HEART RATE VARIABILITY THRESHOLD

Abstract

1424 Increased sympathetic activity is related to elevation of blood lactate concentration [La]. Heart rate variability (HRV), a parasympathetic activity indicator, in a graded test, declines steadily up to 40-60% of peak power and reaches a plateau at values lower than 3 ms - HRV threshold (HRV-Thr). The objective of this work was to validate HRV-Thr by comparing to lactate threshold (Lac-Thr). Twenty two male subjects (24,4 ± 3,7 years of age; 55,6 ± 9,5 ml.kg-1.min-1 VO2peak; 1400 ± 125 kpm.min-1 peak power) performed on a mechanically-braked cycloergometer a graded test from 0 kpm.min-1, increments of 90 kpm.min-1 each minute, until exhaustion. HRV was calculated each 10 s by Polar Vantage NV® heart rate monitor as a square root of the mean square of the differences between two adjacent R-R intervals and the HRV-Thr was the first power at which the mean HRV was lower than 3 ms. The [La] was measured by Accusport® portable lactimeter and Lac-Thr was the power of lowest [La] / power ratio. Mean HRV-Thr (681 ± 123 kpm.min-1) and Lac-Thr (709 ± 157 kpm.min-1) were not different (Wilcoxon nonparametric test - p<0,05) and Pearson correlation (r = 0.76) was significant. These results indicate that HRV-Thr can be used as a noninvasive alternative method of estimation of anaerobic threshold. FigureFigure