Latest research in football - week 45 - 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 Changes in muscle damage, inflammation, and fatigue-related parameters in young elite soccer players after a match
Reference: J Sports Med Phys Fitness. 2016 Oct;56(10):1198-1205. Epub 2015 Nov 11.
Authors: Romagnoli M, Sanchis-Gomar F, Alis R, Risso-Ballester J, Bosio A, Graziani RL, Rampinini E
Summary: Professional soccer players are subjected to substantial physical loads during competitive seasons. We aimed to explore the changes induced by a soccer match on muscle damage and inflammation biomarkers, and their relationship with fatigue parameters. Twenty young male professional in-field soccer players from an Italian Serie A team (age 17-20 years, weight 73.0±7.0 kg, height 1.81±0.05m) played a 90-minute soccer match. Players' distances and velocities were recorded during the match. Before the match and 30 minutes, 24 and 48 hours after the match, blood samples were drawn and a full blood cell count was determined, along with serum creatine kinase (CK), interleukin 6 (hsIL-6), cortisol and testosterone. At the same time intervals, counter-movement jump (CMJ) performance was recorded. The players covered fewer meters at low velocities in the second period while the meters covered at higher intensity remained unchanged. CMJ height was lower at all postgame time-points compared to the pregame measurement. Immediately after the match, CK, hs-IL6 and neutrophil counts were elevated. 24 and 48 hours after the match, CK and neutrophil counts remained significantly elevated. The distance covered during the game was found to be correlated with the values for postmatch hsIL-6 (ρ=0.521, P=0.027), post 24-hour cortisol (r=0.502, P=0.034) and the increase in cortisol at 48 hours with respect to prematch values (r=0.515, P=0.029). A soccer match provokes a transient systemic imbalance that results in muscle damage and inflammatory and performance-related parameter changes. HsIL-6 and cortisol could be used to monitor recovery processes and as fatigue markers, even for short time periods.

#2 New score based on early repolarization in precordial leads for detection of left ventricular hypertrophy in young soccer players
Reference: J Sports Med Phys Fitness. 2016 Oct;56(10):1258-1259. Epub 2015 Nov 10.
Authors: Fabregat-Andrés Ó, Muñoz-Macho A, Pina-Buded S, Cal Vente-Nomdedeu A, Soriano-Navarro CJ, Usó H

#3 The effects of anthropometry and leg muscle power on drive and transition phase of acceleration: a longitudinal study on young soccer players
Reference: J Sports Med Phys Fitness. 2016 Oct;56(10):1156-1162. Epub 2015 Sep 23.
Authors: Nikolaidis PT, Ingebrigtsen J, Jeffreys I
Summary: The aim of this study was to examine the effect of anthropometry and leg muscle power on accelerative ability and its phases (drive and transition). Thirty-six soccer players (age 12.4±1.2 years, body mass 49.9±8.9 kg and height 154.2±10.3 cm) were tested twice, in the beginning and in the end of competitive season, for anthropometric characteristics, countermovement jump and 20-meter acceleration (split 0-10 meters and 10-20 meters, indices of drive and transition, respectively). The soccer players were grouped according to seasonal changes in 20-meter acceleration (Δacc) in responders (Δacc≤-0.10 s), control (-0.05≤Δacc≤0.08 s) and non-responders (Δacc≥0.10 s). Compared with the non-responders at baseline, the responders were younger (-2.0 years [-2.8;-1.1]), shorter (-10.1 cm [-19.4;-0.7]), with higher body fat percentage (7.7% [2.7%;12.6%]) and fat mass (4.1 kg [0.7;7.4]), and lower performance in the countermovement jump (-8.9 cm [-13.9;-4.0]) and 20 m acceleration (0.63 s [0.39;0.87]); during the season they had smaller body mass gain (-2.8 kg [-5.4;-0.1]), decreased Body Mass Index (BMI, -1.0 kg/m2 [-1.9;0]) and greater improvement in the 20-meter acceleration (-0.33 s [-0.38;-0.28]). The effect size for these between-group differences was large (η2≥0.18). The Δacc and Δ10-20 were moderately correlated with body mass difference (r=0.48 and r=0.53, P<0.01, respectively) and ΔBMI (r=0.50 and r=0.51, P<0.01, respectively), whereas the Δ0-10 was correlated with ΔBMI (r=0.34, P<0.05) and ΔCMJ (r=-0.34, P<0.05). The findings indicated that the changes in body mass had the largest effect on changes in accelerative ability and on both two phases (drive and transition). On the contrary, changes in leg muscle power had impact only on the drive phase of the acceleration.

#4 Physical and anthropometric changes during pre- and in-season in professional soccer players
Reference: J Sports Med Phys Fitness. 2016 Oct;56(10):1163-1170. Epub 2015 Sep 10.
Authors: Fessi MS, Zarrouk N, Filetti C, Rebai H, Elloumi M, Moalla W.
Summary: The purpose of this study was to examine the changes in anthropometric and physical fitness characteristics in professional soccer players at the beginning of the season, after preseason camp and during in-season. Seventeen players were evaluated on three different periods (June: T0, August: T1 and December: T2). Each evaluation consisted of anthropometric measurements (body mass, height, and body fat) and physical fitness tests (counter movement jump [CMJ], counter movement jump with arm (CMJA), 10-m sprint, 30-m sprint and maximal aerobic speed [MAS]). Comparatively with T0, all physical performances achieved in T1 were significantly improved (MAS: P<0.01, 10-m sprint: P<0.05, 30-m sprint: P<0.05, CMJ: P<0.01, and CMJA: P<0.05). The decrease in training load during in-season is associated by significant decrement in MAS (P<0.05) and preserved performances in 10 (P=0.85) and 30-m sprint (P=0.99), CMJ (P=0.34) and CMJA (P=0.87) completed in T2 comparatively with T1. Physical fitness performances achieved in T2 remain higher than that obtained in T0 (MAS: P<0.01, 10-m sprint: P<0.01, 30-m sprint: P<0.05 and CMJ: P<0.05) and remain similar for CMJA (P=0.13). No significant changes were observed in anthropometric measurements throughout the study. The main finding of this study was that a greater training load accomplished during preseason could lead to an improvement in the physical fitness during in-season in professional soccer players. We suggest that this higher training load meets the needed required for the professional soccer although the training loads are declined during in-season.

#5 Relationship Between Pre-Season Training Load and In-Season Availability in Elite Australian Football Players
Reference: Int J Sports Physiol Perform. 2016 Nov 11:1-21. [Epub ahead of print]
Authors: Murray NB, Gabbett TJ, Townshend AD
Summary: Investigate the relationship between the proportion of pre-season training sessions completed, and load and injury during the ensuing Australian Football League season. Forty-six elite male Australian football players from one club participated in this study. Players were divided into three equal groups based on the amount of pre-season training completed (high, HTL, >85% sessions completed; medium, MTL, 50-85% sessions completed, and low, LTL, <50% sessions completed). Global Positioning System (GPS) technology was used to record training and game loads, with all injuries recorded and classified by club medical staff. Differences between groups were analysed using a two-way (group x training/competition phase) repeated measures ANOVA, along with magnitude-based inferences. Injury incidence was expressed as injuries per 1,000 hours. The HTL and MTL group completed a greater proportion of in-season training sessions (81.1% and 74.2%) and matches (76.7% and 76.1%) than the LTL (56.9% and 52.7%) group. Total distance and Player load were significantly greater during the first half of the in-season period for the HTL (p=0.03, ES=0.88) and MTL (p=0.02, ES=0.93) groups than the LTL group. The relative risk of injury for the LTL group (26.8/1,000 hours) was 1.9 times greater than the HTL group (14.2/1,000 hours) (χ2=3.48, df=2, p=0.17). Completing a greater proportion of pre-season training resulted in higher training loads and greater participation in training and competition during the competitive phase of the season.

#6 The Prevalence of Selected Intrinsic Risk Factors for Ankle Sprain Among Elite Football and Basketball Players
Reference: Asian J Sports Med. 2016 May 23;7(3):e35287. eCollection 2016.
Authors: Halabchi F, Angoorani H, Mirshahi M, Pourgharib Shahi MH, Mansournia MA
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Summary: Lateral ankle sprains (LAS) are among the most common sports- related injuries and the reinjury rate is very high. This study aimed to evaluate the prevalence of some intrinsic risk factors among professional football and basketball players with or without history of acute or recurrent ankle sprain.One hundred and six professional football and basketball players who were referred for pre-participation examinations were recruited in this study. Prepared checklist was completed for each participant. Athletes were asked for any history of previous ankle sprain and the severity (based of self-description of signs and symptoms by the athlete), level and number of injuries in the last two years. All players were assessed for measures of foot posture index- 6, foot length and width, Beighton generalized joint laxity score, anterior drawer and talar tilt tests, star excursion and single leg balance tests and goniometric assessment of ankle plantarflexion, ankle dorsiflexion and first metatarsophalangeal dorsiflexion. Forty eight basketball players (45.3%) and 58 football players (54.7%) with mean (SD) age of 19.8 (4.5) years participated. About 58.5% and 14.2% of athletes had a history of ankle sprain and recurrent sprain in at least one extremity, respectively. Sprains were more prevalent in basketball players and in dominant leg. There was no significant difference in assessed risk factors between athletes with and without history of ankle sprain, except for positive single leg balance test which was more prevalent in athletes with history of ankle sprain and also for positive talar tilt test and decreased ankle plantarflexion range of motion in acute and recurrent injury of left ankle. Some intrinsic risk factors including lateral ankle ligaments laxity, balance and ankle plantarflexion seem to be related to acute or recurrent LAS in athletes. Further research is needed to reveal the role of different arthrokinematics following lateral ankle sprain.

#7 Persistent effects of playing football and associated (subconcussive) head trauma on brain structure and function: a systematic review of the literature
Reference: Br J Sports Med. 2016 Nov 4. pii: bjsports-2016-096593. doi: 10.1136/bjsports-2016-096593. [Epub ahead of print]
Authors: Tarnutzer AA, Straumann D, Brugger P, Feddermann-Demont N
Summary: There is ongoing controversy about persistent neurological deficits in active and former football (soccer) players. We reviewed the literature for associations between football activities (including heading/head injuries) and decline in brain structure/function. MEDLINE, Embase, PsycINFO, CINAHL, Cochrane-CRCT, SportDiscus, Cochrane-DSR=4 (accessed 2 August 2016) database were searched. Original studies reporting on football-related persistent effects on brain structure/function. Results from neurocognitive testing, neuroimaging and EEG were compared with controls and/or correlated with heading frequency and/or head injuries. Methodological quality was rated for risk-of-bias, including appropriateness of controls, correction for multiple statistical testing and assessment of heading frequency and head injuries. 30 studies with 1691 players were included. Those 57% (8/14) of case-control studies reporting persistent neurocognitive impairment had higher odds for inappropriate control of type 1 errors (OR=17.35 (95% CI (10.61 to 28.36)) and for inappropriate selection of controls (OR=1.72 (1.22 to 2.43)) than studies observing no impairment. Studies reporting a correlation between heading frequency and neurocognitive deficits (6/17) had lower quality of heading assessment (OR=14.20 (9.01 to 22.39)) than studies reporting no such correlation. In 7 of 13 studies (54%), the number of head injuries correlated with the degree of neurocognitive impairment. Abnormalities on neuroimaging (6/8 studies) were associated with subclinical neurocognitive deficits in 3 of 4 studies. Various methodological shortcomings limit the evidence for persistent effects of football play on brain structure/function. Sources of bias include low-quality assessment of heading frequency, inappropriate control for type 1 errors and inappropriate selection of controls. Combining neuroimaging techniques with neurocognitive testing in prospective studies seems most promising to further clarify on the impact of football on the brain.

#8 Football and dementia: A qualitative investigation of a community based sports group for men with early onset dementia
Reference: Dementia (London). 2016 Nov;15(6):1358-1376. Epub 2014 Nov 26.
Authors: Carone L, Tischler V, Dening T
Summary: This study investigates the impact of a weekly group providing sport and physical activities for men with early onset dementia established by Notts County Football in the Community (NCFC). There were three aims: to investigate the effect of early onset dementia on individuals with the condition and their carers; to examine the perceptions of current levels of service provision for people with early onset dementia; and to analyse the impact of the group. Men with dementia (n = 5) attending the sessions, their carers (n = 5), NCFC coaching staff (n = 5) and people organizing/facilitating the sessions (n = 5) were interviewed. Semi-structured interviews explored the participants' experiences of dementia, their opinions on current service provisions and on the sessions. Data were analysed using thematic analysis. Four main themes were found: loss related to the condition of dementia and its impact on relationships ('Loss'); lack of age-appropriate services for people with early onset dementia ('Lack of Resources'); enjoyment and positive anticipation related to the group for all involved ('Enjoyment and Anticipation'); and 'the Notts County Effect' which attributed the success of the sessions to the strong brand of the football club, and to personalized service in a "dementia-free" environment. The NCFC sessions provided a safe low-cost intervention with positive effects upon quality of life for both people with early onset dementia, their carers and the staff involved. This suggests that the service may be valuable to a wider range of people living in different areas.

#9 Index of fatigue quadriceps in soccer athletes after anterior cruciate ligament reconstruction
Reference: Rev Bras Ortop. 2016 Aug 17;51(5):535-540.
Authors: Cavalcante ML, Teixeira PR, Sousa TC, Lima PO, Oliveira RR
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Summary: The present study aimed to evaluate the muscle fatigue of the quadriceps muscle in high-performance soccer players undergoing (anterior cruciate ligament) ACL reconstruction. We evaluated 17 high-performance soccer players from three professional soccer teams of a state in Brazil from August 2011 to July 2012. All subjects were evaluated between 5.5 and 7 months after ACL reconstruction with a Biodex® isokinetic dynamometer (System 4 Pro) with test protocol CON/CON at 60°/s and 300°/s with 5 and 15 repetitions, respectively. In the calculation of local muscle fatigue, the fatigue index was used, which is calculated by dividing the labor done in the first one-third of the repetitions by that done at the final one-third of the repetitions, and multiplying by 100 to express a unit in percentage (i.e., as a discrete quantitative variable). All subjects were male, with a mean age of 21.3 ± 4.4 years and mean BMI 23.4 ± 1.53 cm; left dominance was observed in 47% (n = 8) of athletes, and right dominance, in 53% (n = 9) of athletes; and the limb involved in the lesion was the dominant in 29% (n = 5) and the non-dominant in 71% (n = 12). Fatigue rates were 19.6% in the involved limb and 29.0% in the non-involved limb. The results allow us to conclude that there was no significant difference between the limbs involved and not in ACL injuries regarding local muscle fatigue. No association was observed between the dominant side and the limb involved in the ACL injury.

#10 Physical and balance performance following exercise induced muscle damage in male soccer players
Reference: J Phys Ther Sci. 2016 Oct;28(10):2942-2949. Epub 2016 Oct 28.
Authors: Khan MA, Moiz JA, Raza S, Verma S, Shareef MY, Anwer S, Alghadir A
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Summary: The present study aimed to determine the changes in physical and balance performance following exercise-induced muscle damage using a sport-specific protocol. Fifteen collegiate soccer players were asked to perform a sport-specific sprint protocol to induce muscle damage. The markers of muscle damage (soreness, range of motion, limb girth, muscle strength, creatine kinase and lactate dehydrogenase), physical performance (speed, agility and power) and balance (static and dynamic balance) were assessed at baseline and 24, 48 and 72 hours following the sprint protocol. All variables, including the markers of muscle damage, physical performance and balance showed a significant difference when assessed at the 4 time points. [Conclusion] The study demonstrated that both the physical and balance performance were affected following repeated sprint protocol in soccer players. It is recommended the balance performance of an athlete be continually assessed following exercise-induced muscle damage so as to determine the appropriate return to sport decision thereby, minimizing the risk of further injury.

#11 No Association Between Return to Play After Injury and Increased Rate of Anterior Cruciate Ligament Injury in Men's Professional Soccer
Reference: Orthop J Sports Med. 2016 Oct 27;4(10):2325967116669708. eCollection 2016.
Authors: Lundblad M, Waldén M, Hägglund M, Ekstrand J, Thomeé C, Karlsson J
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Summary: Studies have shown that previous injury, not necessarily anatomically related, is an important injury risk factor. However, it is not known whether a player runs an increased risk of anterior cruciate ligament (ACL) injury after returning to play from other injury types. The purpose was to analyze whether professional soccer players are more susceptible to ACL injury after returning to play from any previous injury. A total of 101 elite male soccer players suffering a first-time complete ACL injury between 2001 and 2014 were included and matched according to team, age, and playing position with control players who did not have a current injury (1:1 match). For each injured player, the 90-day period prior to the ACL injury was analyzed for injuries and compared with that of control players by using odds ratios (ORs) and 95% CIs. The odds of a player with an ACL injury sustaining a previous injury in the 90-day period did not differ significantly from that of controls (OR, 1.20; 95% CI, 0.66-2.17; P = .65). Testing the frequency of absence periods due to injury between the groups revealed that the odds of a player with an ACL injury having a previous period of absence due to injury did not differ compared with controls (OR, 1.14; 95% CI, 0.64-2.01; P = .77). Players with ACL injury did not have a greater occurrence of absence due to injury in the 3 months preceding their ACL injury compared with matched controls. This indicates that previous injury of any type does not increase the risk of suffering an ACL injury.

#12 Very-Heavy Sled Training for Improving Horizontal Force Output in Soccer Players
Reference: Int J Sports Physiol Perform. 2016 Nov 11:1-13. [Epub ahead of print]
Authors: Morin JB, Petrakos G, Jimenez-Reyes P, Brown SR, Samozino P, Cross MR
Summary: Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground reaction force and mechanical effectiveness of force application are paramount. We tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal force production, via an increased effectiveness of application. Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-week protocol (16 sessions of 10x20-m sprints). 16 male amateur soccer players were assigned to either a very-heavy sled (80% body-mass sled load) or a control group (unresisted sprints). The main outcome of this pilot study is that very-heavy sled resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal force production compared to standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-group difference) and mechanical effectiveness (i.e. more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-group difference). In addition, 5-m and 20-m sprint performance improvement were moderate and small for the very-heavy sled group, and small and trivial for the control group, respectively. This brief report highlights the usefulness of very-heavy sled (80% body-mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal force capabilities in soccer players and other team sport athletes. This study may encourage further research to confirm the usefulness of very-heavy sled in this context.

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