χ² variable importance results for Apple Watch and Fitbit from the Rotation Forest model
| Ranking | Apple Watch | Fitbit |
| 1 | Heart rate | Distance |
| 2 | Normalised heart rate | Steps |
| 3 | Steps | Heart rate |
| 4 | Intensity | Normalised heart rate |
| 5 | Calories | Steps*distance |
| 6 | Distance | Intensity _low energy |
| 7 | Steps*distance | Calories |
| 8 | SD normalised HR | SD normalised HR |
| 9 | Correlation heart rate and steps | Entropy steps per day |
| 10 | Weight | Resting heart rate |