Quantitative analysis of ankle hypertonia after prolonged stretch in subjects with stroke

The aims of this study are to validate the hypertonia treatment/assessment system and to quantify the immediate effect of prolonged muscle stretch (PMS) on the inhibition of ankle hypertonia in stroke patients. For PMS treatment, ankle plantarflexors were stretched with a constant torque in 25 subjects with hemiplegia and ankle plantarflexors hypertonia. Using the developed hypertonia treatment/assessment system, the effects of the PMS treatment were quantified by comparing the reactive torque measurements of the ankle joint before and after the treatment sessions in terms of elastic (elastic-inertia) (K(ei)) and viscous (K(v)) components. It was shown that an application of PMS for 30 min using a constant stretching force, approximately 80% of the torque measured at the maximal passive ROM dorsiflexion position, significantly reduces both components of the ankle joint torque (P < 0.05). The present results suggested that the application of PMS with a constant torque could reduce not only the elasticity of the hypertonic muscles, but also their viscosity in the stroke patients.