Amazfit Helio Strap: 6-Month Scientific Review
These notes were generated by AI and may contain inaccuracies.
The Amazfit Helio Strap has become one of the most popular Whoop Strap alternatives of 2025. It's much cheaper with no subscription, leading many to switch from Whoop. Testing heart rate tracking and sleep stage tracking performance under different circumstances to see if it's as good or better than Whoop.
Rob is a post-doctoral scientist specializing in biological data analysis. Reviewed about 2 months of data with the special edition Helio Strap; sensor and build identical to normal Helio Strap, only strap differs. Worn on biceps for long-term testing as wrists needed for other devices.
Overview compares Amazfit Helio Strap to other devices like smartwatches, Whoop Strap, Polar Loop. Horizontal axis: agreement with reference device (correlation, higher better). Vertical axis: devices ordered worst to best. Better devices top right.
Showed all 2025 devices tested. Amazfit Helio Strap (biceps) one of the best, comparable to Apple Watches, Huawei Watch 5, Huawei Watch Fit models, Amazfit Balance 2. Wrist testing also good. Excellent for indoor cycling (spinning).
Spinning session: Polar H10 reference (blue-green) vs Helio Strap (red) shows near-perfect agreement. Interval session: perfect except minor low HR deviations. All spinning sessions similar, high correlation.
Recommends Runner app for runs (plans, custom plans, guidance; affiliate link for 2-week trial). Amazfit Helio Strap (biceps) super high correlation, outperforms most devices. Wrist version less good. Recommends for HR tracking.
Polar Loop (biceps) equal. Whoop Strap (biceps) slightly worse but ≥0.95 good enough. Examples: perfect agreement, 1-2 BPM differences, perfect even in intervals.
Hardest for devices. Helio Strap (biceps retest) 0.96-0.97 correlation, one of the best. Wrist worse. Polar Loop struggled on biceps for outdoor cycling. Whoop (biceps) like Helio on wrist. Helio outperforms Whoop.
Examples: minor deviations, occasional signal loss or auto-pause. Few rides with bigger deviations, but amazing vs competition.
Helio Strap (biceps) does well, same as original biceps test, comparable to Apple Watch (best wrist tracker). Better than Polar Loop (wrist), Whoop (biceps).
Examples: misses some peaks but detects most fully (few BPM off). Some sessions miss peaks, but best optical HR performance; only ECG chest strap better. Recommends sports watch + chest strap for accuracy. Helio close.
Indoor cycling: perfect, points on/near blue line. Running: mostly perfect, minor deviations in 1-2 runs. Outdoor cycling: most on line, few below. Weightlifting: higher HR misses some peaks, but very good vs competition.
Early 2025 poor; improved. Initial special edition test better, but REM struggled. ~30 nights vs ZMAX EEG headband reference (brain waves, eye movements; near gold standard PSG).
Confusion matrix (columns normalized 100%):
- Deep sleep: 82% agreement (17% confused with light).
- Light sleep: 78% agreement (confused with deep).
- REM sleep: ~50% agreement (struggles).
Ignore awake (reference detects false shorts). Overall ~70% average good if focusing deep/light, but REM pulls down.
Horizontal: average agreement (deep/light/REM). Vertical: worst stage (REM ~50% for Helio). Helio middle: Whoop MG outperforms, Polar Loop underperforms.
2025 top: Eight Sleep Pod 5 (best on body), Apple Watch Ultra 3/Series 11, Pixel Watches, Galaxy Watch 8/8 Classic/Ultra (improving), Oura Ring (consistent; top in U. Salzburg study). Whoop/Apple/Pixel strong.
Recommends Whoop over Helio for sleep stages, or expensive Eight Sleep Pod (mattress cooler/heater, independent sides; affiliate link).
Best price/quality ratio. Sleep stages < Whoop, app < Whoop/Oura (Zepp improving, resembles older Whoop). Whoop excels in sleep/HR/app combo but subscription. Helio great no-sub alternative; Amazfit improving.
Data from reviewer's body. Affiliate links for Amazfit Helio, Whoop, Polar Loop, Suunto watches, Coros Pace 4, Amazon, Runner app, Strava Premium (20% off).
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