Heart Rate Monitors Don't Lie (But Your Wrist Might)

The moment my Garmin’s wrist HR (red) realised it forgot to train for this sprint.

I’ll admit it: I bought the Polar H10 because a study said it was 99% accurate, and and I can that it picks up data way quicker.. I just had to be sure so after more than six months of wearing a chest strap like some kind of cyborg, here’s the truth about wrist-based heart rate tracking:

When Wrist HR Works

• Zone 2 rides/runs: Nearly identical to the Polar. If you’re just cruising, your wrist is fine.
• Daily metrics: Resting HR, sleep data, no problem.

When It Doesn’t

• Intervals? The graph says it all. Wrist HR takes ages to catch up (if it even does!).
• Quick spikes? By the time it catches up, you’re already wheezing.

Accurate Data Whout Spending £££

Turns out, you don’t need to spend £70 on a chest strap. I’ve been testing a £20 Coospo H9Z from AliExpress (spoiler: it’s shockingly good), and I’ll pit it against the Polar in my next post. Because nothing says “serious athlete” like bargain-hunting for sensors.

Bottom line: If you care about accuracy during hard efforts, strap something to your chest. Otherwise, enjoy the convenience - and the lies.

Also if you noticed on the graph there are 2 more lines. I wanted to see the difference (if any) between the power reported by my Wahoo Kickr V5 and my crank based powermeter, 4iii PRECISION 3. Good news. All the same.