Key result
Single-step tests elicited faster phase II time constants for oxygen uptake (45 vs 53 s, p=0.017) and minute ventilation compared with cycle ergometry in patients with COPD.
Why the study?
Eccentric muscle contractions during stepping may speed cardioventilatory and metabolic adjustments toward a steady state compared to cycling, which could benefit exercise-limited patients needing shorter tests.
Do step tests elicit faster oxygen uptake and ventilatory kinetics compared with cycle ergometry in patients with COPD during moderate-intensity exercise?
Do step tests elicit faster oxygen uptake and ventilatory kinetics compared with cycle ergometry in patients with COPD during moderate-intensity exercise?
Absolute Event Rate: 45% vs 53%
p-value: p=0.017
Step tests elicit faster oxygen uptake and ventilatory kinetics compared with cycle ergometry in COPD patients, suggesting they may be a more efficient modality for evaluating aerobic performance.
Step tests are a stressful and feasible cost-effective modality to evaluate aerobic performance. However, 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, as well as higher heart rate/cardiac output adjustments to the same metabolic demand. Moreover, shorter tests are ideal for exercise-limited subjects. Nine subjects with chronic obstructive pulmonary disease were invited to participate in comprehensive lung function tests and constant work tests performed on different days 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 ± 18 s vs 53 ± 17 s, p = 0.017) and minute ventilation (61 ± 13 s vs 74 ± 17 s, p = 0.027) were observed in the 6-min step tests compared with cycle ergometry, respectively. Despite an absence of heart rate time constant difference (43 ± 20 s vs 69 ± 46 s, p = 0.167), there was a significantly faster rate constant toward a steady state for heart rate (p = 0.02). In addition, 4-min compared with 6-min analysis presented similar results (p > 0.05), providing an appropriate steady-state. We conclude that step tests might elicit faster time constants compared with cycle ergometry, at the same average metabolic level, and 4-min analysis has similar mean errors compared with 6-min analysis within an acceptable range. New studies, comprising mechanisms and detailed physiological backgrounds, are necessary.
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Müller et al. (2019) studied Chronic obstructive pulmonary disease (COPD) (n=9). Single-step tests vs. Cycle ergometry was evaluated on Phase II time constants for oxygen uptake (p=0.017). Single-step tests elicited faster phase II time constants for oxygen uptake (45 vs 53 s, p=0.017) and minute ventilation compared with cycle ergometry in patients with COPD.
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