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

In the present study, we investigated the effects of three levels of chronic physical activity on HRV (heart rate variability) in healthy older women. ECG recordings were taken in three (low-, moderate- and high-) activity groups in supine position with free and with controlled breathing, and during orthostatic stress. Temporal and spectral HRV indices were obtained from the ECG signal processing. The main results showed that, in supine position with free and controlled breathing, the HF (high-frequency) spectral component (P<0.01) and the rMSSD (square root of the mean squared differences) between two adjacent RR intervals (P<0.05 and P<0.01 respectively) were elevated in the high-activity group compared with the low-activity group. No significant difference was observed between groups during the orthostatic test. Within groups, in the supine position, the change from free to controlled breathing produced a decrease in the LF (low-frequency) spectral component in all three groups (P<0.01). The change from supine to standing position produced a decrease in RR in all three groups (P<0.05 in low- and moderate-activity groups, and P<0.01 in high-activity group); the rMSSD and the HF spectral component decreased only in the high-activity group (P<0.01). In conclusion, this study performed on older women showed that parasympathetic indices of resting HRV were significantly elevated in a high physical activity group compared with in a low physical activity group. Furthermore, parasympathetic indices of HRV decreased during an orthostatic test only in the high-activity group. The influence of chronic moderate physical activity on HRV in older women was small in the present study.