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Friday, September 21, 2012

Interventions to prevent ACL injuries-Recent studies in football (Part III)


Recent studies in football –Part III
Abstracts modified from PubMed
 
Gagnier JJ, Morgenstern H, Chess L. Interventions Designed to Prevent Anterior Cruciate Ligament Injuries in Adolescents and Adults: A Systematic Review and Meta-analysis. Am J Sports Med. 2012 Sep 12. [Epub ahead of print]
 Source
Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan.
Abstract
Anterior cruciate ligament (ACL) injuries are common, result in significant morbidity, and are expensive to repair surgically and to rehabilitate. Several randomized and observational studies have tested neuromuscular interventions as preventive measures for these injuries. The aim of this study was to conduct a systematic review and meta-analysis of all known comparative studies for estimating and testing the effect of neuromuscular and educational interventions on the incidence of ACL injuries in adolescents and adults, both male and female. Several databases were used to identify eligible studies through July 4, 2011: MEDLINE, EMBASE, SPORTDiscus, Cumulative Index to Nursing and Allied Health Literature, the Cochrane Central Register of Controlled Trials, and Health Technology Assessment. Eligible studies were assessed for risk of bias, and meta-analyses were performed on the estimated intervention effect (log incidence rate ratio) using inverse-variance weighting, subgroup analysis, and random-effects meta-regression to estimate the overall (pooled) effect and explore heterogeneity of effect across studies (measured by I(2) and tested with the Q statistic). Eight cohort (observational) studies and 6 randomized trials were included, involving a total of approximately 27,000 participants. The random-effects meta-analysis yielded a pooled rate-ratio estimate of 0.485 (95% confidence interval [CI], 0.299-0.788; P = .003), indicating a lower ACL rate in the intervention groups, but there was appreciable heterogeneity of the estimated effect across studies (I(2) = 64%; P = .001). In the meta-regressions, the estimated effect was stronger for studies that were not randomized, performed in the United States, conducted in soccer players, had a longer duration of follow-up (more than 1 season), and had more hours of training per week in the intervention group, better compliance, and no dropouts. Nevertheless, residual heterogeneity was still observed within subgroups of those variables (I(2) > 50%; P < .10).

Conclusion: Various types of neuromuscular and educational interventions appear to reduce the incidence rate of ACL injuries by approximately 50%, but the estimated effect varied appreciably among studies and was not able to explain most of that variability.



Hoier B, Nordsborg N, Andersen S, Jensen L, Nybo L, Bangsbo J, Hellsten Y. Pro- and anti-angiogenic factors in human skeletal muscle in response to acute exercise and training. J Physiol. 2012 Feb 1;590(Pt 3):595-606. Epub 2011 Dec 12.
 Source
Department of Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark.
Abstract
This study examined the effect of acute exercise and 4 weeks of aerobic training on skeletal muscle gene and protein expression of pro- and anti-angiogenic factors in 14 young male subjects. Training consisted of 60 min of cycling (60% of ), 3 times/week. Biopsies were obtained from vastus lateralis muscle before and after training. Muscle interstitial fluid was collected during cycling at weeks 0 and 4. Training increased (P < 0.05) the capillary: fibre ratio and capillary density by 23% and 12%, respectively. The concentration of interstitial vascular endothelial growth factor (VEGF) in response to acute exercise increased similarly (>6-fold; P < 0.05) before and after training. Resting protein levels of soluble VEGF receptor-1 in interstitial fluid, and of VEGF, thrombospondin-1 (TSP-1) and tissue inhibitor of matrix metalloproteinase-1 (TIMP1) in muscle were unaffected by training, whereas endothelial nitric oxide synthase protein levels in muscle increased by 50% (P < 0.05). Before and after training, acute exercise induced a similar increase (P < 0.05) in the mRNA level of angiopoietin 2, matrix metalloproteinase 9 and TSP-1. After training, TIMP1 mRNA content increased with exercise (P < 0.05).

Conclusions: Acute exercise induced a similar increase in the gene-expression of both pro- and anti-angiogenic factors in untrained and trained muscle. We propose that the increase in anti-angiogenic factors with exercise is important for modulation of angiogenesis. The lack of effect of training on basal muscle VEGF protein levels and VEGF secretion during exercise suggests that increased VEGF levels are not a prerequisite for exercise-induced capillary growth in healthy muscle.




Hoier B, Passos M, Bangsbo J, Hellsten Y. Intense intermittent exercise provides weak stimulus for VEGF secretion and capillary growth in skeletal muscle. Exp Physiol. 2012 Sep 7. [Epub ahead of print]

Source
University of Copenhagen, Copenhagen, Denmark;
Abstract
The effect of acute intense intermittent exercise compared to moderate intensity exercise, on angiogenic factors and the effect of four weeks of intense intermittent training on capillary growth were examined in nine young healthy males, pre-conditioned by moderate intensity endurance training. The intense training consisted of 24 one-min cycling bouts at an initial work rate of 316 ± 19W (~117% of pre VO2 max), performed 3 times/week. Skeletal muscle biopsies and muscle microdialysates were otained from m.v. lateralis before, during, and after acute exercise performed at either moderate or high intensity. Comparison of the response in angiogenic factors to acute moderate versus high intensity exercise, performed prior to the intense training intervention, revealed that intense exercise resulted in a markedly lower (~60%; P < 0.05) increase in interstitial VEGF than did moderate intensity exercise. Muscle interstitial fluid obtained during moderate intensity exercise increased endothelial cell proliferation in vitro more than interstitial fluid obtained during intense exercise (6-fold vs. 2.5-fold, respectively; P < 0.05). The four weeks of high intensity training did not lead to an increased capillarization in the muscle but abolished the exercise induced increase in mRNA for several angiogenic factors, increased the eNOS protein levels, lowered TSP-1 protein levels in muscle but increased interstitial TSP-1 protein levels.
Conclusions: Intense intermittent exercise provides a weak stimulus for VEGF secretion and endothelial cell proliferation and that intense intermittent training does not induce a sufficient angiogenic stimulus to induce capillary growth in muscle previously conditioned by moderate intensity exercise.



Gunnarsson TP, Christensen PM, Holse K, Christiansen D, Bangsbo J. Effect of additional speed endurance training on performance and muscle adaptations. Med Sci Sports Exerc. 2012 Oct;44(10):1942-8.
Source
Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, DENMARK.
Abstract
The present study examined the effect of additional speed endurance training (SET) during the season on muscle adaptations and performance of trained soccer players. Eighteen sub-elite soccer players performed one session with six to nine 30-s intervals at an intensity of 90%-95% of maximal intensity (SET) a week for 5 wk (SET intervention). Before and after the SET intervention, the players carried out the Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test, a sprint test (10 and 30 m), and an agility test. In addition, seven of the players had a resting muscle biopsy specimen taken and they carried out a running protocol on a motorized treadmill before and after the SET intervention. After the SET intervention, the Yo-Yo IR2 test (n = 13) performance was 11% better (P < 0.05), whereas sprint (n = 15) and agility (n = 13) performances were unchanged. The expression of the monocarboxylate transporter 1 (n = 6) was 9% higher (P < 0.05). and the expression of the Na/K pump subunit β1 (n = 6) was 13% lower (P < 0.05) after the SET intervention. The Na/K pump subunits α1, α2, as well as the monocarboxylate transporter 4 and the Na/H exchanger 1 (n = 6) were unchanged. After the SET intervention, the relative number of Type IIx fibers and oxygen consumption at 10 km·h were lower (P < 0.05), whereas V˙O2max was unchanged.
Conclusions:  Adding 30 min of SET once a week during the season for trained soccer players did lead to an improved ability to perform repeated high-intensity exercise, with a concomitant increase in the expression of monocarboxylate transporter 1 and an improved running economy.





Scott BR, Lockie RG, Knight TJ, Clark AC, Janse de Jonge X AK. A Comparison of Methods to Quantify the In-Season Training Load of Professional Soccer Players. Int J Sports Physiol Perform. 2012 Sep 5. [Epub ahead of print]
Source
Exercise and Sport Science, Faculty of Science and Information Technology, University of Newcastle, Ourimbah, New South Wales, Australia.
Abstract
The aim of the study was to compare various measures of training load (TL), derived from physiological (heart rate [HR]), perceptual (rating of perceived exertion [RPE]) and physical (global positioning system [GPS] and accelerometer) data, during in-season field-based training for professional soccer. Fifteen professional male soccer players (age: 24.9 ± 5.4 yr, body mass: 77.6 ± 7.5 kg, height: 181.1 ± 6.9 cm) were assessed in-season, across 97 individual training sessions. Measures of external-TL (total distance [TD], the volume of low-speed activity [LSA; <14.4km·h-1], high-speed running [HSR; >14.4 km·h-1] and very high-speed running [VHSR; >19.8 km·h-1], and Player Load™), HR and session-RPE (sRPE) scores were recorded. Internal-TL scores (HR-based and sRPE-based) were calculated, and their relationships with measures of external-TL were quantified using Pearson's product moment correlations. Physical measures of TD, LSA volume and Player Load™ provided large, significant (r = 0.71-0.84; P < 0.01) correlations with the HR-based and sRPE-based methods. Volume of HSR and VHSR provided moderate to large, significant (r = 0.40-0.67; P < 0.01) correlations with measures of internal-TL.
Conclusions:  Whilst the volume of HSR and VHSR provided significant relationships with internal-TL, physical performance measures of TD, LSA volume and Player Load™ appear to be more acceptable indicators of external-TL, due to the greater magnitude of their correlations with measures of internal-TL.




Bradley PS, Bendiksen M, Dellal A, Mohr M, Wilkie A, Datson N, Orntoft C, Zebis M, Gomez-Diaz A, Bangsbo J, Krustrup P. The Application of the Yo-Yo Intermittent Endurance Level 2 Test to Elite Female Soccer Populations. Scand J Med Sci Sports. 2012 Jun 19. doi: 10.1111/j.1600-0838.2012.01483.x. [Epub ahead of print]

Source
Department of Sport and Exercise, University of Sunderland, Sunderland, UK.
Abstract
The aim of this study was to evaluate the application of the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) to elite female soccer populations. Elite senior (n = 92), youth (n = 42), domestic (n = 46) and sub-elite female soccer players (n = 19) carried out the Yo-Yo IE2 test on numerous occasions across the season. Test-retest coefficient of variation (CV) in Yo-Yo IE2 test performance in domestic female players was 4.5%. Elite senior female players' Yo-Yo IE2 test performances were better (P < 0.01) than elite youth, domestic and sub-elite players (mean ± standard deviation; 1774 ± 532 vs 1490 ± 447, 1261 ± 449, and 994 ± 373 m). For elite senior female players, wide midfielders (2057 ± 550 m) had a higher Yo-Yo IE2 test performance (P < 0.05) than central defenders (1588 ± 534 m) and attackers (1516 ± 401 m), but not central midfielders (1764 ± 473 m) or full-backs (1964 ± 522 m). Large correlations were observed between Yo-Yo IE2 test performance and the total and high-intensity distance covered (r = 0.55; P < 0.05) during elite senior soccer matches (r = 0.70; P < 0.01). A large correlation was also obtained between Yo-Yo IE2 test performance and (r = 0.68; P < 0.01). Performances in the Yo-Yo IE2 test were greater (P < 0.05) in the middle and the end of the season compared with the preparation period for elite youth female players (1767 ± 539 and 1742 ± 503 vs 1564 ± 504 m) and in elite senior female players, Yo-Yo IE2 test performance increased by 14% (P < 0.01) after completing 4 weeks of intense training prior to the FIFA Women's World Cup Finals (2049 ± 283 vs 1803 ± 342 m).
Conclusions: The Yo-Yo IE2 test is reproducible and is an indicator of the match-specific physical capacity of female soccer players. Furthermore, the Yo-Yo IE2 test illustrates sensitivity by differentiating intermittent exercise performance of female players in various competitive levels, stages of the season and playing positions.



Hulton AT, Edwards JP, Gregson W, Maclaren D, Doran DA. Effect of Fat and CHO Meals on Intermittent Exercise in Soccer Players. Int J Sports Med. 2012 Sep 12. [Epub ahead of print]
 Source
Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Abstract
Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1 km time trial 3 ½ h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, β-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, β-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1 km time trial (HFM: 228.6+14.4 s; HCM: 229.4+26.5 s) (mean+SD).
Conclusions: The type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance.

Thursday, September 13, 2012

Practical neuromuscular warm-up strategies applied consistently for long periods can reduce lower extremity injury incidence

fifa.com
Recent studies in football –Part II
Abstracts modified from PubMed


Eirale C, Farooq A, Smiley FA, Tol JL, Chalabi H. Epidemiology of football injuries in Asia: A prospective study in Qatar. J Sci Med Sport. 2012 Aug 1. [Epub ahead of print]


Source
Aspetar, Qatar Orthopaedic and Sports Medicine Hospital, Qatar.
Abstract
In a prospective cohort study, authors investigated the incidence, characteristics and patterns of football injuries at club level in Qatar. Data were prospectively collected from the first division football league clubs in Qatar, in accordance with the international consensus statement on football injury epidemiology. An injury was defined as any physical complaint sustained during football activity resulting in the inability to participate fully in the next training or match. Individual injuries and exposure of each player were recorded by the medical staff of each team over one season. A total of 217 injuries were recorded, with an injury rate during matches of 14.5/1000h (95% CI: 11.6-18.0) compared with 4.4/1000h during training sessions (95% CI: 3.7-5.2). More than one third of all injuries were muscle strains (36.4%). Hamstring strains (54.4% of all muscle strains) exhibited a higher incidence than all other injury types (p<0.001). The thigh was the most frequent injury location (41.9%, p<0.001). Reinjuries (15% of total injuries) were mainly comprised of muscle strains associated with a higher severity compared with new injuries.
CONCLUSIONS: Despite the different environmental, social and cultural setting, our findings are comparable with previous data from European club football, confirming the previous finding at national team level that there are no regional peculiarities of football injuries in this part of the Asiatic continent. The relatively high overuse injury incidence rate and the high recurrence rate for (severe) thigh muscle strains, especially during games, warrants prevention strategies.




Herman K, Barton C, Malliaras P, Morrissey D. The effectiveness of neuromuscular warm-up strategies, that require no additional equipment, for preventing lower limb injuries during sports participation: a systematic review. BMC Med. 2012 Jul 19;10:75.

Source
Centre for Sports and Exercise Medicine, William Harvey Research Institute, Bart's and the London School of Medicine and Dentistry, Queen Mary University of London
Abstract
Seven electronic databases were searched from inception to January 2012 for studies investigating neuromuscular warm-up strategies and injury prevention. The quality of each included study was evaluated using a modified version of the van Tulder scale. Data were extracted from each study and used to calculate the risk of injury following application of each evaluated strategy. Nine studies were identified including six randomized controlled trials (RCT) and three controlled clinical trials (CCT). Heterogeneity in study design and warm-up strategies prevented pooling of results. Two studies investigated male and female participants, while the remaining seven investigated women only. Risk Ratio (RR) statistics indicated 'The 11+' prevention strategy significantly reduces overall (RR 0.67, confidence interval (CI) 0.54 to 0.84) and overuse (RR 0.45, CI 0.28 to 0.71) lower limb injuries as well as knee (RR 0.48, CI 0.32 to 0.72) injuries among young amateur female footballers. The 'Knee Injury Prevention Program' (KIPP) significantly reduced the risk of noncontact lower limb (RR 0.5, CI 0.33 to 0.76) and overuse (RR 0.44, CI 0.22 to 0.86) injuries in young amateur female football and basketball players. The 'Prevent Injury and Enhance Performance' (PEP) strategy reduces the incidence of anterior cruciate ligament (ACL) injuries (RR 0.18, CI 0.08 to 0.42). The 'HarmoKnee' programme reduces the risk of knee injuries (RR 0.22, CI 0.06 to 0.76) in teenage female footballers. The 'Anterior Knee Pain Prevention Training Programme' (AKP PTP) significantly reduces the incidence of anterior knee pain (RR 0.27, CI 0.14 to 0.54) in military recruits.
CONCLUSIONS: Effective implementation of practical neuromuscular warm-up strategies can reduce lower extremity injury incidence in young, amateur, female athletes and male and female military recruits. This is typically a warm-up strategy that includes stretching, strengthening, balance exercises, sports-specific agility drills and landing techniques applied consistently for longer than three consecutive months.



Haugen TA, Tønnessen E, Seiler S. Anaerobic Performance Testing of Professional Soccer Players 1995-2010. Int J Sports Physiol Perform. 2012 Aug 6. [Epub ahead of print]

Source
Norwegian Olympic Federation, Oslo, Norway.
Abstract
The purpose of this investigation was to compare sprint and countermovement jump (CMJ) performance among competitive soccer players as a function of performance level, field position and age. In addition, we wanted to quantify the evolution of these physical characteristics among professional players over a 15 year period. 939 athletes (22.1 ±4.3 yr), including national team players, tested 40m sprint with electronic timing and CMJ on a force platform at the Norwegian Olympic Training Center between 1995 and 2010. National team and 1st division players were faster (p<0.05) than 2nd division (1.0-1.4 %), 3rd-5th division (3.0-3.8 %), junior national team (1.7-2.2 %) and junior players (2.8-3.7 %). Forwards were faster than defenders (1.4 %), midfielders (2.5 %) and goalkeepers (3.2 %) over 0-20m (p<0.001). Midfielders jumped ~2.0 cm lower than the other playing positions (p<0.05). Sprinting velocity peaked in the age range 20-28 yr and declined significantly thereafter (p<0.05). Players from time epoch 2006-2010 had 1-2 % faster 0-20m and peak velocity than players from the 1995-1999 and 2000-2005 epochs, whereas no differences in CMJ performance were observed.
CONCLUSIONS: This study provides effect magnitude estimates for the influence of performance level, position and age on sprint and CMJ performance in soccer. While CMJ performance has remained stable over the time, there has been a small but positive development in sprinting velocity among professional players.



Ingebrigtsen J, Bendiksen M, Randers MB, Castagna C, Krustrup P, Holtermann A. Yo-Yo IR2 testing of elite and sub-elite soccer players: Performance, heart rate response and correlations to other interval tests. J Sports Sci. 2012 Aug 6. [Epub ahead of print]

Source
Centre of Practical Knowledge, Department of Sports , University of Nordland , Bodø , Norway.
Abstract
This study examined performance, heart rate response and construct validity of the Yo-Yo IR2 test by testing 111 elite and 92 sub-elite soccer players from Norway and Denmark. VO(2)max, Yo-Yo IR1 and repeated sprint tests (RSA) (n = 51) and match-analyses (n = 39) were also performed. Yo-Yo IR2 and Yo-Yo IR1 performance was 41 and 25% better (P < 0.01) for elite than sub-elite players, respectively, and heart rate after 2 and 4 min of the Yo-Yo IR2 test was 20 and 15 bpm (9 and 6% HRmax), respectively, lower (P < 0.01) for elite players. RSA performance and VO(2)max was not different between competitive levels (P > 0.05). For top-teams, Yo-Yo IR2 performance (28%) and sprinting distance (25%) during match were greater (P < 0.05) than for bottom-teams. For elite and sub-elite players, Yo-Yo IR2 performance was correlated (P < 0.05) with Yo-Yo IR1 performance (r = 0.74 and 0.76) and mean RSA time (r = -0.74 and -0.34).
Conclusion: The Yo-Yo IR2 test has a high discriminant and concurrent validity, as it discriminates between players of different within- and between-league competitive levels and is correlated to other frequently used intermittent elite soccer tests.


Castellano J, Casamichana D, Dellal A. Influence of game format and number of players on heart rate responses and physical demands in small-sided soccer games. J Strength Cond Res. 2012 Jul 25. [Epub ahead of print]

Source
Faculty of Physical Activity and Sport Sciences. University of the Basque Country, España, Olympique Lyonnais Football Club, Lyon, France, Santy Orthopedicae clinical, sport science and research department Lyon, France, & Tunisian Research Laboratory "Sport Performance Optimization", National Center of Medicine and Science in Sport, Tunisia
Abstract
The aim of the study was to examine the extent to which changing the game format (possession play vs. regulation goals and goalkeepers vs. small goals only) and the number of players (3 vs. 3, 5 vs. 5 and 7 vs. 7) influenced the physiological and physical demands of small-sided soccer games (SSGs) in amateurs and semi-professional players. Fourteen semi-professional male soccer players were monitored with GPS and heart-rate devices. Heart rate, player-load, distance covered, running speed and the number of accelerations were recorded for nine different SSGs. The results show that changes both in game format and the number of players affect the players' physiological and physical demands. Possession play places greater physiological and physical demands on players, although reducing the number of players only increases the physiological load. In the 7 vs. 7 games, changing the game format did not alter the heart rate responses. Finally, in the possession play format, changing the number of players did not produce significant differences in heart rate responses, although physical demands did decrease in line with a reduction in the number of players.
Conclusions: These results should help coaches to understand how modifying different aspects of SSGs has a differential effect on the players' physiological and physical demands. Moreover, coaches in semi-professional and amateurs have now consistent information's to design and optimize their training time in mixing the technical, tactical and physical aspects.


Deprez D, Vaeyens R, Coutts AJ, Lenoir M, Philippaerts R. Relative Age Effect and Yo-Yo IR1 in Youth Soccer. Int J Sports Med. 2012 Jul 12. [Epub ahead of print]

Source
Movement and Sports Sciences, Ghent University, Ghent, Belgium.
Abstract
The aims of the study were to investigate the presence of a relative age effect and the influence of birth quarter on anthropometric characteristics, an estimation of biological maturity and performance in the Yo-Yo Intermittent Recovery Test level 1 in 606 elite, Flemish youth soccer players. The sample was divided into 5 chronological age groups (U10-U19), each subdivided into 4 birth quarters. Players had their APHV estimated and height, weight and Yo-Yo IR1 performance were assessed. Differences between quarters were investigated using uni- and multivariate analyses. Overall, significantly (P<0.001) more players were born in the first quarter (37.6%) compared to the last (13.2%). Further, no significant differences in anthropometric variables and Yo-Yo IR1 performance were found between the 4 birth quarters. However, there was a trend for players born in the first quarter being taller and heavier than players born in the fourth quarter. Players born in the last quarter tended to experience their peak in growth earlier, this may have enabled them to compete physically with their relatively older peers.
Conclusions: Our results indicated selection procedures which are focused on the formation of strong physical and physiological homogeneous groups. Relative age and individual biological maturation should be considered when selecting adolescent soccer players.

Friday, September 7, 2012

Low injury rate correlates with team success-Recent studies in football (part I)


espn.go.com

Abstracts modified from PubMed
 
Eirale C, Tol JL, Farooq A, Smiley F, Chalabi H. Low injury rate strongly correlates with team success in Qatari professional football. Br J Sports Med. 2012 Aug 17. [Epub ahead of print]

Source
Department of Sports Medicine, Aspetar-Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
Abstract
Using a prospective cohort study design, this study captured exposure and injuries in Qatar male elite football for a season. Club performance was measured by total league points, ranking, goal scored, goals conceded and number of matches won, drawn or lost. Lower injury incidence was strongly correlated with team ranking position (r=0.929, p=0.003), more games won (r=0.883, p=0.008), more goals scored (r=0.893, p=0.007), greater goal difference (r=0.821, p=0.003) and total points (r=0.929, p=0.003).
CONCLUSIONS: Lower incidence rate was strongly correlated with team success. Prevention of injuries may contribute to team success.


Dallinga JM, Benjaminse A, Lemmink KA. Which screening tools can predict injury to the lower extremities in team sports?: a systematic review. Sports Med. 2012 Sep 1;42(9):791-815

Source
Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Abstract
The aim of this article is to determine the predictive values of anthropometric and/or physical screening tests for injuries to the leg, anterior cruciate ligament (ACL), knee, hamstring, groin and ankle in team sports. The analysis showed that different screening tools can be predictive for injuries to the knee, ACL, hamstring, groin and ankle. For injuries in general there is some support in the literature to suggest that general joint laxity is a predictive measure for leg injuries. The anterior right/left reach distance >4 cm and the composite reach distance <4.0% of limb length in girls measured with the star excursion balance test (SEBT) may predict leg injuries. Furthermore, an increasing age, a lower hamstring/quadriceps (H : Q) ratio and a decreased range of motion (ROM) of hip abduction may predict the occurrence of leg injuries. Hyperextension of the knee, side-to-side differences in anterior-posterior knee laxity and differences in knee abduction moment between both legs are suggested to be predictive tests for sustaining an ACL injury and height was a predictive screening tool for knee ligament injuries. There is some evidence that when age increases, the probability of sustaining a hamstring injury increases. Debate exists in the analysed literature regarding measurement of the flexibility of the hamstring as a predictive screening tool, as well as using the H : Q ratio. Hip-adduction-to-abduction strength is a predictive test for hip adductor muscle strain. Studies do not agree on whether ROM of the hamstring is a predictive screening tool for groin injury. Body mass index and the age of an athlete could contribute to an ankle sprain. There is support in the literature to suggest that greater strength of the plantar flexors may be a predictive measure for sustaining an ankle injury. Furthermore, there is some agreement that the measurement of postural sway is a predictive test for an ankle injury.
Conclusions: The screening tools mentioned above can be recommended to medical staff and coaches for screening their athletes. Future research should focus on prospective studies in larger groups and should follow athletes over several seasons.



Wilkerson GB, Giles JL, Seibel DK. Prediction of core and lower extremity strains and sprains in collegiate football players: a preliminary study. J Athl Train. 2012;47(3):264-72.

Source
Graduate Athletic Training Education Program, University of Tennessee at Chattanooga, USA.
Abstract
Poor core stability is believed to increase vulnerability to uncontrolled joint displacements throughout the kinetic chain between the foot and the lumbar spine. All team members (National Collegiate Athletic Association Division I Football Championship Subdivision football program ) who were present for a mandatory physical examination on the day before preseason practice sessions began (n = 83). Preparticipation administration of surveys to assess low back, knee, and ankle function; documentation of knee and ankle injury history; determination of body mass index; 4 different assessments of core muscle endurance; and measurement of step-test recovery heart rate. All injuries were documented throughout the preseason practice period and 11-game season. Receiver operating characteristic analysis and logistic regression analysis were used to identify dichotomized predictive factors that best discriminated injured from uninjured status. The 75th and 50th percentiles were evaluated as alternative cutpoints for dichotomization of injury predictors. Players with ≥2 of 3 potentially modifiable risk factors related to core function had 2 times greater risk for injury than those with <2 factors (95% confidence interval = 1.27, 4.22), and adding a high level of exposure to game conditions increased the injury risk to 3 times greater (95% confidence interval = 1.95, 4.98). Prediction models that used the 75th and 50th percentile cutpoints yielded results that were very similar to those for the model that used receiver operating characteristic-derived cutpoints.
CONCLUSIONS: Low back dysfunction and suboptimal endurance of the core musculature appear to be important modifiable football injury risk factors that can be identified on preparticipation screening. These predictors need to be assessed in a prospective manner with a larger sample of collegiate football players.



Mills A, Butt J, Maynard I, Harwood C. Identifying factors perceived to influence the development of elite youth football academy players. J Sports Sci. 2012 Aug 13. [Epub ahead of print]

Source
Centre for Sport and Exercise Science, Sheffield Hallam University , UK.

Abstract
Based on the developmental theory presented by Gagné (2009), we examined the factors perceived to influence the development of elite youth football players at a critical stage in their progression to the professional level. Transcribed interviews with ten expert development coaches were inductively and deductively content analysed. Conceptualisation of the data revealed six interrelated higher-order categories that represented the factors perceived to either positively or negatively influence player development. These were: awareness (e.g. self-awareness, awareness of others); resilience (e.g. coping with setbacks, optimistic attitude); goal-directed attributes (e.g. passion, professional attitude); intelligence (e.g. sport intelligence, emotional competence); sport-specific attributes (e.g. coachability, competitiveness); and environmental factors (e.g. significant others, culture of game). In this investigation, awareness emerged as a fundamental and mediating element for understanding how young players are able to transition to the professional level.
Conclusions: The findings underline the multidimensional nature of talent development and suggest that an intricate combination of stage-specific factors must manifest for gifted young players to translate their potential into excellence. Mechanisms by which academies could be helped to shape the characteristics and conditions associated with effective development are discussed.


Aguiar M, Botelho G, Gonçalves B, Sampaio J. Physiological responses and activity profiles of football small-sided games. J Strength Cond Res. 2012 Jul 18. [Epub ahead of print]

Source
Research Center for Sport Sciences, Health and Human Development, University of Trás-os-Montes e Alto Douro and CERNAS Research Unit, Coimbra College of Agriculture, Polytechnic Institute of Coimbra, Bencanta, Portugal
Abstract
The aim of this study was to identify the acute physiological responses and activity profiles of football small-sided games (SSG) formats. Ten professional football players participated in four variations of SSG (2-, 3-, 4- and 5-a-side) with an intermittent regime involving 3 × 6 minute bouts with 1 minute of passive planned rest in which the heart rate (30), rating of perceived exertion (40), activity profile and body load were recorded. The higher % HRmax values were found in 2- and 3-a-side formats (p ≤ 0.05). The lowest RPE value was found at the 5-a-side and the highest was found at the 2-a-side (13.48 ± 2.67 and 17.01 ± 1.80, respectively, p ≤ 0.05). The distance covered in the 2-a-side format (598.97 ± 78.91 m) was smaller than in all other formats. The 2-a-side format presented the lowest number of sprints (0.71 ± 0.86) and the 3-a-side the highest (2.50 ± 1.65). Statistically significant differences were found across SSG in the total body load. The 4-a-side presented the highest and the 5-a-side the lowest values (95.18 ± 17.54 and 86.43 ± 14.47, respectively). The body load per minute declined each 2 minutes of play.
Conclusions: Maintaining a constant area:player ratio, coaches can use lower number of players (2- and 3-a-side) to increase cardiovascular effects, but use higher number of players (4- and 5-a-side) to increase variability and specificity according to the competition demands.