Descriptions and descriptive statistics for each feature included in all models averaged over the entire study protocol
| Variable | Description | Apple Watch Mean (SD) | Fitbit Mean (SD) |
| Steps/min | Number of steps/min | 181.4 (270.4) | 7.7 (21.8) |
| Heart rate (bpm) | Average heart rate/min | 91.1 (26.8) | 75.3 (38.7) |
| Energy expenditure | Amount of calories expended | 5.8 (7.3) | 40.8 (33) |
| Distance (m) | Distance ran in metres | 0.1 (0.1) | 23.8 (58) |
| Heart rate entropy | Measure of heart rate variability | 6.1 (0.2) | 5 (2.3) |
| Steps entropy | Measure of steps variability | 6.1 (0.2) | 3.9 (2.7) |
| Resting heart rate (bpm) | 10th percentile of HR data | 68.3 (11.9) | 59.1 (38.9) |
| Correlation heart rate and steps | Correlation coefficient between heart rate and steps | 0 (0.7) | 0.7 (0.6) |
| Intensity (Karvonen formula) | Intensity zone during activity | 0.2 (0.2) | 0.1 (0.2) |
| Steps*distance | Product measure of total amount of steps and distance covered in metres | 40.3 (113.5) | 967.6 (5275.1) |
| SD normalised heart rate | SD of normalised heart rate | 8.8 (10.1) | 7.7 (15.7) |