A fitness tracker can be used interchangeably with a reference method for underwater single-lead electrocardiography but not heart rate variability analysis in swimming horses.

This research has found that a fitness tracker can reliably monitor heart rate in swimming horses, but it may not be as accurate when measuring heart rate variability.

Study Objective and Methodology

The study aimed to test the reliability and accuracy of a single-lead ECG fitness tracker (FT) in comparison to a multilead ECG recording device (RM), traditionally used as a reference. The main considerations were heart rate (HR) and heart rate variability (HRV) in swimming horses.

• The study involved 40 race-fit Thoroughbred racehorses who swam 63.65 m across a pool for five consecutive days in May 2024.
• Both the fitness tracker and the reference method were used concurrently to record the ECG of the horses while they were swimming.
• Any recorded artifacts were corrected where necessary, and the HR and HRV parameters from both devices were compared and analyzed.
• Statistical tests were used to evaluate the concordance between the data produced by both devices.

Research Findings

The research discovered:

• A negligible bias, almost non-existent, was observed for heart rate readings between the two devices. This was evidenced by a correlation coefficient of 0.99, almost perfect, and a root mean squared error of 0.28 beats per minute.
• However, when assessing HRV parameters, the fitness tracker showed additional variability and bias compared to the reference method, signaling that it may not be relied upon to monitor heart rate variability as accurately.

Conclusions and Implications

The study concludes that the tested fitness tracker can be reliably used to monitor heart rate in swimming horses. This finding has implications in training scenarios where fitness and workload can be monitored conveniently with the device.

However, the study does not recommend the use of the fitness tracker to undertake comprehensive analysis of HRV while swimming, until the observed bias and variability are corrected. This indicates a need for further testing and validation of the fitness tracker for HRV assessment in swimming horses.