Muscle conditioning in late poliomyelitis.

To study the adaptability of postpolio muscles, 12 subjects (mean age 54 years) participated in a high-intensity resistance exercise program. Seventy-five percent met the criteria for postpolio syndrome. Isometric and isokinetic strength and muscle endurance were measured. Polio-affected muscles were identified in muscle biopsies. The biopsies were also used for measurements of enzymatic activities and for histochemical and histopathologic analyses. Pretraining strength values were less than half those of healthy controls, mean fiber areas were twice those of healthy controls, and oxidative enzyme activity was low. After training, a significant increase in isometric (mean 29%) and isokinetic (mean 24%) strength was observed and maintained for some time. This demonstrates remaining adaptability in muscles already compensated from long-standing polio.