[LorenPechtel]

You need the band on your tracker to be very snug or this is likely to happen. You're actually seeing the tracker move, not the heart rate.

I've seen substantial mismatches between wrist and chest strap if my tracker had any ability to wiggle. With an infinitely adjustable metal band set so there's no slack but no pressure I see a good correspondence, although I haven't put it a test as hard as rowing (my activity of choice is hiking.) But my wife absolutely doesn't like such a band, wearing a soft, loose band and using her arms her "heart rate" has gone above 200.

I have also seen an environmental effect--these days I use the chest strap sensor because if my wrist is cold (conditions just below when I would add another layer) the wrist data can go totally bonkers.

[NotCamelCase]

That's a good point, thanks.