Ventilatory chemosensitive adaptations to intermittent hypoxic exposure with endurance training and detraining

1 Research Center of Health, Physical Fitness and Sports and 2 Space Medicine Research Center, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan The present study was performed to clarify the effects of intermittent exposure to an altitude of 4,500 m with endurance training and detraining on ventilatory chemosensitivity. Seven subjects (sea-level group) trained at sea level at 70% maximal oxygen uptake ( O 2 max ) for 30 min/day, 5 days/wk for 2 wk, whereas the other seven subjects (altitude group) trained at the same relative intensity (70% altitude O 2 max ) in a hypobaric chamber. O 2 max , hypoxic ventilatory response (HVR), and hypercapnic ventilatory response, as an index of central hypercapnic chemosensitivity (HCVR) and as an index of peripheral chemosensitivity (HCVR SB ), were measured. In both groups O 2 max increased significantly after training, and a significant loss of O 2 max occurred during 2 wk of detraining. HVR tended to increase in the altitude group but not significantly, whereas it decreased significantly in the sea-level group after training. HCVR and HCVR SB did not change in each group. After detraining, HVR returned to the pretraining level in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training and detraining than that to hypercapnia. hypoxic ventilatory chemosensitivity; hypercapnic ventilatory chemosensitivity; altitude training