- The current study's experiments tested the hypothesis that limb movement frequency is a significant determinant of exercise hyperpnoea. To this end, 19 healthy participants walked on a treadmill, where work was varied sinusiodally by alterations in either treadmill speed or grade. Measured responses were fitted with sine waves to determine their amplitudes and phase angles. Walking pace amplitude was greater during speed tests than grade tests, and phase lag relative to the treadmill smaller, as expected. Ventilation, carbon dioxide production, and oxygen uptake amplitudes were higher during speed tests than grade tests. Further, phase angle lags relative to the treadmill for these measures were shorter during speed tests than grade tests. We concluded that these findings demonstrate the presence of changes in breathing during exercise that can be attributed to changes in limb movement frequency.