Latest research in football - week 21 - 2018

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 Commotio Cordis in a Professional Soccer Player: Value of MRI in Unraveling Myocardial Damage
Reference: Circ Cardiovasc Imaging. 2018 Jun;11(6):e007848. doi: 10.1161/CIRCIMAGING.118.007848.
Authors: Zeldetz V, Greenberg S, Zeller L, Zahger D, Shalev A

#2 No Effect of Generalized Joint Hypermobility on Injury Risk in Elite Female Soccer Players: Response
Reference: Am J Sports Med. 2018 Jun;46(7):NP28-NP29. doi: 10.1177/0363546518773721.
Authors: Thijs KM, Blokland D, Backx FJG, Goedhart EA, Huisstede BMA.
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#3 Injuries in formal and informal non-professional soccer - an overview of injury context, causes, and characteristics
Reference: Eur J Sport Sci. 2018 May 29:1-9. doi: 10.1080/17461391.2018.1475507. [Epub ahead of print]
Authors: Gebert A, Gerber M, Puhse U, Gassmann P, Stamm H, Lamprecht M
Summary: The objective of this study is to analyse context, causes, and characteristics of injuries in non-professional soccer. Therefore, a retrospective telephone survey was carried out with persons who were injured while playing soccer and who reported this accident to the Swiss National Accident Insurance Fund (Suva). Based on these data, an analysis of 708 soccer injuries was performed. The findings show that 30.1% of the injuries occurred during informal soccer play, and 75.4% of the injured persons were soccer club members. 53.0% of all injuries were caused by contact and 29.5% by foul play. Foul play was not associated with injury severity. With respect to injury severity, twisting/turning and being tackled by an opponent were identified as the most influental injury causes. Moreover, the risk of being severely injured was particularly high players of the 30+/40+ amateur leagues. In conclusion, the findings highlight that 30+/40+ league players are a major target group for the prevention of severe soccer injuries. Soccer clubs may constitute an appropriate multiplier for implementing prevention strategies such as fair play education, healthy play behaviours, and prevention programmes. Finally, a better understanding of injury situations leading to severe injuries is needed to improve injury prevention.

#4 Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor
Reference: Int J Sports Physiol Perform. 2018 May 29:1-23. doi: 10.1123/ijspp.2018-0131. [Epub ahead of print]
Authors: McHugh MP, Clifford T, Abbott W, Kwiecien SY, Kremenic IJ, DeVita JJ, Howatson G
Summary: The purpose of this study was to assess the utility of an inertial sensor for assessing recovery in professional soccer players. In a randomized, crossover design, 11 professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or uncooled packs (control) for 3 h after a 90 minute match. Countermovement jump (CMJ) performance was assessed simultaneously with an inertial sensor and an optoelectric system, pre match, and 12, 36 and 60 h post match. Inertial sensor metrics were flight height, jump height, low force, countermovement distance, force at low point, rate of eccentric force development, peak propulsive force, maximum power, and peak landing force. The only optoelectric metric was flight height. CMJ decrements, and effect of PCM cooling were assessed with repeated measures ANOVA. Jump heights were also compared between devices. For the inertial sensor data there were decrements in CMJ height on the days after matches (88±10% of baseline at 36 h P=0.012, effect size 1.2, for control condition) and accelerated recovery with PCM cooling (105±15% of baseline at 36 h, P=0.018 vs. control, effect size 1.1). Flight heights were strongly correlated between devices (r=0.905, P<0.001) but inertial sensor values were 1.8±1.8 cm lower (P=0.008). Low force during countermovement was increased (P=0.031) and landing force was decreased (P=0.043) after matches, but neither were affected by the PCM cooling intervention. Other CMJ metrics were unchanged after matches. This small portable inertial sensor provides a practical means of assessing recovery in soccer players.

#5 Neuromechanical response to passive cyclic loading of the ACL in non-professional soccer players: A pilot study
Reference: Phys Ther Sport. 2018 May 15;32:187-193. doi: 10.1016/j.ptsp.2018.05.013. [Epub ahead of print]
Authors: Nuccio S, Labanca L, Rocchi JE, Macaluso A, Sbriccoli P
Summary: The purpose was to investigate the effects of passive cyclic loading (CYC) on anterior tibial translation (ATT), knee extensor and flexor muscle strength and activation in soccer players. Functional Assessment Laboratory; Participants: Eight healthy competitive soccer players. The knee of the dominant limb was subjected to 10 min of CYC at 200 N force. ATT was measured before and after CYC. Percentage of variation was used to estimate ACL creep. Knee extension and flexion maximal voluntary contractions (MVCs) were assessed both before and after CYC. EMG amplitudes of both Biceps Femoris (BF) and Vastus Lateralis (VL) were recorded during both MVCs and CYC. There was a 20.7% increase in ATT after CYC application (p<0.001). Post-CYC agonist and antagonist BF activations were 37.7% and 18.4% lower than pre-CYC ones during MVCs (p<0.05). BF EMG activity in the last 30s of CYC was 19.9% higher than in the first 30s (p<0.05). The increased ATT and the variations in neuromuscular activation of the BF in response to loading may expose the knee at higher injury risk by increasing joint instability. Further studies are required to thoroughly investigate these aspects in both laboratory and real-field settings.

#6 Scheduling of Eccentric Lower-limb Injury Prevention Exercises during the Soccer micro-cycle: Which day of the week?
Reference: Scand J Med Sci Sports. 2018 May 24. doi: 10.1111/sms.13226. [Epub ahead of print]
Authors: Lovell R, Whalan M, Marshall PW, Sampson JA, Siegler JC, Buchheit M
Summary: Scheduling eccentric-based injury prevention programs (IPP) during the common 6-day micro-cycle in Soccer is challenged by recovery and tapering phases. This study profiled muscle damage, neuromuscular performance, and perceptual responses to a lower-limb eccentric-based IPP administered 1 (MD+1) versus 3 days (MD+3) post-match. 18 semi-professional players were monitored daily during 3 in-season 6-day micro-cycles, including weekly competitive fixtures. Capillary creatine kinase concentration (CK), posterior lower limb isometric peak force (PF), counter-movement jump (CMJ) performance, and muscle soreness were assessed 24 h prior to match-day (baseline), and every 24 h up to 120 h post-match. The IPP consisted of lunges, single stiff leg dead-lifts, single leg-squats and Nordic hamstring exercises. Performing the IPP on MD+1 attenuated the decline in CK normally observed following match-play (CON: 142%; MD+3: 166%; small differences). When IPP was delivered on MD+3, CK was higher versus CON and MD+1 trials on both MD+4 (MD+3: 260%; CON: 146%; MD+1: 151%; moderate differences) and MD+5 (MD+3: 209%; CON: 125%; MD+1: 127%; small differences). Soreness ratings were not exacerbated when the IPP was delivered on MD+1, but when prescribed on MD+3, hamstring soreness ratings remained higher on MD+4 and MD+5 (small differences). No between trial differences were observed for PF and CMJ. Administering the IPP in the middle of the micro-cycle (MD+3) increased measures of muscle damage and soreness, which remained elevated on the day prior to the next match (MD+5). Accordingly, IPP should be scheduled early in the micro-cycle, to avoid compromising preparation for the following match.

#7 Hamstring-to-Quadriceps Torque Ratios of Professional Male Soccer Players: A Systematic Review
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002609. [Epub ahead of print]
Authors: Baroni BM, Ruas CV, Ribeiro-Alvares JB, Pinto RS
Summary: The goal of this review was to determine the isokinetic hamstring-to-quadriceps (H/Q) torque ratios of professional male soccer players. Systematic searches were independently carried out by 2 researchers in 7 electronic databases. Only studies with teams from the first or second national leagues were included. From these studies, we extracted the players' H/Q conventional (concentric/concentric) and/or functional (eccentric/concentric) ratios. The initial search resulted in 2,128 articles that were filtered to 30 articles (1,727 players) meeting the inclusion criteria. The H/Q conventional ratio was assessed in 27 studies (1,274 players), whereas the H/Q functional ratio was assessed in 15 studies (1,082 players). The H/Q conventional ratio mean scores of professional male soccer players were close to 60% when tested at low to intermediate angular velocities (12°·s = 52 ± 7%; 30°·s = 52 ± 8%; 60°·s = 65 ± 12%; 90°·s = 57 ± 6%; 120°·s = 65 ± 16%; 180°·s = 67 ± 17%) and around 70-80% at fast angular velocities (240°·s = 80 ± 40%; 300°·s = 70 ± 15%; 360°·s = 80 ± 13%). The H/Q functional ratio mean scores of professional male soccer players were close to 80% at 60°·s (79 ± 19%), around 100-130% at intermediate to fast angular velocities (120°·s = 127 ± 42%; 180°·s = 96 ± 19%; 240°·s = 109 ± 22%; 300°·s = 123 ± 18%), and near or above 130% when angular testing velocities were mixed (eccentric hamstring < concentric quadriceps; 30/240°·s = 132 ± 26%; 60/180°·s = 129 ± 20%; 60/240°·s = 153 ± 30%). In conclusion, considering the tested isokinetic angular velocity, professional male soccer players do not meet the traditional reference landmarks used to assess the strength balance between quadriceps and hamstring muscles (i.e., 60 and 100% for H/Q conventional and functional ratios, respectively), which supports a need for specific reference values according to the angular velocity selected for testing H/Q torque ratios.

#8 Acupuncture techniques in professional football
Reference: Unfallchirurg. 2018 Jun;121(6):450-454. doi: 10.1007/s00113-018-0500-0. [Article in German]
Authors: Pfab F, Sommer B, Haser C
Summary: The number of scientific studies about acupuncture has increased significantly during recent years. Acupuncture can be used as an evidence-based adjunct therapy for a variety of indications in professional football. This review summarizes various acupuncture techniques and related techniques for utilization in the field of professional soccer. Besides knee, shoulder, spinal, elbow and postoperative pain, scientific meta-analyses also point towards the effectiveness of acupuncture in ankle sprains, allergic rhinoconjunctivitis and nausea. Dry needling is an emerging option for treatment of myofascial trigger points and could potentially result in improved prevention of muscular injuries and enhancement of muscular performance.

#9 Position specific player load during match-play in a professional football club
Reference: PLoS One. 2018 May 24;13(5):e0198115. doi: 10.1371/journal.pone.0198115. eCollection 2018.
Authors: Baptista I, Johansen D, Seabra A, Pettersen SA
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Summary: There is a rapid growing body of knowledge regarding physical aspects of a football match due to studies using computer-assisted motion analysis. The present study used time-motion analysis and triaxial-accelerometers to obtain new insights about differences in physical profiles of elite football players across playing-positions. Player performance data in 23 official home matches from a professional football club, during two seasons were collected for analysis. Eighteen players from five different playing positions (central backs: n = 3; full-backs: n = 5; central midfielders: n = 6; wide midfielders: n = 3; and central forwards: n = 4), performing a total of 138 observations. A novel finding was that central backs and central midfielders had significantly lower work-rate in sprints, decelerations and accelerations than full-backs, wide midfielders and central forwards (p<0.001). Furthermore, wide midfielders and full-backs performed significantly more turns (>90°) than central backs. The most common distance covered in high-intensity runs (≥19.8 km·h-1) for central backs, central midfielders, wide midfielders and central forwards was 1-5 m, but for full-backs was 6-10 m. This may help coaches in developing individualized training programs to meet the demands of each position in match-play.

#10 Normative Quadriceps and Hamstring Muscle Strength Values for Female, Healthy, Elite Handball and Football Players
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002579. [Epub ahead of print]
Authors: Risberg MA, Steffen K, Nilstad A, Myklebust G, Kristianslund E, Moltubakk MM, Krosshaug T
Summary: This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

#11 WAVE~Ripples for Change Obesity Two-Year Intervention in High School Soccer Players: Process Evaluation, Best Practices, and Youth Engagement
Reference: Nutrients. 2018 Jun 1;10(6). pii: E711. doi: 10.3390/nu10060711.
Authors: Meng Y, Wong SS, Manore MM, Patton-Lopez M
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Summary: This paper reports the process data on program fidelity, best practices for intervention implementation, youth and coach engagement, and youth application of knowledge and skills for the two-year WAVE~Ripples for Change (WAVE) obesity prevention intervention program focused on healthy eating, physical activity, and life skills with high school (HS) soccer players aged 14⁻19 years. Internal (staff: n = 7; volunteers: n = 27) and external (youth: n = 100; coaches: n = 9) stakeholders were interviewed/ surveyed. Staff rated program fidelity as high (94%), as did volunteers (85%). Best practices included coach encouragement for athlete participation, use of on-line consent for enrollment, building relationships with HS staff to complete assessments, sending text reminders, and providing incentives. Study results showed an enrollment rate of 72%, completion of baseline assessments of 89⁻98%, attendance of sports nutrition lessons in Year 1 and Year 2 of 90% and 39%, respectively, and team-building workshop (TBW) attendance of 25⁻31%. Activities exceeding youth expectations (>90%) included, (1) activities with their soccer team; (2) the TBW-cooking; and (3) sports nutrition lessons. The obesity prevention skills most applied by youth were obtained from the TBW-gardening and harvesting (49%), the TBW-cooking (43%), and sports nutrition lessons (44%). Coaches also rated the sports nutrition lessons highly and reported increased awareness for hydration/fueling during sport by the athletes. Using sport teams/clubs to engage youth in obesity prevention is a feasible model for future study.

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