Table 2.
Joint moment (normalized to body weight times height) 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 | < 0.01 | 0.20 | 0.96 | 0 | < 0.01 | 0.18 | 0.99 | 0 |
| LB | < 0.01 | 0.00 | 0.61 | 6 | < 0.01 | 0.02 | 0.57 | − 19 | |
| AR | < 0.01 | 0.01 | 0.95 | 0 | < 0.01 | 0.02 | 0.87 | − 5 | |
| 0.2 (Walk) | FE | < 0.01 | 0.11 | 0.96 | 0 | < 0.01 | 0.11 | 0.99 | 0 |
| LB | < 0.01 | 0.04 | 0.68 | 8 | < 0.01 | 0.05 | 0.72 | − 16 | |
| AR | < 0.01 | < 0.01 | 0.84 | 2 | < 0.01 | 0.00 | 0.94 | − 4 | |
| 0.3 (Walk) | FE | < 0.01 | 0.07 | 0.91 | 0 | < 0.01 | 0.08 | 0.98 | 0 |
| LB | < 0.01 | 0.01 | 0.76 | -9 | < 0.01 | 0.01 | 0.80 | − 11 | |
| AR | < 0.01 | 0.01 | 0.86 | 3 | < 0.01 | 0.01 | 0.90 | − 5 | |
| 0.6 (Run) | FE | 0.01 | 0.16 | 0.99 | 2 | < 0.01 | 0.14 | 0.99 | 1 |
| LB | < 0.01 | < 0.01 | 0.62 | − 2 | < 0.01 | 0.13 | 0.69 | − 6 | |
| AR | < 0.01 | 0.01 | 0.91 | 2 | < 0.01 | 0.01 | 0.94 | 0 | |
| 0.8 (Run) | FE | 0.01 | 0.12 | 0.99 | 1 | < 0.01 | 0.10 | 0.97 | 0 |
| LB | < 0.01 | 0.01 | 0.42 | − 23 | < 0.01 | 0.06 | 0.66 | − 7 | |
| AR | < 0.01 | 0.02 | 0.91 | 0 | < 0.01 | 0.01 | 0.91 | 0 | |
| 1.0 (Run) | FE | 0.01 | 0.11 | 0.99 | 3 | < 0.01 | 0.11 | 0.99 | 2 |
| LB | < 0.01 | 0.02 | 0.67 | − 2 | < 0.01 | 0.02 | 0.77 | − 8 | |
| AR | < 0.01 | 0.03 | 0.91 | 0 | < 0.01 | 0.00 | 0.94 | 0 | |
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).