Table 6.

Accuracy of the estimated knee flexion/extension (F/E) angles (by ANN₁) and vertical ground reaction forces (vGRF) (by ANN₂) using different training outputs (namely: IMU or Plug-in Gait-based) by training on data of all subjects except for one which is used for the evaluation at 12 km/h.

Knee F/E angle accuracy
Subjects	IMU				Plug-in Gait
	Left F/E		Right F/E		Left F/E		Right F/E
	ρ	RMSE (σ)	ρ	RMSE (σ)	ρ	RMSE (σ)	ρ	RMSE (σ)
S01	0.88	19.11 (4.92)	0.83	19.47 (3.66)	0.77	25.05 (2.20)	0.83	23.57 (2.13)
S02	0.99	8.57 (0.74)	0.99	8.09 (0.79)	0.98	11.87 (1.08)	0.98	6.76 (0.71)
S03	0.95	14.92 (1.54)	0.94	11.08 (1.32)	0.91	15.19 (1.54)	0.91	22.57 (4.03)
S04	0.98	8.35 (0.76)	0.98	6.68 (1.12)	0.93	11.36 (0.93)	0.98	6.90 (0.94)
S05	0.98	9.89 (1.10)	0.98	7.00 (1.28)	0.96	19.62 (3.62)	0.97	7.41 (1.43)
S06	0.98	7.33 (1.00)	0.99	6.99 (1.07)	0.97	7.70 (0.99)	0.98	8.76 (1.46)
S07	0.98	5.88 (0.68)	0.99	4.83 (0.99)	0.98	6.83 (0.81)	0.98	6.62 (0.85)
S08	0.98	6.36 (1.18)	0.99	4.66 (0.92)	0.98	6.29 (1.09)	0.99	7.21 (0.89)
vGRF accuracy
Subjects	IMU				Plug-in Gait
	Left vGRF		Right vGRF		Left GRF		Right vGRF
	ρ	RMSE (σ)	ρ	RMSE (σ)	ρ	RMSE (σ)	ρ	RMSE (σ)
S01	0.92	0.45 (0.10)	0.90	1.25 (0.25)	0.94	0.52 (0.11)	0.86	0.56 (0.08)
S02	0.95	0.31 (0.08)	0.99	0.16 (0.03)	0.98	0.22 (0.04)	0.97	0.27 (0.05)
S03	0.95	0.50 (0.18)	0.98	0.60 (0.09)	0.83	0.81 (0.19)	0.97	0.38 (0.07)
S04	0.98	0.26 (0.06)	0.95	0.32 (0.05)	0.95	0.34 (0.19)	0.98	0.30 (0.05)
S05	0.99	0.21 (0.05)	0.97	0.32 (0.07)	0.97	0.33 (0.08)	0.99	0.20 (0.07)
S06	0.98	0.25 (0.04)	0.94	0.36 (0.03)	0.97	0.28 (0.04)	0.99	0.20 (0.04)
S07	0.96	0.30 (0.04)	0.98	0.22 (0.04)	0.97	0.29 (0.05)	0.97	0.27 (0.05)
S08	0.93	0.46 (0.05)	0.98	0.24 (0.04)	0.91	0.44 (0.05)	0.98	0.28 (0.04)

Pearson's correlation coefficient (ρ) is calculated for each stride and averaged over approximately 200 strides for each different test subject (S01, S02, S03, S04, S05, S06, S07 and S08). The Root Mean Squared Error (RMSE) is calculated similarly over all strides.