McNamara RJ, et al. - Researchers sought to analyze the potential determinants of the different constructs of exercise capacity (functional, peak and endurance exercise capacity using the 6-minute walk distance (6MWD), peak oxygen uptake (VO₂peak) and peak work load, and sub-maximal constant work rate test (CWRT) cycle time, respectively) in people with COPD. Cardiac function was shown to be associated with exercise capacity, however, was not a primary determinant. Although variance was apparent among the determinants of the different constructs of exercise capacity, a strong association was shown between quadriceps force and functional and endurance exercise performance, and between lung function and peak exercise capacity.