Evaluation of quantitative measures of upper extremity speed and coordination in healthy persons and in three patient populations

Upper extremity tracking tests have been used extensively in clinical studies in patients with neurologic disorders. We evaluated several new measures of upper extremity performance derived from step-response and phase-plane analysis techniques; both techniques are founded in automatic control theory. Using a computer-based tracking test, a visual step function stimulus was applied in 15 healthy subjects and 45 patients from multiple sclerosis, myasthenia gravis, and Parkinson disease populations. The upper extremity response of the subject was analyzed to find the reliability and discriminating power measures that quantify speed, coordination, and steadiness of the upper extremity response during the tracking task. Results show that reliability of the measures, although variable across the populations tested, is generally high (>0.7). The speed and coordination measures derived from phase-plane analysis are more discriminating than the measures of step-response analysis for the populations tested. Some of the measures may be useful for monitoring patient performance, the other measures can be potentially helpful in diagnosis of the disorders.