Neuro-mechanical and chemical influences on locomotor respiratory coupling in humans.

Mechanisms of coordination between breathing and movement during dynamic exercise are still a matter of debate. This study aimed to examine the degree of coordination between breathing and arm propulsion patterns and to compare the relative contribution of neuro-mechanical and chemical factors. Thirteen trained cross-country skiers performed constant submaximal 6-min roller skiing exercises on a motorized driven treadmill in two different poling techniques (V2A and V2 skating techniques) at two exercise intensity levels corresponding to the first and second ventilatory thresholds. The timing of arm propulsion movements in V2A and V2 techniques was considered as a mechanical/neural influence on breathing whereas exercise intensity represented the metabolic demand to breathing. The degree of coordination, expressed as the percentage of breaths presenting a constant phase interval (time between an arbitrarily chosen point of the arm movement cycle and the onset of expiration) was significantly higher in V2A than V2 (P<0.05) while exercise intensity had no effect on the degree of coordination. We concluded that locomotor-respiratory coupling occurs in cross-country skiing as simulated by roller skiing because of strong influences from neuro-mechanical factors.

Paced breathing in roller-ski skating: effects on metabolic rate and poling forces.

PURPOSE: This study aimed (1) to determine whether paced breathing (synchronization of the expiration phase with poling time) would reduce the metabolic rate and dictate a lower rate of perceived exertion (RPE) than does spontaneous breathing and (2) to analyze the effects of paced breathing on poling forces and stride-mechanics organization during roller-ski skating exercises. METHODS: Thirteen well-trained cross-country skiers performed 8 submaximal roller-skiing exercises on a motorized driven treadmill with 4 modes of skiing (2 skating techniques, V2 and V2A, at 2 exercise intensities) by using 2 patterns of breathing (unconscious vs conscious). Poling forces and stride-mechanics organization were measured with a transducer mounted in ski poles. Oxygen uptake (VO2) was continuously collected. After each bout of exercise RPE was assessed by the subject. RESULTS: No difference was observed for VO2 between spontaneous and paced breathing conditions, although RPE was lower with paced breathing (P < .05). Upper-limb cycle time and recovery time were significantly (P < .05) increased by paced breathing during V2A regardless of the exercise intensity, but no changes for poling time were observed. A slight trend of increased peak force with paced breathing was observed (P = .055). CONCLUSION: The lack of a marked effect of paced breathing on VO2 and some biomechanical variables could be explained by the extensive experience of our subjects in cross-country skiing.