Acute effects of exercise on posture in arthritic patients.

In this study, we aimed to investigate the acute effects of exercise on postural measures in arthritic patients. We obtained posturographic measurements of 8 women with lower extremity arthritis for 30 s before and after a 60-min aquatic exercise. The center of pressure (COP) was recorded while the volunteers were in an upright position with their eyes open. The time domain measures and the frequency domain measures of the COP time series in the anterior-posterior (AP) and medial-lateral (ML) directions were calculated. In addition, the frequency domain measures were calculated for the COP velocity time series. A paired T-test revealed no significant differences in any time domain measures between pre- and post-exercise; however, there were significant decreases in the 95% power frequency of the COP in the AP direction (0.834 ± 0.296 to 0.627 ± 0.230 Hz, p=0.027) for the frequency domain measures. For the velocity time series, the mean power frequency in both the AP (1.47 ± 0.528 to 1.22 ± 0.360 Hz, p=0.047) and ML (1.28 ± 0.245 to 1.13 ± 0.151 Hz, p=0.022) directions, and the 95% power frequency in the ML direction (3.41 ± 0.653 to 2.96 ± 0.468 Hz, p=0.038) decreased significantly in the post-exercise condition. This study reports that a single session of exercise has a subtle but detectable acute effect on postural balance in arthritic patients.

Assessment of the primary effect of aging on heart rate variability in humans.

Beat-to-beat heart rate variability (HRV), reflecting cardiac autonomic control mechanisms, is known to change with age. However, the degree to which this change is mediated by aging per se or by physiologic changes characteristic of normative aging is still unclear. This study was designed to examine the association of aerobic fitness, body habitus or obesity, and blood pressure with age-related changes in HRV. Resting HRV data was recorded from 373 healthy subjects (124 men, 249 women; age range, 16-69 y) and analyzed by coarse-graining spectral analysis to decompose the total spectral power into its harmonic and fractal components. The low- and high-frequency (LF, 0.0-0.15 Hz; HF, >0.15 Hz) harmonic components were calculated from the former, whereas the latter was used to calculate the integrated power (FR) and the spectral exponent , beta, which were, in turn, used to evaluate the overall complexity of HRV. Factor analysis was performed to test whether potentially age-related changes in the components of HRV might be observed secondarily through other variables affecting HRV. Significant (p <0.05) age-related changes in the harmonic (HF and LF) and fractal (FR and beta) components of HRV were generally consistent with those described in the literature. In addition, factor analysis showed that there was a unique common factor that primarily explained correlations among age, HF, and beta (p <0.05) without the contributions from LF, FR, aerobic fitness, body habitus or obesity, and blood pressure. It was concluded that, in this population-based sample, age-related changes in HF and beta, both of which reflect vagal modulation of heart rate, were primarily mediated by aging per se and not by physiologic changes characteristic of normative aging.