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

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. Thirty healthy men participated in this study. The Biering-Sørensen 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