Objective: 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).
Design: Descriptive study using a repeated-measures design.
Setting: A research laboratory within a rehabilitation center.
Participants: 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.
Interventions: Not applicable.
Main outcome measures: 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.
Results: 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.
Conclusions: 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.