Portable, One-Dimensional, Trunk-Flexor Muscle Strength Measurement System.

Trunk-flexor muscle strength plays a fundamental role in athletic performance, but objective measurements are usually obtained using expensive and nonportable equipment, such as isokinetic dynamometers. The aim of this study was to assess the concurrent validity of a portable, one-dimensional, trunk-flexor muscle strength measurement system (Measurement System) that uses calibrated barbells and the reliability of the measurements obtained using the Measurement System, by conducting test-retests. As a complementary assessment, the measurements obtained during a maximum contraction test performed by a group of 15 subjects were also recorded. Four conditions were assessed: repeatability, time reproducibility, position reproducibility, and subject reproducibility. The results demonstrate that both the concurrent validity and the measured reliability (intraclass correlation coefficient > .98) of the Measurement System are acceptable. The Measurement System provides valid and reliable measures of trunk-flexor muscle strength.