Comparison of heart-rate-variability recording with smartphone photoplethysmography, Polar H7 chest strap, and electrocardiography - Plews, D. J.; Scott, B.; Altini, M.; Wood, M.; Kilding, A. E.; Laursen, P. B. (International Journal of Sports Physiology and Performance, 2017)
Keywords: heart rate; variability; measuring procedure; technology; training control; heart rate variability; training science