Influence of hypoxia on coordination between breathing and cycling rhythms in women.

To investigate interactions between neural (movement) and chemical (hypoxia) respiratory drives during exercise, we analyzed coordination between breathing and cycling rhythms in normoxia (N) and hypoxia (H, 14.5% O(2)). Twenty women [28 (1) years old] cycled for 6 min at three workloads (55%, 75%, and 95% peak oxygen consumption, VO(2peak); WL1, WL2, and WL3) in N and H. Leg movements, respiratory parameters, peripheral oxygen saturation, and heart rate were continuously recorded. The degree of coordination (%COORD) was quantified as the percentage of breaths starting during the same phase of leg movement. Ventilatory response to isocapnic hypoxia (VRH) was assessed at rest during an exposure to an end-tidal PO(2) of 50 mmHg. There were no differences in %COORD between N and H at any of the three workloads, but %COORD increased significantly from WL1 to WL3 in H. There was no correlation between VRH and %COORD. In conclusion, chemical and neural respiratory drives did not competitively interact: coordination between breathing and cycling rhythms was not reduced during H and did not depend on individual VRH.