Effects of exercise modality on patterns of ventilation and respiratory timing

Ventilatory patterns and respiratory timing were measured in 14 subjects during cycling (CYC) and treadmill exercise (TM) at similar leg frequencies (fLEG) to determine if mode of exercise affects patterns of ventilation and respiratory timing. Measurements of breathing frequency (fR), tidal volume (VT), expired ventilation (VE), and inspiratory (TI) and expiratory (TE) time were obtained at fLEG of 50, 70, and 90 rev.min-1 (rpm) for CYC and at similar incremental fLEG (strides.min-1; spm) during TM achieved by increasing belt speed at 0% grade. CYC exercise intensity was approximately 50% VO2,max at all fLEG, whereas VO2 increased progressively with TM. fR increased significantly (P < 0.001) with increasing fLEG of TM (20.5 +/- 4.6, 25.4 +/- 5.8, and 36.3 +/- 7.6 breaths.min-1; mean +/- SD), but during CYC fR changed significantly (P < 0.05) only between fLEG of 70 and 90 rpm (25.0 +/- 5.9 vs 28.5 +/- 6.9 breaths.min-1). Both average breath TI and TE obtained by grouping into incremental ranges of fR decreased significantly (P < 0.05) with increasing fR up to 36 breaths.min-1 and the relationships of TI and TE to fR, TI to TE, and central inspiratory drive (VT/TI) to VE were the same for CYC and TM. Group average fR and fLEG were synchronized during TM, but individual subjects did not exhibit a high degree of entrainment. This study shows respiratory timing patterns to be independent of mode of exercise over the range of fR observed when describing patterns by grouping into incremental ranges of fR.