Faster oxygen uptake, heart rate and ventilatory kinetics in Stepping compared to Cycle ergometry in COPD patients during moderate intensity exercise

Although step tests are a stressful and feasible cost-effective modality to evaluate aerobic performance, the eccentric in addition to concentric muscle contractions of the legs on stepping emerge as a potential speeding factor for cardioventilatory and metabolic adjustments towards a steady-state, since eccentric contractions would prompt an earlier and stronger mechanoreceptor activation, besides higher heart rate/cardiac output adjustments to the same metabolic demand. Moreover, shorter tests are ideal for exercise-limited subjects. Nine COPD subjects were invited to participate in comprehensive lung function tests and replicated-on different days-constant work tests at a 90% gas exchange threshold for 6-min, in single-step tests or cycle ergometry. After careful monoexponential regression modelling, statistically relevant faster phase II time constants for oxygen uptake (45±18s vs 53±17s, p=0.017) and minute-ventilation (61±13s vs 74±17s, p=0.027) were observed in the 6-min step tests compared to cycl...