I got an apple watch for my birthday last week. I had been coveting one for ages, for the main reason of being able to measure heart rate during exercise
It doesn't seem to measure my HR accurately (I seem to have it positioned correctly according to instructions). I got a reading of 138 for a brisk walk and 139 for a very heavy spin class (that would normally be c.160 on my Polar HR chest strap)
I'm quite slim with very (horrid) veiny arms. Could this 'throw' it off?"