Monitoring Heart Rate Variability

Heart rate variability measures the variation in time between each heartbeat. Monitoring an athlete’s heart rate variability helps maximize their performance by optimizing training and reducing the risk of injury. Modern sports watches and mobile phone apps include heart rate variability monitoring technologies.

Santiago A. Ruiz-Alias and colleagues compared two popular heart rate variability monitoring methods in a recent study. They examined two different systems: the Polar Nightly Recharge function present in Polar sport watches and the Polar H10 chest strap synchronized with the Kubios software app.

Eleven recreational athletes were recruited to participate in an 8-week training program to monitor daily heart rate variability. The researchers found a “very large correlation” with an r-value of 0.714 and “good reliability” with an intraclass correlation coefficient value of 0.817 between the two devices for the 8-week duration.  

The researchers also used data from the first two weeks of the training program to determine the baseline heart rate variability. Then, they monitored the weekly heart rate variability changes during the next six weeks. Random errors led to a “60.6% of discordance in the likelihood interpretation of the change for the 66 weeks evaluated (11 athletes × 6 weeks).” 

The researchers conclude that athletes and practitioners “should be aware of these differences if their training groups use different devices or if an athlete interchanges them.” Nuances between different devices may result in discordant data. This may lead to inaccurate interpretations of an athlete’s autonomic nervous system modulation and overall state of health. However, as long as athletes and practitioners are aware of such differences, heart rate variability monitoring methods can help optimize training and performance.