Contractile properties of lower leg muscles are normal in Parkinson's disease.

Contraction parameters (time-to-peak and half relaxation time), responses to short tetani and resistance to stretch were studied in the lower leg muscles of Parkinsonian patients and in age-matched controls. It was possible to distinguish between muscle groups of different fibre type composition in normal subjects on the basis of their contraction and relaxation velocities. These parameters, however, failed to show any abnormalities in the patient group. The only abnormal finding in Parkinsonian subjects was an increased resistance to passive stretch under static conditions, presumably elastic in origin. The results are evidence against a contribution of altered contractile properties to muscular rigidity in Parkinsonism.