Training-induced increases in sea level VO2max and endurance are not enhanced by acute hypobaric exposure

The present study used untrained subjects to examine the effect of acute hypobaric exposure during endurance training on subsequent exercise performance at sea level. Two groups, each of nine subjects, completed 5 weeks of endurance training [cycle ergometer exercise for 45 min, three times per week at a heart rate corresponding to 70% of that achieved at the maximal O-2 consumption ((V) over dotO(2max)) either at sea level or at high altitude] in a hypobaric chamber, under either normobaric [sea level, SL; 750 mmHg (100 kPa) approximate to 90 m] or hypobaric [altitude, ALT; 554 mmHg (73.4 kPa) approximate to 2500 m] conditions and the changes in SL (V) over dotO(2max), SL endurance time and peak blood lactate during the endurance test compared. While each group showed increases in both SL (V) over dotO(2max), (approximate to 12%) and SL endurance time (approximate to 71%), there were no significant differences between the groups [SL (V) over dotO(2max), mean (SE)- SL group: pre-training = 42.4 (3.5), post-training = 46.1 (3.5)ml . kg(-1) . min(-1) P < 0.005; ALT group: pre-training = 40.8 (2.6), post-training = 47.2 (3.4) ml . kg(-1) . min(-1), P < 0.01; SL endurance time - SL group: pre-training 7.1 (1.5), post-training 11.8 (2.9) min, P < 0.01; ALT group: pre-training = 7.5 (0.6), post-training = 13.3 (1.4) min, P < 0.001]. Peak blood lactate during the endurance test was not altered by either training regimen. It is concluded that acute exposure of untrained subjects to hypobaric hypoxia during endurance training has no synergistic effect on the degree of improvement in either SL (V) over dotO(2max) or endurance time.