To present a theoretical construct and pilot data from an analytic technique to simultaneously quantify
positive and negative upper motor neuron (UMN) features.
Computerised hand dynamometry was used to measure hand contraction-relaxation cycles during a repetitive
grasp and release task. Measurements of force, time, force velocity and ‘grip work’ were collected on a pilot sample of 5
post-stroke subjects and 5 matched controls. Within and between group differences were analysed.
Force, time and velocity dependent aspects of hand performance did not differ between the dominant and nondominant
upper-limbs of control subjects. In contrast, the post-stroke group generated less grip force over longer cycle
times with their affected limb, consistent with negative UMN features. In controls, 97% of grip work was task specific,
with 3% associated with involuntary, non-task grip work. Conversely, the post-stroke group generated high levels of
involuntary, non-task grip work (39%), a feature consistent with positive UMN features of muscle overactivity. Force
velocity and maximal force were lower in the non-affected limbs of the stroke group than matched dominant limbs of the
control group, supporting functional Magnetic Resonance Imaging data that the function of non-affected cerebral
hemisphere is abnormal following stroke.
The computerised dynamometry analysis paradigm was able to simultaneously quantitate aspects of hand
performance affected by positive and negative UMN features within an individual and between groups. This approach
uses a clinically relevant, functionally based assessment technique that appears to have greater ecological validity and
fewer limitations than current measures of spasticity.