The use of heart rate variability (HRV) to monitor athletic training status in field settings is continuing to gain popularity among practitioners. This is because HRV is an objective, physiological marker that is sensitive to changes in fatigue and fitness. It has been used to evaluate how athletes are adapting to training and to avoid excessive fatigue. However, a major limitation of implementing HRV in the field is maintaining compliance from athletes. For HRV to be really effective, data must be collected near daily for meaningful interpretation of training status. However, getting your athletes to perform an HRV recording every day when they wake up is not an easy task. Fortunately, smartphone applications have been made available that have streamlined the process of an HRV recording. One of the latest technologies for HRV data acquisition is a pulse-wave finger sensor (PWFS) app that measures pulse rate from your finger tip via photo-plethysmography. Essentially, the apparatus emits an infrared light source to that detects changes in the microcirculation of the finger-tip. However, there is much skepticism as to the accuracy of such a device for accurately measuring HRV.
A new study published ahead of print in the Journal of Strength and Conditioning Research tested the accuracy of the PWFS (ithlete) in the supine, seated and standing position among 30 college-aged students (15 males and 15 females). Most subjects were athletes or strength and conditioning interns. Each subject reported to the laboratory in a fasted state and was connected to an ECG, which provided the gold standard HRV data. Both ECG and PWFS were recorded simultaneously for each position with one-minute stabilization periods between positional changes. This was provided to accommodate the changes in heart rate that occur in response to postural change. The data was then compiled for each position and the HRV values (i.e., lnRMSSD) were compared between the ECG and PWFS.
The mean values for the supine position were 81.5 ± 11.7 for the ECG and 81.6 ± 11.3 for PWFS; for the seated position were 76.5 ± 8.2 for the ECG and 77.5 ± 8.2 for the PWFS; and for the standing position 66.5 ± 9.2 for the ECG and 67.8 ± 9.1 for the PWFS. Effect sizes were trivial (<0.20) for all comparisons. Correlation coefficients were near perfect for all positional measurements (r values 0.98 – 0.99). Furthermore, the limits of agreement were tight for all measures. Therefore, it appears that coaches can confidently use the ithlete PWFS in the field for obtaining HRV measures with their athletes. This may further enhance convenience of HRV data acquisition and enhance compliance among athletes.
Esco, MR., Flatt, AA., Nakamura, FY. (2016) Agreement between a smartphone pulse sensor application and ECG for determining ln RMSSD. J Str Cond Res. Ahead of print.