Normal Trunk Muscle Strength and Endurance in Women and the Effect of Exercises and Electrical Stimulation: Part 1: Normal Endurance and Trunk Muscle Strength in 101 Women

Abstract

The lack of trunk muscle strength and endurance has frequently been cited as a suspected factor in the etiology of low-back pain. Several investigators have suggested that asymptomatic patients have stronger trunk muscles than patients with low-back pain. People who are physically fit appear to have a decreased incidence of low-back pain. Increased trunk muscle endurance also have been observed to decrease the incidence of low-back pain. The objective evaluation of the strength and endurance of trunk musculature may, therefore, be significant. Part 1 of this study was designed to develop a reproducible strength–endurance screening procedure and to establish normal isometric–isokinetic trunk muscle strength and endurance parameters for women. This study showed that isometric trunk flexion varied from 19–109 Nm and trunk extension from 38–168 Nm. Peak values for isokinetic trunk flexion at two speeds (30° per second and 60° per second) varied from 17–191 Nm and isokinetic trunk extension from 14–208 Nm. The average endurance time for trunk extensors tested with the Sorensen test was 196 seconds.