HYPEROXIC TRAINING INCREASES WORK CAPACITY AFTER MAXIMAL TRAINING AT MODERATE ALTITUDE

High-intensity training may be difficult to sustain due to limitations in systemic oxygen transport, particularly at high altitudes. The pur pose of this study was to examine the effects of a high-intensity trai ning protocol using hyperoxic gas breathing in athletes ''maximally tr ained'' at an altitude of 1,600 m. Five subjects underwent progressive cycle training until they reached a plateau of aerobic capacity, maxi mal workload, and endurance time at 85 percent maximal workload. Signi ficant decreases (2 to 6 percent) in arterial oxygen saturation were f ound after the 85 percent maximal workload tests. Training intensity w as then increased to 95 percent maximal workload while the subjects br eathed a gas mixture containing at least 70 percent oxygen. After 6 we eks of hyperoxic training, exercise parameters were compared with the plateau values obtained during the baseline training period. Total tim e during maximal cycle testing increased from 19.1 to 19.6 min (p = 0. 0 15), heart rate at 85 percent maximal workload decreased from 168 to 163 bpm (p = 0.047), and endurance time at 85 percent maximal workloa d increased from 6.2 to 8.2 min (p = 0.0 12). There was a trend toward improvement of maximal workload. We conclude that hyperoxic training increases work capacity after attainment of ''maximal training'' at mo derate altitude.