Quantification of lumbar function. Part 2: Sagittal plane trunk strength in chronic low-back pain patients.

A prototype sagittal plane trunk strength tester was used to measure trunk strength in 286 chronic low-back pain patients. Initial data for this patient group are compared with data acquired previously from a group of controls, adjusted for age, sex, and body weight. Distinct patterns characterize the patient sample as opposed to the controls: Patient values for both flexors and extensors were markedly decreased, with greater variability; Extensor strength was affected more significantly than flexor strength; Discrepancies between patients and controls were greater for females than for males; High-speed dropoff ratios were much lower for patients, both in flexion and extension. These results demonstrate that strength deficits are a major factor in the deconditioning syndrome associated with chronic low-back pain.