TABLE 3.
Mean (SD) root mean square error (RMSE) and range-normalized RMSE of knee angle and angular velocity during level walking, incline walking, decline walking, stair ascent and stair descent. Joint kinematics were predicted by Gaussian process regression models trained and tested on features from five sensing modalities: 1) surface electromyography (EMG), 2) anterior sonomyography (Ant. SMG), 3) posterior sonomyography (Pos. SMG), 4) sensor fusion of Ant. SMG with EMG (Ant. Fusion), and 5) sensor fusion of Pos. SMG with EMG (Pos. Fusion). Overall average values are mean across all ambulation tasks.
| Ambulation task | Mean (SD) knee angle RMSE (deg) | nRMSE knee angle (%) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| EMG | Ant. SMG | Pos. SMG | Ant. Fusion | Pos. Fusion | EMG | Ant. SMG | Pos. SMG | Ant. Fusion | Pos. Fusion | |
| Level walk | 7.36 (2.08) b , c , d | 4.73 (1.25) | 5.84 (3.00) | 3.77 (0.81) | 4.42 (1.85) | 11.7% | 7.6% | 9.2% | 6.0% | 6.9% |
| Incline walk | 6.62 (0.99) a | 4.03 (1.39) | 4.53 (1.10) | 3.22 (0.91) | 3.58 (0.94) | 13.0% | 7.7% | 3.9% | 6.2% | 7.0% |
| Decline walk | 7.37 (2.12) a | 4.97 (1.10) | 5.40 (1.36) | 3.94 (1.03) | 4.02 (1.03) | 11.2% | 7.6% | 8.3% | 6.0% | 6.1% |
| Stair ascent | 13.78 (7.21) b , c | 8.56 (1.56) | 11.52 (4.75) | 7.63 (1.56) | 10.92 (4.26) | 19.8% | 12.7% | 16.5% | 11.4% | 15.4% |
| Stair descent | 14.90 (3.28) b , c | 8.25 (2.95) | 12.40 (4.37) e | 7.67 (2.57) | 11.09 (3.74) | 17.9% | 9.9% | 14.9% | 9.3% | 13.3% |
| Overall average | 10.01 (3.13) a | 6.11 (1.65) | 7.94 (2.92) e | 5.25 (1.38) | 6.80 (2.36) | 14.7% | 9.1% | 11.6% | 7.8% | 9.8% |
| Ambulation task | Mean (SD) knee angular velocity RMSE (deg/s) | nRMSE knee angular velocity (%) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| EMG | Ant. SMG | Pos. SMG | Ant. Fusion | Pos. Fusion | EMG | Ant. SMG | Pos. SMG | Ant. Fusion | Pos. Fusion | |
| Level walk | 93.67 (16.54) b , c | 67.33 (22.56) | 80.96 (20.74) | 64.57 (19.03) | 79.50 (15.69) | 15.6% | 11.3% | 13.4% | 10.9% | 13.2% |
| Incline walk | 51.59 (8.66) b , c , d | 35.93 (14.58) | 40.98 (6.61) e | 27.61 (9.13) | 35.27 (7.99) | 14.4% | 9.6% | 11.4% | 7.4% | 9.8% |
| Decline walk | 61.63 (11.82) | 53.12 (14.00) | 61.70 (18.98) | 45.37 (11.22) | 48.50 (14.05) | 12.4% | 10.7% | 12.0% | 9.1% | 9.5% |
| Stair ascent | 90.61 (28.58) c | 62.77 (10.78) | 81.20 (30.33) | 55.20 (13.59) | 74.55 (28.59) | 19.0% | 13.0% | 16.8% | 11.3% | 15.8% |
| Stair descent | 111.38 (27.31) b , c | 72.41 (21.90) | 104.14 (37.79) | 67.12 (16.00) | 93.59 (35.41) | 18.9% | 12.3% | 17.7% | 11.5% | 15.9% |
| Overall average | 81.77 (18.58) b , c | 58.31 (16.76) | 73.80 (22.89) e | 51.97 (13.79) | 66.28 (20.35) | 16.1% | 11.4% | 14.3% | 10.0% | 12.8% |
Indicates significant difference (p< 0.05) between RMSE, of EMG, and all other sensing modalities.
Indicates significant difference between (p< 0.05) RMSE, of EMG, and anterior SMG.
Indicates significant difference between (p< 0.05) RMSE, of EMG, and anterior sensor fusion (anterior SMG, with EMG).
Indicates significant difference between (p< 0.05) RMSE, of EMG, and posterior sensor fusion (posterior SMG, with EMG).
Indicates significant difference between (p< 0.05) RMSE, of posterior SMG, and anterior sensor fusion (anterior SMG, with EMG).