Some Metabolic Responses to Reduced Breathing Frequency During Constant Load Exercise

Abstract

Introduction: Hypoxia has not been detected only during altitude exercise but also during specific conditions during exercise at sea level, such exercise with reduced breathing frequency (RBF). Training with RBF is often referred to as “hypoxic training”. It was thought that, by limiting inspired air, the reduction of oxygen available for muscular work would result and therefore cause muscle hypoxia, similar to that experienced at altitude. Therefore, the aim of this study was to examine the possible effect of RBF on ventilatory parameters, blood gases, oxygen saturation and some metabolic responses during the constant load exercise to exhaustion. Methods: Eight healthy male subjects performed an incremental cycling test with RBF at 10 breaths per minute. A constant load test with RBF (B10) was then performed to exhaustion at the peak power output obtained during the incremental test. Finally, the subjects repeated the constant load test with the spontaneous breathing (SB) using the same protocol as B10. Results: RBF during the constant load exercise resulted in a profound reduction in V E , when compared to the spontaneous breathing, despite significantly increases in V T . Consequently, there were significantly lower SO 2 and PO 2 and higher PCO 2 during B10 than during SB. However, there were no significant differences in VO 2 and [LA ] between different breathing conditions. Conclusions: Therefore, it may be concluded that RBF during the constant load exercise induced marked hypoventilation and consequently hypoxia and hypercapnia. However, it seemed that this degree of the breathing reduction did not influence on aerobic metabolism due to unchanged VO 2 and [LA