Abstract
Post-stroke individuals presented deleterious changes in skeletal muscle and in the cardiovascular system, which are related to reduced oxygen uptake ([Formula: see text]) 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 [Formula: see text] 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 ([Formula: see text]) were collected using a portable metabolic system (Oxycon Mobile®) during the six-minute walk test (6MWT). The time to achieve 63% of [Formula: see text] during a steady state (MTRON) and recovery (MRTOFF) were analyzed by the monoexponential model and corrected by a work rate (wMRTON and wMRTOFF) during 6MWT. Correlation analyses were made using Spearman's rank correlation coefficient (rs) 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 wMRTOFF was correlated with the following: skeletal muscle mass (rs = -0.46), skeletal muscle mass index (rs = -0.45), augmentation index (rs = 0.44), augmentation index normalized to a heart rate of 75 bpm (rs = 0.64), reflection magnitude (rs = 0.43), erythrocyte (rs = -0.61), hemoglobin (rs = -0.54), hematocrit (rs = -0.52) and high-sensitivity C-reactive protein (rs = 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.
Highlights
Standing up and walking to the workplace requires proper oxygen uptake (V_ O2), which is regulated over time by well-controlled mechanisms
44 participants were recruited, twenty were excluded from the final analysis due to missing data, inability to reach the steady state during the 6MWT, and refusal to participate after initial consent
This study unprecedently showed that wMRTOFF presented correlation with skeletal muscle mass (SMM), SMMI, augmentation index (AIx), AIx75, reflection magnitude (RM), RBC, Hgb, Hct, and hsCRP
Summary
Standing up and walking to the workplace requires proper oxygen uptake (V_ O2), which is regulated over time by well-controlled mechanisms. Whether the ending of the activity is considered, the time interval between V_ O2SS and V_ O2 during postactivity recovery (V_ O2RECOVERY) is expressed by MRTOFF that represents the amount of V_ O2 needed to restore the body to its resting level of metabolic function (see Fig 1) [1,2,3]. MRTOFF is an outcome of V_ O2 kinetics to understand the recovery phase when the V_ O2 is used to produce energy related to thermal, hormonal, and metabolic processes, as well as to resynthesize stored creatine phosphate in the muscle and refill oxygen stores in blood and muscle, used during walking [1,2,3]. Understanding the mechanisms limiting V_ O2 is essential for improving bioenergetics kinetics (i.e. V_ O2 on- and off-kinetics), and aerobic endurance [4]
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