Effects of muscle fatigue, pain and warm-up on elite performance

Abstract

Human performance is a broad research domain with both direct and translational applications to a wide array of medical and occupational fields. Study of elite performance, specifically, allows us to discover the extent and limits of human capability and its response to dysfunction. Investigation of elite performance has typically focussed on populations of sport athletes, however has recently expanded to include instrumental musicians based on emerging evidence highlighting the similar physical demands of athletes and instrumental musicians. Various intervention strategies are often employed to enhance performances and prevent injuries in instrumental musicians, yet quality scientific evidence regarding the efficacy of such strategies is especially scarce in this population. Accordingly, this thesis was designed to address knowledge gaps regarding three domains related to performance enhancement and injury prevention in elite performance populations, with particular attention given to domains most likely to provide practical benefits for instrumentalists: warm-up, pain, and fatigue. Investigation of warm-up strategies began with a systematic review of upper body warm-ups (Chapter 2), with the initial goal of using this review to provide a basis for a novel randomised controlled trial investigation of warm-up in elite violinists. The review revealed that no evidence exists to support any warm-up strategies for either performance enhancement in submaximal activities or injury prevention, despite widespread advocacy for the benefits of warm-up in populations of submaximal athletes such as instrumental musicians. High load dynamic warm-ups were shown to improve maximal strength and power performance only. Thus, with no clear ‘gold standard’ warm-up, an investigation of warm-up on muscle activity, musical performance, and perceived exertion in elite violinists was designed using a range of warm-up strategies: instrument-specific, muscular, and cardiovascular (Chapter 3). The results of this trial were consistent with findings of the upper body warm-up systematic review—none of the investigated warm-ups significantly impacted muscle activity or musical performance. All three investigated warm-ups, however, resulted in an acute decrease in perceived exertion compared to a control group. Epidemiological literature has revealed that an extremely large proportion of musicians— often reported to be >80%--experience pain or other physical symptoms over the course of their careers. Less clear, however, is the acute impact of continued playing with these physical symptoms on the musicians’ technique and biomechanics. A cross-sectional analysis of EMG data collected during the warm-up RCT (Chapter 3) was undertaken to investigate the impact of pain and other physical symptoms (e.g. cramps, tingling, numbness) on muscle activity levels in elite violinists. The results suggested that proximal and distal right arm symptoms may be the cause or be the result of differential bowing mechanics (Chapter 4). Finally, effective fatigue management permits consistent achievement of peak performance with minimal injury risk, yet our ability to manage acute fatigue is limited by an inability to reliably predict its onset. Further, acute fatigue has only been sparselent investigated in elite performance populations. To address this gap, a meta-analysis of available electromyographic (EMG) and demographic data from studies investigating fatigue protocols in healthy populations was conducted (Chapter 5). This meta-analysis yields the first comprehensive, data-driven predictive model for muscle fatigue; this model takes into account age, sex, muscle fibre type, contraction force, and initial EMG amplitude and provides an evidencebased foundation for fatigue management programmes in elite performance populations. Further, a novel and robust univariate relationship between EMG change rate and time to task failure during fatiguing contractions was discovered. In addressing knowledge gaps regarding the impact of warm-up, pain, and fatigue on muscular and/or musical performance, this thesis has raised further questions regarding warm-up efficacy, proposed differential mechanisms for biomechanical responses to proximal and distal physical symptoms, and presented a comprehensive framework for muscle fatigue prediction. In addition to providing a basis for future research, these findings will immediately benefit elite performers, musician and athlete, and will also have translational benefits to occupational and rehabilitative domains.