I wore Whoop, Apple Watch and a Polar H10 at the same time for 81 workouts. Here's where Whoop falls apart
Wore a Polar H10 chest strap, a Whoop on the wrist and an Apple Watch all at the same time across 81 workouts. Recorded every device at 1-second intervals. Treating the Polar as ground truth (chest straps are what every fitness study uses as the baseline), here's where Whoop consistently goes wrong.
Three screenshots below from real sessions. In all of them: Polar is blue, Apple Watch is green, Whoop is orange.
Walking — Whoop reads too HIGH. You can see the orange line sitting clearly above Polar and Watch the whole time I was actually walking. Polar and Watch agree with each other almost perfectly. Whoop drifts up by 15-20 BPM. Only when I stopped moving in the middle did all three line up.
Stretching — Whoop reads too LOW. The actual heart rate (Polar) climbs up toward 140-150, Watch follows it almost exactly, but Whoop is stuck around 100-115. Lost the signal completely. Average gap was about 25 BPM.
Elliptical — Whoop sees the shape of the heart rate (peaks and valleys are in roughly the right places) but the whole line sits about 20 BPM below the truth for the entire workout. Polar and Watch are agreeing up at 140-160, Whoop is reading 110-135. The trend is there, the number isn't. This is the dangerous one because the trace looks plausible — you wouldn't know it's wrong unless you had something to compare it to.
The one place Whoop on the wrist actually nails it is steady cycling — basically dead-on with the chest strap.
Apple Watch on the wrist was much closer to Polar than Whoop was, almost the whole time. Both run a bit low vs the chest strap on average, but Whoop's errors are roughly double the Watch's across the 81 workouts.
Anyone else seeing this? Curious if it's just my Whoop unit or if this is everyone.
P.S. when I moved the Whoop to my bicep instead of the wrist, it was actually in sync with Polar most of the time. Had to take it off for punchbag sessions though, kept falling off the arm from the hits.