Latest research in football - week 3 - 2015

#1 Soccer Increases Bone Mass in Prepubescent Boys During Growth: A 3-Yr Longitudinal Study
Reference: J Clin Densitom. 2015 Jan 13. pii: S1094-6950(14)00238-8. doi: 10.1016/j.jocd.2014.10.004. [Epub ahead of print]
Authors: Zouch M, Zribi A, Alexandre C, Chaari H, Frere D, Tabka Z, Vico L
Summary: The aim of this study was to examine the effect of 3-yr soccer practice on bone acquisition in prepubescent boys. We investigated 65 boys (aged 10-13 yr, Tanner stage I) at baseline, among which only 40 boys (Tanner stages II and III) have continued the 3-yr follow-up: 23 soccer players (F) completed 2-5 h of training plus 1 competition game per week and 17 controls (C). Bone mineral density (BMD, g/cm2) and bone mineral content (BMC, g) were measured by dual-energy X-ray absorptiometry at different sites. At baseline, BMD was higher in soccer players than in controls in the whole body and legs. In contrast, there was nonsignificant difference BMD in head, femoral neck, arms, and BMC in all measured sites between groups. At 3-yr follow-up, soccer players were found to have higher BMD and BMC at all sites than controls, except for head BMD and BMC and arms BMC in which the difference was nonsignificant between groups. During the 3-yr follow-up, the soccer players were found to gain significantly more in lumbar spine (31.2% ± 2.9% vs 23.9% ± 2.1%; p < 0.05), femoral neck (24.1% ± 1.8% vs 11.4% ± 1.9%; p < 0.001), whole body (16.5% ± 1.4% vs 11.8% ± 1.5%; p < 0.05), and nondominant arm BMD (18.2% ± 1.4% vs 13.6% ± 1.7%; p < 0.05) as well as lumbar spine (62.5% ± 20.1% vs 39.5% ± 20.1%; p < 0.001), femoral neck, (37.7% ± 14.2% vs 28.9% ± 12.8%; p < 0.05) and nondominant arm BMC (68.6% ± 22.9% vs 50.1% ± 22.4%; p < 0.05) than controls. In contrast, soccer players have less %BMD and %BMC changes in the head than controls. A nonsignificant difference was found in legs, dominant arm, head %BMD and %BMC changes, and whole-body %BMC changes between groups. In summary, we suggest that soccer has an osteogenic effect BMD and BMC in loaded sites in pubertal soccer players. The increased bone mass induced by soccer training in the stressed sites was associated to a decreased skull bone mass after 3 yr of follow-up.


#2 Effects of treadmill versus overground soccer match simulations on biomechanical markers of anterior cruciate ligament injury risk in side cutting
Reference: J Sports Sci. 2015 Jan 13:1-10. [Epub ahead of print]
Authors: Raja Azidin RM, Sankey S, Drust B, Robinson MA, Vanrenterghem J.
Summary: This study aimed to investigate whether treadmill versus overground soccer match simulations have similar effects on knee joint mechanics during side cutting. Nineteen male recreational soccer players completed a 45-min treadmill and overground match simulation. Heart rate (HR) and rating of perceived exertion (RPE) were recorded every 5 min. Prior to exercise (time 0 min), at "half-time" (time 45 min) and 15 min post-exercise (time 60 min), participants performed five trials of 45° side-cutting manoeuvres. Knee abduction moments and knee extension angles were analysed using two-way repeated measures analysis of variance (α = 0.05). Physiological responses were significantly greater during the overground (HR 160 ± 7 beats ∙ min-1; RPE 15 ± 2) than the treadmill simulation (HR 142 ± 5 beats ∙ min-1; RPE 12 ± 2). Knee extension angles significantly increased over time and were more extended at time 60 min compared with time 0 min and time 45 min. No significant differences in knee abduction moments were observed. Although knee abduction moments were not altered over time during both simulations, passive rest during half-time induced changes in knee angles that may have implications for anterior cruciate ligament injury risk.


#3 Influences of baseline heart rate variability on repeated sprint performance in young soccer players
Reference: J Sports Med Phys Fitness. 2015 Jan 13. [Epub ahead of print]
Authors: Cataldo A, Zangla D, Cerasola D, Vallone V, Russo G, Lo Presti R, Traina M.
Summary: The aim of this study was to assess the influence of the autonomic system on the performance of repeated sprints, involving predominantly neuromuscular power, in young soccer players. Twelve young soccer players, selected for the Sicilian Regional Football Representative, mean age 15 years, were recruited. Baseline heart rate variability (HRV) was measured and indices of power spectral analysis (LF, HF, and ratio LF/HF) were calculated to evaluate the sympathovagal balance. The athletes performed 10 maximal 6--sec cycling sprints (RS), interspersed with 30--sec of recovery, to measure the peak power output (PP) represented by the highest power value recorded during a 6--sec sprint, and the mean peak power output (MPP) represented by the average of all highest power values recorded within a repeated--sprint bout. PP was negatively correlated with LF (r = --0.685, P = 0.0141) and LF/HF (r = --0.709, P =0.0098), and positively correlated with HF (r = 0.684, P = 0.0142). MPP was negatively correlated with LF (r = --0.610, P = 0.0350) and LF/HF (r = --0.606, P = 0.0366), and positively correlated with HF (r = 0.731, P = 0.0070). Our study shows that a baseline parasympathetic predominance in the ANS balance is associated with a better neuromuscular contribution to performance, resulting in higher values of PP and MPP during brief repeated maximal cycling sprints. The assessment of baseline HRV before exercise may be useful for to monitor the physical condition of young soccer players and their readiness status to a higher performance.


#4 Influence of the COL5A1 rs12722 on musculoskeletal injuries in professional soccer players
Reference: J Sports Med Phys Fitness. 2015 Jan 13. [Epub ahead of print]
Authors: Massidda M, Bachis V, Corrias L, Piras F, Scorcu M, Calò CM.
Summary: The aim of this study was to investigate whether COL5A1 rs12722 polymorphism is associated with musculoskeletal injuries in elite soccer players. Fifty--four male professional soccer players of European origin (25.9±4.3 years) were recruited from a team participating at the Official Italian Professional Championship during four consecutive seasons (2009-2013). The incidence and severity of musculoskeletal injuries and its relationship to COL5A1 rs12722 polymorphism were analyzed. DNA was extracted from buccal swab. The cohort was genotyped for the COL5A1 rs12722 single nucleotide polymorphism (SNP) through PCR and enzyme digestion with BstUI, and musculoskeletal injuries data were collected during the four seasons. Injuries were categorized under 5 degrees of severity based on the number of days' absence, while musculoskeletal injuries incidence was calculated per 1,000 hours of exposure to training and matches ((Σ injuries/Σ exposure hours) x 1,000). No significant differences were found among genotypes for incidence of musculoskeletal injuries (P=0.683). Participants with TT genotype (3.71±0.5, n=4) showed a trend (P=0.193) versus an higher severity of injuries than individuals with TC (2.98±0.8, n=10) or CC (2.75±0.95, n=4) genotypes. The COL5A1 rs12722 accounted for 44% of severity of injuries (P=0.002). In conclusion, the COL5A1 rs12722 was found to be associated with severity of musculoskeletal injuries but not with incidence of musculoskeletal injuries in top--level soccer players.


#5 Injury risk factors, screening tests and preventative strategies: a systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues
Reference: Br J Sports Med. 2015 Jan 9. pii: bjsports-2014-094104. doi: 10.1136/bjsports-2014-094104. [Epub ahead of print]
Authors: McCall A, Carling C, Davison M, Nedelec M, Le Gall F, Berthoin S, Dupont G
Summary: To systematically review the scientific level of evidence for the 'Top 3' risk factors, screening tests and preventative exercises identified by a previously published survey of 44 premier league football (soccer) teams. Also, to provide an overall scientific level of evidence and graded recommendation based on the current research literature. A systematic literature search (Pubmed [MEDLINE], SportDiscus, PEDRO and Cochrane databases). The quality of the articles was assessed and a level of evidence (1++ to 4) was assigned. Level 1++ corresponded to the highest level of evidence available and 4, the lowest. A graded recommendation (A: strong, B: moderate, C: weak, D: insufficient evidence to assign a specific recommendation) for use in the practical setting was given. Fourteen studies were analysed. The overall level of evidence for the risk factors previous injury, fatigue and muscle imbalance were 2++, 4 and 'inconclusive', respectively. The graded recommendation for functional movement screen, psychological questionnaire and isokinetic muscle testing were all 'D'. Hamstring eccentric had a weak graded 'C' recommendation, and eccentric exercise for other body parts was 'D'. Balance/proprioception exercise to reduce ankle and knee sprain injury was assigned a graded recommendation 'D'. The majority of perceptions and practices of premier league teams have a low level of evidence and low graded recommendation. This does not imply that these perceptions and practices are not important or not valid, as it may simply be that they are yet to be sufficiently validated or refuted by research.


#6 Knowledge, attitudes and beliefs of technical staff towards doping in Spanish football
Reference: J Sports Sci. 2015 Jan 9:1-9. [Epub ahead of print]
Authors: Morente-Sánchez J, Zabala M.
Summary: The aim of this study was to understand the attitudes, beliefs and knowledge among technical staff members of Spanish football teams regarding doping. The sample was drawn from 88 football teams that ranged from elite to under-18 categories. The 237 stakeholders (34.45 ± 8.59 years) were categorised as follows: coaches (COA) (n = 101), physical trainers (PT) (n = 68) and rest of technical staff (RTS) (n = 68). The descriptive exploratory design used an instrument that combined a validated questionnaire (Performance Enhancement Attitude Scale; PEAS) with specific, qualitative open-ended questions. The overall mean score from the PEAS (range, 17-102, with higher scores representing more permissive attitudes towards doping) was 31.64 ± 10.77; for COA, 31.91 ± 11.42; for PT, 31.28 ± 9.44; and for RTS, 31.58 ± 11.18. Regarding participants' knowledge and beliefs, most respondents (57.6%) did not know the meaning of WADA (World Anti-Doping Agency); 84.9% did not know the prohibited list; and 39.2% had used/recommended supplements. In addition, 87.2% recognised "differential treatment of doping among sports," with cycling considered most affected (62.6%) and team sports least (27.2%, with football at 15%). The dangerous lack of knowledge highlights the necessity for anti-doping education and prevention programs for all football stakeholders, not just athletes.


#7 Moderate to severe injuries in football: a one-year prospective study of twenty-four female and male amateur teams
Reference: Bull Soc Sci Med Grand Duche Luxemb. 2014;(3):43-55.
Authors: Lion A, Theisen D, Windal T, Malisoux L, Nührenbörger C, Huberty R, Urhausen A, Seil R
Summary: This study aimed to realize a prospective follow-up of the injuries occurring in female and male football players involved in the highest league in the Grand-Duchy of Luxembourg. Data concerning anthropometric characteristics and football activities were gathered in 125 female and 243 male football players via questionnaires at the beginning of the study. Then, a follow-up of moderate to severe injuries (> 15 days of interruption in football practice) was performed throughout the season 2013-2014. Sixteen injuries (injury incidence = 0.7 injuries/1000 h of exposure) were observed in 13 female football players (10.4%). These injuries concerned mainly the knee (n = 7; 43.7%), with capsules and ligaments being the most often concerned tissues (n = 7; 43.7%). In male football players, 41 severe injuries (injury incidence = 0.6 injuries/1000 h of exposure) were observed in 36 players (14.8%). These injuries concerned mainly the thighs (n = 12; 29.3%) and the muscles and tendons were the most often concerned tissues (n = 18; 43.9%). Injuries in football are predominantly located at the lower limbs, particularly the knees in female football players. The predominant muscle and tendon lesions of the thighs occurring in males could reveal that physical preparation is insufficient or inadequate for a number of players. Regarding these results, it is necessary to implement an injury prevention strategy. The "FIFA 11+" programme could be used as the basic method, but should be personalized according to sex. The injury collection methodology could be optimized with the use of an electronic database, such as the Training and Injury Prevention Platform for Sports (TIPPS). Beside the systematic recording of injury data (as well as the training load) by the players or the medical staff, this system allows to share of important information between stakeholders, follow-up the players, provide risk factor warnings and increase the awareness of the injury problem.


#8 Specific Determination of Maximal Lactate Steady State in Soccer Players
Reference: J Strength Cond Res 29(1): 101–106, 2015
Authors: Loures, JP, Chamari, K, Ferreira, EC, Campos, EZ, Zagatto, AM, Milioni, F, da Silva, ASR, and Papoti, M
Summary: Specific determination of maximal lactate steady state in soccer players—The aim of this study was to establish the validity of the anaerobic threshold (AT) determined on the soccer-specific Hoff circuit (ATHoff) to predict the maximal lactate steady-state exercise intensity (MLSSHoff) with the ball. Sixteen soccer players (age: 16.0 ± 0.5 years; body mass: 63.7 ± 9.0 kg; and height: 169.4 ± 5.3 cm) were submitted to 5 progressive efforts (7.0–11.0 km·h−1) with ball dribbling. Thereafter, 11 players were submitted to 3 efforts of 30 minutes at 100, 105, and 110% of ATHoff. The ATHoff corresponded to the speed relative to 3.5 mmol·L−1 lactate concentration. The speed relative to 4.0 mmol·L−1 was assumed to be ATHoff4.0, and the ATHoffBI was determined through bisegmented adjustment. For comparisons, Student's t-test, intraclass correlation coefficient (ICC), and Bland and Altman analyses were used. For reproducibility, ICC, typical error, and coefficient of variation were used. No significant difference was found between AT test and retest determined using different methods. A positive correlation was observed between ATHoff and ATHoff4.0. The MLSSHoff (10.6 ± 1.3 km·h−1) was significantly different compared with ATHoff (10.2 ± 1.2 km·h−1) and ATHoffBI (9.5 ± 0.4 km·h−1) but did not show any difference from LAnHoff4.0 (10.7 ± 1.4 km·h−1). The MLSSHoff presented high ICCs with ATHoff and ATHoff4.0 (ICC = 0.94; and ICC = 0.89; p ≤ 0.05, respectively), without significant correlation with ATHoffBI. The results suggest that AT determined on the Hoff circuit is reproducible and capable of predicting MLSS. The ATHoff4.0 was the method that presented a better approximation to MLSS. Therefore, it is possible to assess submaximal physiological variables through a specific circuit performed with the ball in young soccer players.


#8 High-Intensity Intermittent Training in Hypoxia: A Double-Blinded, Placebo-Controlled Field Study in Youth Football Players
Reference: J Strength Cond Res 29(1): 226–237, 2015
Authors: Brocherie, F, Girard, O, Faiss, R, and Millet, GP.
Summary: This study examined the effects of 5 weeks (∼60 minutes per training, 2 d·wk−1) of run-based high-intensity repeated-sprint ability (RSA) and explosive strength/agility/sprint training in either normobaric hypoxia repeated sprints in hypoxia (RSH; inspired oxygen fraction [FIO2] = 14.3%) or repeated sprints in normoxia (RSN; FIO2 = 21.0%) on physical performance in 16 highly trained, under-18 male footballers. For both RSH (n = 8) and RSN (n = 8) groups, lower-limb explosive power, sprinting (10–40 m) times, maximal aerobic speed, repeated-sprint (10 × 30 m, 30-s rest) and repeated-agility (RA) (6 × 20 m, 30-s rest) abilities were evaluated in normoxia before and after supervised training. Lower-limb explosive power (+6.5 ± 1.9% vs. +5.0 ± 7.6% for RSH and RSN, respectively; both p < 0.001) and performance during maximal sprinting increased (from −6.6 ± 2.2% vs. −4.3 ± 2.6% at 10 m to −1.7 ± 1.7% vs. −1.3 ± 2.3% at 40 m for RSH and RSN, respectively; p values ranging from <0.05 to <0.01) to a similar extent in RSH and RSN. Both groups improved best (−3.0 ± 1.7% vs. −2.3 ± 1.8%; both p ≤ 0.05) and mean (−3.2 ± 1.7%, p < 0.01 vs. −1.9 ± 2.6%, p ≤ 0.05 for RSH and RSN, respectively) repeated-sprint times, whereas sprint decrement did not change. Significant interactions effects (p ≤ 0.05) between condition and time were found for RA ability–related parameters with very likely greater gains (p ≤ 0.05) for RSH than RSN (initial sprint: 4.4 ± 1.9% vs. 2.0 ± 1.7% and cumulated times: 4.3 ± 0.6% vs. 2.4 ± 1.7%). Maximal aerobic speed remained unchanged throughout the protocol. In youth highly trained football players, the addition of 10 repeated-sprint training sessions performed in hypoxia vs. normoxia to their regular football practice over a 5-week in-season period was more efficient at enhancing RA ability (including direction changes), whereas it had no additional effect on improvements in lower-limb explosive power, maximal sprinting, and RSA performance.