Test-retest reliability and validity of a newly instrumented device for measuring trunk extensor muscles endurance in healthy male participants: a randomized cross-over study

Purpose: Measuring trunk extensor muscle endurance is important for identifying non-specific low back pain (LBP) risk factors and prognostic indicators, planning treatment goals, and measuring patient progress. This randomized cross-over study evaluated the reliability and validity of a newly instrumented device for measuring lumbar spine extensor muscle endurance.MethodsThirty healthy men participated in this study. The Biering-Sorensen test (for the endurance time) and the newly invented device (for the number of repetitions) were applied to measure lumbar spine extensor muscle endurance in two separate weeks at a similar time of a day and with the same rater. Test-retest reliability and validity of the devices were examined via an intra-class correlation coefficient [ICC (2,1)], 95% confidence intervals (95% CI), standard errors of the measurement (SEM), minimal detectable change (MDC), and Pearson's correlation coefficient, respectively.ResultsTest-retest reliability of the newly instrumented device demonstrated an excellent level of reliability [ICC (2,1): 0.969; 95% CI: 0.934-0.985; SEM: 2.65 repetition; MDC: 3.75 repetition]; while a moderate to good degree of test-retest reliability was found between the Biering-Sorensen test measurements [ICC (2,1): 0.884; 95% CI: 0.758-0.944; SEM: 13.31 s; MDC: 18.82 s]. Compared to the Biering-Sorensen test, the newly instrumented device had a moderately positive correlation (r = 0.283).ConclusionThe newly instrumented device demonstrated adequate reliability and validity compared with the Biering-Sorensen test. Future studies should assess its clinometric properties in patients with musculoskeletal pain also including female participants.