Ventilation and Heart‐Rate Responses to Ramp‐Function Changes in Work Load

Publisher Website
Google Scholar
Abstract
Ventilation and heart‐rate responses were recorded continuously and simultaneously during supine leg exercise in six male athletes using positive and negative ramp changes in work load, starting or ending at the fixed minimal and maximal load levels of 250 and 1050 kpm/min. The parameter Tl (“lag time”) is used to define the time by which a ramp response in its stationary condition lags behind the input signal. Three different positive and negative ramp slopes were used, the durations of the ramps being 7, 5 and 3 min (= 114, 160 and 267 kpm min‐2). For ventilation Tl was found to be largely independent of the slope of the ramp and averaged 66 sec. For heart rate, on the other hand, the mean values for Tl obtained from the responses to corresponding positive and negative slopes were 84.0, 56.4 and 38.8 sec, respectively, and proved to be significantly shorter the steeper the ramp. Granted second‐order dynamics of the heart‐rate response to work load, the slope‐dependence of Tl suggests that the share of the shorter time constant becomes larger the steeper the ramp. For the responses of the heart rate to the two steepest ramps, Tl was negatively correlated to work capacity (r= ‐0.968 and ‐0.824).