STRETCH-SHORTENING CYCLE IN PATIENTS WITH UPPER MOTOR-NEURON LESIONS DUE TO STROKE

The stretch-shortening cycle (SSC) is a natural muscle function where a concentric action is preceded by an eccentric action, and this leads to a higher concentric torque value in healthy persons. This study ai med to investigate the concentric torque output with and without prece ding eccentric or isometric actions in patients with upper motor neuro n lesions due to cerebro-vascular disease, Strength measurements of th e plantar flexions were made in a dynamometer at different angular vel ocities (120 degrees . s(-1) and 240 degrees . s(-1)) and recordings o f electromyogram (EMG) were made simultaneously. The assessment was ba sed on comparisons of the concentric torque values with and without pr eceding actions, The study showed a significantly higher percentage in crease in concentric torque values after preceding: actions in the aff ected leg compared with the nonaffected leg except at 120 degrees . s( -1) with preceding isometric action, Relative EMG changes showed no di fferences between the legs except al 120 degrees . s(-1) with precedin g isometric action. We would suggest that the higher performance of th e affected leg was caused by better utilization of elastic energy due to muscle stiffness which, despite reduced muscle strength, may have r eturned the patient's functional ability towards normal.