Table 1.
Generalized linear model: effect of functional calibration movement, segment reference frame, and optical functional calibration on the accuracy.
| Accuracy Indicator | RMSE (°) | ∆ROM (°) | DRIFT (°) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Calibration Factor | Functional Calibration Movement |
Segment Reference Frame |
Optical Functional Calibration |
Functional Calibration Movement |
Segment Reference Frame |
Optical Functional Calibration |
Functional Calibration Movement |
Segment Reference Frame |
Optical Functional Calibration |
||||
| Mean (SD) | Mean Difference between Methods | Mean (SD) | Mean Difference between Methods | Mean (SD) | Mean Difference between Methods | ||||||||
| Pelvis | Sagittal | 0.9 (0.5) | - | - | - | 0.4 (0.6) | 1.0 | - | - | 0.4 (0.6) | - | - | - |
| Frontal | 1.1 (0.9) | 1.3 | - | - | 0.5 (0.7) | 1.1 | - | - | 0.5 (0.7) | - | - | - | |
| Transverse | 1.5 (1.8) | - | - | - | 0.2 (0.2) | - | - | - | 0.2 (0.2) | - | - | - | |
| Hip right | Sagittal | 2.0 (1.2) | - | - | - | 1.6 (1.6) | - | 1.0 | - | 1.6 (1.6) | - | - | - |
| Frontal | 2.7 (2.1) | - | - | - | 2.3 (1.5) | - | - | - | 2.3 (1.5) | - | - | - | |
| Transverse | 2.4 (1.5) | - | - | - | 2.2 (1.3) | - | - | - | 2.2 (1.3) | - | - | - | |
| Knee right | Sagittal | 4.1 (3.1) | - | 1.5 | - | 2.4 (3.8) | 3.9 | - | - | 2.4 (3.8) | 1.2 | - | - |
| Frontal | 3.6 (2.3) | 4.0 | - | - | 4.7 (6.4) | 9.2 | - | - | 4.7 (6.4) | - | - | - | |
| Transverse | 3.3 (2.1) | - | 2.4 | - | 3.2 (5.2) | 4.3 | 3.1 | - | 3.2 (5.2) | - | - | - | |
| Ankle right | Sagittal | 2.5 (1.7) | - | 0.9 | - | 2.7 (5.1) | - | - | - | 2.7 (5.1) | - | - | - |
| Frontal | 3.3 (2.5) | 3.7 | - | 4.2 (5.6) | 7.2 | - | - | 4.2 (5.6) | - | - | 0.5 | ||
| Transverse | 2.4 (4.3) | 4.3 | 2.6 | - | 5.1 (6.6) | 5.6 | 2.8 | - | 5.1 (6.6) | 2.0 | 1.0 | - | |
| Hip left | Sagittal | 2.5 (0.8) | - | - | - | 0.8 (0.7) | - | - | - | 0.8 (0.7) | - | - | - |
| Frontal | 2.1 (1.6) | - | - | - | 1.9 (1.7) | - | - | - | 1.9 (1.7) | - | - | - | |
| Transverse | 2.1 (1.6) | - | - | - | 2.0 (1.8) | 1.9 | 0.6 | - | 2.0 (1.8) | - | - | - | |
| Knee left | Sagittal | 3.7 (3.5) | - | 1.9 | - | 1.9 (3.6) | - | - | - | 1.9 (3.6) | - | - | - |
| Frontal | 3.5 (1.7) | 1.9 | - | - | 4.3 (4.0) | 4.9 | - | - | 4.3 (4.0) | - | - | - | |
| Transverse | 3.0 (1.6) | - | 1.4 | - | 2.7 (3.9) | 3.0 | 2.6 | - | 2.7 (4.0) | - | - | - | |
| Ankle left | Sagittal | 3.2 (1.5) | - | - | - | 2.3 (4.0) | 4.6 | 2.2 | - | 2.3 (4.0) | - | - | - |
| Frontal | 2.9 (1.6) | 2.8 | - | - | 3.6 (3.9) | 3.8 | - | - | 3.6 (3.9) | - | - | - | |
| Transverse | 3.2 (4.3) | 4.8 | 2.4 | - | 3.6 (5.1) | 6.7 | 2.0 | - | 3.6 (5.1) | - | - | - | |
Numerical values indicate significant effects, dashes indicate non-significant effects. Mean differences between calibration factors are presented in degrees for significant effects (p < 0.05) and in bold for angles >3°. For the functional calibration movement factor, the highest mean difference between the six movements is presented. RMSE: root mean square error, ∆ROM: absolute difference in range of motion, DRIFT: absolute difference between IMU and optical system at end of recording, SD: standard deviation.