Are you serious about your sport. If so you need a serious heart rate monitor.Mio Alpha is the world’s first strapless, continuous heart rate monitorthat is as accurate as a chest strap, even at performance speeds.Totally unobtrusive, Alpha delivers maximum performance in ultimatecomfort. With no chest strap you won't have to worry about it sliding down or chafing.Alpha’s soft, stretchable silicone wrist band ensures a snug fit in a formfactor that won’t slow you down. So comfortable, you can wear it all day!Alpha is a true scientific breakthrough. Technology proven accurate in medical use, is now robust enough for sport. Sophisticatedalgorithms are applied to the pulse signal so that the heart’s true rhythmcan be detected even while running at performance speeds.