Short-term Heart Rate Variability And Its Correlation With Acute Maximal Graded Exercise In Healthy Adults

Abstract

The influence of short-term heart rate variability (HRV) on acute maximal graded exercise performance is not clearly understood and there are considerable discrepancies in the literature regarding the same. PURPOSE: To investigate the correlation if any, between the short-term HRV parameters and the acute maximal graded treadmill exercise parameters in healthy adult volunteers. METHODS: Designed as a cross-sectional study, consecutive, consenting healthy adult volunteers of mean age 20.56 ± 2.49 years (n=30, M/F 22/8) underwent recording of supine resting electrocardiogram under standard test conditions for HRV analysis. The volunteers then underwent pre-exercise assessment of resting heart rate (HR), blood pressure (BP) and respiratory rate (RR) in supine position and after five minutes of assuming standing posture followed by an acute maximal graded treadmill exercise test (Ball State University Protocol) until volitional exhaustion providing total test time (TT), cumulative work output (WO) achieved, cumulative metabolic equivalent of task (METs) achieved, derived VO2max achieved and drop in recovery HR data. Spectral analysis of short-term heart rate variability was performed using Kubios HRV software version 2.1 yielding time-domain (mean of RR intervals, root mean square of successive differences - rMSSD, standard deviation of normal to normal intervals - SDNN, the number of pairs of successive NNs that differ by more than 50 ms - NN50, the proportion of NN50 divided by total number of NNs - pNN50) and frequency-domain (VLF, LF, and HF band powers and peak frequencies) measures. Data were analysed using Pearson’s Correlation Coefficient with Bootstrap confidence interval statistics. RESULTS: The spectral analysis of heart rate variability parameters do not correlate significantly with the acute maximal graded treadmill exercise parameters. However, resting supine heart rate and resting supine systolic BP show significant negative correlation with drop in recovery heart rate at 5th minute (r = -0.501 and -0.496 at 95% confidence interval of -0.686 to -0.304 and -0.710 to -0.242 respectively, at p value < 0.05). CONCLUSIONS: Short-term heart rate variability parameters do not have any influence on the acute maximal exercise performance parameters of an individual. Resting heart rate and systolic blood pressure correlate with heart rate recovery which is a predominantly parasympathetic function.