hamster wrote:Chest ones remain the gold standard for accuracy and take the electric signals to the heart.
However wrist-mount ones can work well: they work on skin flush and need good contact with the skin as watch vibration lets stray light in. Depending on handlebar grip, wrist dimensions, exact watch shape and even blood vessel position then they may work well or not at all for you when riding.
+1 on wrist shape /size and blood vessel. I gave my wrist HRM (Fitbit) to my niece and she could not get a bleep out of it, after numerous emails to the company they replied and said her blood vessels were too 'fine' to get an accurate reading. Apparently the thickness of the skin on your wrist and make a difference to a good reading also.