Reproducibility of the RMSSD Index of Heart Rate Variability in Recovery After Exercise

Heart rate variability (HRV) is an important parameter that allows evaluate parasympathetic reactivation after physical exercise. However, because its a cardiac phenomenon evaluated in non-stationary conditions, it is fundamental to evaluate its reproducibility in post exercise recovery. PURPOSE: To analyze whether the RMSSD index of HRV shows reproducibility in both passive and active after maximal exercise recovery. METODOLOGY: Eleven young healthy (22.1 ± 3.2 years, 23.5 ± 2.3 kg/m2) and untrained men (36.1 ± 5.2 mL/kg/min) were evaluated. HRV was evaluated by LnRMSSD (heart rate monitors - transformed into a natural logarithm), which reflects the parasympathetic activity, after maximal progressive exercise (cycle ergometer) every 30s throughout the 10 min of test and retest of passive recovery (seated position) and active (5 min at 15W e then at 5 min passively) after exercise. The Shapiro Wilk test was used to test the normality of data, test T-Student’s and Wilcoxon were used to compare each recovery of test and retest (p<0,05). Intraclass correlation coefficient (ICC) was used to evaluate the relative reproducibility and standard error of measurement (SEM) and coefficient of variation (CV) to the absolute reproducibility. RESULTS: There was difference between test and retest for LnRMSSD only at 120s (p: 0.00) in passive recovery and at 420s (p: 0.04) in active. Reproducibility was observed to both recovery types - in passive recovery: very high at 90, 270, 480 and 570s (ICC: 0.90 - 0.95) and high at 60, 120 to 240, 300 to 450, 510, 540, 600s (ICC: 0.72 - 0.89); at active recovery: high at 30, 150, 240, 270, 330 to 420, 480, 510 and 540s (ICC: 0.70 - 0.87) and moderate at 60, 120, 180, 210, 300, 450, 570 and 600s (ICC: 0.50-0.69). During passive recovery CV varied between 12.83 - 39.73% and SEM between 0.33 - 1.14 ms and during active recovery varied between 16.58 - 39.51% and 0.43 - 1.05 ms. CONCLUSION: The RMSSD index is reproducible in both passive and active recovery after maximal exercise in young men. Therefore, it can be used as a reliable index to evaluate cardiac parasympathetic reestablishment after maximal exercise. Supported by CNPq (process 443361/2014-2) and CAPES.