Determinants of change in perceived disability of patients with non-specific chronic low back pain.

OBJECTIVE Change in psychophysical capacity, calculated as the ratio between physical capacity and perceived effort, may be a determinant of change in perceived disability. The aim of this study was to identify determinants for change in perceived disability, as measured with the Roland Morris Disability Questionnaire (RMDQ), in patients with non-specific chronic low back pain after rehabilitation. METHODS Data were gathered for 84 outpatients. Psychophysical capacity (psychophysical static leg lift, psychophysical static trunk lift, and psychophysical dynamic lifting capacity), physical lifting capacity, perceived lifting effort, aerobic capacity and RMDQ were assessed. Associations between change in RMDQ and potential determinants were calculated. Variables associated with change in RMDQ were entered in a multivariate linear regression analysis (backward). RESULTS Change in psychophysical static trunk lift (r = -0.51), psychophysical dynamic lifting capacity (r = -0.53) and psycho-physical static leg lift capacity (r = -0.23) were significantly associated with change in RMDQ. The RMDQ score at baseline (beta = -0.438), change in psychophysical dynamic lifting capacity (beta = -0.109), psychophysical static trunk lift capacity (beta = -0.038), psychophysical static leg lift capacity (beta = -0.012) and static leg lift capacity (beta = 0.007) all contributed significantly to the regression model (r2 = 52%). CONCLUSION Improvements in psychophysical lifting capacity are determinants for a reduction in perceived disability.