Stretch-shortening contraction in Parkinson patients: evidence of normal muscle contraction execution with low efficiency.

The aim of this study was to compare different muscle contraction types in Parkinson patients and controls. Ten patients with mild to moderate Parkinsonism (7 men, 3 women, mean age 62.3) and 11 controls (7 men, 4 women, mean age 66.0) were investigated. Measurements in eccentric, concentric contraction and stretch-shortening contraction were made using modified Cybex 11 equipment. The torque areas in ankle dorsiflexors at 30 degrees/second, 120 degrees/second and 180 degrees/second were measured. The power (Nm/second) was calculated in a defined range of motion. The power at different angular velocities and contraction types was significantly lower in the patient group than in the control group. In both groups the power in eccentric and stretch-shortening contraction was significantly larger than in concentric contraction. The relative improvement in power in stretch-shortening contraction in patients was equal to the improvement made by the controls. Patients generated significantly more EMG than controls in concentric and eccentric contractions. The EMG in the stretch-shortening cycle was the same in both groups at higher velocities. The patients performed voluntary isolated muscle contraction in the same way as controls, but with a lower efficiency in contraction. The eccentric torque and the supplement of torque generated from the combined eccentric and concentric (stretch-shortening) contraction might be important for achievement of adequate dynamic movements in patients with Parkinson's disease.