Latest research in football - week 26 - 2013

Latest research in football

As previous literature updates, we 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 of short-passing ability with athletic performances in youth soccer players
Authors: Benounis O, Benabderrahman A, Chamari K, Ajmol A, Benbrahim M, Hammouda A, Hammami MA, Zouhal H.
Reference: Asian J Sports Med. 2013 Mar;4(1):41-8. Epub 2012 Dec 1.
Summary: This study was designed to examine the relationship between multiple short-passing ability [measured using the Loughborough Soccer Passing Test (LSPT)] and athletic performances in youth soccer players. Forty-two young soccer players (age 14.8±0.4years) performed the LSPT, the squat-jump (SqJ), the counter movement jump (CMJ), the 30m sprints (with 5m and 20m split times also recorded), the 15m agility run (Agility-15m), the 15m ball dribbling (Ball-15m), the Illinois agility test (IAGT) and the Yo-Yo IRT Level 1 tests. LSPT total performance (LSPT TP) showed significant positive correlation with 5m, 20m, and 30m sprint times, Agility-15m, Ball-15m and Illinois agility test (r=0.60, r=0.58, r=0.49, r=0.75, r=0.71 and r=0.72; P<0.01, respectively). Significant negative correlation were found between LSPT TP and SqJ and CMJ (r=-0.62 and r=-0.64; P<0.01, respectively). It was determined that Agility-15m, Illinois agility test and Ball-15m were the most effective factors associated with LSPT TP among other factors in multiple regression analysis. This study showed that LSPT TP of young elite soccer players is determined by their agility abilities, thus enabling this test to be used for talent identification purposes.

#2 The Acute Effect of Whole Body Vibration on Repeated Shuttle-Running in Young Soccer Players
Authors: Padulo J, Di Giminiani R, Ibba G, Zarrouk N, Moalla W, Attene G, M Migliaccio G, Pizzolato F, Bishop D, Chamari K.
Reference: Int J Sports Med. 2013 Jun 18. [Epub ahead of print]
Summary: The aim of this study was to investigate the acute effects of whole-body vibration (WBV) on Repeated Sprint Ability (RSA). Seventeen male soccer players (16.71±0.47 y) performed three RSA tests (Randomized crossover study design). The second RSA test was done with WBV (RSA2) to assess the effect of WBV. The studied variables were: best time (BT), worst time (WT), total time (TT), the fatigue index (FI) of RSA, and post-test blood lactate (BLa). ANOVA with repeated measures showed no differences between RSA1 and RSA3, while there were significant differences in all variables studied. TT= [RSA2 0.93% and 1.68% lower than RSA1 and RSA3 respectively; p<0.05], BLa= [RSA2 16.97% and 14.73% greater than RSA1 and RSA3 respectively; p<0.001], WT= [RSA2 1.90% and 2.93% lower than RSA1 and RSA3 respectively; p<0.01], and FI = [RSA2 30.64% and 40.15% lower than RSA1 and RSA3 respectively; p<0.0001]. When comparing individual sprints, WBV showed a significant effect at the 5th sprint: RSA2 2.29 % and 2.95% lower than RSA1 and RSA3 respectively (p<0.005), while at the 6th sprint: RSA2 2.75% and 4.09% lower than RSA1 and RSA3 respectively; p<0.005. In conclusion, when applying WBV during the recovery periods of Repeated Sprint Ability efforts, most of the performance variables improved.

#3 Reliability and validity of the soccer specific INTER field test
Authors: Aandstad A, Simon EV.
Reference: J Sports Sci. 2013 Jun 17. [Epub ahead of print]
Summary: The aims of this study were to explain how the Intermittent Endurance Running (INTER) test is executed, describe physiological responses during testing, and evaluate reliability and content validity in this new soccer specific test. The test consists of 20 m shuttle running, interspersed with straight sprints, agility sprints, walking and resting. Shuttle run speed is increased at each level until exhaustion. Thirteen male professional players participated in the present study. Exercise tolerance time, distance covered, mean blood lactate and mean heart rate were 25:51 ± 2:41 min, 2892 ± 324 m, 5.5 ± 1.2 mmol · L-1 and 161 ± 11 beats · min-1, respectively, during the INTER test. Sprint and agility performance decreased significantly at higher levels. Eight of the players performed a retest for reliability evaluations. Mean difference ± 95% limits of agreement, coefficient of variation (CV) and intraclass correlation coefficient (ICC) for exercise tolerance time between test and retest were -00:41 ± 02:25 min, 2.5% and 0.75, respectively. The CV for sprint and agility performance between test and retest was <1%. The INTER test mimics soccer games on distance/time ratio, frequency of sprints, heart rate and blood lactate values, and could be an alternative field test for evaluating essential physical performance aspects in soccer players.

#4 Biochemical responses to level-1 yo-yo intermittent recovery test in young Tunisian football players
Authors: Hammouda O, Chtourou H, Chaouachi A, Chahed H, Zarrouk N, Miled A, Chamari K, Souissi N.
Reference: Asian J Sports Med. 2013 Mar;4(1):23-8. Epub 2012 Sep 29.
Summary: The aim of this work was to investigate the metabolic and muscle damage responses after the level-1 Yo-Yo intermittent recovery test (YYIRT) in young football players. Fifteen male football players (17.42 ± 0.2 yrs, 69.91 ± 4.4 kg, 178.64 ± 3.8 cm; mean ± SD) participated in this study. Fasting blood samples for various biochemical parameters (i.e. lactate (Lac), glucose (GLC), triglycerides (Tri), creatine kinase (CK), uric acid (UA)) collected from a forearm vein after 5-min of seated rest and 3-min after the test. Moreover, rating of perceived exertion (RPE) and maximal heart rate during and after the YYIRT were recorded. Mean levels of the selected biochemical markers were raised after the YYIRT exercise (P<0.001 for the other markers). Moreover, lipid parameters increased significantly after the test (P<0.01 for Tri and P<0.001 for HDL). These findings confirm the higher metabolic demand of aerobic as well as anaerobic metabolism and reflect a significant mobilization of purine cycle during the YYIRT. The increase of muscle damage markers also reflects the higher anaerobic solicitation. From these findings, we can conclude the importance of aerobic and anaerobic metabolism during soccer-specific endurance performance (i.e. YYIRT, soccer match).

#5 Static stretching of the hamstring muscle for injury prevention in football codes: a systematic review
Authors: Rogan S, Wüst D, Schwitter T, Schmidtbleicher D.
Reference: Asian J Sports Med. 2013 Mar;4(1):1-9. Epub 2012 Nov 20.
Summary: Hamstring injuries are common among football players. There is still disagreement regarding prevention. The aim of this review is to determine whether static stretching reduces hamstring injuries in football codes. A systematic literature search was conducted on the online databases PubMed, PEDro, Cochrane, Web of Science, Bisp and Clinical Trial register. Study results were presented descriptively and the quality of the studies assessed were based on Cochrane's 'risk of bias' tool. The review identified 35 studies, including four analysis studies. These studies show deficiencies in the quality of study designs. The study protocols are varied in terms of the length of intervention and follow-up. No RCT studies are available, however, RCT studies should be conducted in the near future.

#6 Recurrence of Achilles tendon injuries in elite male football players is more common after early return to play: an 11-year follow-up of the UEFA Champions League injury study
Authors: Gajhede-Knudsen M, Ekstrand J, Magnusson H, Maffulli N.
Reference: Br J Sports Med. 2013 Jun 14. [Epub ahead of print]
Summary: To investigate the incidence, injury circumstances, lay-off times and reinjury rates of Achilles tendon disorders in male professional football. A total of 27 clubs from 10 countries and 1743 players have been followed prospectively during 11 seasons between 2001 and 2012. The team medical staff recorded individual player exposure and time-loss injuries. A total of 203 (2.5% of all injuries) Achilles tendon disorders were registered. A majority (96%) of the disorders were tendinopathies, and nine were partial or total ruptures. A higher injury rate was found during the preseason compared with the competitive season, 0.25 vs 0.18/1000 h (rate ratio (RR) 1.4, 95% CI 1.1 to 2.0; p=0.027). The mean lay-off time for Achilles tendinopathies was 23±37 (median=10, Q1=4 and Q3=24) days, while a rupture of the Achilles tendon, on average, caused 161±65 (median=169, Q1=110 and Q3=189) days of absence. Players with Achilles tendon disorders were significantly older than the rest of the cohort, with a mean age of 27.2±4 years vs 25.6±4.6 years (p<0.001). 27% of all Achilles tendinopathies were reinjuries. A higher reinjury risk was found after short recovery periods (31%) compared with longer recovery periods (13%) (RR 2.4, 95% CI 2.1 to 2.8; p<0.001). Achilles tendon disorders account for 3.8% of the total lay-off time and are more common in older players. Recurrence is common after Achilles tendinopathies and the reinjury risk is higher after short recovery periods.

#7 Different injury pattern in goalkeepers compared to field players: A three-year epidemiological study of professional football
Authors: Eirale C, Tol JL, Whiteley R, Chalabi H, Hölmich P.
Reference: J Sci Med Sport. 2013 Jun 13. pii: S1440-2440(13)00130-8. doi: 10.1016/j.jsams.2013.05.004. Summary: Goalkeepers have a specific physiological and biomechanical profile including hip loading with increased frontal plane kinetics and explosive side jumps. The aim of this study is to analyze the injury incidence in professional goalkeepers and to compare this with field players. Prospective (3 seasons, 2008-2011) registration of injuries and exposure of first division professional footballers of Qatar. Of the 527 players, 49 were goalkeepers. Sixty-seven injuries occurred during 17.858h of exposure. Goalkeepers had a lower total (p=0.01) and training (p=0.007) injury incidence than field players, while there was no injury difference during matches (p=0.279). Moreover, goalkeepers presented a lower incidence of injuries that were: non contact (p=0.002), traumatic (p<0.001), strains (p<0.001), thigh (p<0.001), and hamstring (p=0.038). Adductor strains were the most common subtype of injury for goalkeepers and this incidence was higher in goalkeepers than in field players (p=0.045). In goalkeepers, mean lay off time for adductor strains was 2.5 times longer than for hamstring strains. More than one third of the overuse injuries were hip and groin injuries. While the overall and lower body injury incidence in goalkeepers was lesser than in field players, upper body incidence was higher. Football goalkeepers have a peculiar injury epidemiology, possibly due to their specific physiological and biomechanical performance requirements. Goalkeepers are prone to acute adductor and overuse hip and groin injuries, while muscle strains, in particular located in the hamstrings, are lower compared with field players. Specific prevention program should be implemented in this category of footballers.

#8 Sudden cardiac death in football
Authors: Bohm P, Kästner A, Meyer T.
Reference: J Sports Sci. 2013 Jun 17. [Epub ahead of print]
Summary: Abstract Football is the most popular sport worldwide and includes the largest population of sports participants, especially in the field of recreational sport. It remains controversial whether football represents a sport discipline with a particular high risk of sudden cardiac death (SCD). The true incidence of SCD among football players is not known due to a lack of football-specific studies. In particular, recreational football players over an age of 35 years with a predominance of coronary artery disease (CAD) who do not exercise regularly are exposed to a higher risk of SCD. Surprisingly, the few European studies that included football as a sport discipline, showed that CAD already plays an important role in the young athlete. Potential pathophysiological mechanisms in football that may lead to a higher risk of SCD include the high release of catecholamines, increased platelet aggregation, dehydration and electrolyte disturbances. Establishment of sport-specific and national registers for SCD should certainly contribute to a better understanding of this highly important topic.

#9 Combined strength and power training in high-level amateur football during the competitive season: a randomised-controlled trial
Authors: Faude O, Roth R, Di Giovine D, Zahner L, Donath L.
Reference: J Sports Sci. 2013 Jun 17. [Epub ahead of print]
Summary: We aimed to analyse the effects of combined strength and power training during the competitive season on physical fitness in high-level amateur football players. Sixteen male players (22.5 (SD 2.5) years, 1.79 (0.05) m, 76.8 (6.1) kg) from one team were randomly assigned to either a strength training (ST, N = 8) or a control (CON, N = 8) group. ST conducted lower extremity resistance exercises combined with plyometrics and/or sprints 2 × 30 min per week for 7 weeks. CON performed technical-tactical training during the same time period. Before and after training several physical fitness parameters were assessed: one-repetition maximum (1-RM, half squat), isometric peak strength and rate of force development (RFD, leg press), jump height (countermovement, CMJ, drop jump, DJ), sprint times, agility, and intermittent endurance. Large significant test × group interactions were found for 1-RM, CMJ, and DJ reactivity index with increases in CT relative to CON(+11 to 18%). Although not significant (P < 0.20), likely practically relevant effects were observed for isometric peak strength and RFD (+24 to 29%). We found no relevant interaction effects for agility, sprint times, and intermittent endurance. A 7-week in-season combined strength and power training program can improve relevant strength and jump parameters in high-level amateur football players.

#10 Resting ECG findings in elite football players
Authors: Bohm P, Ditzel R, Ditzel H, Urhausen A, Meyer T.
Reference: J Sports Sci. 2013 Jun 17. [Epub ahead of print]
Summary: The purpose of the study was to evaluate ECG abnormalities in a large sample of elite football players. Data from 566 elite male football players (57 of them of African origin) above 16 years of age were screened retrospectively (age: 20.9 ± 5.3 years; BMI: 22.9 ± 1.7 kg · m-2, training history: 13.8 ± 4.7 years). The resting ECGs were analysed and classified according to the most current ECG categorisation of the European Society of Cardiology (ESC) (2010) and a classification of Pelliccia et al. ( 2000 ) in order to assess the impact of the new ESC-approach. According to the classification of Pelliccia, 52.5% showed mildly abnormal ECG patterns and 12% were classified as distinctly abnormal ECG patterns. According to the classification of the ESC, 33.7% showed 'uncommon ECG patterns'. Short-QT interval was the most frequent ECG pattern in this group (41.9%), followed by a shortened PR-interval (19.9%). When assessed with a QTc cut-off-point of 340 ms (instead of 360 ms), only 22.2% would have had 'uncommon ECG patterns'. Resting ECG changes amongst elite football players are common. Adjustment of the ESC criteria by adapting proposed time limits for the ECG (e.g. QTc, PR) should further reduce the rate of false-positive results.

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