The effects of treadmill inclination and speed on the activity of three trunk muscles in the trotting horse.
Authors: Robert C, Valette J P, Denoix J M
Journal: Equine veterinary journal
Summary
# Editorial Summary Robert and colleagues used surface electromyography to investigate how treadmill speed (3.5–6 m/s) and incline (0–6%) influenced the recruitment patterns of three key trunk stabilisers—the splenius, longissimus dorsi and rectus abdominis—during trotting in horses. Faster speeds caused all three muscles to activate and deactivate earlier in the stride cycle, with the longissimus dorsi showing prolonged activity and the rectus abdominis contracting for shorter periods; integrated EMG (a measure of overall muscle effort) increased linearly with speed for the latter two muscles but remained relatively stable for the splenius. Uphill work produced a distinctly different response, delaying muscle activation timing for the longissimus dorsi and rectus abdominis whilst significantly amplifying the integrated EMG output of all three muscles proportionally to gradient. For practitioners designing conditioning programmes, these findings suggest that incline work is a more effective stimulus for strengthening trunk musculature than speed alone, whilst speed changes primarily alter the temporal coordination of muscle recruitment without substantially loading the splenius; this objective data supports strategic use of slope-based training for horses requiring core stability development, particularly those with postural or performance-related issues.
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Practical Takeaways
- •Speed and slope have distinct effects on trunk muscle recruitment; slope produces greater overall muscle activation and should be used strategically in conditioning programmes to increase muscular demand
- •Higher speeds shift trunk muscle activity earlier in the stride cycle, which may improve efficiency but requires adequate muscular conditioning to prevent fatigue
- •Treadmill inclination (slope) is a more effective tool than speed alone for progressively loading trunk stabilizer muscles during training
Key Findings
- •Increasing treadmill speed (3.5-6 m/s) causes earlier onset and offset of trunk muscle activity within the stride cycle across all three muscles studied
- •Longissimus dorsi activity duration increases with speed while rectus abdominis duration decreases; splenius duration remains unchanged
- •Integrated EMG of longissimus dorsi and rectus abdominis increases linearly with speed, while splenius activity is minimally affected by speed changes
- •Increasing treadmill slope (0-6%) causes significant progressive increases in integrated EMG activity of all three trunk muscles, with temporal changes in longissimus dorsi and rectus abdominis but not splenius