[rrss1122]

You can try getting a tighter fit and see if that helps.

I've noticed with any consumer heart rate monitor, if the fit is not tight and the monitor moves even a little bit, the heart rate the monitor reports will be off. I'm assuming the same will apply to the Apple watch.

[brandonb]

That's good advice. When I had a Moto 360, I also sometimes did the opposite: loosen the strap one notch, and slide it up my arm slightly till it was taught again. Your forearm is a slightly easier place to measure pulse than on a bony wrist.

[collias]

Interesting thought. I'm going to try to place it further up my arm and see if it helps.

Thanks!