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 (VCO2) increased as much as 6 times the resting value. The goats responded to exercise with hyperventilation and respiratory alkalosis, which was proportional to VCO2. 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 PaCO2. There were differences in ventilatory pattern. At a given VCO2, f was higher and tidal volume (VT) lower at 0% grade than at 15% grade. We conclude that ventilatory pattern (at a given VCO2) is influenced by the grade used during treadmill exercise and therefore stimuli other than VCO2 alone must be involved in the generation of ventilatory pattern during treadmill exercise.