Volitional hyperventilation during ramp exercise to exhaustion.
The purpose of this study was to determine whether volitional hyperventilation at 20 L x min(-1) above normal exercise values affected exercise duration while performing ramp exercise to exhaustion. Nine healthy subjects performed a ramp exercise test to exhaustion. On a subsequent test they hyperventilated, with the aid of visual and audio feedback, at 20 L x min(-1) greater than their initial test. Ramp exercise time to exhaustion was substantially reduced from 771.6 +/- 85.2 s to 726.6 +/- 86.6 s (p < 0.002) with the additional hyperventilation. Subjects underwent 2 more ramp exercise tests and performed a 5 s maximum voluntary ventilation or a forced vital capacity test at work rates corresponding to rest, below lactate threshold (LT), above LT, immediately after exercise, and 3 min recovery. Generally, the flow rates were not affected by exercise below LT and were enhanced during above-LT exercise, exhaustion, and recovery. This indicated a change in pulmonary function that is dependent on exercise intensity. In spite of this increased ability to generate high flow rates, exercise performance was diminished when respiratory muscle work was increased volitionally by 20 L x min(-1), indicating a strong coupling between respiratory muscle work and fatigue during ramp exercise in normal subjects.