TABLE II.

Metric Descriptions

Category	Metric	Units	Qualitative Description	Refer -ence
CAP	Duration	S	Total time to complete the ambulation circuit or a subtask of the ambulation circuit.
	Floor surface speed ratio		Measures the effect of walking velocity on two different floor surfaces.
	Walking speed	m/s	The walking velocity as determined by distance divided by time.
WBM	COM peak angular velocity	°/s	Maximum rotational velocity of the COM around the Z-axis while rising from a seated position in the chair to a standing position.
	Root mean square (RMS)	m/s2 /s	Square root of the mean of the squares of each axes of the acceleration signal on the COM. Represents the magnitude of the signal (normalized by time).	[3]
	Smoothness index		Ratio of even to odd harmonics of the vertical Y-axis COM acceleration signal. A higher harmonic ratio represents a smoother walking pattern.	[4]
	Smoothness of RMS	m/s3 /s	Root mean square of the derivatives of each X, Y, and Z signal. Synonymous with RMS of jerk (normalized by time).	[3]
GF	Cadence	steps/min	Step rate as expressed by the number of steps per minute.
	Double support percent	%	Percentage of the gait cycle that both feet are on the ground. Computed as the sum of the initial double support time and the terminal double support time.	[8], [10]
	Gait cycle time	S	Duration to complete one stride (time between two consecutive initial contacts of the same foot).	[8], [10]
	Number of gait cycles		The number of complete gait cycles (strides) that occurred.
	Shank peak angular velocity	°/s	Maximum rotational velocity of the shank around the Z-axis during the gait cycle. This occurs during the swing phase.
	Shank range of motion	°	Integrated angular velocity for each gait cycle. Provides an estimate of the degrees of shank movement.	[8], [10]
	Step length	m	Distance between initial contacts of opposite feet.	[18]
	Step regularity	%	Expression of the regularity of the acceleration of sequential steps. Computed using the autocorrelation of the vertical Y-axis of the COM acceleration.	[18]
	Stride regularity	%	Expression of the regularity of the acceleration of sequential strides (see step regularity).	[18]
	Step symmetry	%	Ratio of step regularity to stride regularity.	[18]

CAP = clinical assessments of progress, COM = center of mass, GF = gait features, m = meters, S = seconds, WBM = whole body movement, ° = degrees.