A portable system for collecting anatomical joint angles during stair ascent: a comparison with an optical tracking device

Table 1 Pearson correlations, Root Mean Square Errors and maximum Range of Motions

	Pearson correlation coefficient (p < 0.01) Mean (SD)	Root Mean Square Error in degrees Mean (SD)	Maximum Range of Motion in degrees Mean (SD)
			IMUs	Optical device
Ankle angles	0.93(± 0.05)	4 (± 2)	63 (± 8) *	54 (± 8)
Knee angles	0.98(± 0.05)	4 (± 3)	91 (± 8)	92 (± 6)
Thigh angles	0.96(± 0.06)	5 (± 3)	56 (± 5) *	49 (± 4)

Mean correlations and Root Mean Square Errors between joint angles in the sagittal plane, acquired by the IMUs and the optical tracking device over all the 14 subjects and 12 trials (n = 168). Maximum Range of Motion obtained with both measurement devices per subject (n = 14). SD: standard deviation. Asterisks indicate difference (p < 0.01) between maximum Range of Motion with respect to the optical tracking device.