Heart Rate Variability Monitoring in Athletes

Introduction: Heart Rate Variability (HRV) is a popular assessment of the autonomic nervous system (ANS). It is a non-invasive measure commonly used in clinical settings to evaluate cardiovascular health and ANS function. In athletes/athletic populations it provides insight into recovery status and readiness for training. Although this assessment has been validated in clinical populations, the reliability of using HRV measurements in practical settings has not been comprehensively studied nor is there any universal guidelines dictating best practice for use with athletes. This thesis outlines some of the concerns pertaining to the reliability of this assessment and the steps in developing new guidelines to ensure best practice can be met, both for research and practical uses. The aim of this thesis is to investigate the reliability and practicality of using HRV to monitor athletes, (1) in a systematic review of studies examining the reliability of HRV in athletes and (2) through a test-retest reliability study of HRV. Methods: Elite or regularly active athletes of all sports, (including endurance, team sport and power-based sports) were eligible for inclusion in both the systematic review and research study. In the systematic review, the reliability of different HRV measurement protocols were examined. The systematic review included 11 papers and a total of 215 participants. In the test-retest reliability study participants were tested for HRV on 4 occasions determined from a 30 minute 3-lead ECG measurement. The research study included 16 athletes (5 male, 11 female). Results: The systematic review found that the 1996 guidelines created by the Electrophysiology Task Force of the European Society of Cardiology and the North American Society of Pacing for HRV measurements in athletes are underutilised and the reporting of methodologies was not consistent amongst studies. Reliability results were also not consistent among the studies investigated (CV ranging from 1.80 – 61.0% for lnRMSSD). The original research study conducted showed that the use of an average of two 30minute HRV measures within a one-week period is a reliable method to assess HRV (ICC = 0.798, CV = 5.88 +/- 4.34%). It also showed that shorter HRV measurements are as reliable as the 30minute reference measure when using this protocol. Conclusions: The current recommended guidelines for HRV measurements in the general population are both insufficient and under used in the testing of athletic populations. Care should be taken in future studies to ensure methodologies are appropriately reported. HRV can be a reliable tool for monitoring autonomic function in athletic populations if suitable protocols are followed.