Moderate Hypoxic Exercise Training Diminishes Suppression of Cardiac Performance by Severe Hypoxic Exposure

Abstract

Extremely hypoxic exposure reduces individual's exercise performance by decreased myocardial contractility and subsequently lowered cardiac output. This investigation explored how moderate hypoxic exercise training influences cardiac performance suppressed by severe hypoxic exposure. Twelve sedentary males were trained on a bicycle ergometer at about 60%VO2max under 15% O2 air condition for 20 minutes per day, 5 days per week for 4 weeks. Cardiac output was measured using a new, noninvasive, bio‐reactance technology. Our results showed that 4 weeks of hypoxic exercise training improved maximal aerobic capacity of subjects. Acute exposure to 12%O2 decreased stroke volume and increased heart rate at performed 60%VO2max exercise. However, the suppressive effect in exercising cardiac contractility by severe hypoxic exposure was ameliorated following the hypoxic exercise training. Simultaneously, this training also decreased exercising heart rate, total peripheral resistance and mean arterial pressure under the 12% O2 air condition. Therefore, we conclude that moderate hypoxic exercise training increases the tolerance to severe hypoxia‐limited cardiac performance during exercise.