Changes in macro electromyography over time in patients with a history of polio: a comparison of 2 muscles.

OBJECTIVE: To investigate whether changes over time are different in a weight-bearing leg muscle than in a less heavily used arm muscle.

DESIGN: Prospective study.

SETTING: University hospital laboratory.

PARTICIPANTS: Twenty-three patients with a history of poliomyelitis.

INTERVENTION: Two investigations were performed 5 years apart, using macro electromyography and the patients' own assessments of symptoms in the tibial anterior and the biceps brachii muscles. Test-retest of macro electromyography was performed in controls and in patients with old polio.

MAIN OUTCOME MEASURES: Macro motor unit potential (MUP) and symptoms in the tibial anterior and biceps brachii over time.

RESULTS: The macro MUP amplitude increased by 24% (P<.05) in the tibial anterior but was unchanged in the biceps brachii muscle.

CONCLUSIONS: An increase in the macro MUP amplitude of the tibial anterior muscle, but not of the biceps brachii, most likely indicates a more pronounced ongoing denervation-reinnervation process over time in the tibial anterior. This difference could be activity dependent, but other factors cannot be excluded.