Abstract
BackgroundHeart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function. Maximal exercise can affect autonomic function, and it is unknown if there are sex differences in autonomic recovery following exercise. Therefore, the purpose of this study was to determine sex differences in several measures of autonomic function and the response following maximal exercise.MethodsSeventy-one (31 males and 40 females) healthy, nonsmoking, sedentary normotensive subjects between the ages of 18 and 35 underwent measurements of HRV and BPV at rest and following a maximal exercise bout. HRR was measured at minute one and two following maximal exercise.ResultsMales have significantly greater HRR following maximal exercise at both minute one and two; however, the significance between sexes was eliminated when controlling for VO2 peak. Males had significantly higher resting BPV-low-frequency (LF) values compared to females and did not significantly change following exercise, whereas females had significantly increased BPV-LF values following acute maximal exercise. Although males and females exhibited a significant decrease in both HRV-LF and HRV-high frequency (HF) with exercise, females had significantly higher HRV-HF values following exercise. Males had a significantly higher HRV-LF/HF ratio at rest; however, both males and females significantly increased their HRV-LF/HF ratio following exercise.ConclusionsPre-menopausal females exhibit a cardioprotective autonomic profile compared to age-matched males due to lower resting sympathetic activity and faster vagal reactivation following maximal exercise. Acute maximal exercise is a sufficient autonomic stressor to demonstrate sex differences in the critical post-exercise recovery period.
Highlights
Heart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function
Percent 2.5 5 20 22.5 2.5 5 2.5 7.5 5 5 2.5 7.5 2.5 2.5 5 2.5 0 100 were eliminated after controlling for VO2 peak; (2) females had significantly lower BPV-LF and BPV-LF/ high frequency (HF) values at rest compared to males but had more pronounced increases with maximal exercise; (3) males displayed a higher heart rate variability (HRV)-LF/HF ratio at rest, and females had higher HRV-HF values following exercise
This was demonstrated in lower BPV-LF values at rest and higher HRV-HF values following exercise compared to males, suggesting greater vagal modulation and vagal reactivation following maximal exercise in females with males displaying elevated resting sympathetic dominance
Summary
Heart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function. Females display lower sympathetic activity and increased cardiac vagal modulation which could reflect the lower prevalence of arrhythmias blood pressure compared to males [11]. This may not be maintained following recovery after a short supramaximal exercise bout [12]. Little is known with regard to sex differences at rest and following maximal exercise in several established measures of autonomic function It is unknown if an acute maximal bout of exercise will affect young, untrained men and women differently and if autonomic recovery is depressed in both males and females. We hypothesize that females will have enhanced parasympathetic dominance at rest compared to males, but an acute maximal exercise bout will lead to elevated sympathetic dominance in both males and females coupled with delayed parasympathetic reactivation in females
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