Validity of Photoplethysmography Mobile Analysis to Test the Autonomic Stress Status of Tactical Athletes

"Background: The effect of stress on sympathetic modulation measured by HRV has been studied in various population groups exposed to different stressors. HRV measurement tools are based on the electrocardiogram (ECG), portable tools such as POLAR V800, and recently photoplethysmography (PPG). The aim of this study was to analyze the validity of a PPG mobile app to measure HRV with a validated V800 system in a tactical athlete population. Methods HRV of 53 professional militaries were analyzed by POLAR V800 and an HRV Camera app with a smartphone during 5 min and 30 s protocol respectively. Results: The HRV values obtained by the PPG presented a significant negative significant correlation in the HRVI index, LF, HF, LF (n.u.), HF (n.u.), and a positive significant correlation in TINN index by the Polar V800 system with the application of a regression equation over the data obtained. Conclusions: HRV Camera PPG App 30s record analysis protocol could be applied using a regression formula depending on the HRV variables after the comparison with a standard 5-minute test conducted with a validated Polar V800. In future research, it is suggested to validate PPG protocols with longer durations."