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Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training: the DREW study.

ABSTRACT: 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.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.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.Clinicaltrials.gov NCT 00011193.

SUBMITTER: Earnest CP

PROVIDER: S-EPMC2387062 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training: the DREW study.

Earnest Conrad P CP Lavie Carl J CJ Blair Steven N SN Church Timothy S TS

PloS one 20080604 6

<h4>Background</h4>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.<h4>Methodology/principal findings</h4>Our primary aim was to me ...[more]

PMID: 18523583

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Project description:This study investigates the effect of 6 weeks of supramaximal exercise training (SET) on heart rate variability (HRV) and associated factors in sedentary obese (OB) and normal-weight (NW) adults. In this study, 19 OB [22.9 (8.4) years; body mass index (BMI) 33.4 (1.4) kg/m2] and 18 NW [23.2 (4.4) years; BMI 23.3 (1.2) kg/m2] adults completed a 6-week SET intervention. Anthropometric and aerobic indicators as well the homeostasis model assessment index for insulin resistance index (HOMA-IR) were assessed at baseline and after SET. The low- and high-frequency [(LF (0.03-0.15 Hz) in ms2 and HF (0.15-0.4 Hz) in ms2)] analysis of HRV as well as adrenaline (A in nmol/l) and noradrenaline (NA in nmol/l) responses were assessed at resting condition and during ventilatory threshold 1 (VT1) of a graded maximal test at baseline and after SET. At baseline, resting HF, LF and the LF/HF ratio were different among groups (P < 0.01, respectively) and were significantly associated with waist-to-hip ratio (β = -0.26; p = 0.01, β = -0.12; p = 0.01 and, β = 0.21; p = 0.01). During exertion at VT1, only LF/HF ratio was associated with NA responses (β = 0.23; p = 0.01). After SET, the frequency domain marker improved significantly for both groups in comparison to baseline. These improvements are manifested by LF and HF increases and LF/HF ratio decreases in the rest condition (p < 0.01, respectively) and during exertion at VT1 (p < 0.01, respectively). The improvement in LH and HF were associated with VO2max increases (β = 0.22 p = 0.01 and β = 0.33; p = 0.01). The decreases observed for the LF/HF ratio are mainly associated to NA decreases observed at rest (β = 0.31; p = 0.001) and at VT1 (β = 0.38; p = 0.001). Obese adults have altered HRV, and 6 weeks of SET improves HRV variables at rest and during VT1 exertion. While LF and HF improvement were associated with VO2max increases, the LF/HF ratio was mainly associated with noradrenaline decreases observed at rest and at VT1.

Project description:The goal of the endurance exercise training study in young adult rats was to perform exercise training studies in young adult (6-month-old) F344 rats, and from these rats collect multiple tissues in order to provide high quality samples for detailed analysis by chemical analysis sites. Tissues were collected from 10-12 rats sedentary control rats concurrent with the collection of the 8-week training groups. The 8-week training group and controls were from the same cohort and same age at euthanasia. For the older age group, an additional set of controls (n=5-6) were collected with the 1-2 week training group. Rats were either sedentary or underwent an exercise training program. Rats were exercised on the rodent treadmill 5 days per week using a progressive training protocol designed to exercise the rats at approximately 70% of VO2max and training was performed no earlier than 10:00 am and no later than 5:00 pm over 5 consecutive days per week. Training was initiated with the treadmill set at 70% of VO2 max and 5 degrees grade for 20 minutes. The duration of exercise was increased by one minute each day until day 31 of training (start of week 7), when a duration of 50 min was reached. Speed and grade of each training session increased in larger increments due to treadmill parameters. The highest intensity and duration of training began on day 31. This intensity was maintained for the final 10 days of the protocol to ensure steady state had been achieved. If any rats were unable to perform at least 4 days of training per week they were removed from the study and euthanized. It is important to note that the starting treadmill speed varied depending on the sex and age of the rat. The initial and maximum speeds were based on VO2max measurements obtained during the pre-training testing of the compliant rats. Rats assigned to the control group followed a schedule similar to the training group. They were placed in one lane on the treadmill for 15 minutes/day, 5 days per week. The treadmill was set at 0 m/min at an incline that corresponded to the incline being used by the training group.

Project description:The goal of the endurance exercise training study in young adult rats was to perform exercise training studies in young adult (6-month-old month) F344 rats, and from these rats collect multiple tissues in order to provide high quality samples for detailed analysis by chemical analysis sites. Tissues were collected from 10-12 rats sedentary control rats concurrent with the collection of the 8-week training groups. The 8-week training group and controls were from the same cohort and same age at euthanasia. For the older age group, an additional set of controls (n=5-6) were collected with the 1-2 week training group. Rats were either sedentary or underwent an exercise training program. Rats were exercised on the rodent treadmill 5 days per week using a progressive training protocol designed to exercise the rats at approximately 70% of VO2max and training was performed no earlier than 10:00 am and no later than 5:00 pm over 5 consecutive days per week. Training was initiated with the treadmill set at 70% of VO2 max and 5 degrees grade for 20 minutes. The duration of exercise was increased by one minute each day until day 31 of training (start of week 7), when a duration of 50 min was reached. Speed and grade of each training session increased in larger increments due to treadmill parameters. The highest intensity and duration of training began on day 31. This intensity was maintained for the final 10 days of the protocol to ensure steady state had been achieved. If any rats were unable to perform at least 4 days of training per week they were removed from the study and euthanized. It is important to note that the starting treadmill speed varied depending on the sex and age of the rat. The initial and maximum speeds were based on VO2max measurements obtained during the pre-training testing of the compliant rats. Rats assigned to the control group followed a schedule similar to the training group. They were placed in one lane on the treadmill for 15 minutes/day, 5 days per week. The treadmill was set at 0 m/min at an incline that corresponded to the incline being used by the training group.

Dataset Information

Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training: the DREW study.

Publications

Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training: the DREW study.

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