Cardiac autonomic modulation in healthy elderly after different intensities of dynamic exercise

Purpose: To investigate the heart rate (HR) and its autonomic modulation at baseline and during dynamic postexercise (P-EX) with intensities of 40% and 60% of the maximum HR in healthy elderly. Methods: This cross-sectional study included ten apparently healthy people who had been submitted to a protocol on a cycle ergometer for 35 minutes. Autonomic modulation was evaluated by spectral analysis of HR variability (HRV). Results: A relevant increase in HR response was observed at 15 minutes postexercise with intensities of 60% and 40% of the maximum HR (10 +/- 2 bpm versus 5 +/- 1 bpm, respectively; P=0.005), and a significant reduction in HRV was also noted with 40% and 60% intensities during the rest period, and significant reduction in HRV (RR variance) was also observed in 40% and 60% intensities when compared to the baseline, as well as between the post-exercise intensities (1032 +/- 32 ms versus 905 +/- 5 ms) (P<0.001). In the HRV spectral analysis, a significant increase in the low frequency component HRV and autonomic balance at 40% of the maximum HR (68 +/- 2 normalized units [nu] versus 55 +/- 1 nu and 2.0 +/- 0.1 versus 1.2 +/- 0.1; P<0.001) and at 60% of the maximum HR (77 +/- 1 nu versus 55 +/- 1 nu and 3.2 +/- 0.1 versus 1.2 +/- 0.1 [P<0.001]) in relation to baseline was observed. A significant reduction of high frequency component at 40% and 60% intensities, however, was observed when compared to baseline (31 +/- 2 nu and 23 +/- 1 nu versus 45 +/- 1 nu, respectively; P<0.001). Moreover, significant differences were observed for the low frequency and high frequency components, as well as for the sympathovagal balance between participants who reached 40% and 60% of the maximum HR. Conclusion: There was an increase in the HR, sympathetic modulation, and sympathovagal balance, as well as a reduction in vagal modulation in the elderly at both intensities of the P-EX.