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 (V9;O2) and take longer to produce energy from oxygen-dependent sources at the onset of exercise (mean response time, MTRON) and during post-exercise recovery (MRTOFF). However, to the best of our knowledge, no previous study has investigated the potential mechanisms related to VO2 kinetics response (MRTON and MRTOFF) in post-stroke populations. The main objective of this study was to determine whether the MTRON and MRTOFF 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 (VO2) were collected using a portable metabolic system (Oxycon Mobile(R)) during the six-minute walk test (6MWT). The time to achieve 63% of VO2 during a steady state (MTRON) and recovery (MRTOFF) 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.