Does Wrist Based Heart Rate Monitoring Work for Heavy Lifting

I am starting to wonder if wrist based heart rate monitoring actually works for heavy lifting. I have been wearing my watch during my powerlifting sessions in London and the heart rate it shows seems very low for how much I am straining.

I think the way we grip the bar and the tension in the forearms messes with the optical sensor. I often see my heart rate drop during a heavy set of squats which makes no sense at all. It usually only spikes about thirty seconds after I have finished the set.

Should I just invest in a chest strap for the gym or is there a better way to wear the watch? I have tried moving it higher up my arm but it still seems to struggle with the quick bursts of intensity. I would love to hear if anyone has found a wrist sensor that actually handles the gym well.