Underlying mechanisms of oxygen uptake kinetics in chronic post-stroke individuals: A correlational, cross-sectional pilot study

Post-stroke individuals presented deleterious changes in skeletal muscle and in the cardiovascular system, which are related to reduced oxygen uptake (V ˙ O 2) and take longer to produce energy from oxygen-dependent sources at the onset of exercise (mean response time, MTR ON ) and during post-exercise recovery (MRT OFF ). However, to the best of our knowledge, no previous study has investigated the potential mechanisms related toV ˙ O 2kinetics response (MRT ON and MRT OFF ) in post-stroke populations. The main objective of this study was to determine whether the MTR ON and MRT OFF are related to: 1) body composition; 2) arterial compliance; 3) endothelial function; and 4) hematological and inflammatory profiles in chronic post-stroke individuals. Data on oxygen uptake (V ˙ O 2) were collected using a portable metabolic system (Oxycon Mobile ® ) during the six-minute walk test (6MWT). The time to achieve 63% ofV ˙ O 2during a steady state (MTR ON ) and recovery (MRT OFF ) were analyzed by the monoexponential model and corrected by a work rate (wMRT ON and wMRT OFF ) during 6MWT. Correlation analyses were made using Spearman’s rank correlation coefficient (r s ) and the bias-corrected and accelerated bootstrap method was used to estimate the 95% confidence intervals. Twenty-four post-stroke participants who were physically inactive took part in the study. The wMRT OFF was correlated with the following: skeletal muscle mass (r s = -0.46), skeletal muscle mass index (r s = -0.45), augmentation index (r s = 0.44), augmentation index normalized to a heart rate of 75 bpm (r s = 0.64), reflection magnitude (r s = 0.43), erythrocyte (r s = -0.61), hemoglobin (r s = -0.54), hematocrit (r s = -0.52) and high-sensitivity C-reactive protein (r s = 0.58), all p < 0.05. A greater amount of oxygen uptake during post-walking recovery is partially related to lower skeletal muscle mass, greater arterial stiffness, reduced number of erythrocytes and higher systemic inflammation in post-stroke individuals.