The Use of Computerised Dynamometry to Quantify Functional Grip and Release in People Post Stroke: A Pilot Study

Abstract

Purpose: To present a theoretical construct and pilot data from an analytic technique to simultaneously quantify positive and negative upper motor neuron (UMN) features. Method: 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. Results: Force, time and velocity dependent aspects of hand performance did not differ between the dominant and non- dominant 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. Conclusions: 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.