Does the level of chronic physical activity alter heart rate variability in healthy older women?

Habitual aerobic exercise in healthy postmenopausal women does not augment basal cardiac autonomic activity yet modulates autonomic-metabolic interactions

OBJECTIVES

The aim of the present study was to examine the effects of habitual exercise training and metabolic health on basal cardiac autonomic function and cardiac autonomic recovery after exercise in healthy postmenopausal women (PMW).

METHODS

Habitually aerobically trained PMW (PMW-tr; 56 ± 1y; n = 11), and untrained PMW (PMW-un; 57 ± 1y; n = 13) and premenopausal women (PreM; ages 26 ± 1y; n = 14) were studied. Cardiac autonomic function, assessed using heart rate variability (HRV), was measured before and one hour after 45-minutes of moderate-intensity exercise (60% VO2peak). Fast Fourier frequency domain measures of high (HF; 0.15 Hz-0.4 Hz), low (LF; 0.04 Hz-0.15 Hz), very low (VLF; 0.01 Hz-0.04 Hz), and Total (VLF+LF+HF) HRV were assessed. Serum estradiol, insulin, and glucose were determined, and HOMA-IR, an index of insulin resistance, was calculated.

RESULTS

In PMW groups, body composition and serum markers did not differ (P>0.05). Pre-exercise, heart rate was lower (P<0.05) in PMW-tr than PMW-un, yet HRV did not differ (P>0.05). In PMW-tr only, HF was inversely associated (P<0.05) with insulin (r = -0.738) and HOMA-IR (r = -0.758). In PreM, HRV was higher than PMW (P<0.05) and was positively correlated with estradiol (P<0.05). Postexercise, HRV was decreased within all groups (P<0.05) yet remained higher in PreM (P<0.05), and similar (P>0.05) between PMW.

CONCLUSION

Basal and postexercise HRV does not differ between habitually aerobically trained and untrained PMW. However, greater insulin sensitivity was associated with higher cardiac parasympathetic tone in trained PMW only. Exercise training may favorably modulate cardiac autonomic-metabolic interactions in PMW.

Cardiac autonomic modulation impairments in advanced breast cancer patients

AIM

To compare cardiac autonomic modulation in early- versus advanced-stage breast cancer patients before any type of cancer treatment and investigate associated factors.

METHODS AND RESULTS

This cross-sectional study included women (30-69 years old) with primary diagnosis of breast cancer and women with benign breast tumors. We evaluated cardiac modulation by heart rate variability and assessed factors of anxiety, depression, physical activity, and other relevant medical variables. Patients were divided into three groups based on TNM staging of cancer severity: early-stage cancer (n = 42), advanced-stage cancer (n = 37), or benign breast tumors to serve as a control (n = 37). We analyzed heart rate variability in time and frequency domains. The advanced-stage cancer group had lower vagal modulation than early-stage and benign groups; also, the advance-stage group had lower overall heart rate variability when compared to benign conditions. Heart rate variability was influenced by age, menopausal status, and BMI.

CONCLUSIONS

Heart rate variability seems to be a promising, non-invasive tool for early diagnosis of autonomic dysfunction in breast cancer and detection of cardiovascular impairments at cancer diagnosis. Cardiac autonomic modulation is inversely associated with breast cancer staging.

Physical activity and heart rate variability in older adults: the Cardiovascular Health Study

BACKGROUND

Cardiac mortality and electrophysiological dysfunction both increase with age. Heart rate variability (HRV) provides indices of autonomic function and electrophysiology that are associated with cardiac risk. How habitual physical activity among older adults prospectively relates to HRV, including nonlinear indices of erratic sinus patterns, is not established. We hypothesized that increasing the levels of both total leisure-time activity and walking would be prospectively associated with more favorable time-domain, frequency-domain, and nonlinear HRV measures in older adults.

METHODS AND RESULTS

We evaluated serial longitudinal measures of both physical activity and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study. After multivariable adjustment, greater total leisure-time activity, walking distance, and walking pace were each prospectively associated with specific, more favorable HRV indices, including higher 24-hour standard deviation of all normal-to-normal intervals (Ptrend=0.009, 0.02, 0.06, respectively) and ultralow-frequency power (Ptrend=0.02, 0.008, 0.16, respectively). Greater walking pace was also associated with a higher short-term fractal scaling exponent (Ptrend=0.003) and lower Poincaré ratio (Ptrend=0.02), markers of less erratic sinus patterns.

CONCLUSIONS

Greater total leisure-time activity, and walking alone, as well, were prospectively associated with more favorable and specific indices of autonomic function in older adults, including several suggestive of more normal circadian fluctuations and less erratic sinoatrial firing. Our results suggest potential mechanisms that might contribute to lower cardiovascular mortality with habitual physical activity later in life.

Brief assessment of supine heart rate variability in normal weight, overweight, and obese females

BACKGROUND

Little research has been conducted on the heart rate variability (HRV) parameters in late adolescent females. The present study aimed to assess HRV time and frequency domain parameters in overweight and obese late adolescent females. Also to assess any possible correlation between HRV parameters and obesity indices in that particular age group.

SUBJECTS AND METHODS

Fifteen-minute period of standardized ECG recording was implemented to record HRV time and frequency parameters in 42 normotensive euglycemic female medical students aged (18-21 years); lean (n = 13), overweight (n = 13), and obese (n = 16). For the analysis of results, 2.5-minute data were used.

RESULTS

Root mean squares of successive differences between adjacent RR intervals (rMSSD) and high-frequency (HF) power were significantly decreased in overweight and obese late adolescent females. Parameters reflecting sympathetic activity which include low-frequency (LF) power and LF/HF ratio showed significant increase in overweight group. Interestingly, LF power was significantly reduced in obese group while the LF/HF ratio was insignificantly different. No significant correlations were observed between HRV indices and parameters of total or visceral obesity in the study groups.

CONCLUSION

HRV indices showed sympathetic hyperactivity in overweight late adolescent females and diminished sympathetic response in matching obese group. Both overweight and obese females showed decreased protective vagal influence on the heart.

The relationship between physical activity and heart rate variability in orthotopic heart transplant recipients

AIMS AND OBJECTIVES

To investigate the relationship between physical activity and heart rate variability in orthotopic heart transplant recipients, to compare the difference in heart rate variability between patients one year after orthotopic heart transplant and healthy adults matched to the heart transplant recipients in terms of age, gender and physical activity levels.

BACKGROUND

Although physical activity affects the heart rate variability in patients with heart disease, there is a paucity of literature discussing the correlation between physical activity and heart rate variability among heart transplant recipients.

DESIGN

This was a descriptive and cross-sectional study.

METHODS

A total of 120 eligible subjects were divided into the orthotopic heart transplant recipient group (n = 60) and the healthy adult group (n = 60). The Seven-day Physical Activity Recall questionnaire was used to record the subjects' amount of physical activity per week. Heart rate variety parameters were determined by separate frequency domain components.

RESULTS

Results indicated heart transplant recipients' heart rate variety was significantly lower than that of healthy adults in terms of mean, sdr, total power (ms(2)), low frequency (ms(2)), low frequency (nu), high frequency (ms(2)) and low frequency/high frequency. Heart transplant recipients' heart rate variety including total power (ms(2)), low frequency (ms(2)) and high frequency (ms(2)) was 18·2, 2 and 7·2% of healthy controls, respectively; the amount of absolutely and relatively moderate physical activity was positively related to high frequency (ms(2)) and high frequency (nu), but was negatively related to low frequency/high frequency. High frequency (nu) increases while the total amount of weekly physical activity increases.

CONCLUSIONS

Results confirmed that the more the moderate physical activity performed, the better the patient's heart rate variability.

RELEVANCE TO CLINICAL PRACTICE

We suggest that clinical care providers have to encourage heart transplant recipients to engage in moderate physical activity.

Heart rate variability and exercise in aging women

BACKGROUND

Our group has shown a positive dose-response in maximal cardiorespiratory exercise capacity (VO(2max)) and heart rate variability (HRV) to 6 months of exercise training but no improvement in VO(2max) for women ≥60 years. Here, we examine the HRV response to exercise training in postmenopausal women younger and older than 60 years.

METHODS

We examined 365 sedentary, overweight, hypertensive, postmenopausal women randomly assigned to sedentary control or exercise groups exercising at 50% (4 kcal/kg/week, [KKW]), 100% (8 KKW) and 150% (12 KKW) of the National Institutes of Health (NIH) Consensus Development Panel physical activity guidelines. Primary outcomes included time and frequency domain indices of HRV.

RESULTS

Overall, our analysis demonstrated a significant improvement in parasympathetic tone (rMSSD and high frequency power) for both age strata at 8 KKW and 12 KKW. For rMSSD, the age-stratified responses were: control, <60 years, 0.20 ms, 95% confidence interval (CI)-2.40, 2.81; ≥60 years, 0.07 ms, 95% CI -3.64, 3.79; 4 KKW, <60 years, 3.67 ms, 95% CI 1.55, 5.79; ≥60 years, 1.20 ms, 95% CI -1.82, 4.22; 8-KKW, <60 years, 3.61 ms, 95% CI 0.88, 6.34; ≥60 years, 5.75 ms, 95% CI 1.89, 9.61; and 12-KKW, <60 years, 5.07 ms, 95% CI 2.53, 7.60; ≥60 years, 4.28 ms, 95% CI 0.42, 8.14.

CONCLUSIONS

VO(2max) and HRV are independent risk factors for cardiovascular disease (CVD) mortality. Despite no improvement in VO(2max), parasympathetic indices of HRV increased in women ≥60 years. This is clinically important, as HRV has important CVD risk and neurovisceral implications beyond cardiorespiratory function.

Autonomic function and change in insulin for exercising postmenopausal women

PURPOSE

Obesity, physical inactivity and altered estrogen metabolism play an integrated role contributing to the disease risk profiles of postmenopausal women. These same risk factors also affect modulation of the autonomic nervous system (ANS).

METHODS

We examined 332 postmenopausal, overweight, previously sedentary women (mean+/-SD; age, 57.6+/-6.3 years; weight, 84.3+/-11.9kg; BMI, 31.7+/-3.7kg/m(2)) participating in a 6-month, moderate intensity, aerobic exercise training intervention to determine the relationship between heart rate variability (HRV) derived autonomic function and fasting insulin. We analyzed quartiles of change in time and frequency domain indices of ANS activity and changes in insulin for between and within group differences using ANCOVA and Tukey post hoc tests adjusted for age, ethnicity, randomization group, change in fitness, and change in weight.

RESULTS

We observed at baseline that insulin was positively correlated with body anthropometry (body weight, r(2)=0.34; BMI, r(2)=0.39; waist circumference, r(2)=0.29; all, P<0.001), and inversely associated with rMSSD (r(2)=-0.12) and SDNN (r(2)=-0.18; all, P<0.01). After the intervention, changes in rMSSD (r(2)=-0.21, P<0.002) and SDNN r(2) -0.19, P<0.0001) were inversely correlated to insulin change. Further ANCOVA analysis revealed that rMSSD and SDNN were both significant (P<0.0001); however, only rMSSD exhibited a step-wise pattern of improvement when quartiles of rMSSD were compared to corresponding insulin reductions: Q1 (referent group, 8.41+/-3.2uIU/ml), Q2 (-3.30+/--3.2uIU/ml), Q3 (-5.66+/--3.2uIU/ml; P<0.02), and Q4 (-9.60+/--3.2uIU/ml; P<0.006).

CONCLUSION

Our study shows that changes in autonomic function are associated with changes in insulin and that exercise training may influence this relationship in postmenopausal women.

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes

Objective

To examine the responsiveness of cardiac autonomic function and baroreflex sensitivity (BRS) to exercise training in obese individuals without (OB) and with type 2 diabetes (ObT2D).

Design

Subjects were tested in the supine position and in response to a sympathetic challenge before and after a 16 week aerobic training program. All testing was conducted in the morning following a 12-hour fast.

Subjects

34 OB and 22 ObT2D men and women (40-60 yr)

Measurements

Heart rate variability (HRV) was measured at rest via continuous ECG (spectral analysis with the autoregressive approach) and in response to upright tilt. The dynamics of heart rate complexity were analyzed with sample entropy and Lempel-Ziv entropy, and BRS was determined via the sequence technique. Subjects were aerobically trained 4x/wk for 30-45 min for 16 wks.

Results

Resting HR decreased and total power (lnTP, msec²) of HRV increased in response to exercise training (P<0.05). High frequency power (lnHF) increased in OB subjects but not in OBT2D, and no changes occurred in ln low frequency/HF power with training. Upright tilt decreased lnTP and lnHF and increased LF/HF (P<0.01) but there were no group differences in the magnitude of these changes nor were they altered with training in either group. Tilt also decreased complexity (sample entropy and Lempel-Ziv; P<0.001), but there was no group or training effect on complexity. BRS decreased with upright tilt (P<0.01) but did not change with training. Compared to OB subjects the ObT2D had less tilt-induced changes in BRS.

Conclusion

Exercise training improved HRV and parasympathetic modulation (lnHF) in OB subjects but not in ObT2D, indicating plasticity in the autonomic nervous system in response to this weight-neutral exercise program only in the absence of diabetes. HR complexity and BRS were not altered by 16 wk of training in either OB or ObT2D individuals.

The effect of aerobic training and cardiac autonomic regulation in young adults

OBJECTIVES

We tested the effect of aerobic exercise on autonomic regulation of the heart in healthy young adults.

METHODS

Healthy, sedentary young adults (n = 149; age = 30.4 +/- 7.53 years) were randomized to receive 12 weeks of either aerobic conditioning or strength training. Primary outcomes were heart rate and RR interval variability (RRV) measured before and after training and after 4 weeks of sedentary deconditioning. RRV, a noninvasive index of cardiac autonomic regulation, reflects variability in the intervals between consecutive R waves of the electrocardiogram.

RESULTS

Aerobic conditioning but not strength training led to a significant increase in aerobic capacity (3.11 mL/kg/min), a decrease in heart rate (-3.49 beats per minute), and an increase in high-frequency RRV (0.25 natural log msec2), each of which returned to pretraining levels after deconditioning. Significant 3-way interactions, however, revealed autonomic effects only in men.

CONCLUSIONS

In sedentary, healthy young adults, aerobic conditioning but not strength training enhances autonomic control of the heart, but post hoc analyses suggested that gender plays a significant role in this exercise-related cardioprotection.

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.

The many metrics of cardiac chronotropy: a pragmatic primer and a brief comparison of metrics

This paper focuses on pragmatic issues in obtaining measures of cardiac vagal control, and overviews a set of freely available software tools for obtaining several widely used metrics that putatively reflect sympathetic and/or parasympathetic contributions to cardiac chronotropy. After an overview of those metrics, and a discussion of potential confounds and extraneous influences, an empirical examination of the relationships amongst these metrics is provided. This study examined 10 metrics in 96 unselected college students under conditions of resting baseline and serial paced arithmetic. Intercorrelations between metrics were very high. Factor analyses were conducted on the metrics reflecting variability in cardiac rate, once at baseline and again during mental arithmetic. Factor structure was highly stable across tasks, and included a factor that had high loadings of all variables except Toichi's "cardiac sympathetic index" (CSI), and a second factor that was defined predominantly by the CSI. Although generally highly correlated, the various metrics responded differently under challenge.

Cold pressor test protocol to evaluate cardiac autonomic function

The primary objective of this study was to develop a cold pressor test (CPT) protocol to evaluate cardiac autonomic function. Secondary objectives were to assess CPT protocol reliability and to examine gender differences in response to orthostatic stress and the CPT. Healthy, normotensive men and women (n = 12 per group) completed 2 trials on different days in the left lateral decubitus and standing postures and during a 6 min CPT (hand immersion while seated). Measurements included R-R interval, blood pressure, ventilatory responses, spontaneous baroreflex sensitivity, and heart rate variability indices. During the CPT, blood pressure and the sympathetic nervous system (SNS) indicator increased significantly and low-frequency power, high-frequency power (normalized for tidal volume), and the parasympathetic nervous system (PNS) indicator decreased significantly. Standing caused significant increases in the SNS indicator and decreases in the R-R interval in both genders. The PNS indicator was higher in women than in men in the left lateral decubitus posture. The 6 min hand-immersion CPT provoked cardiac sympathetic activation and parasympathetic withdrawal; however, it is best suited to studies with a repeated measures design, as analysis of reliability suggests that responses are highly variable between individuals. Performing the CPT in the left lateral decubitus position may prevent vasovagal responses.Key words: cold pressor test, sympathetic nervous system, parasympathetic nervous system, gender, posture.

Reliability of heart rate variability in healthy older women at rest and during orthostatic testing

BACKGROUND AND AIMS

In the older population, the reliability of heart rate variability (HRV) has only been evaluated in a few studies, in the supine position, and covering a broad sample of age and patients of both sexes. To document the relevance of using HRV analysis in healthy older women, the aim of this study was to evaluate the reliability of HRV indexes during three classical tests.

METHODS

33 healthy women (66.9+/-0.7 years old) performed two test sessions. Each session consisted of an ECG recorded in the supine position, first with free breathing (Test 1), then with controlled breathing (Test 2), and in the upright position (Test 3). Time and frequency HRV indexes were obtained by processing the ECG signals. Reliability was assessed between sessions using Student's paired t-test, intraclass correlation coefficient (ICC) and coefficient of variation (CV).

RESULTS

There were no differences between the sessions. ICC showed good reliability for all HRV indexes. CV was low for absolute HRV indexes, except in Test 3 for parasympathetic indexes with modest CV. The CV of HRV ratio indexes were modest to high in all three tests.

CONCLUSIONS

Time and absolute frequency HRV indexes are reliable when testing healthy older women. Our results support the use of such indexes in gerontology research, to assess the effects of clinical or pharmacological interventions on the autonomic nervous system.