Latest research in football - week 14 - 2016

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 Economic impact study: neuromuscular training reduces the burden of injuries and costs compared to standard warm-up in youth soccer.
Reference: Br J Sports Med. 2016 Mar 31. pii: bjsports-2015-095666. doi: 10.1136/bjsports-2015-095666. [Epub ahead of print]
Authors: Marshall DA, Lopatina E, Lacny S, Emery CA
Summary: There is randomised controlled trial (RCT) evidence that neuromuscular training (NMT) programmes can reduce the risk of injury in youth soccer. We evaluated the cost-effectiveness of such an NMT prevention strategy compared to a standard of practice warm-up. A cost-effectiveness analysis was conducted alongside a cluster RCT. Injury incidence rates were adjusted for cluster using Poisson regression analyses. Direct healthcare costs and injury incidence proportions were adjusted for cluster using bootstrapping. The joint uncertainty surrounding the cost and injury rate and proportion differences was estimated using bootstrapping with 10 000 replicates. Along with a 38% reduction in injury risk (rate difference=-1.27/1000 player hours (95% CI -0.33 to -2.2)), healthcare costs were reduced by 43% in the NMT group (-$689/1000 player hours (95% CI -$1741 to $234)) compared with the control group. 90% of the bootstrapped ratios were in the south-west quadrant of the cost-effectiveness plane, showing that the NMT programme was dominant (more effective and less costly) over standard warm-up. Projecting results onto 58 100 Alberta youth soccer players, an estimated 4965 injuries and over $2.7 million in healthcare costs would be conservatively avoided in one season with implementation of a neuromuscular training prevention programme. Implementation of an NMT prevention programme in youth soccer is effective in reducing the burden of injury and leads to considerable reduction in costs. These findings inform practice and policy supporting the implementation of NMT prevention strategies in youth soccer nationally and internationally.

#2 Isokinetic imbalance of adductor-abductor hip muscles in professional soccer players with chronic adductor-related groin pain.
Reference: Eur J Sport Sci. 2016 Mar 28:1-6. [Epub ahead of print]
Authors: Belhaj K, Meftah S, Mahir L, Lmidmani F, Elfatimi A
Summary: This study aims to compare the isokinetic profile of hip abductor and adductor muscle groups between soccer players suffering from chronic adductor-related groin pain (ARGP), soccer players without ARGP and healthy volunteers from general population. Study included 36 male professional soccer players, who were randomly selected and followed-up over two years. Of the 21 soccer players eligible to participate in the study, 9 players went on to develop chronic ARGP and 12 players did not. Ten healthy male volunteers were randomly selected from the general population as a control group. Comparison between the abductor and adductor muscle peak torques for players with and without chronic ARGP found a statistically significant difference on the dominant and non-dominant sides (p < .005), with the abductor muscle significantly stronger than the adductor muscle. In the group of healthy volunteers, the adductor muscle groups were significantly stronger than the abductor muscle groups on both dominant and non-dominant sides (p < .05). For the group of players who had developed chronic ARGP, abductor-adductor torque ratios were significantly higher on the affected side (p = .008). The adductor muscle strength was also significantly decreased on the affected side. This imbalance appears to be a risk factor for adductor-related groin injury. Therefore, restoring the correct relationship between these two agonist and antagonist hip muscles may be an important preventative measure that should be a primary concern of training and rehabilitation programmes.

#3 ACL injuries in men's professional football: a 15-year prospective study on time trends and return-to-play rates reveals only 65% of players still play at the top level 3 years after ACL rupture
Reference: Br J Sports Med. 2016 Mar 31. pii: bjsports-2015-095952. doi: 10.1136/bjsports-2015-095952. [Epub ahead of print]
Authors: Waldén M, Hägglund M, Magnusson H, Ekstrand J
Summary: Studies investigating the development of ACL injuries over time in football are scarce and more data on what happens before and after return to play (RTP) are needed. The aim of the study was to investigate (1) time trends in ACL injury rates, (2) complication rates before return to match play following ACL reconstruction, and (3) the influence of ACL injury on the subsequent playing career in male professional football players. 78 clubs were followed between 2001 and 2015. Time trend in ACL injury rate was analysed using linear regression. ACL-injured players were monitored until RTP and tracked for 3 years after RTP. We recorded 157 ACL injuries, 140 total and 17 partial ruptures, with a non-significant average annual increase in the ACL injury rate by 6% (R2=0.13, b=0.059, 95% CI -0.04 to 0.15, p=0.20). The match ACL injury rate was 20-fold higher than the training injury rate (0.340 vs 0.017 per 1000 h). 138 players (98.6%) with a total rupture underwent ACL reconstruction; all 134 players with RTP data (4 players still under rehabilitation) were able to return to training, but 9 of them (6.7%) suffered complications before their first match appearance (5 reruptures and 4 other knee surgeries). The median layoff after ACL reconstruction was 6.6 months to training and 7.4 months to match play. We report 3-year follow-up data for 106 players in total; 91 players (85.8%) were still playing football and 60 of 93 players (65%) with ACL reconstruction for a total rupture played at the same level. The ACL injury rate has not declined during the 2000s and the rerupture rate before return to match play was 4%. The RTP rate within a year after ACL reconstruction was very high, but only two-thirds competed at the highest level 3 years later.

#4 Role of illness in male professional football: not a major contributor to time loss.
Reference: Br J Sports Med. 2016 Mar 31. pii: bjsports-2015-095921. doi: 10.1136/bjsports-2015-095921. [Epub ahead of print]
Authors: Bjørneboe J, Kristenson K, Waldén M, Bengtsson H, Ekstrand J, Hägglund M, Rønsen O, Andersen TE
Summary: There are limited data on the nature, type and incidence of illness in football. Previous studies indicate that gastrointestinal and respiratory tract illnesses are most common. The aim of the study was to describe the incidence and burden of illness in male professional football. Over the 4-year study period, 2011-2014, 73 professional football teams in Europe participated, with a total of 1 261 367 player-days recorded. All time-loss illnesses were recorded by the medical staff of each club. A recordable illness episode was any physical or psychological symptom (not related to injury) that resulted in the player being unable to participate fully in training or match play. A total of 1914 illness episodes were recorded. The illness incidence was 1.5 per 1000 player-days, meaning that, on average, a player experienced an illness episode every second season, with a median of 3 days absence per illness episode. Severe illness (absence >4 weeks) constituted 2% of all illnesses. Respiratory tract illness was the most common (58%), followed by gastrointestinal illness (38%). Respiratory tract illness, gastrointestinal illness and cardiovascular illness caused the highest illness burden. The illness incidence among male professional football players is low compared with the injury incidence. We found that the highest illness burden was caused by illness to the respiratory tract, gastrointestinal tract and cardiovascular system.

#5 The metabolic power and energetic demands of elite Gaelic football match play
Reference: J Sports Med Phys Fitness. 2016 Mar 31. [Epub ahead of print]
Authors: Malone S, Solan B, Collins K, Doran D.
Summary: Metabolic power has not yet been investigated within elite Gaelic football. The aim of the current investigation was to compare the metabolic power demands between positional groups and examine the temporal profile of elite Gaelic football match play. Global positional satellite system (GPS) data were collected from 50 elite Gaelic football players from 4 inter-county teams during 35 elite competitive matches over a three season period. A total of 351 complete match samples were obtained for final analysis. Players were categorised based on positional groups; full-back, half-back, midfield, half- forward and full-forward. Instantaneous raw velocity data was obtained from the GPS and exported to a customised spreadsheet which provided estimations of both speed based, derived metabolic power and energy expenditure variables (total distance, high speed distance, average metabolic power, high power distance and total energy expenditure). Match mean distance was 9222 ± 1588 m, reflective of an average metabolic power of 9.5-12.5 W∙kg-1, with an average energy expenditure of 58-70 Kj∙kg-1 depending on position. There were significant differences between positional groups for both speed-based and metabolic power indices. Midfielders covered more total and high-speed distance, as well as greater average and overall energy expenditure compared to other positions (p < 0.001). A reduction in total, high-speed, and high-power distance, as well as average metabolic power throughout the match (p < 0.001) was observed. Positional differences exist for both metabolic power and traditional running based variables. The middle three positions (midfield, half-back and half-forward) possess greater activity profiles when compared to other positional groups. The reduction in metabolic power and traditional running based variables are comparable across match play. The current study demonstrates that metabolic power may contribute to our understanding of Gaelic football match-play.

#6 The effect of an acute sleep hygiene strategy following a late-night soccer match on recovery of players
Reference: Chronobiol Int. 2016 Mar 31:1-16. [Epub ahead of print]
Authors: Fullagar H, Skorski S, Duffield R, Meyer T
Summary: Elite soccer players are at risk of reduced recovery following periods of sleep disruption, particularly following late-night matches. It remains unknown whether improving sleep quality or quantity in such scenarios can improve post-match recovery. Therefore, the aim of this study was to investigate the effect of an acute sleep hygiene strategy (SHS) on physical and perceptual recovery of players following a late-night soccer match. In a randomised cross-over design, two highly-trained amateur teams (20 players) played two late-night (20:45) friendly matches against each other seven days apart. Players completed an SHS after the match or proceeded with their normal post-game routine (NSHS). Over the ensuing 48 h, objective sleep parameters (sleep duration, onset latency, efficiency, wake episodes), countermovement jump (CMJ; height, force production), YoYo Intermittent Recovery test (YYIR2; distance, maximum heart rate, lactate), venous blood (creatine kinase, urea and c-reactive protein) and perceived recovery and stress markers were collected. Sleep duration was significantly greater in SHS compared to NSHS on match night (P = 0.002, d = 1.50), with NSHS significantly less than baseline (P < 0.001, d = 1.95). Significant greater wake episodes occurred on match night for SHS (P = 0.04, d = 1.01), without significant differences between- or within-conditions for sleep onset latency (P = 0.12), efficiency (P = 0.39) or wake episode duration (P = 0.07). No significant differences were observed between conditions for any physical performance or venous blood marker (all P > 0.05); although maximum heart rate during the YYIR2 was significantly higher in NSHS than SHS at 36 h post-match (P = 0.01; d = 0.81). There were no significant differences between conditions for perceptual "overall recovery" (P = 0.47) or "overall stress" (P = 0.17). Overall, an acute SHS improved sleep quantity following a late-night soccer match; albeit without any improvement in physical performance, perceptual recovery or blood-borne markers of muscle damage and inflammation.

#6 US Youth Soccer Concussion Policy: Heading in the Right Direction
Reference: JAMA Pediatr. 2016 Mar 28. doi: 10.1001/jamapediatrics.2016.0338. [Epub ahead of print]
Authors: Yang YT, Baugh CM

#7 Arthroscopic debridement of the ankle for mild to moderate osteoarthritis: a midterm follow-up study in former professional soccer players
Reference: J Orthop Surg Res. 2016 Mar 30;11(1):37. doi: 10.1186/s13018-016-0368-z.
Authors: Osti L, Del Buono A, Maffulli N
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Summary: The aim of this study is to report the clinical and functional outcomes following arthroscopic management of anterior impingement, grade III-IV cartilage lesions, and mild to moderate osteoarthritis of the ankle in former soccer players. The study included 15 former male professional soccer players with mild to moderate degenerative changes of the ankle who had undergone arthroscopic debridement and management of secondary injuries of the ankle. Preoperatively and at the last follow-up, at an average of 7.4 years, the American Orthopaedic Foot and Ankle Society (AOFAS) and the Kaikkonen scales and visual analogue scale (VAS) assessment were administered to all patients. Ankle osteoarthritis was assessed from weightbearing anteroposterior and lateral radiographs of both ankles. At the last follow-up, the average AOFAS score had increased significantly from 48 (range, 29-69) to 86 (range, 63-94) (P < 0.0001), with good to excellent scores in 11 patients (74 %). The average Kaikkonen preoperative score of 43 (range, 28-70) had significantly improved to 85 (range, 61-95) (P < 0.0001), with good excellent scores in 11 patients (74 %). VAS values were also improved at the last follow-up. At the last appointment, only one (7 %) patient had abandoned altogether any sport, as he did not feel safe with his ankle and he felt too old to continue. Anterior ankle arthroscopy for management of mild to moderate ankle arthritis is safe, effective, and low cost and allows former athletes to safely return to ordinary daily activities and recreational sport activities.

#8 Morning melatonin ingestion and diurnal variation of short-term maximal performances in soccer players
Reference: Acta Physiol Hung. 2016 Mar;103(1):94-104. doi: 10.1556/036.103.2016.1.9.
Authors: Ghattassi K, Hammouda O, Graja A, Boudhina N, Chtourou H, Hadhri S, Driss T, Souissi N
Summary: Aim Very few studies have investigated the temporal specificity of melatonin (MEL) ingestion upon short-term maximal athletic performances. The aim of the present study was to explore the effect of morning MEL ingestion on cognitive and physical performances measured in the afternoon. Methods Twelve soccer players from a Tunisian squad (17.9 ± 1.3 years, 1.74 ± 0.06 m and 62.0 ± 8.8 kg) participated in the present study. They performed two testing sessions at 08:00 h, 12:00 h and 16:00 h after either MEL (5mg) or placebo (PLA) ingestion, in a randomized order. During each period, the participants performed the following cognitive and physical tests: reaction time and vigilance tests, medicine-ball throw (MBT), five jumps, handgrip strength (HG), and agility tests. Results cognitive and physical performances were significantly higher at 16:00 h compared to 08:00 h during the two conditions (p < 0.05). Moreover, performances of MBT and HG were lower in the morning with MEL in comparison to PLA (p < 0.05). However, MEL ingestion did not affect physical and cognitive performances measured at 12:00 h and 16:00 h. Conclusion morning MEL ingestion has no unfavourable effect on afternoon physical and cognitive performances in soccer players.

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