Observation of the voluntary movement of the upper-limb is the primary method by which recovery is determined in the motor-impaired. Here, an analytical infrastructure is presented for the decomposition of the kinematical record into two constitutive components: the essential motor activity, and spontaneous motor noise. These tools are subsequently used to perform novel hypothesis tests on the symmetry and variability of discrete single-joint articulation of the elbow in chronic stroke patients and healthy control subjects.

Firstly, elbow-joint goniometric data from 41 healthy volunteers was modeled with a high accuracy to a set of analytical curves, parameterized to account for movement delay and average velocity. From this it was determined that single-joint trajectories are not uniformly symmetric, nor are their trace morphologies highly stereotyped. Additional analysis of trajectory waveform variability following a pseudo-wavelet domain transformation revealed modest spontaneous behavior in the medial domains of joint articulation. Among 14 subjects with impaired motor control due to chronic stroke, though significantly greater transience was observed throughout the joint domain, cohort tendency to adopt symmetric trajectories within a narrow (but non-singular) set of morphology themes did not depart significantly from that of unimpaired subjects.

It is concluded that motor dysfunction in the hemiparetic upper-limb, as observed via the motor activity of the elbow joint in stroke-afflicted persons, pertains to the proclivity to accelerative transience across the joint range, and not to an essential motor behavior associated with basic task execution.