Isokinetic and psychophysical lifting strength, static back muscle endurance, and magnetic resonance imaging of the paraspinal muscles as predictors of low back pain in men.

Magnetic resonance imaging was used to determine the cross-sectional areas and the T2-weighted and proton density-weighted signal intensities of the paraspinal muscles in a group of 128 men, aged 35-63, who had varied histories of occupational and leisure-time physical activities. These measures, and the isokinetic lifting, psychophysical lifting, and static back muscle endurance tests were examined as predictors of low back pain over 12 months of follow-up, in the 43 men who reported no low back pain in the year preceding testing. None of the imaging measures or the muscle function tests was useful as a predictor of future low back pain. Associations with the frequency of low back pain before testing were investigated in the larger group. Smaller total cross-sectional area of the paraspinal muscles and greater signal intensities had weak but significant correlations with more frequent low back pain in the previous year, possibly due to muscle atrophy.