Electromyographic activity of the palatinus and palatopharyngeus muscles in exercising horses.
Authors: Holcombe S J, Derksen F J, Robinson N E
Journal: Equine veterinary journal
Summary
Dorsal displacement of the soft palate (DDSP) represents a significant performance-limiting condition in horses, yet the precise mechanisms underlying palatal dysfunction remain incompletely understood. Holcombe and colleagues employed fine-wire electromyography to characterise the activity patterns of the palatinus and palatopharyngeus muscles during incremental treadmill exercise, establishing whether these muscles demonstrate intensity-dependent respiratory activity. Both muscles exhibited synchronous expiratory firing that increased substantially with exercise intensity—the palatinus showing a 390% increase and the palatopharyngeus a 198% increase as speed escalated from 6 to 12 m/s—suggesting an active stabilising role rather than passive mechanics. These findings reframe these muscles as important respiratory stabilisers that actively maintain soft palate position during high-speed exercise, a mechanism particularly critical given that horses are obligate nasal breathers. For equine practitioners involved in diagnosing and managing upper airway dysfunction, this work provides mechanistic insight into how muscular fatigue, coordination deficits or neuromuscular dysfunction of the palatinal muscles could precipitate DDSP, potentially informing targeted rehabilitation strategies and identifying novel assessment approaches beyond endoscopic observation alone.
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Practical Takeaways
- •Soft palate dysfunction during exercise may relate to inadequate function of the palatinus and palatopharyngeus muscles, which are critical for stabilizing the airway during high-intensity work
- •Understanding the respiratory role of these muscles provides insight into the mechanisms of dorsal displacement of the soft palate and may inform therapeutic approaches
- •Exercise-induced upper airway obstruction in horses may benefit from interventions targeting palatine muscle function and coordination
Key Findings
- •Palatinus and palatopharyngeus muscles display synchronous expiratory activity that increases significantly with exercise intensity
- •Palatinus muscle expiratory activity increased 390 ± 98% from 6 to 12 m/s treadmill speed
- •Palatopharyngeus muscle expiratory activity increased 198 ± 30% from 6 to 12 m/s treadmill speed
- •These muscles likely function to stabilize soft palate position during intense exercise in obligate nasal breathers