Associative conditioning with leg cycling and inspiratory resistance enhances the early exercise ventilatory response in humans.

Repeated trials of hypercapnic exercise [deltaPET CO2 = 7 (1) mmHg] augment the increase in inspired minute ventilation and tidal volume (V(T)) in the early phase of subsequent trials of unencumbered exercise alone. The increase in V(T) in the first 20 s of exercise was correlated to the increase in V(T) evoked during hypercapnic exercise trials, suggesting that the evoked increase in V(T) during conditioning may be a factor in mediating associative conditioning. To test this hypothesis, inspiratory resistive loading (IRL) was employed to evoke an increase in V(T) [deltaV(T) = 0.4 (0.1) I(BTPS)] during conditioning exercise trials [IRL + EX; deltaP(ET)CO2 = 2 (l) mmHg]. IRL + EX associative conditioning elicited a significant augmentation of the early minute ventilation (+46%) and V(T) (+100%) responses to subsequent unencumbered exercise. The latter was correlated to the evoked increase in V(T) during associative conditioning with IRL + EX. The results support the hypothesis that an evoked increase in V(T) during associative conditioning could be a factor in eliciting long-term modulation of minute ventilation in subsequent unencumbered exercise. The results further indicated that the modulation of ventilation early in exercise is not due to sensitisation to repeated trials of either IRL or exercise alone. Associative conditioning may shape the ventilatory response to exercise through a process of motor learning. Data are presented as mean (SEM) unless otherwise stated.