The role of heart rate variability in sports physiology

Abstract

Heart rate variability (HRV) is a relevant marker reflecting cardiac modulation by sympathetic and vagal components of the autonomic nervous system (ANS). Although the clinical application of HRV is mainly associated with the prediction of sudden cardiac death and assessing cardiovascular and metabolic illness progression, recent observations have suggested its applicability to physical exercise training. HRV is becoming one of the most useful tools for tracking the time course of training adaptation/maladaptation of athletes and in setting the optimal training loads leading to improved performances. However, little is known regarding the role of HRV and the internal effects of physical exercise on an athlete, which may be useful in designing fitness programs ensuring sufficient training load that may correspond with the specific ability of the athlete. In this review, we offer a comprehensive assessment of investigations concerning the interrelation between HRV and ANS, and examine how the application of HRV to physical exercise may play a role in sports physiology.

Keywords: autonomic nervous system; heart rate; heart rate variability; sport.

Figure 1.

Electrocardiogram (ECG) as the basis of measuring heart rate variability (HRV). (A) The electrical activity of the heart is detected by ECG. The waveform components indicate an electrical event during one heart beat. The waveforms are labeled P (first short upward movement of the ECG tracing), the QRS complex (Q-larger upwards deflexion, R-a larger upwards deflexion, S-downwards wave) shows ventricular depolarization and contraction. PR indicates the transit time required for the electrical signal to travel from the sinus to the ventricles of the heart. The T-wave is normally a modest waveform representing ventricular repolarisation. (B) Representation of HRV monitored and analysed to determine the state of the nervous system controlling the heart. The ANS is determined by detecting variation in consecutive time intervals between peaks of the QRS complex, R-R interval (red). Originally, HRV was measured manually from calculation of the mean R-R interval and its deviation was measured on short-term ECGs. Lower HRV corresponds to the smaller standard deviation in R-R intervals. There are several types of arithmetic manipulation of R-R intervals to represent HVR (34,62).