Application of a graded Sorensen test evokes spatially organized lumbar muscle fatigue.

Abstract

The Sorensen test is commonly used to assess back muscle endurance capacity. However, the clinical value of this test, requiring compensation of the entire upper body mass, is limited if pain occurs. Therefore, a test variant using only portions of upper body mass could be an alternative. This study aimed to determine fatigue characteristics in lumbar muscles during a modified Sorensen test utilizing only 50% of the upper body mass and asked if localization-related effects of surface electrodes in the assessment of lumbar muscle fatigue should be considered. Thirty-two young (20-29 years) symptom-free men were enrolled and asked to maintain only 50% upper body mass for 10 minutes. Fatigue characteristics were bilaterally derived from four different lumbar levels using Surface EMG. Side-specific and SEMG parameter-independent repeated measures (four lumbar levels, nine time points) analyses of variance were conducted. All participants were able to complete the test. Over time, a spatial effect of fatigue-related amplitude alterations at the respective segments could be observed. By using this modified Sorensen test, muscular fatigue can be evoked. Electrophysiological assessment of lumbar fatigue should consider spatial differences.