Electromyographic activity in stiff and normal elbows during elbow flexion and extension.

This prospective, controlled pilot study investigated electromyographic activity in elbow muscles during active elbow flexion and extension and during prolonged elbow extension with and without resistance. Biceps brachii, brachialis, brachioradialis, and triceps activity was measured in 10 subjects with elbow motion deficits after injury and in 10 controls. Surface electromyography was recorded during active elbow flexion, extension, and passively positioned elbow extension with and without 3 lb on the distal forearm. All muscles of the stiff elbow group had greater activity compared with controls during active elbow flexion and extension. Biceps brachii of the stiff group showed antagonist activity equivalent to agonist. For all other flexors in both groups, agonist activity was greater than antagonist. During prolonged extension, biceps brachii, unweighted, showed greater activity in the stiff group than in controls. Both groups showed greater flexor activity when weighted. Across time, activity was sustained or increased in all muscles in both groups.