Evaluation of the electromyography activity of hindlimb muscles during core exercises in horses

Abstract

Introduction

Therapeutic exercise is key in rehabilitation programs, so they must be specific, individualised, and reasoned. Biomechanical studies using surface electromyography have allowed us to make an evidence-based selection of the most appropriate exercises for each patient. The literature describes different electromyography activities in many muscles during different exercises, including walking, trotting, galloping, poles, and slopes, among others, but research on exercises performed in standing horses is lacking. Inclusion in rehabilitation programs of these exercises is based on an effect extrapolated from an anatomical and biomechanical concept of the muscles and not on surface electromyography evidence. This study evaluated the effect of six therapeutic exercises commonly used in horse rehabilitation programs on four muscles (m. gluteus medius, m. tensor fasciae latae, m. biceps femoris, and m. gracilis), to objectively measure the activity they generate by surface electromyography.

Material and methods

Six horses performed six selected core exercises: axial tail traction, lateral tail traction, lateral tail traction to the contralateral side, lumbosacral flexion, lumbosacral extension, and caudal weight displacement. The activity was recorded by surface electromyography in four hindlimb muscles, including the m. gluteus medius, m. tensor fasciae latae, m. biceps femoris, and m. gracilis, and the signal registered was rectified and smoothed using the root mean square (RMS) algorithm. Finally, the data obtained was subjected to a statistical analysis using an ANOVA for the differential voltage factor followed by a Duncan multiple range analysis to determine which muscles activated each exercise.

Results

Maximum activity was observed for m. gluteus medius with lateral tail traction (41.55 μV) and lumbosacral flexion (46.72 μV); m. tensor fasciae with lateral tail traction (40.63 μV); m. biceps femoris with lumbosacral flexion (22.22 μV); and m. gracilis with axial tail traction (39.48 μV), lateral tail traction to the contralateral side (56.43 μV), lumbosacral flexion (68.72 μV), and caudal weight displacement (41.12 μV).

Conclusions

M. biceps femoris was moderately activated during lumbar flexion, indicating it is not as relevant in pelvic stability as previously assumed. M. gluteus medius, m. biceps femoris, and m. gracilis activity during lumbar flexion suggests their potential involvement in the stability of the lumbosacral region. m. gracilis exhibited more activity than expected, indicating a significant role in pelvis and hip stability.