Ventilatory response of goats to treadmill exercise: Grade effects

The steady-state ventilatory responses of 7 goats to treadmill exercise were studied at several different combinations of speed (0–7.7 km per hr) and grade (0–15%). Carbon dioxide production (V̇ CO 2 ) increased as much as 6 times the resting value. The goats responded to exercise with hyperventilation and respiratory alkalosis, which was proportional to V̇ CO 2 . The increased ventilation was due chiefly to increases in breathing frequency (f). When responses to increasing speed at 0% grade were compared to those at 15% grade, there were no differences in expired minute ventilation or Pa CO 2 . There were differences in ventilatory pattern V̇ CO 2 , f was higher and tidal volume (V T) lower at 0% grade than at 15% grade. We conclude that ventilatory pattern (at a given V̇ CO 2 ) is influenced by the grade used during treadmill exercise and therefore stimuli other than V̇ CO 2 alone must be involved in the generation of ventilatory pattern during treadmill exercise.