The exercise power-duration relationship in patients with COPD: determinants and effects of rehabilitation

Abstract

Health-quality of life in COPD has been better correlated with exercise endurance capacity than with peak performance. Endurance for the intense exercise is intimately related to work rate; in normals, this relationship is hyperbolic, with the slope defining the shape and intercept, the asymptote. Interestingly, the asymptote (the highest work rate that the subject may sustain for 20 min or more) lies above the subject’s anaerobic threshold and it is shifted upward with training with no change of shape. There are, however, neither data concerning the existence of such a hyperbola in COPD nor the effects of pulmonary rehabilitation in the power-duration relationship. In order to study these issues, a group of 20 mild to moderate COPD patients will be evaluated before and after a comprehensive six-week pulmonary rehabilitation program. The patients will be submitted to standard pulmonary function tests, ECG, questionnaire of health-quality of life (MRC Dysponea Scale), maximal incremental cardiopulmonary exercise test and, on separated days, to 4 constant-load tests to limit of tolerance, at 30, 60, 90 and 120% of the differences between the anaerobic threshold and peak VO2. Thus, we will be able to analyze the power-duration curve characteristics, its relationship with standard measures of impairment and handicap in COPD and as it may or not be changed with pulmonary rehabilitation. (AU)