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 PEX.