Latest research in football - week 8 - 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 Quantification of Seasonal Long Physical Load in Soccer Players With Different Starting Status From the English Premier League: Implications for Maintaining Squad Physical Fitness
Reference: Int J Sports Physiol Perform. 2016 Feb 26. [Epub ahead of print]
Authors: Anderson L, Orme P, Di Michele R, Close GL, Milsom J, Morgans R, Drust B, Morton JP
Summary: The purpose of the study was to quantify the accumulative training and match load during an annual season in English Premier League soccer players classified as starters (n=8, started ≥60% of games), fringe players (n=7, started 30-60% of games) and non-starters (n=4, started <30%% of games). Players were monitored during all training sessions and games completed in the 2013-2014 season with load quantified using GPS and Prozone technology, respectively. When including both training and matches, total duration of activity (10678 ± 916, 9955 ± 947, 10136 ± 847 min; P=0.50) and distance covered (816.2 ± 92.5, 733.8 ± 99.4, 691.2 ± 71.5 km; P=0.16) was not different between starters, fringe and non-starters, respectively. However, starters completed more (all P<0.01) distance running at 14.4-19.8 km/h (91.8 ± 16.3 v 58.0 ± 3.9 km; ES=2.5), high speed running at 19.9-25.1 km/h (35.0 ± 8.2 v 18.6 ± 4.3 km; ES=2.3) and sprinting at >25.2 km/h (11.2 ± 4.2, v 2.9 ± 1.2 km; ES=2.3) than non-starters. Additionally, starters also completed more sprinting (P<0.01. ES=2.0) than fringe players who accumulated 4.5 ± 1.8 km. Such differences in total high-intensity physical work done were reflective of differences in actual game time between playing groups as opposed to differences in high-intensity loading patterns during training sessions. Unlike total seasonal volume of training (i.e. total distance and duration), seasonal high-intensity loading patterns are dependent on players' match starting status thereby having potential implications for training programme design.

#2 Susceptibility to Hamstring Injuries in Soccer: A Prospective Study Using Muscle Functional Magnetic Resonance Imaging
Reference: Am J Sports Med. 2016 Feb 24. pii: 0363546515626538. [Epub ahead of print]
Authors: Schuermans J, Van Tiggelen D, Danneels L, Witvrouw E
Summary: Running-related hamstring strain injuries remain a delicate issue in several sports such as soccer. Their unremittingly high incidence and recurrence rates indicate that the underlying risk has not yet been fully identified. Among other factors, the importance of neuromuscular coordination and the quality of interplay between the different hamstring muscle bellies is thought to be a key determinant within the intrinsic injury risk. Muscle functional magnetic resonance imaging (mfMRI) is one of the tools that has been proven to be valid for evaluating intermuscular coordination. The purpose of the study was to investigate the risk of sustaining an index or recurring soccer-related hamstring injury by exploring metabolic muscle characteristics using mfMRI. A total of 27 healthy male soccer players and 27 soccer players with a history of hamstring injuries underwent standardized mfMRI. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise, and a postexercise scan. The exercise-related T2 change, or the signal intensity shift between both scans, was used to detect differences in metabolic characteristics between (1) the different hamstring muscle bellies and (2) the prospective cohorts based on the (re)occurrence of hamstring injuries during a follow-up period of 18 months. The risk of sustaining a first hamstring injury was associated with alterations in the intermuscular hierarchy in terms of the magnitude of the metabolic response after a heavy eccentric effort, with the dominant role of the semitendinosus set aside for a higher contribution of the biceps femoris (P = .017). Receiver operating characteristic (ROC) curve analysis demonstrated that this variable was significantly able to predict the occurrence of index injuries with a sensitivity of 100% and a specificity of 70% when the metabolic activity of the biceps femoris exceeded 10%. The risk of sustaining a reinjury was associated with a substantial deficit in hamstring strength endurance (P = .031). Soccer players who sustained a reinjury were only able to perform prone leg curls for a mean duration of 146.50 ± 76.16 seconds, whereas those with an injury history but no recurrence during follow-up were able to continue for a mean of 237.45 ± 110.76 seconds (95% CI, 11.9-230.5 seconds; P = .031). This was the first study to assess the causal relation between the intramuscular recruitment pattern and the risk of sustaining an index or secondary hamstring strain. Changes in intermuscular interplay seem to significantly increase the risk of sustaining index hamstring injuries in male amateur soccer players. Inadequate eccentric muscle endurance could be associated with an increased risk of sustaining a recurring hamstring injury.

#3 Scoring mode and age-related effects on youth soccer teams' defensive performance during small-sided games
Reference: J Sports Sci. 2016 Feb 24:1-8. [Epub ahead of print]
Authors: Almeida CH, Duarte R, Volossovitch A, Ferreira AP
Summary: This study aimed to examine the scoring mode (line goal, double goal or central goal) and age-related effects on the defensive performance of youth soccer players during 4v4 small-sided games (SSGs). Altogether, 16 male players from 2 age groups (U13, n = 8, mean age: 12.61 ± 0.65 years; U15, n = 8, 14.86 ± 0.47 years) were selected as participants. In six independent sessions, participants performed the three SSGs each during 10-min periods. Teams' defensive performance was analysed at every instant ball possession was regained through the variables: ball-recovery type, ball-recovery sector, configuration of play and defence state. Multinomial logistic regression analysis used in this study revealed the following significant main effects of scoring mode and age: (1) line goal (vs. central goal) increased the odds of regaining possession through tackle and in the defensive midfield sector, and decreased the odds of successful interceptions; (2) double goal (vs. central goal) decreased the odds of regaining possession through turnover won and with elongated playing shapes; (3) the probability of regaining possession through interception significantly decreased with age. Moreover, as youth players move forward in age groups, teams tend to structurally evolve from elongated playing shapes to flattened shapes and, at a behavioural level, from defending in depth to more risky flattened configurations. Overall, by manipulating the scoring mode in SSGs, coaches can promote functional and coadaptive behaviours between teams not only in terms of configurations of play, but also on the pitch locations that teams explore to regain possession.

#4 How Valid is the Performance Diagnostic in Soccer?
Reference: Sportverletz Sportschaden. 2016 Feb 24. [Epub ahead of print] [Article in German]
Authors: Schwesig R, Miserius M, Hermassi S, Delank KS, Noack F, Fieseler G
Summary: Background: Assessments of physical and physiological performance tests in soccer sports are still unspecific yet. There is also a lack of scientific validation using those as a "golden standard". Concerning match performance a large deficit also exist in sports and medical science. Objective: The aim and purpose of this multicentric and prospective diagnostic study was to evaluate the validity of current established and recommended diagnostic tests for endurance and match performance (golden standard: real time of playing) in soccer. Materials and methods: In a prospective study protocol two German soccer teams from the fourth (n = 22) and third (n = 24) national league first underwent different tests of performance and diagnostics ahead of the competition season (tapping, drop jump, counter movement jump, speed dribbling, treadmill running test). Afterwards, match performance of each athlete was assessed by real time of playing (as a surrogate parameter) during the half season (14 and 25 matches). We finally compared test parameters with the match performance in a linear regression analysis. Results: Our analysis showed no statistical relevant relationship between test parameters and match performance (r2<  0.10). Only the assessment in maximum of relative oxygen uptake during the treadmill test for endurance was associated with a higher amount of variance (12 %). Conclusions: According to the study results there is no relevant and valid correlation between current established diagnostic tests in soccer sport and sport-specific performance. The time of real engagement during a match might be associated with a quality of performance for the single athlete. Therefore, the assessment of this match activity is the most important parameter for improving diagnostic tests in soccer. The existence of a "golden standard" is essential for validation of any tests and parameters and the development of new specific assessments. At the moment, physical performance tests have no scientific evidence in soccer sports.

#5 Single level anterior cervical discectomy and fusion for cervical disc herniation in a professional soccer player
Reference: J Sports Med Phys Fitness. 2016 Feb 19. [Epub ahead of print]
Authors: Casagrande J, Zoia C, Clerici G, Uccella L, Tabano A.
Summary: The purpose of the study was to report a safe and effective treatment option for cervical disc herniation in a professional soccer player. Radiculopathy caused by cervical disc herniation can influence the performance of a professional athlete and also reduce his/her quality of life. Only few cases of surgical treatment of this condition in professional athletes are reported in literature and no one about soccer players. We present a case of a professional soccer player that underwent surgery for cervical disc herniation. The patient underwent an anterior cervical discectomy and fusion with autologous bone and a plate. The patient was successfully operated; he returned to activity after 3 months and is still playing 5 years after surgery. Anterior cervical decompression and fusion is a safe treatment in professional soccer players and allow our patient to a very quickly return to play.

#6 The Effect of Recovery Duration on Vastus Lateralis Oxygenation, Heart Rate, Perceived Exertion and Time Motion Descriptors during Small Sided Football Games
Reference: PLoS One. 2016 Feb 26;11(2):e0150201. doi: 10.1371/journal.pone.0150201.
Authors: McLean S, Kerhervé H, Lovell GP, Gorman AD, Solomon C
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Summary: Small sided games (SSG) of football are an effective and efficient format to simultaneously train the physiological, technical, and tactical components of football. The duration of the recovery period between bouts of SSG will affect the physiological response to subsequent bouts. It was hypothesised that decreasing the duration of recovery periods separating serial SSG bouts would increase physiological, and perceptual responses, and decrease high speed running, and distance during SSG bouts. Twelve experienced footballers (mean ± SD; age 21 ± 3 yrs; VO2peak 64 ± 7 ml·min·kg-1; playing experience 15 ± 3 yrs) completed two SSG sessions. Each SSG consisted of 3 vs. 3 players and 6 bouts of 2 min duration, with bouts separated by either 30 s recovery (REC-30) or 120 s recovery (REC-120). Deoxygenated haemoglobin (HHb) in the vastus lateralis (VL) (using near infrared spectroscopy), heart rate (HR) and time motion descriptors (TMD) (speed and distance) were measured continuously during the SSG sessions and perceived exertion (RPE) was measured for each bout. During the recovery periods, in REC-30 compared to REC-120, there was a significant (p < 0.05) main effect of a higher HHb and HR. During the bouts, in REC-30 compared to REC-120, there were no significant differences in HHb, HR, RPE, or TMD, but within both REC-30 and REC-120 there were significant increases as a function of bout number in RPE. Although a four-fold increase in recovery period allowed a significant increase in the recovery of HHb and HR, this did not increase the physiological, and perceptual responses, or time motion descriptors during the bouts. These results could have been due to the regulation of effort (pacing), in these experienced players performing an exercise task to which they were well adapted.

#7 The medical care in the practice of football. its early process of institucionalization in Córdoba in the first decades of the 20th century
Reference: Rev Fac Cien Med Univ Nac Cordoba. 2015;72(3):180-9. [Article in Spanish]
Author: Reyna FD.
Summary: The article examines the initial advances in the process of medicalización of the practice of football in the sports associations of Córdoba in the first decades of the 20th century. The objective is to investigate how, in the interaction between the players and these entities, there was becoming institutionalized the access of the sportsmen to medical care. In the research we analyze the development of football as a factor of health and hygiene, the evolution of the medical attention to the players and his process of decentralization as result of its spatial anchorage in the sports entities.

#8 Functional Changes of P300 Values among Young Football Players as a Measure of a Cognitive Function
Reference: Coll Antropol. 2015 Sep;39(3):641-5.
Authors: Andelinović M, Titlić M, Andelinović D
Summary: Numerous studies have shown that evaluation of evoked potentials (EP) is an excellent estimation tool for a cognitive function. During daily practices footballers are exposed to headers that can leave mild head traumas. In this study, young footballers were examined, while the control group included their coevals who don't practice contact sports. Results of the study have shown that footballers have longer latency value of the P300 wave when target stimulus is presented on N1, N2 and P3, but not on P2. Also, they have longer latency values when non-target stimulus is presented. Amplitude values of target stimulus are not different, but footballers have lower amplitudes of non-target stimulus. This study suggests that EP evaluation method can be used to detect first and mild changes of the brain function.

#9 Strength Training Reduce Injury Rate In Elite Young Soccer Players During One Season
Reference: J Strength Cond Res. 2016 Feb 25. [Epub ahead of print]
Authors: Zouita S, Amira Zouita BM, Kebsi W, Dupont G, Ben Abderrahman A, Salah FB, Zouhal H.
Summary: The purpose of this study was to examine the effect of strength training on physical fitness parameters and injuries occurrence in young elite soccer players.Fifty-two elite young soccer players (13-14 yrs) were divided on a randomized order on Experimental Group (EG, n=26) and Control Group (CG, n=26). For EG, 2 to 3 sessions of strength training (90min) were introduced weekly in their training program for 12 weeks (4x3 weeks separated by 1 week recovery). Sprint tests (10-20-30m), T-test time, and jumping tests, were measured at the start (T0), at the middle (T1), and at the end of the experiment period (T2). The injury rate was recorded by the medical and fitness training staff throughout the soccer season.Compared to CG, EG performed significantly better in sprint running and T-test time at T2 (p<0.01). Similarly, the improvement amount for jumping tests was significantly greater (p<0.05) in EG compared to CG. A total of 17 injuries were recorded over the soccer season. The rate was higher in CG (13 injuries) compared to TG (4 injuries). This study showed that strength training accurately and efficiently scheduled in youth soccer players, induced performance improvement and reduced the rate of injuries.

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