Intermittent normobaric hypoxic exposures at rest: effects on performance in normoxia and hypoxia.

INTRODUCTION It has been speculated that short (-1-h) exposures to intermittent normobaric hypoxia at rest can enhance subsequent exercise performance. Thus, the present study investigated the effect of daily resting intermittent hypoxic exposures (IHE) on peak aerobic capacity and performance under both normoxic and hypoxic conditions. METHODS Eighteen subjects were equally assigned to either a control (CON) or IHE group and performed a 4-wk moderate intensity cycling exercise training (1 h x d(-1), 5 d x wk(-1)). The IHE group additionally performed IHE (60 min) prior to exercise training. IHE consisted of seven cycles alternating between breathing a hypoxic gas mixture (5 min; F1O2 = 0.12-0.09) and room air (3 min; F1O2 = 0.21). Normoxic and hypoxic peak aerobic capacity (VO2(peak)) and endurance performance were evaluated before (PRE), during (MID), upon completion (POST), and 10 d after (AFTER) the training period. RESULTS Similar improvements were observed in normoxic VO2(peak) tests in both groups [IHE: delta(POST-PRE) = +10%; CON: delta(POST-PRE) = + 14%], with no changes in the hypoxic condition. Both groups increased performance time in the normoxic constant power test only [IHE: delta(POST-PRE) = +108%; CON: delta(POST-PRE) = +114%], whereas only the IHE group retained this improvement in the AFTER test. Higher levels of minute ventilation were noted in the IHE compared to the CON group at the POST and AFTER tests. CONCLUSION Based on the results of this study, the IHE does not seem to be beneficial for normoxic and hypoxic performance enhancement.