A measure of kinematic limb instability modulation by rhythmic auditory stimulation.

A mathematical method based on computations of residual absolute value sums (RAVS) was developed for the quantitative analysis of tremor-like perturbations of knee angle during the gait cycle. The method was tested on simulation data created by adding sinusoidal tremor of varying frequency and amplitude to the knee-angle graph of a healthy test subject. The method was then applied to compare knee tremor reduction, with and without auditory rhythm, in a group of five traumatically brain-injured patients with gait hemiparesis. Deviations from normal gait performance due to tremor were assessed by using self-comparison to a 17th-degree regression polynomial of each subject's own motion-, time-, and point-normalized knee- angle curve. With rhythmic cueing, the five subjects had a statistically significant RAVS-measured mean tremor reduction of 39.5+/-22.6% (t=-3.91; p=0.017).