A preliminary evaluation of surface electromyography as a tool to measure muscle fatigue in the National Hunt racehorse

Abstract

Background: Within equestrian sports, training is commonly based on historic and anecdotal good practice. Telemetric surface electromyography (sEMG) systems facilitate assessment of muscle recruitment including mean motor unit action potential (mM-UAP). Mean EMG frequency (mEMGF) provides an objective measure of fitness levels while a shift in the median EMG frequency (MeEMGF) over time can illustrate fatigue. Aim: This study aimed to investigate if sEMG could be used in the field to evaluate muscle activity of the Gluteus superficialis in a cohort of National Hunt racehorses during one canter interval training session. Method: Sensors were secured bilaterally to horses' Gluteal superficialis prior to exercise and data were collected over a standardised 10 metre interval. A repeated measure ANOVA assessed differences in mEMGF between runs across the cohort and between runs for individual horses. A Pearson's correlation identified if mEMGF was related to perceived fitness level as assessed by the trainer. mEMGF and MeEMGF for individual horses were plotted over time (0.25 second intervals) to assess fitness and fatigue. Results: Individual horses exhibited a wide variety of mMUAP values. No differences were found between runs for the overall cohort (p>0.05) however significant differences were found between runs within some individual horses (p<0.01). No relationship between fitness level and mEMGF was found (p>0.05), mEMGF varied throughout runs and MeEMGF for most horses remained consistent indicative of a lack of fatigue. Conclusion: The results suggest that this technology exhibits potential to be used to aid analysis of efficacy of training programmes for individual horses.