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Revista Portuguesa de Ciências do Desporto
Print version ISSN 1645-0523
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 (HRRest), 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 HRRest 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.