Cardiorespiratory factors related to the increase in oxygen consumption during exercise in individuals with stroke

BACKGROUND: Understanding the cardiorespiratory factors related to the increase in oxygen consumption ([Image: see text] ) during exercise is essential for improving cardiorespiratory fitness in individuals with stroke. However, cardiorespiratory factors related to the increase in [Image: see text] during exercise in these individuals have not been examined using multivariate analysis. This study aimed to identify cardiorespiratory factors related to the increase in [Image: see text] during a graded exercise in terms of respiratory function, cardiac function, and the ability of skeletal muscles to extract oxygen. METHODS: Eighteen individuals with stroke (aged 60.1 ± 9.4 years, 67.1 ± 30.8 days poststroke) underwent a graded exercise test for the assessment of cardiorespiratory response to exercise. The increases in [Image: see text] from rest to first threshold and that from rest to peak exercise were measured as a dependent variable. The increases in respiratory rate, tidal volume, minute ventilation, heart rate, stroke volume, cardiac output, and arterial-venous oxygen difference from rest to first threshold and those from rest to peak exercise were measured as the independent variables. RESULTS: From rest to first threshold, the increases in arterial-venous oxygen difference (β = 0.711) and cardiac output (β = 0.572) were significant independent variables for the increase in [Image: see text] (adjusted R(2) = 0.877 p < 0.001). Similarly, from rest to peak exercise, the increases in arterial-venous oxygen difference (β = 0.665) and cardiac output (β = 0.636) were significant factors related to the increase in [Image: see text] (adjusted R(2) = 0.923, p < 0.001). CONCLUSION: Our results suggest that the ability of skeletal muscle to extract oxygen is a major cardiorespiratory factor related to the increase in [Image: see text] during exercise testing in individuals with stroke. For improved cardiorespiratory fitness in individuals with stroke, the amount of functional muscle mass during exercise may need to be increased.