Electromyographic activity of the palatinus and palatopharyngeus muscles in exercising horses.

REASONS FOR PERFORMING STUDY

Determining the respiratory related activity of the palatinus and palatopharyngeus muscles in exercising horses is relevant because dysfunction of these muscles has been implicated in the pathogenesis of dorsal displacement of the soft palate.

OBJECTIVE

To determine if the palatinus and palatopharyngeus muscles have respiratory activity that increases with intensity in exercising horses.

METHODS

Electromyographic activity was measured in the palatinus and palatopharyngeus muscles using bipolar fine-wire electrodes while the horses completed an incremental exercise treadmill protocol.

RESULTS

Both muscles displayed synchronous expiratory activity that increased significantly (P < 0.05) with exercise intensity. Phasic expiratory activity of the palatinus increased 390 +/- 98%, whereas phasic expiratory activity of the palatopharyngeus increased by 198 +/- 30% as the treadmill speed increased from 6 to 12 m/s.

CONCLUSIONS

The palatinus and palatopharyngeus muscles may be important respiratory muscles, functioning to stabilise the position of the soft palate during intense exercise.

CLINICAL RELEVANCE

The predominant expiratory activity of these muscles may be associated with specific muscle function related to exercise or distinct upper airway phenomena of an obligate nasal breather, such as the horse.