DESIGN: Two-factor within-subjects design.
SETTING: Spinal Mechanics Laboratory, University of Sydney.
INTERVENTION: A convenience sample of 41 subjects, asymptomatic for back pain, participated. PA stiffness at T12-L4 was measured in the unconstrained and constrained ribcage conditions with a mechanical device. For the constrained condition, we used a clamping device to apply a force to the subject's lower thorax to reduce movement. Main outcome measures: PA stiffness at T12-L4 under both ribcage conditions.
RESULTS: PA stiffness at T12-L4 significantly increased when the ribcage was constrained (P<.05). However, the effect of ribcage movement did not depend on the location of the PA force.
CONCLUSIONS: These findings suggest that the properties of the ribcage influence measures of PA stiffness in the thoracolumbar (T12-L4) spine uniformly. Variations in PA stiffness in segments T12-L4 may reflect the properties of the intervertebral joints.
Click on the above link for the PubMed record for this letter; full text by subscription.