There are several mobile and easy to use heart rate monitors which which allow heart rate variability (HRV)
IntroductionHeart rate variability (HRV) remains a powerful source for autonomic nervous system (ANS) assessment by using simple and non-invasive techniques. It is used in both clinical and research environments and over a broad spectrum of disciplines concerned with autonomic control of the heart ranging from cardiology to psychology. Advances in technology have allowed the development of mobile and easy to use heart rate monitors that allow the quantification of inter-beat intervals (RR intervals) and thus the analysis of heart rate variability. Commercial devices (like Polar, Garmin, Tomtom, or Suunto heart rate monitors, among others) appear as a cheaper alternative, usually providing software which allows for an affordable and a user-friendly method to determine short-term HRV outside of the laboratory setting.These heart rate monitors have been used by scientists for HRV analysis in sport sciences, medicine and other fields of research [1][2][3]. Several studies have validated these devices against different ECG systems, showing promising results at rest [4][5][6]. However, there are very few studies that validate HRV measurements from heart rate monitor devices during dynamic exercise of high intensity, which is characterized by a higher level of noise than in static exercise, larger variations in mean heart rate (HR) and respiratory frequency and the appearance of cardiolocomotor coupling (CC) components during high intensities.In a previous study [12], we evaluated the agreement and reliability between the HRV analysis derived from the RR series recorded by the HR monitor Polar RS800 and HRV analysis derived from a simultaneous ECG during dynamic exercise of low, medium and high intensity. At rest, Polar measurements showed high agreement and reliability indices as expected. During high intensities of exercise, however, high frequency (HF) parameters showed low agreement.The aim of this study is to evaluate changes in ANS during high intensity exercise using Polar measurements, despite the low agreement in HF parameters, to see whether the same information can be extracted than from measure-