Cardiovascular response to hypoxia after endurance training at altitude and sea level and after detraining

The pur pose of this study was to elucidate 1) the effects of endurance exercise training during hypoxia or normoxia and of detraining on ventilatory and cardiovascular responses to progressive isocapnic hypoxia and 2) whether the change in the cardiovascular response to hypoxia is correlated to changes in the hypoxic ventilatory response (HVR) after training and detraining. Seven men (altitude group) performed endurance training using a cycle ergometer in a hypobaric chamber of simulated 4,500 m, whereas the other seven men (sea-level group) trained at sea level (K. Katayama, Y. Sate, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura. J. Appl. Physiol. 86: 1805-1811, 1999). The HVR, systolic and diastolic blood pressure responses (Delta SBP/Delta Sa(O2), Delta DBP/Delta Sa(O2)), and heart rate response (Delta HR/Delta Sa(O2) Sa(O2) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. Delta SBP/Delta Sa(O2) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed Delta SBP/Delta Sa(O2) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the Delta DBP/Delta Sa(O2) and Delta HR/Delta Sa(O2) throughout the experimental period. The changes in Delta SBP/Delta Sa(O2)? after training and detraining were significantly correlated with those in HVR. These results suggest that Delta SBP/Delta Sa(O2), to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but Delta DBP/Delta Sa(O2) and Delta HR/Sa(O2) are not. It also suggests that there is an interaction between the changes in Delta SBP/Delta Sa(O2) and HVR after endurance training or detraining.