EFFECTS OF INTERMITTENT HYPOXIC EXPOSURE WITH TRAINING ON HYPOXIC AND HYPERCAPNIC VENTILATORY RESPONSES

Abstract

1085 The purpose of this study was to assess the effects of combined intermittent exposure to high altitude with endurance exercise training for short periods on hypoxic and hypercapnic ventilatory response (HVR and HCVR) or maximum oxygen uptake (˙VO2max). In a hypobaric chamber at a simulated high altitude of 4,500 m (432 torr), seven subjects (trained group) performed exercise training for 6 consecutive days (30 min · day-1), while six subjects (untrained group) stayed at rest during the same period (2h · day-1). All subjects lived at sea level during the study except during hypoxic exposure for approximately 2hr · day-1. Resting hypoxic ventilatory response (▵ ˙VI/ ▵ SaO2) at sea level for each subject was measured using a progressive isocapnic hypoxic test. On the other hand, resting hypercapnic ventilatory response (▵ ˙VI/ ▵ PETCO2) was measured by the rebreathing method. HVR, as index of peripheral chemosensitivity to hypoxia, in untrained group was increased significantry(P<0.05) post intermittent exposure to hypoxia. Conversely, there was no significant increase in HVR in trained group post hypoxic exposure. HCVR in both groups was found no change. In trained group ˙VO2max increased significantly (P<0.05) post hypoxic exposure with endurance training. These results suggest that endurance exercise training in hypoxic situation plays a role of depressing the increment of hypoxic chemosensitivity, and that intermittent hypoxic exposure does not induce to increase in hypercapnic chemosensitivity.