively (P = .74). Early draft-round players and unskilled late draft-round players had greater rates of RTP compared to skilled late draft-round players and both unskilled and skilled undrafted free agents (UDFAs). Skilled early draft-round players constituted the only cohort that played significantly fewer games after an injury. Unskilled UDFAs constituted the only cohort to show a significant increase in the number of games started and ratio of games started to games played, starting more games in which they played, after an injury. Early draft-round and unskilled players were more likely to return compared to their later draft-round and skilled peers. Skilled early draft-round players, who displayed relatively high rates of RTP, constituted the only cohort to show a decline in performance. Unskilled UDFAs, who exhibited relatively low rates of RTP, constituted the only cohort to show an increase in performance. The significant effect of draft round and position type on RTP may be caused by a combination of differences in talent levels and in opportunities given to returning to play.


#2 Recurrent Labral Tearing on Magnetic Resonance Imaging Is Not Predictive of Diminished Participation Among National Football League Athletes
Reference: Arthroscopy. 2017 Sep 30. pii: S0749-8063(17)30703-X. doi: 10.1016/j.arthro.2017.07.007. [Epub ahead of print]
Authors: Knapik DM, Gebhart JJ, Sheehan J, Tanenbaum JE, Salata MJ, Voos JE
Summary: The purpose was to investigate the prevalence of shoulder labral repair and utility of magnetic resonance imaging (MRI) in determining the risks of recurrent labral tearing and impact on future participation in the National Football League (NFL). Athletes invited to the NFL Combine between 2012 and 2015 were retrospectively reviewed. Athletes with a history of labral repair and MRI of the operative shoulder at the Combine were included in the study for further analysis, excluding athletes without a history of labral repair, labral repair without MRI at the Combine, additional procedure to the operative shoulder, or athletes still undergoing rehabilitation at the time of the Combine after labral repair. All MRIs were reviewed to determine initial labral repair location, the presence of recurrent tearing, and any concomitant shoulder pathology. Prospective information on future NFL participation in regard to draft status, games played, and games started in the athlete's first NFL season after the Combine was compared between athletes with a history of labral repair with and without recurrent tearing versus all other athletes participating in the Combine. A total of 132 (10.1%) athletes underwent 146 shoulder labral repair procedures before the NFL Combine, of whom 32% (n = 39 athletes, n = 46 shoulders) had recurrent labral tears on MRI. Athletes with recurrent tears were more likely to have undergone bilateral labral repairs (P = .048) and possess concomitant shoulder pathology (P < .001). Recurrent labral tearing was significantly more common in the posterior labrum in athletes with a history of posterior labral repairs (P = .032). Prospective participation in the NFL in terms of games played (P = .38) or started (P = .98) was not significantly reduced in athletes with a history of labral repair compared with those without repair. Participation was not diminished in athletes with recurrent labral tears compared with those with intact repairs or those with evidence of degenerative joint disease. Athletes invited to the NFL Scouting Combine with a history of bilateral repair, posterior labral repair, and concomitant shoulder pathology are at high risk of recurrent labral tearing on MRI. No significant reduction in NFL participation the year after the Combine was seen in athletes with a history of labral repair, recurrent labral tearing, or degenerative joint disease who were successfully drafted into the NFL. In athletes with a history of labral repair, assessment of labral integrity on MRI alone is not predictive of future short-term participation.

Wed

11

Oct

2017

Football is...(#24)

Football specific cutting maneuvers for muscular development.

Mon

09

Oct

2017

Football is...(#23)

Knee stability for movements.

Sun

08

Oct

2017

Football is...(#22)

Number of players affect intensity in SSG

Fri

06

Oct

2017

Football is...(#21)

Appropriate training load = performance + injury prevention

Wed

04

Oct

2017

Football is...(#20)

One option to train for keeping the ball in offensive 1 vs. 1.

Wed

04

Oct

2017

Latest research in football - week 39 - 2017

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 Resting metabolic rate of Indian Junior Soccer players: Testing agreement between measured versus selected predictive equations
Reference: Am J Hum Biol. 2017 Sep 30. doi: 10.1002/ajhb.23066. [Epub ahead of print]
Authors: Cherian KS, Shahkar F, Sainoji A, Balakrishna N, Yagnambhatt VR
Summary: Owing to a dearth of research related to Resting Metabolic Rate (RMR) among adolescent athletes in India, our study aimed to document RMR among junior soccer players (JSP) and to identify suitable RMR predictive models for JSP from nine existing equations. Forty Indian JSP (Boys = 21, Girls = 19) representing the under-12 and under-16 age categories were assessed for body composition (skinfold technique) and RMR (oxycon mobile). Two-way ANOVA and ANCOVA were used to examine the differences across age and sex. Bland-Altman plot was used to test agreement between measured vs. predicted RMR using the equations of Cunningham (, The American Journal of Clinical Nutrition, 33), Soares et al. (, European Journal of Clinical Nutrition, 47; 1998, British Journal of Nutrition, 79), Henry (, Public Health Nutrition, 8), and Patil and Bharadwaj (, Journal of Postgraduate Medicine, 59) for non-athletic populations and the equations of De Lorenzo et al. (, The Journal of Sports Medicine and Physical Fitness, 39), Wong et al. (, Singapore Medical Journal, 53), and ten Haaf & Weijs (, PloS One, 9) for adult athletes. RMR showed significant (P < .01) sex differences (Boys: 1343 ± 297.1; Girls: 1135 ± 116.7 kcal·day-1 ). While RMR values adjusted for fat-free mass (FFM) were similar across age and sex. The equation of Soares et al. (, British Journal of Nutrition, 79) for girls and Wong et al. (, Singapore Medical Journal, 53) for boys showed better RMR predictability. FFM explained variation in RMR across age and sex. The FFM-based Soares et al. (, British Journal of Nutrition, 79) equation for girls and body weight-based Wong et al. (, Singapore Medical Journal, 53) equation for boys are best suited for predicting RMR


#2 Effects of age on the soccer-specific cognitive-motor performance of elite young soccer players: Comparison between objective measurements and coaches' evaluation
Reference: PLoS One. 2017 Sep 27;12(9):e0185460. doi: 10.1371/journal.pone.0185460. eCollection 2017.
Authors: Hicheur H, Chauvin A, Chassot S, Cheneviere X, Taube W
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0185460&type=printable
Summary: The cognitive-motor performance (CMP), defined here as the capacity to rapidly use sensory information and transfer it into efficient motor output, represents a major contributor to performance in almost all sports, including soccer. Here, we used a high-technology system (COGNIFOOT) which combines a visual environment simulator fully synchronized with a motion capture system. This system allowed us to measure objective real-time CMP parameters (passing accuracy/speed and response times) in a large turf-artificial grass playfield. Forty-six (46) young elite soccer players (including 2 female players) aged between 11 and 16 years who belonged to the same youth soccer academy were tested. Each player had to pass the ball as fast and as accurately as possible towards visual targets projected onto a large screen located 5.32 meters in front of him (a short pass situation). We observed a linear age-related increase in the CMP: the passing accuracy, speed and reactiveness of players improved by 4 centimeters, 2.3 km/h and 30 milliseconds per year of age, respectively. These data were converted into 5 point-scales and compared to the judgement of expert coaches, who also used a 5 point-scale to evaluate the same CMP parameters but based on their experience with the players during games and training. The objectively-measured age-related CMP changes were also observed in expert coaches' judgments although these were more variable across coaches and age categories. This demonstrates that high-technology systems like COGNIFOOT can be used in complement to traditional approaches of talent identification and to objectively monitor the progress of soccer players throughout a cognitive-motor training cycle.


#3 Comparison of Thigh Muscle Strain Occurrence and Injury Patterns between Male and Female High School Soccer-Athletes
Reference: J Sport Rehabil. 2017 Sep 27:1-35. doi: 10.1123/jsr.2016-0178. [Epub ahead of print]
Authors: Cross KM, Gurka KK, Saliba S, Conaway M, Hertel J
Summary: Thigh muscles strains are among the most common injuries in high school soccer for both males and females. Similar results have been reported among collegiate soccer players, specifically for hamstring strains. In collegiate soccer, males have a higher injury rate than women although they share common injury characteristics. Currently, no studies exist comparing the injury rate or injury characteristics of thigh muscle strains between sexes playing high school soccer. The objective of the study was to compare thigh muscle strain injury rates and injury event characteristics among sexes participating in high school soccer. High school soccer athletes who had a thigh muscle strain were involved in this study. Injury rates of thigh muscle strains were calculated between sexes. The occurrence of the following variables during a thigh muscle injury were compared between sexes: grade level, age, level of play, event type, time of practice, time of competition, basic injury mechanism, soccer activity, player position, field location, practice type, time of season. Males had a lower injury rate of thigh muscle strains during competition than females. (RR=0.66; 95% CI, 0.47, 0.93) No differences between sexes existed in the distribution of first-time or recurrent event characteristics. When combining sexes, recurrent strains (93%) occurred more frequently on the offensive side of the field than first-time strains (59%), P<0.0001. The majority of strains occurred among the varsity players (71%), during running activities (60%) and during practices (58%). Males were less likely to sustain a thigh muscle strain during competitions, but no other differences existed between sexes. The events surrounding all thigh muscle strains may be described with some common properties. Consideration of these characteristics may assist in the development of preventive and rehabilitative programs as well as direct future research on thigh muscle strains among high school soccer players.


#4 Locomotor and Heart Rate Responses of Floaters During Small-Sided Games in Elite Soccer Players: Effect of Pitch Size and Inclusion of Goal Keepers
Reference: Int J Sports Physiol Perform. 2017 Sep 27:1-13. doi: 10.1123/ijspp.2017-0340. [Epub ahead of print]
Authors: Lacome M, Simpson BM, Cholley Y, Buchheit M
Summary: The purpose was to (1) compare the locomotor and heart rate responses between floaters and regular players during both small and large small sided games (SSGs) and (2) examine whether the type of game (i.e., game simulation vs possession game) affects the magnitude of the difference between floaters and regular players. Data were collected in 41 players belonging to an elite French football team during three consecutive seasons (2014-2017). 5-Hz GPS were used to collect all training data, with the Athletic Data Innovation analyser (v5.4.1.514, Sydney, Australia) used to derive total distance (m), high-speed distance (> 14.4 km.h-1, m) and external mechanical load (MechL, a.u). All SSGs included exclusively one floater, and were divided into two main categories, according to the participation of goal-keepers (GK) (game simulation, GS) or not (possession games, PO) and then further divided into small and large (>100 m2/player) SSGs based on the area per player ratio. Locomotor activity and mechanical load performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, while differences in HR responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO. Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher HR responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.


#5 Successful return to play following adductor longus proximal tendon rupture in professional soccer without re-injury at 12 months: A case report
Reference: J Back Musculoskelet Rehabil. 2017 Sep 8. doi: 10.3233/BMR-170857. [Epub ahead of print]
Authors: Gozubuyuk OB, Moen MH, Akman M, Ipseftel I, Karakuzu A
Summary: Treatment of total ruptures of adductor longus is challenging in professional sports. Time for return to pre-injury level as well as re-injury rates are of concern and surgical and conservative treatment approaches are debated; yet no consensus approach described for professional athletes. We present a case of a professional soccer player who experienced a rupture in his left adductor longus proximal tendon during a game and was treated conservatively. This case was followed-up during clinical assessment, imaging and strength testing until and after return to play. Primary outcome measure was the return to standard play condition at his pre-injury level without any functional deficits, measured by isokinetic testing. Second outcome measure was the recurrence. No recurrence was observed during the first year of follow-up. Total ruptures are very challenging for both the physician and the player to make a quick decision due to minimal or lack of pain. Functional outcomes are almost identical although operative treatments need longer time to return to play. This case report adds another example to the literature of a successful return to play after non-operative treatment of adductor longus rupture at elite level soccer.


#6 Is strength-training frequency a key factor to develop performance adaptations in young elite soccer players?
Reference: Eur J Sport Sci. 2017 Sep 24:1-11. doi: 10.1080/17461391.2017.1378372. [Epub ahead of print]
Authors: Otero-Esquina C, de Hoyo Lora M, Gonzalo-Skok O, Dominguez-Cobo S, Sanchez H
Summary: The aim of this study was to analyse the effects of a combined strength-training programme (full-back squat, YoYoTM leg curl, plyometrics and sled towing exercises) on performance in elite young soccer players and to examine the effects when this training programme was performed one or two days per week. Thirty-six male soccer players (U-17 to U-19) were recruited and assigned to experimental groups (EXP1: 1 s w-1; EXP2: 2 s w-1) or a control group (CON). Performance was assessed through a countermovement jump (CMJ) test (relative peak power [CMJPP] and CMJ height [CMJH]), a 20-m linear sprint test with split-times at 10-m, and a change of direction test (V-cut test) 1 week before starting the training programme and also 1 week after performing such training programme. Within-group analysis showed substantial improvements in CMJ variables (ES: 0.39-0.81) and COD (ES: 0.70 and 0.76) in EXP1 and EXP2, while EXP2 also showed substantial enhancements in all linear sprinting tests (ES: 0.43-0.52). Between-group analysis showed substantially greater improvements in CMJ variables (ES: 0.39-0.68) in experimental groups in comparison to CON. Furthermore, EXP2 achieved a substantial better performance in 20-m (ES: 0.48-0.64) than EXP1 and CON. Finally, EXP2 also showed greater enhancements in 10-m (ES: 0.50) and V-cut test (ES: 0.52) than EXP1. In conclusion, the combined strength-training programme improved jumping ability, independently of training frequency, though the achievement of two sessions per week also enhanced sprinting abilities (linear and COD) in young soccer players.


#7 Neuromuscular responses and physiological patterns during a soccer simulation protocol. Artificial turf versus natural grass
Reference: J Sports Med Phys Fitness. 2017 Sep 22. doi: 10.23736/S0022-4707.17.07768-4. [Epub ahead of print]
Authors: Lopez-Fernandez J, Garcia-Unanue J, Sanchez-Sanchez J, Leon M, Hernando E, Gallardo L
Summary: Latest studies suggest similar performance of soccer players either on artificial turf (AT) or natural grass (NG). However, it is not clear if their muscular and physiological responses are also similar on both surfaces. This research aims to assess the influence of game surface on physiological patterns and neuromuscular responses of soccer players during a soccer simulation protocol (SSP) that incorporates repeated sprints and nonlinear actions at maximum speed. Sixteen amateur soccer players completed three bouts of the SSP on both AT and NG. The mechanical behaviour of both surfaces was recorded and the order was randomly established for each player. The physiological responses were measured during the SSP. A contra-movement jump and a tensiomyography analysis of the rectus femurs (RF) and biceps femoris (BF) were assessed right before and right after the SSP. Both surfaces presented different mechanical properties. No differences among either surfaces or bouts were found for heart rate (HR) peak and HR mean (p >0.05). While the half-relaxation time of the RF on NG decreased after the SSP (right-leg:-44.430 ms; p = 0.049; left-leg: -52.131 ms; p = 0.008), the sustain time of the BF decreased after the SSP on AT (right-leg: +64.868 ms; p = 0.007; left-leg: +87.564 ms; p<0.001). No differences between surfaces were found for the contra-movement jump. The mechanical behaviour of both surfaces does not differ enough to cause different physiological and neuromuscular responses. Playing on AT should cause similar neuromuscular responses to NG.


#8 Variability of GPS-derived running performance during official matches in elite professional soccer players
Reference: J Sports Med Phys Fitness. 2017 Sep 22. doi: 10.23736/S0022-4707.17.07500-4. [Epub ahead of print]
Authors: Al Haddad H, Mendez-Villanueva A, Torreno N, Munguia-Izquierdo D, Suarez-Arrones L
Summary: The aim of this study was to assess the match-to-match variability obtained using GPS devices, collected during official games in professional soccer players. GPS-derived data from nineteen elite soccer players were collected over two consecutive seasons. Time-motion data for players with more than five full-match were analyzed (n=202). Total distance covered (TD), TD >13-18 km/h, TD >18-21 km/h, TD >21 km/h, number of acceleration >2.5-4 m.s-2 and >4 m.s-2 were calculated. The match-to-match variation in running activity was assessed by the typical error expressed as a coefficient of variation (CV,%) and the magnitude of the CV was calculated (effect size). When all players were pooled together, CVs ranged from 5% to 77% (first half) and from 5% to 90% (second half), for TD and number of acceleration >4 m.s-2, and the magnitude of the CVs were rated from small to moderate (effect size = 0.57-0.98). The CVs were likely to increase with running/acceleration intensity, and were likely to differ between playing positions (e.g., TD > 13-18 km/h 3.4% for second strikers vs 14.2% for strikers and 14.9% for wide-defenders vs 9.7% for wide-midfielders). Present findings indicate that variability in players' running performance is high in some variables and likely position-dependent. Such variability should be taken into account when using these variables to prescribe and/or monitor training intensity/load. GPS-derived match-to-match variability in official games' locomotor performance of professional soccer players is high in some variables, particularly for high-speed running, due to the complexity of match running performance and its most influential factors and reliability of the devices.


#9 Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial
Reference: J Physiother. 2017 Sep 20. pii: S1836-9553(17)30102-9. doi: 10.1016/j.jphys.2017.08.004. [Epub ahead of print]
Authors: Al Attar WSA, Soomro N, Pappas E, Sinclair PJ, Sanders RH
Download link: http://www.journalofphysiotherapy.com/article/S1836-9553(17)30102-9/pdf
Summary: Does adding a post-training Fédération Internationale de Football Association (FIFA) 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduce injury rates among male amateur soccer players? Twenty-one teams of male amateur soccer players aged 14 to 35 years were randomly assigned to the experimental group (n=10 teams, 160 players) or the control group (n=11 teams, 184 players). Both groups performed pre-training FIFA 11+ exercises for 20minutes. The experimental group also performed post-training FIFA 11+ exercises for 10minutes. The primary outcomes measures were incidence of overall injury, incidence of initial and recurrent injury, and injury severity. The secondary outcome measure was compliance to the experimental intervention (pre and post FIFA 11+ program) and the control intervention (pre FIFA 11+ program). During one season, 26 injuries (team mean=0.081 injuries/1000 exposure hours, SD=0.064) were reported in the experimental group, and 82 injuries were reported in the control group (team mean=0.324 injuries/1000hours, SD=0.084). Generalised Estimating Equations were applied with an intention-to-treat analysis. The pre and post FIFA 11+ program reduced the total number of injuries (χ2 (1)=11.549, p=0.001) and the incidence of initial injury (χ2 (2)=8.987, p=0.003) significantly more than the pre FIFA 11+ program alone. However, the odds of suffering a recurrent injury were not different between the two groups (χ2 (1)=2.350, p=0.125). Moreover, the severity level of injuries was not dependent upon whether or not the pre and post FIFA 11+ program was implemented (χ2 (1)=0.016, p=0.898). Implementation of the FIFA 11+ program pre-training and post-training reduced overall injury rates in male amateur soccer players more than the pre FIFA 11+ program alone.


#10 Symptoms of common mental disorders and related stressors in Danish professional football and handball
Reference: Eur J Sport Sci. 2017 Sep 29:1-7. doi: 10.1080/17461391.2017.1381768. [Epub ahead of print]
Authors: Kilic O, Aoki H, Haagensen R, Jensen C, Johnson U, Kerkhoffs GMMJ, Gouttebarge V
Summary: The aim of the study was twofold, namely (i) to determine the prevalence of symptoms of common mental disorders (CMDs) among current and retired professional football and handball players and (ii) to explore the relationship of psychosocial stressors with the outcome measures under study. A total of 1155 players were enrolled in an observational study based on a cross-sectional design. Questionnaires based on validated scales were set up and distributed among current and retired professional football and handball players by the Danish football and handball players' union. In professional football, the highest prevalence (4 weeks) of symptoms of CMDs was 18% and 19% for anxiety/depression among current and retired players, respectively. In professional handball, the highest prevalence (4 weeks) of symptoms of CMDs was 26% and 16% for anxiety/depression among current and retired players, respectively. For both the current and retired professional football and handball players, a higher number of severe injuries and recent adverse life events (LE) were related to the presence of symptoms of CMD. Players exposed to severe injuries and/or recent adverse LE were 20-50% times more likely to report symptoms of CMD. The results suggest that it is possible to recognize the population of professional athletes that are more likely to develop symptoms of CMD. This could create the opportunity to intervene preventively on athletes that suffered from severe injury and/or recent adverse LE that could lead to a faster and safer recovery and psychological readiness to return to play.


American Football
#1 Evaluating behavioral skills training to teach safe tackling skills to youth football players
Reference:  J Appl Behav Anal. 2017 Sep 20. doi: 10.1002/jaba.412. [Epub ahead of print]
Authors: Tai SSM, Miltenberger RG
Summary: With concussion rates on the rise for football players, there is a need for further research to increase skills and decrease injuries. Behavioral skills training is effective in teaching a wide variety of skills but has yet to be studied in the sports setting. We evaluated behavioral skills training to teach safer tackling techniques to six participants from a Pop Warner football team. Safer tackling techniques increased during practice and generalized to games for the two participants who had opportunities to tackle in games.


#2 Return to play after shoulder instability in National Football League athletes
Reference: J Shoulder Elbow Surg. 2017 Sep 20. pii: S1058-2746(17)30448-2. doi: 10.1016/j.jse.2017.07.027. [Epub ahead of print]
Authors: Okoroha KR, Taylor KA, Marshall NE, Keller RA, Fidai M, Mahan MC, Varma V, Moutzouros V
Summary: We hypothesized that National Football League (NFL) players sustaining a shoulder destabilizing injury could return to play (RTP) successfully at a high rate regardless of treatment type. We identified and evaluated 83 NFL players who sustained an in-season shoulder instability event while playing in the NFL. NFL RTP, incidence of surgery, time to RTP, recurrent instability events, seasons/games played after the injury, and demographic data were collected. Overall RTP was determined, and players who did and did not undergo operative repair were compared. Ninety-two percent of NFL players returned to NFL regular season play at a median of 0.0 weeks in those sustaining a shoulder subluxation and 3.0 weeks in those sustaining a dislocation who did not undergo surgical repair (P = .029). Players who underwent operative repair returned to play at a median of 39.3 weeks. Forty-seven percent of players had a recurrent instability event. For players who were able to RTP, those who underwent surgical repair (31%) had a lower recurrence rate (26% vs. 55%, P = .021) and longer interval between a recurrent instability event after RTP (14.7 vs. 2.5 weeks, P = .050). There is a high rate of RTP after shoulder instability events in NFL players. Players who sustain shoulder subluxations RTP faster but are more likely to experience recurrent instability than those with shoulder dislocations. Surgical stabilization of the shoulder after an instability event decreases the chances of a second instability event and affords a player a greater interval between the initial injury and a recurrent event.


#3 Concussion Nondisclosure During Professional Career Among a Cohort of Former National Football League Athletes
Reference: Am J Sports Med. 2017 Sep 1:363546517728264. doi: 10.1177/0363546517728264. [Epub ahead of print]
Authors: Kerr ZY, Register-Mihalik JK, Kay MC, DeFreese JD, Marshall SW, Guskiewicz KM
Summary: Despite a focus on the incidence and effects of concussion, nondisclosure of sports-related concussions among retired players from the National Football League (NFL) has yet to be examined. The purpose was to examine the prevalence of and factors associated with nondisclosure of sports-related concussions in former NFL athletes. A sample of 829 former NFL players completed a general health survey. This historical cohort included players who had played before World War II to 2001. Respondents retrospectively recalled sports-related concussions that they sustained during their professional careers and whether at least one of these sports-related concussions was not reported to medical staff. We computed the prevalence of nondisclosure among those recalling sport-related concussions during their professional careers. Multivariable binomial regression estimated adjusted prevalence ratios (PR) with 95% confidence intervals (CIs) controlling for race/ethnicity, number of years played, primary position played, professional career concussion history, and playing era. Playing era was categorized by whether the majority of a player's career was before or after a 1976 rule change to limit contact ("spearing"). Overall, 417 (50.3%) respondents reported they had sustained a concussion and did not inform medical staff at least once during their professional playing career. Nonwhite respondents had a higher prevalence of nondisclosure than white/non-Hispanic respondents (adjusted PR = 1.19; 95% CI, 1.02-1.38). An interaction between professional career concussion history and playing era was also found ( P = .08). Compared with those in the pre-spearing rule change group with 1 or 2 concussions, all other groups had larger prevalences of nondisclosure (increases ranging from 41% to 153% in multivariable models). Across concussion strata, nondisclosure prevalence was generally higher in the post-spearing rule change group than the pre-spearing rule change group, with the largest differences found among those with 1 or 2 concussions or those with 3 or 4 concussions. A large proportion of former NFL players in this historical cohort reported at least one instance of not disclosing sports-related concussions to medical staff. Future research on concussion nondisclosure needs to identify mechanisms to improve football players' intentions to disclose concussion-related symptoms to health care providers and to equip health care providers with more effective strategies for timely identification of concussion.


#5 A Narrative Review of the Physical Demands and Injury Incidence in American Football: Application of Current Knowledge and Practices in Workload Management
Reference: Sports Med. 2017 Sep 25. doi: 10.1007/s40279-017-0783-2. [Epub ahead of print]
Authors: Edwards T, Spiteri T, Piggott B, Haff GG, Joyce C
Summary: The sport of American football (AmF) exposes athletes to high-velocity movements and frequent collisions during competition and training, placing them at risk of contact and non-contact injury. Due to the combative nature of the game, the majority of injuries are caused by player contact; however, a significant number are also non-contact soft-tissue injuries. The literature suggests that this mechanism of injury can be prevented through workload monitoring and management. The recent introduction of microtechnology into AmF allows practitioners and coaches to quantify the external workload of training and competition to further understand the demands of the sport. Significant workload differences exist between positions during training and competition; coupling this with large differences in anthropometric and physical characteristics between and within positions suggests that the training response and physiological adaptations will be highly individual. Effective athlete monitoring and management allows practitioners and coaches to identify how athletes are coping with the prescribed training load and, subsequently, if they are prepared for competition. Several evidence-based principles exist that can be adapted and applied to AmF and could decrease the risk of injury and optimise athletic performance.


#6 The Epidemiology of Overuse Conditions in Youth Football and High School Football Players
Reference: J Athl Train. 2017 Sep 26. doi: 10.4085/1062-6050-52.10.04. [Epub ahead of print]
Authors: Morris K, Simon J, Grooms DR, Starkey C, Dompier TP, Kerr ZY
Summary: High-intensity sport training at the youth level has led to increased concern for overuse conditions. Few researchers have examined overuse conditions in youth sports. The purpose was to examine the rates, risks, and distributions of overuse conditions between youth and high school football. The Youth Football Safety Study (YFSS) investigated youth football athletes from age 5 to 14 years. The National Athletic Treatment, Injury and Outcomes Network (NATION) focused on high school football athletes 14 to 18 years old. The YFSS data consisted of 210 team-seasons, and the NATION data consisted of 138 team-seasons. Athletic trainers collected football injury and exposure data during the 2012 and 2013 seasons. Injury rates, risks, and distributions were calculated, with injury rate ratios, risk ratios, and injury proportion ratios with 95% confidence intervals (CIs) comparing high school and youth football players. The YFSS reported 1488 injuries, of which 53 (3.6%) were overuse conditions. The NATION reported 12 013 injuries, of which 339 (2.8%) were overuse conditions. The overuse condition rate did not differ between high school and youth football (3.93 versus 3.72/10 000 athlete exposures; injury rate ratio = 1.06; 95% CI = 0.79, 1.41). However, the 1-season risk of overuse condition was higher in high school than in youth football players (2.66% versus 1.05%; risk ratio = 2.53; 95% CI = 1.84, 3.47). Compared with high school football players, youth football players had greater proportions of overuse conditions that were nontime loss (ie, <24 hours participation-restriction time; 83.0% versus 67.0%; injury proportion ratio = 1.24; 95% CI = 1.07, 1.43) and affecting the lower extremity (92.5% versus 62.5%; injury proportion ratio = 1.48; 95% CI = 1.32, 1.65). Overuse conditions may not present a primary concern in youth and high school football players. However, differences existed between the 2 levels of competition. Although additional research on the incidence of overuse conditions across all youth and high school sports is needed, these findings may highlight the need for programming that is specific to competition level.


#7 Characteristics and Outcomes of Arthroscopic Femoroacetabular Impingement Surgery in the National Football League
Reference: Am J Sports Med. 2017 Sep 1:363546517729163. doi: 10.1177/0363546517729163. [Epub ahead of print]
Authors: Nwachukwu BU, Bedi A, Premkumar A, Draovitch P, Kelly BT
Summary: Previous studies have reported that hip abnormalities may account for 10% of injuries in professional football players. The effect of femoroacetabular impingement (FAI) and arthroscopic FAI surgery in National Football League (NFL) athletes has not been well studied. The purpose was to investigate the effect of arthroscopic FAI surgery on return to play (RTP) and RTP performance in NFL players. NFL athletes undergoing arthroscopic FAI surgery at a single institution between 2006 and 2014 were identified. Medical records were reviewed for demographic, clinical, and operative variables. RTP and RTP performance were assessed based on a review of publicly available NFL player statistics. RTP and RTP performance data included time to RTP; games played before and after the injury; yearly total yards and touchdowns for offensive players; and yearly total tackles, sacks, and interceptions for defensive players. The offensive power rating (OPR = [total yards/10] + [total touchdowns × 6]) and defensive power rating (DPR = total tackles + [total sacks × 2] + [total interceptions × 2]) were calculated. Paired t tests comparing preinjury and postinjury seasons were performed. A matched cohort of NFL players was created to compare trends for OPR, DPR, and career longevity. Forty-eight hips in 40 NFL players (mean age, 25.6 years) with symptomatic FAI were included; 8 players underwent staged bilateral hip arthroscopic procedures. The majority of players were offensive (n = 24; 60.0%), with offensive lineman (n = 11; 27.5%) being the most common of all positions. Of the 48 included hips, all had labral tears, and 41 (85.4%) underwent labral repair. Forty-two of the 48 hips (87.5%) underwent cam decompression, and 10 (20.8%) underwent rim decompression. Of the 40 included players, 37 (92.5%) achieved RTP to professional competition after their hip arthroscopic surgery at a mean of 6.0 months. Before the injury, included patients played in a mean of 11.0 games compared with 9.5 games in their postoperative season ( P = .26). The mean OPR and DPR demonstrated a nonsignificant decline in the postoperative season (preinjury OPR, 40.2; postinjury OPR, 32.3; P = .34) (preinjury DPR, 49.6; postinjury DPR, 36.4; P = .10). A similar decline in the OPR and DPR across seasons was observed in the control group. NFL athletes played, on average, 3.3 ± 1.5 seasons after undergoing hip arthroscopic surgery; this was not significantly different from the controls (2.5 ± 1.5 seasons; P = .47). There was no significant difference in mean annual salaries based on contracts negotiated before the injury and the first negotiated contract after surgery ($3.3 million vs $3.6 million, respectively; P = .58). There was a very high rate of RTP in the NFL after arthroscopic FAI surgery; this rate is higher than what has been previously reported for other orthopaedic procedures in NFL athletes. Additionally, these NFL athletes achieved RTP at a faster time frame (6 months) than previously reported for other procedures. These findings have important implications for counseling elite football players about the expected outcome of arthroscopic FAI surgery.


#8 Daily Fantasy Football and Self-Reported Problem Behavior in the United States
Reference: J Gambl Stud. 2017 Sep 26. doi: 10.1007/s10899-017-9720-4. [Epub ahead of print]
Authors: Dwyer B, Shapiro SL, Drayer J
Summary: Traditional, season-long fantasy sport participation has grown considerably since the late 1990s, and in an attempt to capitalize on this growing demand, daily fantasy sports (DFS) providers have created a new game where money changes hands instantly. This change has led some legal commentators and state agencies to believe the game is a form of Internet gambling similar to online poker, blackjack, and sports wagering, and thus, it requires increased regulation or even prohibition. Little is known, however, about the gambling behavior associated with DFS participation. Thus, the purpose of the current study was to examine problem gambling severity in conjunction with DFS participant motives, perceptions, and consumption behavior. Over 500 DFS participants were surveyed, and the results suggest DFS participants behave similarly with participants in other forms of gambling activities. In addition, the findings suggest additional consumer protections may be needed to prevent further problem behavior such as chasing.


#9 Lifetime Prevalence of Injuries in Incoming Division I Collegiate Football Players
Reference: Phys Sportsmed. 2017 Sep 27. doi: 10.1080/00913847.2017.1386068. [Epub ahead of print]
Authors: Sarac N, Haynes W, Pedroza A, Kaeding C, Borchers J
Summary: The purpose of this study is to determine the lifetime prevalence of past injuries in incoming first year football players in a Division 1 college football team. Pre-participation questionnaires from 605 first-year football players over 20 years (1996-2015) were examined to determine the prevalence of concussions, stingers