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

Abstract

The purpose 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. Sato, 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 (DeltaSBP/DeltaSa(O(2)), DeltaDBP/DeltaSa(O(2))), and heart rate response (DeltaHR/DeltaSa(O(2)); Sa(O(2)) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. DeltaSBP/DeltaSa(O(2)) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed DeltaSBP/DeltaSa(O(2)) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) throughout the experimental period. The changes in DeltaSBP/DeltaSa(O(2)) after training and detraining were significantly correlated with those in HVR. These results suggest that DeltaSBP/DeltaSa(O(2)) to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) are not. It also suggests that there is an interaction between the changes in DeltaSBP/DeltaSa(O(2)) and HVR after endurance training or detraining.

Intermittent hypoxia increases ventilation and SaO2 during hypoxic exercise and hypoxic chemosensitivity

“…1), respectively (resting ventilatory chemosensitivity tests were always made before the exercise test). The same hypobaric chamber used in our previous studies (19)(20)(21) was utilized for the exercise test and for intermittent hypoxic exposure. The barometric pressure in the chamber was lowered to 432 Torr over a 30-min period and then held at that level for the next hour.…”

“…Resting HVR was determined by using a progressive isocapnic hypoxic test (54). A rebreathing system similar to that in our previous studies (19)(20)(21) was used. Tidal volume (VT), inspired minute ventilation (V I), end-tidal CO 2 and O 2 fraction (FET CO 2 and FET O 2 , respectively), and Sa O 2 were measured continuously during rebreathing.…”

“…Similar to chronic exposure to hypoxia or a sojourn at high altitude, intermittent exposure to hypoxia with or without endurance exercise training using a hypobaric chamber has been utilized for preacclimatization before climbing to high altitude (9,43,44). When combining intermittent exposure to hypoxia with endurance exercise training, increases in HVR have been demonstrated in some (9,21,27) but not other (19) studies. However, there are few reports that have shown the changes in cardiorespiratory acclimatization during intermittent hypoxic exposure without endurance training.…”

Military Applications of Hypoxic Training for High-Altitude Operations

“…Several studies by Katayama (20)(21)(22) have shown that when the subjects exercise trained for 0.5 h of an approximately 1.5 h of daily IHE, they did not increase their hypoxic ventilatory response, a measure of ventilatory acclimatization. Furthermore, Katayama has shown that exercise training at sea level depresses the hypoxic ventilatory response (20,21).…”

Relationship Between Arterial Oxygen Saturation and Hematocrit, and Effect of Slow Deep Breathing on Oxygen Saturation in Himalayan High Altitude Populations

“…3 Therefore, they show adaptive phenotypic features with respect to physiological parameters such as oxygen saturation, haemoglobin concentration, hypoxic ventilatory rate and blood pressure. [4][5][6][7][8] Studies performed in Sherpas living permanently at high altitude suggest they are genetically better adapted to altitude than populations residing at the same altitude in Andes and highlands of Peru. 9,10 Though samples among highlanders of different part of the world are compared to Himalayan high altitude natives, the comparison among native population at two different altitudes of Himalayan population is performed in this study.…”