The role of sprint training in hamstring strain injury prevention for field sport athletes

- Freeman, Brock

Title
The role of sprint training in hamstring strain injury prevention for field sport athletes
Creator
Freeman, Brock
Date
2022
Type
Text; Thesis; PhD
Identifier
http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/185191
Identifier
vital:16627
Abstract
Hamstring strain injuries (HSI) are regularly reported as the most common injury in many field-based sports with a high-speed running (HSR) component. Typically, these injuries occur during sprinting efforts, predominantly in the Biceps Femoris Long Head (BFLH). Furthermore, the burden of HSI is amongst the highest in field sports, and the risk of recurrent injury is elevated, and inflated by age. It is of interest to managers, technical coaches, physical preparation staff and athletes to reduce the risk of sustaining a HSI. Therefore, extensive research in HSI has identified several non-modifiable and modifiable risk factors, such as eccentric hamstring strength, BFLH fascicle length, and HSR exposure. Currently, almost all interventions designed to reduce the risk of HSI have utilised resistance training or stretching interventions. This is despite the scientific literature indicating that; 1) sprinting is the most common mechanism associated with hamstring strain injury, and 2) sprinting places a far greater demand on the hamstrings than interventions that are resistance or flexibility based. Therefore, the primary aim of this thesis was to establish the role of sprint training in HSI prevention in field sport athletes. The aim of Study 1 was to understand the beliefs and practices of professional Australian Football (AF) physical performance coaches towards the training and assessment prescribed to mitigate the risk of HSI. A Delphi-validated mixed methods survey was implemented to assess the beliefs and practices of High-Performance Managers of professional AF teams. All the participants in this study reported that they believed sprinting (acceleration and maximum speed) was the most common activity associated with HSI. Similarly, all participants also indicated they performed sprint training for injury prevention purposes. However, a range of relative speeds were reported to quantify HSR, whilst a sprint was reported as 85%Vmax. Whilst respondents reported they believed that sprint training was important, one participant indicated that they felt the need to be conservative with the prescription of sprint training for fear of injury, and the consequences associated with this. Due to the identified discrepancies in speed thresholds used in practical setting (Study 1) and academic settings (Literature Review), Study 2 was designed to determine the absolute, and relative speeds associated with jogging, running, striding, near maximum sprinting, and sprinting. The secondary aim was to visually describe the gait patterns associated with HSR and sprinting. Fifteen participants completed two data collection periods, where they performed a series of run throughs at different gait patterns. These gait patterns were adapted from a review of time-motion research in field sports. The running gaits of jogging, running, striding, near-maximum sprinting, and sprinting correspond with the relative speeds of 56%Vmax, 66%Vmax, 78%Vmax, 87%Vmax, and 100%Vmax, respectively. Significant (p = 0.01) differences were observed for all variables between striding, near-maximum sprinting, and sprinting. This highlights that previously reported thresholds in Study 1 are likely not quantifying the true sprinting demands. Publicly available injury information indicates a spike in HSI during the 2018 Australian Football League (AFL) season, a trend that occurred in the relatively uninterrupted 2020 AFL season. As Study 2 indicated that thresholds used to quantify the demands of sprinting in training and competition, Study 3 primarily aimed to determine the amount of running completed in relative speed bands during the pre-season and then the first eight weeks of the season. The secondary aim was to determine how individual athletes vary from the group average across the pre-season and the first eight rounds of the season. This study completed a retrospective analysis of 55 professional Australian footballers during the pre-season and first eight rounds of the 2019 season. Significantly less (p < 0.05) weekly volume was reported during the first 8 weeks of the season in the speed thresholds of 71-80%Vmax, 81-90%Vmax, and 91-100%Vmax. However, athletes in this study only completed an average of 18m above 90%Vmax in the pre-season, a stimulus too low to achieve an injury prevention and conditioning effect. Individual analysis highlighted that whilst a small number of athletes achieved a consistent sprinting load, several athletes did not achieve more than 2m above 90%Vmax during both the pre and in-season periods. This lack of preparation may provide a rationale for the injury rates during the first eight rounds. To improve the preparation of athletes using a sprinting stimulus, Study 4 focussed on addressing modifiable risk factors for HSI. The primary aim of this study examined the effects of acceleration and maximum speed sprint training of eccentric hamstring strength, BFLH fascicle length, and sprint performance. Initially, a training study with 60 participants was planned, but due to the Victorian Government’s COVID-19 restrictions, this was modified to a case study design with 11 participants. A 6-week training intervention consisting of acceleration sprinting (<15m) or maximum speed sprinting with a gradual build up (flying 10-20m) was implemented. Participants that performed acceleration or maximum speed sprinting improved Biceps Femoris fascicle length by 23% and 20%, respectively. This was an increase of more than the Minimum Detectable Change (MDC95 = 0.96cm, 95% CI =0.93 – 0.99cm). The participants who completed normal training experienced no change in the BFLH fascicle length. Neither sprint training intervention produced a change in eccentric hamstring strength that was greater than the typical error in the test. Both sprinting interventions improved sprint performance outcomes, however both acceleration and maximum speed training produced a larger improvement in maximum speed (-11% and -9%, respectively) than in acceleration qualities (-2% and -3%, respectively). Both acceleration and maximum speed training incurred positive improvement in relative force production (F(0) (N/kg)) and relative power production (Pmax (W/kg)). This was similar for DRF and RFpeak and indicates that sprint training without resistance will improve Force-Velocity-Power Variables. This project has provided new information regarding the role of sprint training for hamstring strain injury prevention. Firstly, both 6 weeks of low volume acceleration and maximum speed sprinting improve BFLH fascicle length. Secondly, currently employed velocity thresholds in professional AF are likely too slow to quantify the HSR and sprinting demands. Thirdly, analysis using thresholds that are faster than previously reported revealed that the overall volume of sprinting (>90%Vmax) is too low to elicit an injury prevention or training stimulus. This information will inform the future practices of key stakeholders surrounding sprint training in field sport athletes. The identification of the positive benefits of maximum speed sprinting, and a faster, more accurate definition of sprinting has large potential to improve hamstring strain injury prevention and increase physical performance.; Doctor of Philosophy
Publisher
Federation University Australia
Rights
All metadata describing materials held in, or linked to, the repository is freely available under a CC0 licence
Rights
Copyright Brock Freeman
Rights
Open Access
Subject
Sprinting; Hamstring; Resistance training; Australian football; Muscle architecture
Full Text
Thesis Supervisor
Talpey, Scott
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