Ballistic elbow flexion movements in patients with amyotrophic lateral sclerosis

Patients with amyotrophic lateral sclerosis made stereotyped 20 degrees elbow flexion movements as rapidly as possible while surface EMG was recorded from biceps and triceps. The characteristic ballistic movement EMG pattern could be recognised in almost all the patients. The first agonist burst and the first antagonist burst, which are normally limited in duration, were prolonged in patients with clinical signs of pyramidal tract disease or alpha motor neurone disease or both. Prolongation of these components permits the muscles to generate sufficient forces to accomplish the movements.