Abstract

FRONCHETTI, Lenise; NAKAMURA, Fábio; AGUIAR, César  and  OLIVEIRA, Fernando. Indexes of Autonomic Cardiac Regulation in Rest and During Progressive Exercise: Application of the Heart Rate Variability Threshold. Rev. Port. Cien. Desp. [online]. 2006, vol.6, n.1, pp.21-28. ISSN 1645-0523.

This study aimed to verify the degree of association between the resting heart rate (HR_Rest), different resting heart rate variability indexes and the exercise intensity related to the heart rate threshold variability. Twenty men (21,3 ± 2,6 years old) began the test protocol with a resting period sitting on a cycle ergometer and then were submitted to a progressive test (14,6W/minute) until exhaustion. In the first load, the threshold variability was identified as lower than 3 ms in the decreasing variability HR curve. The HR and the variability were registered with a Polar^® heart rate device. Spearman Rank (r) correlation was used to calculate the associations among these variables (p<0,05). The correlations between various variability indexes were statistically significant with r≥0,80. The HR_Rest showed a significant and a negative association with the variability indexes and with the threshold variability intensity (r ≥ -0,63). On the other hand, the threshold variability intensity showed a close relationship with the following indexes: SD1 (r = 0,51), SD2 (r = 0,46), RMSSD (r = 0,48), pNN50 (r = 0,55), HF (r = 0,50) e LF/HF (r = -0,56). These results showed that an elevate resting vagal activity can postpone the increase of the predominance of the sympathetic system during progressive exercises.

Keywords : rest heart rate; heart rate variability; time and frequency domain; heart rate variability threshold; aerobic capacity.

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