Effects of prolonged muscle stretching with constant torque or constant angle on hypertonic calf muscles

Objective: To compare the effectiveness of constant-torque prolonged muscle stretching (PMS) treatment in the inhibition of ankle hypertonia with that of constant-angle PMS treatment. Design: Before-after comparison. Setting: A university-affiliated teaching hospital. Participants: Thirty subjects with hemiplegia and hypertonia in the calf muscles. Intervention: Ankle plantarflexors were stretched using a motor-driven stretching device capable of operating in either a constant-angle or a constant-torque mode for 30 minutes of PMS treatment. Main Outcome Measures: Clinical scales, including the Modified Ashworth Scale (MAS) and passive range of motion (ROM), and biomechanic assessments were used to evaluate the viscoelastic components of the ankle plantarflexors before and after PMS treatment. Results: Both constant-angle and constant-torque PMS treatments significantly improved the clinical scale (MAS, ROM) assessment results and reduced the viscoelastic components of the ankle joint (P<.05). The degree of change in the viscoelastic components was more evident in subjects with constant-torque PMS than in those with constant-angle PMS (P<.05). Conclusions: The present biomechanic assessments indicate that both PMS treatment modes reduced the viscous and elastic components of hypertonic muscles. The proposed constant-torque PMS treatment was more effective than the conventional constant-angle stretching technique.