Neuromuscular function in polio survivors.

Abstract

Although there is no documented, objective evidence that symptomatic post-polio subjects are rapidly losing strength, they have a number of neuromuscular deficits related to a more severe poliomyelitis illness that may explain why they complain of problems with strength, endurance, and local muscle fatigue. Symptomatic post-polio subjects were hospitalized longer during the acute poliomyelitis, recovered more slowly, and had electromyographic evidence of greater loss of anterior horn cells. Additionally, recent assessment demonstrated that they were weaker, had a reduced work capacity, and recovered strength less readily after activity in the quadriceps muscles as compared to asymptomatic subjects. Of great clinical importance, rating of perceived exertion in the muscle during exercise was the same in symptomatic and asymptomatic post-polio and control subjects, indicating that symptomatic subjects have a mechanism to monitor local muscle fatigue that could be used to avoid exhaustion. A study of pacing (interspersing activity with rest breaks) showed that symptomatic subjects had less local muscle fatigue and greater strength recovery when they paced their activity than when they worked at a constant rate to exhaustion. We recommend that post-polio individuals pace their daily activity to avoid excessive fatigue.