Latest research in football - week 44 - 2017

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 Acute and Residual Soccer Match-Related Fatigue: A Systematic Review and Meta-analysis
Reference: Sports Med. 2017 Nov 2. doi: 10.1007/s40279-017-0798-8. [Epub ahead of print]
Authors: Silva JR, Rumpf MC, Hertzog M, Castagna C, Farooq A, Girard O, Hader K

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Summary: Understanding soccer players' match-related fatigue and recovery profiles likely helps with developing conditioning programs that increase team performance and reduce injuries and illnesses. In order to improve match recovery (the return-to-play process and ergogenic interventions) it is also pivotal to determine if match simulation protocols and actual match-play lead to similar responses. The objectives were (1) To thoroughly describe the development of fatigue during actual soccer match play and its recovery time course in terms of physiological, neuromuscular, technical, biochemical and perceptual responses, and (2) to determine similarities of recovery responses between actual competition (11 vs. 11) and match simulations. A first screening phase consisted of a systematic search on PubMed (MEDLINE) and SportDiscus databases until March 2016. Inclusion criteria were: longitudinal study with soccer players; match or validated protocol; duration > 45 min; and published in English. A total of 77 eligible studies (n = 1105) were used to compute 1196 effect sizes (ES). Half-time assessments revealed small to large alterations in immunological parameters (e.g. leukocytes, ES = 1.9), a moderate decrement in insulin concentration (ES = - 0.9) and a small to moderate impairment in lower-limb muscle function (ES = - 0.5 to - 0.7) and physical performance measures (e.g. linear sprint, ES = - 0.3 to - 1.0). All the systematically analyzed fatigue-related markers were substantially altered at post-match. Hamstrings force production capacity (ES = - 0.7), physical performance (2-4%, ES = 0.3-0.5), creatine kinase (CK, ES = 0.4), well-being (ES = 0.2-0.4) and delayed onset muscle soreness (DOMS, ES = 0.6-1.3) remained substantially impaired at G + 72 h. Compared to simulation protocols, 11 vs. 11 match format (CK, ES = 1.8) induced a greater magnitude of change in muscle damage (i.e. CK, ES = 1.8 vs. 0.7), inflammatory (IL-6, ES = 2.6 vs. 1.1) and immunological markers and DOMS (ES = 1.5 vs. 0.7) than simulation protocols at post-assessments. Neuromuscular performances at post-match did not differ between protocols. While some parameters are fully recovered (e.g. hormonal and technical), our systematic review shows that a period of 72 h post-match play is not long enough to completely restore homeostatic balance (e.g. muscle damage, physical and well-being status). The extent of the recovery period post-soccer game cannot consist of a 'one size fits all approach'. Additionally, the 'real match' (11 vs. 11 format) likely induces greater magnitudes of perceptual (DOMS) and biochemical alterations (e.g. muscle damage), while neuromuscular alterations were essentially similar. Overall, coaches must adjust the structure and content of the training sessions during the 72-h post-match intervention to effectively manage the training load within this time-frame.

#2 Head impact locations in US high school boys' and girls' soccer concussions, 2012/13-2015/16
Reference: J Neurotrauma. 2017 Nov 1. doi: 10.1089/neu.2017.5319. [Epub ahead of print]
Authors: Kerr Z, Campbell KR, Fraser MA, Currie DW, Pierpoint LA, Kamimski T, Mihalik J
Summary: This study describes concussions and concussion-related outcomes sustained by high school soccer players by head impact location, sex, and injury mechanism. Data were obtained for the 2012/13-2015/16 school years from the National High School Sports-Related Injury Surveillance System, High School RIO™. This Internet-based sports injury surveillance system captures data reported by athletic trainers from an annual average of 162 US high schools. Data were analyzed to describe circumstances of soccer concussion (e.g., symptomology, symptom resolution and return-to-play time) by impact location [i.e., front- (face included), back-, side-, and top-of-the-head] and sex. Most concussions were from front-of-the-head impacts (boys: 30.5%; girls: 34.0%). Overall, 4.1±2.2 and 4.6±2.3 symptoms were reported in boys and girls, respectively. In boys, symptom frequency was not associated with head impact location (P=0.66); an association was found in girls (p=0.02), with the highest symptom frequency reported in top-of-the-head impacts (5.4±2.2). Head impact location was not associated with symptom resolution time (boys P=0.21; girls P=0.19) or return-to-play time (boys P=0.18; girls P=0.07). Heading was associated with 28.0% and 26.5% of concussions in boys and girls, respectively. Most player-player contact concussions during heading occurred from side-of-the-head impacts (boys: 49.4%; girls: 43.2%); most heading-related ball contact concussions occurred from front-of-the-head (boys: 41.4%; girls: 42.6%) and top-of-the-head (boys: 34.5%; girls: 36.9%) impacts. Head impact location was generally independent of symptom resolution time, return-to-play time, and recurrence among high school soccer concussions. However, impact location may be associated with reported symptom frequency. Further, many of these clinical concussion descriptors were associated with sex.

#3 Acute Effects Of Active, Ballistic, Passive And Proprioceptive Neuromuscular Facilitation Streching On Sprint And Vertical Jump Performance In Trained Young Soccer Players
Reference: J Strength Cond Res. 2017 Oct 27. doi: 10.1519/JSC.0000000000002298. [Epub ahead of print]
Authors: de Paula Oliveira L, Palucci Vieira LH, Aquino R, Vieira Manechini JP, Pereira Santiago PR, Puggina EF.
Summary: The aim of the present study was to compare the acute effects of active (AC), ballistic (BA), passive (PA), proprioceptive neuromuscular facilitation stretching (PNF) methods on performance in vertical jumping, sit and reach, and sprinting in young soccer players. Twelve trained soccer players (17.67 ± 0.87 years) participated in the study. The jump height (H), peak power (PP), and relative power (RP) in the squat jump (SJ) and countermovement jump (CMJ), the range of motion (ROM), the rate of perceived exertion (RPE), and time (s) in 10-20-30 m sprints were evaluated. Significant differences (p <0.05) in H were found in the comparisons between the PA and control condition (CO) for the SJ. For the CMJ, differences in H were observed between the PA and CO, and PNF with CO and BA, and in the PP between the PNF and CO, AC, and BA, as well as in the RP between the PNF and BA. Significant increases in ROM were found in the AC, BA, PA, and PNF, compared to the CO. In relation to RPE, higher scores were reported in the PA and PNF conditions compared to the AC and BA. No significant differences were found in 10-20-30 m sprints. Therefore, the AC and BA methods can be used prior to vertical jump and sprint activities, with the aim of increasing flexibility. However, the PA and PNF methods should be avoided, due to subsequent negative effects on vertical jump performance.

#4 Fractures in German elite male soccer
Reference: J Sports Med Phys Fitness. 2017 Oct 27. doi: 10.23736/S0022-4707.17.07901-4. [Epub ahead of print]
Authors: Schiffner E, Latz D, Grassmann JP, Schek A, Scholz A, Windolf J, Jungbluth P, Schneppendahl J
Summary: Aim of this retrospective cohort study was to identify fracture epidemiology and off times after different types of fractures in German male elite soccer players from the first division Bundesliga based on information from the public media. Exposure and fracture data over 7.5 consecutive seasons (2009/10 -1.Half 2016/17) were collected from two media based register (® and®). 357 fractures from 290 different players were recorded with an incidences of 0.19/1000 h of exposure (95% 0.14 - 0.24). Most fractures in German elite soccer players involved the lower extremities (35.3%), the head/face (30.3%) and the upper extremities (24.9%). The median off time after a fracture in German elite male professional soccer in 7.5 Season was 51.1 days (range 0-144). The number of fractures per 100 players per season decreased between 2009 and 2016. There was no significant difference in overall fracture incidence when comparing players at different position (p=0.11). Goalkeepers have a significantly (p<0.02) higher likelihood of suffering hand and finger fractures and they are significantly (p<0.03) less prone of suffering foot fractures, cranial and maxillofacial fractures (p<0.04) compared to outfield players. This study can confirm that male professional soccer teams experience 1-2 fractures per season in German elite soccer. The incidence of fractures in elite German soccer players decreased between 2009 and 2016. The most fractures occur in the lower extremities and there is no difference in overall fracture risk for players at different playing positions. The information from our study might be of a great importance to medical practitioners, soccer coaches and soccer manager.

#5 Exercise to rest ratios in RSA training in women's soccer
Reference: J Sports Med Phys Fitness. 2017 Oct 27. doi: 10.23736/S0022-4707.17.07741-6. [Epub ahead of print]
Authors: Ruscello B, Esposito M, Partipilo F, DI Cicco D, Filetti C, Pantanella L, D'Ottavio S
Summary: The purpose was to investigate the applicability of three different exercise to rest ratios in RSA training in women's soccer players, applying those ones already adopted in male adult and young players, when performing three different sprinting modes (straight, shuttle and sprinting with changing of direction). 15 trained female soccer players (height: 1.65 ± 0.06 m; weight: 59.3 ± 9.0 kg; BMI 21.6 ± 2.7 kg·m-2; age: 23.3±5.9 years) participated to the study. In order to compare the different values of the time recorded, an Index of Fatigue was used. Recovery times among trials in the sets were administered according to the 1:5, 1:3; 1:2 exercise to rest ratio, respectively. Blood lactate concentrations at the end of each set (3') were analyzed. Significant differences among trials within each set (Repeated Measures Anova; p<0.05) were found, as evidence of fatigue over time, with an average decay of performance of about 5% but no significant differences were found in IF%, among the three different sprinting modalities when applying the investigated exercise to rest ratios (Factorial Anova; between; p>0.05). Significant differences were found in blood lactate concentrations (p<0.05). The results of this study confirm that the exercise to rest ratios considered in this study might be suitable to design effective testing protocols and training sessions aimed at the development of the RSA in women's soccer players, keeping the performances in the speed domain (IF% < ⊕7-8%) but inducing the fatigue processes sought with this kind of training method.

#6 Influence of different types of compression garments on exercise-induced muscle damage markers after a soccer match
Reference: Res Sports Med. 2017 Oct 30:1-16. doi: 10.1080/15438627.2017.1393755. [Epub ahead of print]
Authors: Marques-Jimenez D, Calleja-Gonzalez J, Arratibel-Imaz I, Delextrat A, Uriarte F, Terrados N
Summary: There is not enough evidence of positive effects of compression therapy on the recovery of soccer players after matches. Therefore, the objective was to evaluate the influence of different types of compression garments in reducing exercise-induced muscle damage (EIMD) during recovery after a friendly soccer match. Eighteen semi-professional soccer players (24 ± 4.07 years, 177 ± 5 cm; 71.8 ± 6.28 kg and 22.73 ± 1.81 BMI) participated in this study. A two-stage crossover design was chosen. Participants acted as controls in one match and were assigned to an experimental group (compression stockings group, full-leg compression group, shorts group) in the other match. Participants in experimental groups played the match wearing the assigned compression garments, which were also worn in the 3 days post-match, for 7 h each day. Results showed a positive, but not significant, effect of compression garments on attenuating EIMD biomarkers response, and inflammatory and perceptual responses suggest that compression may improve physiological and psychological recovery.

#7 Tanner-Whitehouse Skeletal Ages in Male Youth Soccer Players: TW2 or TW3?
Reference: Sports Med. 2017 Oct 29. doi: 10.1007/s40279-017-0799-7. [Epub ahead of print]
Authors: Malina RM, Coelho-E-Silva MJ, Figueiredo AJ, Philippaerts RM, Hirose N, Pena Reyes ME, Gilli G, Benso A, Vaeyens R, Deprez D, Guglielmo LF, Buranarugsa R
Summary: The Tanner-Whitehouse radius-ulna-short bone protocol (TW2 RUS) for the assessment of skeletal age (SA) is widely used to estimate the biological (skeletal) maturity status of children and adolescents. The scale for converting TW RUS ratings to an SA has been revised (TW3 RUS) and has implications for studies of youth athletes in age-group sports. The aim of this study was to compare TW2 and TW3 RUS SAs in an international sample of male youth soccer players and to compare distributions of players by maturity status defined by each SA protocol. SA assessments with the TW RUS method were collated for 1831 male soccer players aged 11-17 years from eight countries. RUS scores were converted to TW2 and TW3 SAs using the appropriate tables. SAs were related to chronological age (CA) in individual athletes and compared by CA groups. The difference of SA minus CA with TW2 SA and with TW3 SA was used to classify players as late, average, or early maturing with each method. Concordance of maturity classifications was evaluated with Cohen's Kappa coefficients. For the same RUS score, TW3 SAs were systematically and substantially reduced compared with TW2 SAs; mean differences by CA group ranged from - 0.97 to - 1.16 years. Kappa coefficients indicated at best fair concordance of TW2 and TW3 maturity classifications. Across the age range, 42% of players classified as average with TW2 SA were classified as late with TW3 SA, and 64% of players classified as early with TW2 SA were classified as average with TW3 SA. TW3 SAs were systematically lower than corresponding TW2 SAs in male youth soccer players. The differences between scales have major implications for the classification of players by maturity status, which is central to some talent development programs.

#8 Orthopedic injuries in soccer – an analysis of professional championship tournament in Brazil
Reference:  Acta Ortop Bras. 2017 Sep-Oct;25(5):216-219. doi: 10.1590/1413-785220172505171247.
Authors: Souza RFR, Mainine S, Souza FFR, Zanon EM, Nishimi AY, Dobashi ET, Fernandes FA
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Summary: The purpose was to analyze the incidence of orthopedic injuries which occurred during a professional soccer championship in São Paulo, Brazil in 2010. This assessment collected data from the pre-season until the final stage of the championship. We analyzed 227 professional players from eight of the top teams in this championship. Data were obtained for 71.02% of all games. The athletes were all male with a mean age of 23.1 years; the average number of injuries was 1.6 per athlete, with muscle injuries and sprains resulting from indirect origin predominating in the legs. Injuries were more frequent in forwards and outside backs, and players generally returned to play within one week of treatment.

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