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

Abstract

BackgroundUnderstanding the cardiorespiratory factors related to the increase in oxygen consumption () during exercise is essential for improving cardiorespiratory fitness in individuals with stroke. However, cardiorespiratory factors related to the increase in during exercise in these individuals have not been examined using multivariate analysis. This study aimed to identify cardiorespiratory factors related to the increase in during a graded exercise in terms of respiratory function, cardiac function, and the ability of skeletal muscles to extract oxygen.MethodsEighteen 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 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.ResultsFrom 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 (adjusted R2 = 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 (adjusted R2 = 0.923, p < 0.001).ConclusionOur results suggest that the ability of skeletal muscle to extract oxygen is a major cardiorespiratory factor related to the increase in 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.

Ability of The Cardiorespiratory System to Adapt to Exercise is Impaired in Individuals With Severe Post-Stroke Fatigue

“…The symptom-limited graded exercise test started with a warm-up at 0 W for 3 min followed by a 10-W increment every minute [59]. The test was terminated if the participant showed signs of angina, dyspnoea, inability to maintain a cycling cadence of more than 40 rpm, hypertension (>250 mmHg systolic or >115 mmHg diastolic), or a drop in systolic blood pressure by >10 mmHg, despite the increase in workload [24]. To identify whether the maximal effort was reached during the exercise test, at least one of the following criteria had to be met: V̇O2 increased <150 mL•min -1 for >1 min despite increased work rate, respiratory exchange ratio >1.10, or heart rate achieved 85% of the age-predicted maximal heart rate calculated as 220 minus age [14].…”

“…The impedance cardiography method is a valid and reliable method for measuring cardiac haemodynamics at rest and during exercise [60]. The measurement values of cardiorespiratory variables were interpolated to 1 s intervals, time-aligned, and averaged into 5 s bins to derive the AVO2diff on a second-by-second basis [16,24], which was calculated as the ratio between V̇O2 and CO based on Fick's equation [61]:…”

“…The ventilatory threshold was determined using a combination of the following criteria: the point where the ventilatory equivalent of oxygen reaches its minimum or starts to increase, without an increase in the ventilatory equivalent of carbon dioxide; the point at which the end-tidal oxygen fraction reaches a minimum or starts to increase, without a decline in the end-tidal carbon dioxide fraction; and the point of deflection of carbon dioxide output versus V̇O2 (the V-slope method), as previously described [24,63]. V̇O2, CO, AVO2diff, V̇E, and respiratory exchange ratio at the ventilatory threshold were obtained.…”

“…The primary objective of this study was to examine whether more severe fatigue was associated with a longer τV̇O2 at the onset of exercise measured during a submaximal constant-load exercise test rather than a lower V̇O2 at peak exercise obtained during a symptom-limited graded exercise test in inpatients at a subacute rehabilitation ward. In addition, impairments of respiratory and cardiac function to supply oxygen and the inability of skeletal muscles to extract oxygen may limit the increase in V̇O2 during exercise in individuals with stroke [16,23,24]. Thus, our secondary objective was to identify associations between post-stroke fatigue and cardiorespiratory variables potentially affecting V̇O2 during exercise such as the oxygen uptake kinetics efficiency slope (OUES), cardiac output (CO), and arterial-venous oxygen difference (AVO2diff).…”

Effects of 8-Weeks Concurrent Strength and Aerobic Training on Body Composition, Physiological and Cognitive Performance in Older Adult Women

“…Within the physiological parameters, the maximum oxygen consumption (VO2max) is an indicator to know the level of cardiorespiratory fitness and the functionality of the cardiovascular system [26][27][28][29], which is still highly analysed and used nowadays. Another factor which is improved by moderate regular PE is cognitive function which provokes physiological adaptations, benefits in quality of life and mental health [30,31].…”