Moderate intensity exercise training at 8 or 12 kcal/kg per week significantly increased the parasympathetic index of heart rate variability compared to control in sedentary postmenopausal women.
RCT (n=373)
Double-blind
Randomized
Does exercise training improve heart rate variability in sedentary postmenopausal women?
Moderate intensity exercise training of at least 8 kcal/kg per week is sufficient to improve parasympathetic indices of heart rate variability in previously sedentary postmenopausal women.
Absolute Event Rate: 27.66% vs 23.19%
p-value: p=<0.05
BACKGROUND: Decreased heart rate variability (HRV) is associated with a higher risk of mortality. Overall, postmenopausal women have lower levels of HRV than premenopausal women, which may be additionally complicated by lifestyle related behaviors such as physical inactivity and obesity. Though cardiorespiratory exercise training increases HRV, little is known regarding the exercise dose necessary to promote this improvement. METHODOLOGY/PRINCIPAL FINDINGS: Our primary aim was to measure HRV in post-menopausal women following 6-months of exercise training. We examined supine resting HRV in 373 post-menopausal women (45-75 y) after 6-months of randomly assigned and double-blinded administered exercise training exercise training at 50%, 100% and 150% of the NIH Consensus Development Panel's recommended minimal physical activity level. This corresponded to 4, 8, or 12 kcal/kg per week (KKW) of energy expenditure. At baseline, we observed no significant differences in HRV or hormone replacement use between treatment groups. However, we did observe that Caucasian women and those taking antidepressant medications had lower levels of baseline HRV. After 6-months of exercise intervention, we observed a dose dependent increase in all parasympathetically derived time and frequency domain measurements across exercise groups after adjustment for age, ethnicity, antidepressants, and baseline rMSSD (all, P<0.001). For example, the parasympathetic index rMSSD was greater than control (23.19+/-1.0) for the 4-KKW (25.98+/-0.8; P = 0.14), 8-KKW (27.66+/-1.0; P<0.05), and 12-KKW (27.40+/-0.0; P<0.05) groups at follow-up. CONCLUSIONS/SIGNIFICANCE: Moderate intensity exercise training exercise is sufficient to improve HRV in previously sedentary postmenopausal women in a dose-dependent manner, as 4-KKW is insufficient to improve parasympathetic indices of HRV, while 12-KKW conferred no greater improvement than 8-KKW. TRIAL REGISTRATION: Clinicaltrials.gov NCT 00011193.
Earnest et al. (Tue,) conducted a rct in Sedentary, overweight or obese postmenopausal women (n=373). Moderate intensity exercise training vs. Non-exercise control was evaluated on Parasympathetic nervous system function measured by rMSSD (square root of the mean of the sum of the squares of differences between adjacent R-R intervals) (p=<0.05). Moderate intensity exercise training at 8 or 12 kcal/kg per week significantly increased the parasympathetic index of heart rate variability compared to control in sedentary postmenopausal women.
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