Physiological determinants of the increase in oxygen consumption during exercise in individuals with stroke

Abstract

2 3 Background: Understanding the physiological limitations of the increase in oxygen 2 4 consumption (V ሶ O 2 ) during exercise is essential to improve cardiorespiratory fitness in 2 5 individuals with stroke. However, the physiological determinants of the increase in V ሶ O 2 2 6 during exercise have not been examined using multivariate analysis in individuals with 2 7stroke. This study aimed to identify the physiological determinants of the increase in 2 8 V ሶ O 2 during a graded exercise in terms of the respiratory function, cardiac function, and 2 9ability of skeletal muscles to extract oxygen. 3 0 Methods: Eighteen individuals with stroke (60.1 ± 9.4 years of age, 67.1 ± 30.8 days 3 1 poststroke) underwent a graded exercise test for the assessment of cardiorespiratory 3 2 response to exercise. The increase in V ሶ O 2 from rest to ventilatory threshold and that 3 3 from rest to peak exercise were measured as a dependent variable. The increases in 3 4respiratory rate, tidal volume, heart rate, stroke volume, and arterial-venous oxygen 3 5 difference from rest to ventilatory threshold and those from rest to peak exercise were 3 6 measured as independent variables. 7Results: From rest to ventilatory threshold, the increases in heart rate (β = 0.546) and 3 8 arterial-venous oxygen difference (β = 0.398) were significant determinants of the 3 9 increase in V ሶ O 2 (adjusted R 2 = 0.703, p < 0.001). From rest to peak exercise, the 4 0 4 increases in tidal volume (β = 0.611) and heart rate (β = 0.353) were significant 4 1 determinants of the increase in V ሶ O 2 (adjusted R 2 = 0.702, p < 0.001). 4 2 Conclusion: V ሶ O 2 is well-known to increase nearly linearly with increasing heart rate; 4 3 however, our results suggest that arterial-venous oxygen difference and tidal volume are 4 4 also significant physiological determinants of the increase in V ሶ O 2 from rest to 4 5 ventilatory threshold and that from rest to peak exercise, respectively. Our findings 4 6 could potentially contribute to the development of appropriate therapies to improve 4 7 cardiorespiratory fitness in individuals with stroke. 4 8 4 9