Cycle training intensity for patients with chronic obstructive pulmonary disease (COPD) is normally based on an incremental cycle test. Such tests are expensive and not readily available to clinicians. The six-minute walk test (6MWT) has been proposed as an alternative to an incremental cycle test for this purpose, based on the findings of previous research that the peak oxygen consumption (VO2peak) for the incremental cycle test and the 6MWT was equivalent in participants with COPD. A regression equation relating distance walked on the 6MWT and peak work rate (Wpeak) on the incremental cycle test has been described. The aim of this study is to measure the physiological responses to constant load cycle exercise performed at an intensity of 60% Wpeak determined from the 6MWT in participants with stable COPD.
This study is a prospective, repeated measures design. Thirty-five participants with stable COPD and mild to severe lung disease will be recruited from referrals to pulmonary rehabilitation. Subjects with co-morbidities limiting exercise performance will be excluded. Two 6MWTs will be performed. The better 6MWT will be used to calculate Wpeak for cycle exercise from a regression equation. After 30 minutes rest, subjects will perform ten minutes of constant-load cycle exercise at 60% of the calculated Wpeak. During all exercise, cardiorespiratory and metabolic data (Cosmed K4b2), dyspnoea and rate of perceived exertion (RPE) will be recorded. The VO2 measured at the end of cycle exercise will be compared to VO2peak of the 6MWT (VO2bike/VO2walk). Pearson's correlation coefficient will be calculated for the relationship between VO2bike and VO2walk. A one-way analysis of variance (ANOVA), with Bonferroni correction, will be performed to determine whether the ratio of VO2bike/VO2walk is affected by disease severity.
This novel study will measure the physiological responses to cycle exercise, in terms of VO2peak, performed at an intensity determined from the 6MWT in participants with COPD. Positive findings will enable clinicians to more precisely prescribe cycle training intensity by utilising a simple, reliable and inexpensive 6MWT, thus providing a better standard of care for patients with COPD referred to pulmonary rehabilitation.