Almost certainly true. Also, how accurate are these optical HR sensors? Chest strap monitors are somewhat more accurate than optical monitors: http://www.ware

Almost certainly true. Also, how accurate are these optical HR sensors? Chest strap monitors are somewhat more accurate than optical monitors: http://www.wareable.com/sport/heart-rate-monitors-chest-straps-v-wrist http://www.wareable.com/sport/heart-rate-monitors-chest-stra... And it's unclear whether the optical measures are accurate enough to inform health decisions. I can say we've looked at this at our company and it's a fairly complicated picture...