Table 1.
Joint angle (referenced to initial heel strike value) comparisons between inertial measurement units and optical motion capture.
| Froude | Axis | L5/S1 | T12/L1 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| RMSE | NRMSE | R | Lag | RMSE | NRMSE | R | Lag | ||
| 0.1 (Walk) | FE | 0.08 | 0.21 | 0.46 | 25 | 0.02 | 0.21 | 0.46 | 25 |
| LB | 0.03 | 0.06 | 0.91 | 3 | 0.05 | 0.24 | 0.86 | 0 | |
| AR | 0.30 | 0.29 | 0.99 | − 6 | 0.02 | 0.12 | 0.99 | 3 | |
| 0.2 (Walk) | FE | 0.08 | 0.21 | 0.82 | − 12 | 0.02 | 0.21 | 0.82 | − 12 |
| LB | 0.01 | 0.02 | 0.98 | 4 | 0.05 | 0.14 | 0.93 | 7 | |
| AR | 0.32 | 0.23 | 0.99 | − 3 | 0.01 | 0.03 | 0.99 | 2 | |
| 0.3 (Walk) | FE | 0.08 | 0.26 | 0.77 | − 15 | 0.02 | 0.26 | 0.77 | − 15 |
| LB | 0.02 | 0.02 | 0.98 | 5 | 0.10 | 0.23 | 0.94 | 12 | |
| AR | 0.43 | 0.25 | 1.00 | − 3 | 0.02 | 0.09 | 1.00 | 5 | |
| 0.6 (Run) | FE | 0.25 | 0.18 | 0.69 | 19 | 0.07 | 0.18 | 0.69 | 19 |
| LB | 0.19 | 0.35 | 0.15 | − 32 | 0.47 | 0.37 | 0.83 | 1 | |
| AR | 0.00 | 0.00 | 0.86 | 0 | 0.05 | 0.26 | 0.92 | − 16 | |
| 0.8 (Run) | FE | 0.36 | 0.19 | 0.54 | 20 | 0.10 | 0.19 | 0.54 | 20 |
| LB | 0.13 | 0.15 | 0.79 | − 6 | 0.37 | 0.24 | 0.02 | 28 | |
| AR | 0.04 | 0.02 | 0.64 | 21 | 0.12 | 0.23 | 0.94 | − 14 | |
| 1.0 (Run) | FE | 0.25 | 0.17 | 0.75 | 24 | 0.07 | 0.17 | 0.75 | 24 |
| LB | 0.32 | 0.32 | 0.25 | 11 | 0.58 | 0.34 | 0.06 | − 28 | |
| AR | 1.32 | 0.37 | 0.99 | − 1 | 0.22 | 0.65 | 0.02 | − 10 | |
L5/S1, lumbosacral joint; T12/L1, thoracolumbar joint; FE, flexion–extension; LB, lateral bending; AR, axial rotation; RMSE, root mean squared error; NRMSE, normalized root mean squared error; R , cross-correlation. Lag is % of stride cycle (positive value indicates OMC signal occurs before IMU signal).