Abstract
Differences in cardiovascular function between sexes have been documented at rest and maximal exercise. The purpose of this study was to examine the sex differences in cardiovascular function during submaximal constant-load exercise, which is not well understood.Thirty-one male and 33 female subjects completed nine minutes moderate and nine minutes vigorous intensity submaximal exercise (40 and 75% of peak watts determined by maximal exercise test). Measurements included: intra-arterial blood pressure (SBP and DBP), cardiac index (QI), heart rate (HR), oxygen consumption (VO2) and arterial catecholamines (epinephrine = EPI and norepinephrine = NE), and blood gases. Mean arterial pressure (MAP), stroke volume index (SVI), systemic vascular resistance index (SVRI), arterial oxygen content (CaO2), arterial to venous O2 difference (AVO2) and systemic oxygen transport (SOT) were calculated.At rest and during submaximal exercise QI, SVI, SBP, MAP, NE, CaO2, and SOT were lower in females compared to males. VO2, AVO2, EPI were lower in females throughout exercise. When corrected for wattage, females had a higher Q, HR, SV, VO2 and AVO2 despite lower energy expenditure and higher mechanical efficiency.This study demonstrates sex differences in the cardiovascular response to constant-load submaximal exercise. Specifically, females presented limitations in cardiac performance in which they are unable to compensate for reductions in stroke volume through increases in HR, potentially a consequence of a female’s blunted sympathetic response and higher vasodilatory state. Females demonstrated greater cardiac work needed to meet the same external work demand, and relied on increased peripheral oxygen extraction, lower energy expenditure and improvements in mechanical efficiency as compensatory mechanisms.
Highlights
Control of the cardiovascular system is critical for homeostasis and to respond to stresses such as physical activity (Rowell 1993)
There was no difference in age across sexes (p = 0.44), as expected the males were taller, heavier, and had a higher Body mass index (BMI) and body surface area (BSA) compared to the female participants (p < 0.01 for all)
The Systemic vascular resistance (SVR) remained similar at rest and moderate intensity and only became different during vigorous intensity exercise between the male and female participants suggesting that the regulation and homeostatic relationship between blood pressure and cardiac output is achieved through different mechanisms in males and females
Summary
Control of the cardiovascular system is critical for homeostasis and to respond to stresses such as physical activity (Rowell 1993). The majority of this previous work has been documented at rest and maximal exercise; leaving a major paucity of data regarding the differences in cardiovascular response to submaximal constant-load exercise between men and women, as findings have primarily been drawn from submaximal workloads during a maximal exercise test (Fleg et al 1995; Sullivan et al 1991) As such a number of questions remain unanswered, including: 1) do the reductions in cardiac function demonstrated at peak exercise in females remain at submaximal intensities, 2) what are the underlying mechanisms leading to differences in the cardiovascular response to exercise across sex boundaries, 3) what compensatory mechanisms do females rely on in an attempt to ameliorate limitations, and 4) do the known differences between sexes become more apparent or dissipate when the individuals are non-sedentary (exercising >3 times/week)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
