The effect of dynamic mobilization exercises and therapeutic trunk exercises on superficial epaxial and hypaxial muscle activity in horses

BACKGROUND: Equine back rehabilitation commonly integrates dynamic mobilization exercises (DME), including DME to the chest (DMEChest) and DME to the hip (DMEHip), and therapeutic trunk (TTE) exercises, including pelvic rounding (Rounding), and lateral tail pulls (LatTail). However, limited evidence supports their use for selectively activating trunk muscles. AIMS/OBJECTIVES: To quantify and compare superficial epaxial and hypaxial muscle activity during selected DMEs and TTEs using surface electromyography (sEMG). Increased muscle activity was hypothesized across exercises, specifically in external abdominal oblique (EAO) during lateral bending (DMEHip, LatTail), and longissimus dorsi (LD) and rectus abdominus (RA) during spinal flexion (DMEChest, Rounding) exercises. METHODS: Bilateral sEMG data, from the EAO, RA, and LD (T14 and L1) of n = 7 horses executing DMEChest, DMEHip, LatTail, and Rounding, were band-pass filtered (40-450 Hz), full-wave rectified, and amplitude normalized. Average rectified value (ARV) was calculated and grouped by movement direction (ipsilateral, contralateral) for DMEHip and LatTail. Linear mixed models assessed associations between exercise and normalized ARV, with horse as a random effect. RESULTS: Compared to other exercises, estimated marginal mean ARV (%) [95 % CI] was significantly greater (P < 0.05) during ipsilateral DMEHip for EAO (207.0, [178.7, 235.4]), RA (172.1, [140.8, 203.4]) and LD at T14 (136.8, [126.4, 147.3]), and during both ipsilateral DMEHip (120.4, [114.9 -125.9]) and Rounding (123.0 [117.5, 128.5]) for LD at L1. CONCLUSIONS: Findings support the use of DMEs and TTEs for the targeted activation of EAO, RA and LD, particularly during DMEHip and Rounding where the greatest increases in muscle activity were observed.