Table 3.

Comparison of the fixed effects and random effects of 3 different models for predicting F_med based on the EAM alone or using combinations of the EAM and the EFM^*

	Fmed = a + b × EAM			Fmed = a + b × EAM + c × EFM				Fmed = a + b × EAM + c × |EFM|
	a [%BW]	b [1/height]	RMSE [%BW]	a [%BW]	b [1/height]	c [1/height]	RMSE [%BW]	a [%BW]	b [1/height]	c [1/height]	RMSE [%BW]
Fixed effects	80	34		67	32	1		64	33	5
Random effects
Activity
Walking	4	3	31	18	5	−13	30	26	3	−12	31
Stair climbing	25	1	34	31	4	−1	35	31	3	−3	34
Stair descending	−7	5	34	13	4	−2	33	10	5	−5	33
Sit-to-stand	5	−18	32	−14	−10	8	22	−18	−8	6	19
Stand-to-sit	1	−3	29	−3	−13	8	23	−2	−12	5	23
Squat	−1	3	23	−13	0	6	20	−16	1	3	19
Squat varus	−1	2	18	−12	1	8	14	−18	2	6	13
Squat valgus	−8	−8	18	−21	−10	7	15	−26	−9	4	13
Weight transfer	−7	7	31	−2	8	−6	29	5	7	−3	30
One-legged stance	−11	10	43	1	11	−17	36	6	8	−1	40

^*Errors in the model predictions are reported as the root mean square error (RMSE). F_med = medial tibiofemoral contact force; a, b, c, = free regression parameters; EAM = external knee adduction moment; EFM = external knee flexion moment; %BW = % body weight.