Strength and endurance of knee extensors in subjects after paralytic poliomyelitis

Abstract

Purpose. To compare the strength and endurance of knee extensors in subjects after paralytic poliomyelitis as well as to extend the comparison to healthy subjects.Method. Twenty subjects after poliomyelitis with new symptoms (SYM group), 10 without new symptoms (ASYM group) and 15 healthy controls were included. To determine strength, isometric maximal voluntary contraction (MVC) torque of knee extensors in both legs was determined by Biodex® dynamometer at 60° knee angle. To determine endurance, the subjects were asked to mantain force in the knee extensors in the same position, in the range between 40 – 45% of MVC torque, as long as possible. The ‘tensiomyography’ method was applied to measure the radial displacement of m. rectus femoris during submaximal continuous electrical stimulation until recording a flat response.Results. No significant difference in MVC torque and endurance was found between SYM and ASYM group, as well between the duration of m. rectus femoris response of both groups to submaximal electrical stimulation. MVC torque and endurance of knee extensors with ‘normal’ strength was significantly lower in post-polio subjects compared to healthy controls.Conclusion. Endurance of knee extensor muscles in post-polio subjects is generally and significantly lower than that of knee extensors in healthy subjects, regardless of the implication of normal strength and subjective observations of post-polio subjects.