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Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training : the DREW study . 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 .
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Intervention_Physical
exercise training
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Intervention_Physical
cardiorespiratory exercise training
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Intervention_Physical
exercise training
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Intervention_Physical
exercise training exercise training
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Intervention_Physical
exercise intervention
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Intervention_Physical
Moderate intensity exercise training exercise
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Outcome_Physical
HRV
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Outcome_Physical
hormone
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Outcome_Physical
baseline HRV
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Outcome_Physical
antidepressants
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Outcome_Physical
parasympathetic index rMSSD
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Participant_Condition
postmenopausal women
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Participant_Condition
supine resting HRV in 373 post-menopausal women ( 45-75 y ) after 6-months of randomly assigned