Supplementary Material for: Effect of eccentric cycling on oxygen uptake and hemodynamics in patients with chronic obstructive pulmonary disease - a randomized controlled crossover trial

Background: Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide and contributes significantly to reduced quality of life due to symptoms such as dyspnea and exercise intolerance. Eccentric cycling exercise (ECC) has shown potential as an alternative to conventional concentric cycling exercise (CON) in cardiopulmonary disease, including COPD, as it has a lower metabolic demand and potentially allows for higher exercise intensity with less perceived exertion. Research Question: How do the ventilatory and circulatory responses of COPD patients differ between ECC and CON at identical submaximal workloads? Methods: In a randomized-controlled crossover trial, 17 COPD patients (6 female, mean±SD age 67±7years) completed identical submaximal stepwise incremental cycling tests using ECC and CON, each step increasing by 10W. The main outcome was oxygen uptake (V̇O2). Additional outcomes were breath-by-breath ergospirometric measurements including minute ventilation (V̇E) and hemodynamics by echocardiography at each step. Results: At a mean end-exercise intensity of 41.3±3.5W at, ECC lowered V̇O2 by -122mL/min (-25%, 95%CI -213 to -47, P=0.005) and V̇E by -5.7L/min (-29%, 95%CI -10.0 to -1.6, P=0.012) compared to CON. Perceived dyspnea and leg fatigue did not differ. A trend towards reduced strain on the right ventricle was observed in ECC (37±13mmHg ECC vs. 48±7mmHg CON), but this was not significant (P=0.063). No adverse events occurred. Conclusion: ECC allowed COPD patients to exercise at the same workload but with a lower metabolic and ventilatory demand compared to CON, suggesting it has the potential to further improve exercise capacity in pulmonary rehabilitation.