Latest research in football - week 38 - 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 Soccer-Related Injuries Treated in Emergency Departments: 1990-2014
Reference: Pediatrics. 2016 Sep 12. pii: e20160346. [Epub ahead of print]
Authors: Smith NA, Chounthirath T, Xiang H
Summary: The purpose was to investigate the epidemiology of youth soccer-related injuries treated in emergency departments in the United States. A retrospective analysis was conducted of soccer-related injuries among children 7 through 17 years of age from 1990 through 2014 with data from the National Electronic Injury Surveillance System. Injury rates were calculated from soccer participation data. An estimated 2 995 765 (95% confidence interval [CI], 2 309 112-3 682 418) children 7 through 17 years old were treated in US emergency departments for soccer-related injuries during the 25-year study period, averaging 119 831 (95% CI, 92 364-147 297) annually. The annual injury rate per 10 000 soccer participants increased significantly, by 111.4%, from 1990 to 2014. Patients 12 to 17 years old accounted for 72.7% of injuries, 55.5% of patients were male, and most injuries occurred in a place of sport or recreation (68.5%) or school (25.7%). Struck by (38.5%) and fell (28.7%) were the leading mechanisms of injury. Injuries most commonly were diagnosed as sprain or strain (34.6%), fracture (23.2%), and soft tissue injury (21.9%), and occurred to the upper extremity (20.7%), ankle (17.8%), and head or neck (17.7%). Concussions or other closed head injuries accounted for 7.3% of the injuries, but the annual rate of concussions/closed head injuries per 10 000 participants increased significantly, by 1595.6%, from 1990 to 2014. This study is the first to comprehensively investigate soccer-related injuries and calculate injury rates based on soccer participation data among children at the national level. The increasing number and rate of pediatric soccer-related injuries, especially soccer-related concussions/closed head injuries, underscore the need for increased efforts to prevent these injuries.

#2 Five-week sensory motor training program improves functional performance and postural control in young male soccer players - A blind randomized clinical trial
Reference: Phys Ther Sport. 2016 May 10;22:74-80. doi: 10.1016/j.ptsp.2016.05.004. [Epub ahead of print]
Authors: Heleno LR, da Silva RA, Shigaki L, Araújo CG, Coelho Candido CR, Okazaki VH, Frisseli A, Macedo CS
Summary: Sensory motor training programs are used in the rehabilitation and prevention of injuries among soccer players. Inconsistencies are found in the literature regarding the duration of the protocols and the exercises and equipment used. The objective was to evaluate the benefits of a five-week sensory motor training program on the functional performance and postural control of young soccer players. The study sample comprised 22 young male soccer players who were evaluated using: the Figure-of-Eight Test (F8), Side Hop Test (SHT), Star Excursion Balance Test (SEBT), and a force platform. The players were randomly divided into a control group (N = 10), who continued their soccer practice sessions and an intervention group (N = 12), who continued their soccer practice sessions and were also enrolled in a supervised five-week sensory motor training program. After the five-week training program, the intervention group obtained significant results in the F8, SHT and SEBT, as well as in the following parameters: area of pressure of sway center (COP), mean velocity and mean frequency of COP. The five-week sensory motor training program, carried out with easily available and low cost equipment, was effective at improving functional performance and postural control in young soccer players.

#3 Soccer-Related Facial Trauma: A Nationwide Perspective
Reference: Ann Otol Rhinol Laryngol. 2016 Sep 12. pii: 0003489416668195. [Epub ahead of print]
Authors: Bobian MR, Hanba CJ, Svider PF, Hojjat H, Folbe AJ, Eloy JA, Shkoukani MA
Summary: Soccer participation continues to increase among all ages in the US. Our objective was to analyze trends in soccer-related facial injury epidemiology, demographics, and mechanisms of injury. The National Electronic Injury Surveillance System was evaluated for soccer-related facial injuries from 2010 through 2014. Results for product code "soccer" were filtered for injures to the face. Number of injuries was extrapolated, and data were analyzed for age, sex, specific injury diagnoses, locations, and mechanisms. In all, 2054 soccer-related facial trauma entries were analyzed. During this time, the number of injures remained relatively stable. Lacerations were the most common diagnosis (44.2%), followed by contusions and fractures. The most common sites of fracture were the nose (75.1%). Of fractures with a reported mechanism of injury, the most common was head-to-head collisions (39.0%). Patients <19 years accounted for 66.9% of injuries, and athletes over 18 years old had a higher risk of fractures. The incidence of soccer-related facial trauma has remained stable, but the severity of such injuries remain a danger. Facial protection in soccer is virtually absent, and our findings reinforce the need to educate athletes, families, and physicians on injury awareness and prevention.

#4 The Evaluation of the Match External Load in Soccer: Methods Comparison
Reference: Int J Sports Physiol Perform. 2016 Sep 6. [Epub ahead of print]
Authors: Castagna C, Varley M, Póvoas Araújo SC, D'Ottavio S
Summary: The aim of this study was to test the interchangeability of two match-analysis approaches for external-load detection considering arbitrary selected speeds and metabolic power (MP) thresholds in male top-class level soccer. Data analyses were performed considering match physical performance of 120 team data (1200 player cases) of randomly selected Spanish, German and English first division championship matches (2013-14 season). Match analysis was performed with a validated semi-automated multi-camera system operating at 25 Hz. During a match players covered 10673±348m of which 1778±208m and 2759±241m were performed at High-Intensity using the speed (≥16 km·h-1, HI) and metabolic power notations (≥20 watt·kg-1, MPHI). High-intensity notations were nearly perfect associated (r=0.93, p<0.0001). A huge method bias (980.63± 87.82m. d=11.67) was found when considering MPHI and HI. Very large correlations were found between match total distance covered and MPHI (r=0.84, p<0.0001) and HI (r=0.74, p<0.0001). Players high-intensity decelerations (≥-2 m·s2) coverage was very largely associated with MPHI (r=0.73, p<0.0001). The results of this study showed that the speed and MP methods are highly interchangeable at relative (magnitude rank) but not absolute (measure magnitude) level. The two physical match analysis methods can be independently used to track match external-load in elite level players. However match-analyst decisions must be based on single method use in order to avoid bias in external-load determination.

#5 Effects of Velocity Loss During Resistance Training on Performance in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2016 Sep 6. [Epub ahead of print]
Authors: Pareja-Blanco F, Sánchez-Medina L, Suárez-Arrones L, González-Badillo JJ
Summary: The purpose was to analyze the effects of two resistance training (RT) programs that used the same relative loading but different repetition volume, using the velocity loss during the set as the independent variable: 15% (VL15) vs. 30% (VL30). Sixteen professional soccer players with RT experience (age 23.8 ± 3.5 years, body mass 75.5 ± 8.6 kg) were randomly assigned to two groups: VL15 (n = 8) or VL30 (n = 8) that followed a 6-week (18 sessions) velocity-based squat training program. Repetition velocity was monitored in all sessions. Assessments performed before (Pre) and after training (Post) included: estimated one-repetition maximum (1RM) and change in average mean propulsive velocity (AMPV) against absolute loads common to Pre and Post tests; countermovement jump (CMJ); 30-m sprint (T30); and Yo-yo intermittent recovery test (YYIRT). Null-hypothesis significance testing and magnitude-based inference statistical analyses were performed. VL15 obtained greater gains in CMJ height than VL30 (P < 0.05), with no significant differences between groups for the remaining variables. VL15 showed a likely/possibly positive effect on 1RM (91/9/0%), AMPV (73/25/2%) and CMJ (87/12/1%), whereas VL30 showed possibly/unclear positive effects on 1RM (65/33/2%) and AMPV (46/36/18%) and possibly negative effects on CMJ (4/38/57%). The effects on T30 performance were unclear/unlikely for both groups, whereas both groups showed most likely/likely positive effects on YYIRT. A velocity-based RT program characterized by a low degree of fatigue (15% velocity loss in each set) is effective to induce improvements in neuromuscular performance in professional soccer players with previous RT experience.

#6 The biomechanical and physiological response to repeated soccer-specific simulations interspersed by 48 or 72 hours recovery
Reference: Phys Ther Sport. 2016 Jul 4;22:81-87. doi: 10.1016/j.ptsp.2016.06.011. [Epub ahead of print]
Authors: Page RM, Marrin K, Brogden CM, Greig M
Summary: The purpose was to assess the residual fatigue response associated with the completion of two successive soccer-specific exercise protocols (SSEP). Twenty male soccer players were pair-matched before completing SSEPs, interspersed by either 48 or 72 h. Outcome variables were measured every 15 min, and comprised uni-axial measures of PlayerLoad, mean (HR) and peak heart rate (HRpeak), blood lactate concentration, mean and peak (V˙O2peak) oxygen consumption, and rating of perceived exertion (RPE). No significant (P > 0.05) group interactions were identified for any outcome variables. Uni-axial (and total) PlayerLoad exhibited a significant (P < 0.05) main effect for time, with the exception of the relative contribution of medial lateral PlayerLoad™. Total PlayerLoad during the final 15 min (222.23 ± 15.16 a.u) was significantly higher than all other time points. All other outcome variables also exhibited a significant main effect for time, with HR, HRpeak and V˙O2peak also exhibiting significantly higher values in the first trial. There was also a significant (P = 0.003) trial*time interaction for RPE. With equivalence at baseline, there was no difference in the fatigue response associated with two SSEPs interspersed by either 48 or 72 h recovery. The current study has implications for the design and micro management of training and competition schedules.

#7 Assessment and Training of Visuomotor Reaction Time for Football Injury Prevention
Reference: J Sport Rehabil. 2016 Aug 24:1-26. [Epub ahead of print]
Authors: Wilkerson GB, Simpson KA, Clark RA
Summary: Neurocognitive reaction time has been associated with musculoskeletal injury risk, but visuomotor reaction time (VMRT) derived from tests that present greater challenges to visual stimulus detection and motor response execution may have a stronger association. The purposes of this study were to assess VMRT as a predictor of injury and the extent to which improvement may result from VMRT training. Seventy-six NCAA Division-I FCS football players (19.5 ±1.4 years; 1.85 ± 0.06 m; 102.98 ±19.06 kg) participated in this study. Pre-participation and post-season assessments. A subset of players who exhibited slowest VMRT in relation to the cohort's post-season median value participated in a 6-week training program. Injury occurrence was related to pre-participation VMRT, which was represented by both number of target hits in 60 s and average elapsed time between hits (ms). Receiver operating characteristic analysis identified the optimum cut point for a binary injury risk classification. A non-parametric repeated measures analysis of ranks procedure was used to compare post-training VMRT values for slow players who completed at least half of the training sessions (n=15) to those for untrained fast players (n=27). A pre-participation cut point of ≤ 85 hits (≥ 705 ms) discriminated injured from non-injured players with OR = 2.30 (90% CI: 1.05, 5.06). Slow players who completed the training exhibited significant improvement in visuomotor performance compared to baseline (SRM = 2.53), whereas untrained players exhibited a small performance decrement (group x trial interaction effect, L2 = 28.74; P < .001). Slow VMRT appears to be an important and modifiable injury risk factor for college football players. More research is needed to refine visuomotor reaction time screening and training methods and to determine the extent to which improved performance values can reduce injury incidence.

#8 Small-sided football games on sand are more physical-demanding but less technical-specific compared to artificial turf
Reference: J Sports Med Phys Fitness. 2016 Sep 15. [Epub ahead of print]
Authors: Rago V, Rebelo AN, Pizzuto F, Barreira D
Summary: The use of sand has been suggested as fitness-enhancing surface in field-based team sports. However, concerns have arisen in regard whether physical responses associated to sand training are sport-specific. We compared physical and technical demands during small-sided football games (4v4 + goalkeeper; SSGs) played on artificial turf and on sand. Movement patterns, rating of perceived exertion (RPE) and technical parameters were obtained from eight adult male footballers (20.1±1.0 years, 176±4 cm and 70.1±2.0 kg) using Global Positioning Systems, Visual Analogue Scale questionnaires and Notational analysis respectively. High-intensity actions (high intensity running, high intensity activities), low changes of speed, as well as peak and average speed were higher on artificial turf (p<0.05; Effect sizes (ES) from 0.41 to 0.82). In contrast, time spent by jogging as well as high and maximum changes of speed was higher on sand (p<0.05; ES from 0.59 to 0.82). Moreover, players perceived more demanding to play on sand (p<0.05; ES=0.72). Rating of successful actions was higher during turf SSGs than sand SSGs (p<0.05; ES from 0.44 to 0.73), whereas actions requiring lifting the ball were higher on sand (p<0.05; ES from 0.47 to 0.50). The use of sand can be considered as complemental to on-turf football training, when the training goal is to tax lower-limb muscle strength or to require high-ball situations. Nonetheless, sand training is not appropriate when the achievement of maximal speed is desired. Further research should clarify the suitability of sand training within football conditioning programmes.

#9 A new clinical test for measurement of lower limb specific range of motion in football players: Design, reliability and reference findings in non-injured players and those with long-standing adductor-related groin pain
Reference: Phys Ther Sport. 2016 Jul 31. pii: S1466-853X(16)30063-3. doi: 10.1016/j.ptsp.2016.07.007. [Epub ahead of print]
Authors: Tak IJ, Langhout RF, Groters S, Weir A, Stubbe JH, Kerkhoffs GM
Summary: The association between groin pain and range of motion is poorly understood. The aim of this study was to develop a test to measure sport specific range of motion (SSROM) of the lower limb, to evaluate its reliability and describe findings in non-injured (NI) and injured football players. 6 Dutch elite clubs, 6 amateur clubs and a sports medicine practice consisting of 103 NI elite and 83 NI amateurs and 57 football players with unilateral adductor-related groin pain participated in this study. Sport specific hip extension, adduction, abduction, internal and external rotation of both legs were examined with inclinometers. Test-retest reliability (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) were calculated. Non-injured players were compared with the injured group. Intra and inter tester ICCs were acceptable and ranged from 0.90 to 0.98 and 0.50-0.88. SEM ranged from 1.3 to 9.2° and MDC from 3.7 to 25.6° for single directions and total SSROM. Both non-injured elite and amateur players had very similar total SSROM in non-dominant and dominant legs (188-190, SD ± 25). Injured players had significant (p < 0.05) total SSROM deficits with 187(SD ± 31)° on the healthy and 135(SD ± 29)° on the injured side. The SSROM test shows acceptable reliability. Loss of SSROM is found on the injured side in football players with unilateral adductor-related groin pain. Whether this is the cause or effect of groin pain cannot be stated due to the study design. Whether restoration of SSROM in injured players leads to improved outcomes should be investigated in new studies.

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