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

Overview

• This study investigates how specific dynamic mobilization exercises (DMEs) and therapeutic trunk exercises (TTEs) affect muscle activity in the superficial back (epaxial) and abdominal (hypaxial) muscles of horses.
• Using surface electromyography (sEMG), it compares activation levels of key trunk muscles during different exercises to determine their effectiveness in targeted muscle engagement.

Background

• Equine back rehabilitation often involves exercises aimed at improving mobility and strengthening trunk muscles, including:
  • Dynamic mobilization exercises (DMEs) such as DME to the chest (DMEChest) and to the hip (DMEHip).
  • Therapeutic trunk exercises (TTEs) like pelvic rounding (Rounding) and lateral tail pulls (LatTail).
• Despite their common use, there is limited empirical evidence on how these exercises selectively activate specific trunk muscles.

Research Objective

• To quantitatively measure and compare muscle activity in the superficial epaxial and hypaxial muscles during selected DMEs and TTEs using sEMG.
• The hypothesis predicted increased muscle activity during all exercises with particular expectations:
  • External abdominal oblique (EAO) muscle would show increased activity during lateral bending exercises (DMEHip, LatTail).
  • Longissimus dorsi (LD) and rectus abdominus (RA) would have elevated activity during spinal flexion exercises (DMEChest, Rounding).

Methods

• Seven horses performed four exercises: DMEChest, DMEHip, LatTail, and Rounding.
• Surface electromyography (sEMG) sensors were placed bilaterally on:
  • External abdominal oblique (EAO)
  • Rectus abdominus (RA)
  • Longissimus dorsi (LD) at thoracic (T14) and lumbar (L1) spinal levels
• EMG data processing included:
  • Band-pass filtering between 40-450 Hz to remove noise.
  • Full-wave rectification and amplitude normalization to standardize data across horses.
  • Calculation of the average rectified value (ARV) as a measure of muscle activity.
• Data were grouped by direction of movement — ipsilateral (same side as muscle) and contralateral (opposite side) — for exercises involving lateral bending (DMEHip and LatTail).
• Linear mixed models were used to analyze the relationship between exercise type and muscle activation, accounting for variability between horses.

Results

• Ipsilateral DMEHip produced the highest ARV percentages for all three muscles compared to other exercises:
  • External abdominal oblique (EAO): 207.0% (95% CI 178.7, 235.4)
  • Rectus abdominus (RA): 172.1% (140.8, 203.4)
  • Longissimus dorsi at T14: 136.8% (126.4, 147.3)
• For the longissimus dorsi at lumbar level L1:
  • Both ipsilateral DMEHip (120.4%, 95% CI 114.9, 125.9) and pelvic Rounding (123.0%, 117.5, 128.5) significantly increased muscle activity.
• These values indicate that both dynamic mobilization, especially hip-focused exercises, and therapeutic trunk exercises effectively activate key trunk muscles.

Conclusions and Implications

• This study provides evidence that certain DMEs and TTEs selectively increase activation in targeted trunk muscles in horses.
• Specifically, DMEHip strongly activates the external abdominal oblique, rectus abdominus, and longissimus dorsi muscles, supporting its use for strengthening these areas.
• Pelvic rounding also effectively activates the lumbar longissimus dorsi, suggesting its importance in spinal flexion rehabilitation protocols.
• The findings support incorporating these exercises into equine rehabilitation programs for targeted muscle conditioning and potential improvement in back health and mobility.