Effects of Exercise Training and Intermittent Hypoxia on Ventilatory Chemoreflex Sensitivity in Humans

Exercise training exerts profound beneficial effects on cardiovascular function, reduces cardiovascular risk and improves outcome in patients who suffered cardiovascular events. The underlying mechanisms are incompletely understood but altered autonomic neural regulation may be involved. We recently found that short-term intermittent hypoxia induced by 30 serial hypoxic breathholds raises sympathetic activity and blood pressure, and enhances chemoreflex sensitivity to hypoxia. Because chemoreflex activity is a marker of cardiovascular risk, here we tested the hypothesis that chemoreflex sensitization induced by intermittent hypoxia is attenuated by exercise conditioning. Eleven young healthy subjects (5M/6F, age 25±1 yrs, body-mass-index 24±1 kg/m2) were studied before and following 2 months of endurance training (peak VO2 pre vs. post: 36.4±1.4 vs. 40.1±1.7 ml/min/kg; P<0.05). Chemoreflex sensitivity was determined by the ventilatory responses to a series of 2-8 breaths of N2 inhalation before and after ...