Spinal muscle evaluation using the Sorensen test: a critical appraisal of the literature.

The first test for evaluating the isometric endurance of trunk extensor muscles was described by Hansen in 1964. In 1984, following a study by Biering-Sorensen, this test became known as the "Sorensen test" and gained considerable popularity as a tool reported to predict low back pain within the next year in males. The test consists in measuring the amount of time a person can hold the unsupported upper body in a horizontal prone position with the lower body fixed to the examining table. This test has been used in many studies, either in its original version or as variants. Although its discriminative validity, reproducibility, and safety seem good, debate continues to surround its ability to predict low back pain; in addition, the gender-related difference in position-holding time remains unexplained and the influence of body weight unclear. A contribution of the hip extensor muscles to position holding has been established, but its magnitude remains unknown. The influence of personal factors such as motivation complicates the interpretation of the results. Despite these drawbacks, the Sorensen test has become the tool of reference for evaluating muscle performance in patients with low back pain, most notably before and after rehabilitation programs.