Hyperpnea training attenuates peripheral chemosensitivity and improves cycling endurance

Well-trained endurance athletes frequently have a lower peripheral chemoreceptor (pR(c)) sensitivity and a lower minute ventilation ((V) over dot E) during exercise compared to untrained individuals. We speculated that the decreased pR(c) response may be specifically associated with repeated exposure to the high rates of ventilation occurring during exercise training. We therefore examined the effect of respiratory muscle training (RMT; 20x30 min sessions of voluntary normocapnic hyperpnea) on the pRc sensitivity during exercise and on cycling performance. RMT was chosen to achieve a high (V) over dot E, similar to that of heavy exercise, while avoiding the other accompanying effects of whole body exercise. 20 trained male cyclists were randomized into RMT (N=10) or control (N=10) groups. Subjects' pR(c) response was assessed by a modified Dejours O-2 test (10-12 breaths of 100% O-2, repeated 4-6 times) during cycling exercise at 40% of the maximal work capacity ((W) over dot (max)). Cycling performance was measured during a cycling test to exhaustion (85% (W) over dot (max)). The RMT group exhibited a significantly reduced pR(c) sensitivity (mean +/- S.D.) compared to the control group (-5.8 +/- 6.0% versus 0.1 +/- 4.6%, P<0.5). Cycling endurance improved significantly after RMT in comparison to the control group (+3.26 +/- 4.98 versus -1.46 +/- 3.67 min, P<0.05). However, these changes in pR(c) response were not significantly correlated with exercise ventilation or cycling endurance time. We conclude that the high levels of ventilation achieved during exercise, as simulated by RMT in this study, appear to be accompanied by a reduction in pR(c) sensitivity; however, the role of the pR(c) in the control of ventilation during exercise seems to be minor.