Back muscle strength and fatigue in healthy and chronic low back pain subjects: A comparative study of 3 assessment protocols

da Silva RA Jr, Arsenault AB, Gravel D, Larivière C, de Oliveira E Jr. Back muscle strength and fatigue in healthy and chronic low back pain subjects: a comparative study of 3 assessment protocols. Arch Phys Med Rehabil 2005; 86:722–9. To compare the sensitivity of 3 different back test protocols in measuring differences in strength and fatigue between subjects with and without chronic low back pain (CLBP). Descriptive study using a repeated-measures design. A research laboratory within a rehabilitation center. Eighteen healthy subjects and 13 subjects with CLBP were assessed in a single session to compare the 3 protocols. The protocols were an upright position test (UPP), a semicrouched lifting test (LIF), and the Sorensen fatigue test. Not applicable. Moments of force and surface electromyography were recorded bilaterally from 4 homologous back muscles while the subjects performed static trunk extension efforts for each protocol. Fatigue was quantified by the slopes of the linear regression of electromyography time-series. The back muscle fatigue and strength scores did not differ significantly for the 2 subject groups for any of the 3 protocols. The electromyography fatigue indices revealed that the Sorensen fatigue test and UPP produced more fatigue in the back muscles than the LIF. It was impossible to specify which protocol is more sensitive to low back status because no between-group difference was observed for any of the 3 tests.