Apple Watch vs WHOOP: VO2max compared
How Apple Watch and WHOOP estimate your VO2max, what each needs from you, what else they show and what independent studies say about accuracy.
| Apple Watch | WHOOP | |
|---|---|---|
| Called | Cardio Fitness | VO2 Max |
| Algorithm | Apple in-house | WHOOP in-house machine-learning model |
| App | Health app (iPhone) | WHOOP app |
| From: Outdoor run | Yes | Yes |
| From: Walk | Yes | Not confirmed |
| From: Treadmill | No | Not confirmed |
| From: Bike (power meter) | Not confirmed | Not confirmed |
| From: Resting test | Not confirmed | Not confirmed |
| From: All-day data | Yes | Yes |
| Fitness age | Not confirmed | Not confirmed |
| Race predictor | Not confirmed | Not confirmed |
| Published accuracy studies | 3 | 0 |
| What you need to do | Wear the watch for at least 24 hours, then do several Outdoor Walk, Outdoor Run or Hiking workouts in the Workout app. Fairly flat ground, good GPS and heart rate signal help. | At least 14 recoveries (sleeps) in the last 21 days. Optional: a 15+ min outdoor run with Track Route on (in the last 90 days) and an up-to-date weight. |
Key differences
- Accuracy evidence: we found 3 published studies for Apple Watch and 0 for WHOOP.
How each one works
Apple Watch: Measures how hard your heart works (heart and motion sensors, GPS) during outdoor walks, runs and hikes, plus passive outdoor walking. It also uses your age, sex, weight, height and heart-rate medications.
WHOOP: A passive model uses resting physiology during sleep, activity volume and intensity, sleep habits and profile data. An outdoor run with phone GPS adds pace vs heart rate, and a lab result you enter can anchor future estimates.
Which is better for VO2max?
For VO2max specifically, the best device is the one that sees your hardest efforts: if most of your training is outdoor running, both give an estimate (both use outdoor run, all-day data). If you cycle with a power meter, walk more than you run, or want a resting test, check those rows above. Whichever you choose, compare the number with itself over time and with the norms for your age.
Accuracy studies
Apple Watch
- Lambe et al., Mayo Clin Proc Digit Health, 2026: Series 10 underestimated VO2max by 6.25 ml/kg/min on average; MAPE 13.2%; poor individual agreement.
- Lambe et al., PLoS One, 2025: Apple Watch underestimated VO2max by 6.07 ml/kg/min on average; MAPE 13.31%.
- Caserman et al., JMIR Biomed Eng, 2024: Series 7 estimate was lower than the lab value (41.37 vs 45.88 ml/kg/min); MAPE 15.79%, ICC 0.47.
WHOOP
No published, peer-reviewed validation found.
Frequently asked questions
Is Apple Watch or WHOOP more accurate for VO2max?
Apple Watch has more published validation (3 vs 0 studies). Watch estimates are typically within several ml/kg/min of lab tests for groups, with larger individual errors, so use either one to track your trend.
Does Apple Watch measure VO2max from outdoor run like WHOOP?
Yes: both estimate from outdoor run, all-day data.
Which is better for VO2max: Apple Watch or WHOOP?
Pick the one whose data sources match how you train: Apple Watch uses outdoor run, walk, all-day data; WHOOP uses outdoor run, all-day data.
Built from official documentation (see each brand page for sources). Features vary by model and firmware. Apple Watch and WHOOP are trademarks of their owners; VO2max Health is independent and not affiliated with either.