Prediction of voluntary activation, strength and endurance of elbow flexors in postpolio patients

To examine the long-term effects of polio, maximal voluntary strength and voluntary activation of elbow flexor muscles of 177 patients from a postpolio clinic were investigated using twitch interpolation. Muscle endurance was studied in 142 patients during 45 min of submaximal exercise, and predictors of impaired muscle performance were investigated. Twenty-nine of 177 patients (16.4%) had impaired voluntary drive to their elbow flexor muscles, but only 16 (9.0%) had markedly reduced elbow flexor strength, despite 74 (41.8%) reporting they were initially affected in their tested limb and 172 (97.2%) patients reporting new generalized symptoms. Seven patients had impaired muscle endurance in the tests of strength and voluntary drive. During the submaximal exercise, 16 patients (11.3%) had impaired peripheral muscle endurance with normal voluntary activation. These results confirm a low incidence of impaired upper-limb muscle performance in postpolio patients, despite many patients having subjective symptoms consistent with postpolio syndrome. There was an increased relative risk for impaired muscle function in those patients with a subjective decrease in strength in the tested limb, a recent decline in activities of daily living in their tested limb, and who used orthotic devices in their tested limb. Monitoring of function in prior-polio patients with impaired muscle performance may be useful, particularly when combined with investigation of other potential contributory factors to the functional impairment.