Validity and reliability of a system to measure passive tissue characteristics of the lumbar region during trunk lateral bending in people with and people without low back pain.

The current study examined the validity and reliability of a new system that was developed to measure lumbar region passive stiffness and end range of motion during a trunk lateral bending movement in vivo. Variables measured included force, end range lumbar region motion, torque, lumbar region stiffness, and passive elastic energy. Validity of the force measurements was examined using standard weights. Validity of lumbar region angle measurements was examined using an instrumented trunk with an electrogoniometer. Reliability of the measurements between trials within a session was examined in a sample of 50 people (25 men, 25 women; mean +/- standard deviation age = 30.7 +/- 8.9 yr); 31 people reported a history of chronic or recurrent low back pain (LBP) and 19 reported no prior history of LBP. The end range lumbar region motion and force measurements demonstrated an excellent linear relationship with the criterion standard measures. Average error between the criterion standard and observed measurements was minimal for all measurements. For reliability testing, the majority of intraclass correlation coefficient values were >0.75. The validity and reliability of the current system are sufficient to examine lumbar region stiffness and end range of motion in people with and people without LBP.