The Uptake of Nordic Hamstring Exercise Program for Injury Prevention in Major League Soccer and Its Barriers to Implementation in Practice

Hamstring Injuries, From the Clinic to the Field: A Narrative Review Discussing Exercise Transfer

PURPOSE

The optimal approach to hamstring training is heavily debated. Eccentric exercises reduce injury risk; however, it is argued that these exercises transfer poorly to improved hamstring function during sprinting. Some argue that other exercises, such as isometric exercises, result in better transfer to running gait and should be used when training to improve performance and reduce injury risk. Given the performance requirements of the hamstrings during the terminal swing phase, where they are exposed to high strain, exercises should aim to improve the torque production during this phase. This should improve the hamstrings' ability to resist overlengthening consequently, improving performance and limiting strain injury. Most hamstring training studies fail to assess running kinematics postintervention. Of the limited evidence available, only eccentric exercises demonstrate changes in swing-phase kinematics following training. Studies of other exercise modalities investigate effects on markers of performance and injury risk but do not investigate changes in running kinematics.

CONCLUSIONS

Despite being inconsistent with principles of transfer, current evidence suggests that eccentric exercises result in transfer to swing-phase kinematics. Other exercise modalities may be effective, but the effect of these exercises on running kinematics is unknown.

Assessment of Strength and Power Capacities in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Strength and power represent two crucial physical qualities for the attainment of a high level of performance considering the frequency and the importance of explosive actions occurring during elite soccer match-play. Evaluation of strength and power is a multifaceted concept involving a vast array of tests and outcome variables. Nevertheless, a comprehensive and systematic search of strength and power assessment procedures in elite soccer has yet to be undertaken.

OBJECTIVES

The aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e., mean age of the group); and (4) their playing level was defined as "professional", "international" or "elite".

RESULTS

Regarding strength testing, 115 studies and 29 different tests were identified. The three most frequent strength tests were the knee extensor isokinetic strength test (58 studies), the knee flexor isokinetic strength test (55 studies) and the Nordic hamstring strength test (13 studies). In terms of power testing, 127 studies with 31 different tests were included. The three most frequent power tests were the countermovement jump with hands fixed on hips (99 studies), the squat jump (48 studies) and the vertical jump with arm swing (29 studies).

CONCLUSIONS

The wide range of different tests and outcome variables identified in this systematic review highlights the large diversity in the employed testing procedures. The establishment of a hybrid testing approach, combining standardised and widely accepted tests for establishing normative standards and enabling comparisons across different contexts, with flexible context-specific testing batteries, has the potential to maximise the impact of testing information for practitioners. In addition, the limited reporting of reliability data across studies highlights the need for practitioners to establish their own reliability measure within their specific contexts, informing the selection of certain tests and outcome variables.

The use of sand as an alternative surface for training, injury prevention and rehabilitation in English professional football and barriers to implementation: a cross-sectional survey of medical staff

PURPOSE

The purpose of the present study was to investigate the use of sand as an alternative surface for training, injury prevention and rehabilitation interventions in English professional football. A Secondary aim was to explore the potential barriers to implementation.

MATERIALS AND METHODS

All 92 teams from the male English professional football pyramid during the 2021-22 season were eligible to take part. A cross-sectional survey of the medical personnel (one per club) was conducted between June 2021 and December 2021 based on the RE-AIM framework. A total of 58 respondents (63% of all clubs) completed the survey.

RESULTS AND CONCLUSIONS

Only 18 (31%) of the clubs surveyed used sand-based interventions across the last 3 seasons. Respondents felt sand-based interventions would be effective at improving physiological gains (median 4, interquartile range [IQR] 4-5) and as part of injury prevention and rehabilitation strategies (4, IQR 3-4) but were indifferent in relation to its potential to improve sporting performance (3, IQR 3-4). Barriers to implementation of sand-based interventions within wider football were a lack of facilities, lack of awareness of its potential benefits, lack of high-quality evidence and the surface not being specific to the sport. Medical staff also did not perceive that coaches' positively viewed sand interventions as a training or injury management strategy.

The British Athletics Muscle Injury Classification grading system as a predictor of return to play following hamstrings injury in professional football players

OBJECTIVES

Investigate the British Athletics Muscle Injury Classification (BAMIC) grading system as a predictor of return to play (RTP) following primary hamstring strain injury (HSI) and its agreement with the Peetron's classification system in professional footballers.

METHODS

A retrospective cohort study of 39 hamstrings strains in a professional English football club were identified. Two musculoskeletal radiologists reviewed historical MRI's and classified them against the BAMIC and Peetron's grading system. Classification, oedema length and cross-sectional area were compared against RTP.

RESULTS

Pearson's correlation coefficient demonstrated a weak but statistically significant correlation between BAMIC and RTP (r = 0.32; 95%CI 0.01 to 0.58; p = 0.05). Maximum length of intramuscular oedema demonstrated weak correlations with RTP (r = 0.3; 95%CI -0.02 to 0.56; p = 0.06). Percentage cross sectional demonstrated a weak correlation with RTP (r = 0.02; 95%CI -0.3 to 0.33; p = 0.91). Multiple regression demonstrated that 16% of the variance in RTP was explained by the model. Kappa for the agreement between BAMIC and Peetron's was 0.21 (95%CI 0 to 0.42).

CONCLUSIONS

A significant association between the grade of HSI on the BAMIC system and RTP was found. Findings suggest BAMIC could provide valuable prognostic information on the RTP.