POLAR
Pick Polar if
- Train by HRV and recovery score
- You don't mind wearing a chest strap (e.g. the H10)
- You compete and need lab-grade variability
Polar vs Fitbit
Polar wins on athletic-grade HRV, recovery, and training load. Fitbit wins on signal breadth — sleep stages plus AFib screening, which Polar's own wrist ECG never gives you.
POLAR
18/33signals its devices cover
Sport watch / chest strap
vs
fitbit
22/33signals its devices cover
Daily-wear watch + scale
QUICK VERDICT
If you race or run hard intervals, Polar's chest strap gives you the cleanest HRV signal MyBodyAI can read. If you want one watch handling everything from sleep stages to AFib screening, Fitbit covers a wide signal set without a second device.
COVERAGE BY CATEGORY
Where each brand actually wins
Per-category breakdown of health signals exposed by each vendor's developer API. The number is breadth, not quality.
SIGNAL BY SIGNAL
The full matrix
| Signal | Polar | Fitbit |
|---|---|---|
| Heart & Vitals | ||
| Resting HR | ✓ | ✓ |
| HRV | ✓ | ✓ |
| SpO2 | ✓ | ✓ |
| Respiratory Rate | ✓ | ✓ |
| Skin Temperature | ✓ | ✓ |
| Body Temperature | — | — |
| Blood Pressure | — | — |
| ECG recording | ✓ | ✓ |
| AFib detection | — | ✓ |
| Vascular age | — | — |
| Sleep | ||
| Sleep duration | ✓ | ✓ |
| Sleep stages | ✓ | ✓ |
| Sleep score | ✓ | ✓ |
| Sleep efficiency | ✓ | ✓ |
| Sleep apnea index | — | — |
| Activity | ||
| Steps | ✓ | ✓ |
| Active minutes | ✓ | ✓ |
| Calories | ✓ | ✓ |
| Activities | ✓ | ✓ |
| Floors climbed | — | ✓ |
| Distance | ✓ | ✓ |
| Fitness & Recovery | ||
| VO2max | ✓ | ✓ |
| Training load | ✓ | ✓ |
| Recovery / Readiness | ✓ | ✓ |
| Body Battery | — | — |
| Stress (continuous) | — | ✓ |
| Cardiovascular age | — | — |
| Body Composition | ||
| Weight | — | ✓ via Fitbit Aria Air |
| Body fat % | — | — |
| Muscle mass | — | — |
| Hydration | — | — |
| Bone mass | — | — |
| Visceral fat | — | — |
Verified against vendor developer documentation and MyBodyAI backend code. This counts what a brand's API exposes, which is not the same question as what one device measures: the device catalog scores each model's own hardware, so its numbers differ.
Current Polar models Street X (2026), Grit X2 (2025), Loop (2025), Grit X2 Pro (2024), all 11 Polar devices
Current Fitbit models Google Fitbit Air (2026), Google Pixel Watch 4 (2025), Google Pixel Watch 3 (2024), Fitbit Charge 6 (2023), all 8 Fitbit devices
WHICH ONE FOR YOU
Pick the one that matches your priority
fitbit
Pick Fitbit if
- You want a single wrist device for everything
- AFib screening matters to you
- Sleep stages + SpO2 + skin temperature in one place
POLAR+fitbit
Pick both if
- Polar chest strap during structured workouts
- Fitbit Charge or Pixel Watch 24/7 for sleep + SpO2
- MyBodyAI merges both feeds; richer source wins per field
FAQ
Frequently asked questions
Should I choose Polar or Fitbit?
For most people it is one or the other. Both are daily-wear devices that track the same core things, heart rate, sleep and activity, so wearing both is redundant. Use the matrix above to pick the one that wins the categories you care about.
Which one tracks more health signals?
Polar tracks 18 of the 33 signals I compare, Fitbit tracks 22. The matrix above breaks it down by category, and they often win different categories.
Is it worth switching from Polar to Fitbit?
Only if Fitbit wins the categories you actually care about. If you already own Polar and it covers your main goal, the upgrade is rarely worth it. The matrix above shows exactly what changes.
How did you compare Polar and Fitbit?
From each brand's official spec sheets and support pages, cross-checked against independent hands-on reviews (DC Rainmaker, the5krunner, Tom's Guide). Signal-level edge cases are noted in the matrix, not hidden behind a single check mark.
WHERE TO BUY
Check prices at the source
Links to each vendor's store. None of them changed any pick above.
MORE COMPARISONS
Explore other pairs
OPTIONAL — IF YOU WANT MORE
Want one place that merges both feeds?
MyBodyAI is what I build with these signals — it pulls from any combination of the brands above and derives Biological Age and 12 health indices from the raw numbers. Free to try, no card. It's optional — the comparison above stands on its own.
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