The influence of initial resting posture on range of motion of the lumbar spine.

The aim of this study was to investigate the influence of initial resting posture on range of motion of the lumbar spine in 18 normal subjects. Subjects resting posture and active range of motion was measured using the CA-6000 Spinal Motion Analyser (OSI, USA) in five test positions, namely in flat standing and with a variety of heel raises. Analysis showed that there was no significant correlation between subject's normal resting posture and active range of motion. However, when subjects resting posture was artificially altered with heel raises, significant effects on the active range of motion were demonstrated. Increasing heel height significantly influenced resting posture in the sagittal plane only. As heel height increased, the lumbar lordosis decreased and a significant reduction in the range of lumbar spine flexion (P<0.001) was observed. Simulating pelvic asymmetry influenced resting posture in the frontal plane and significant effects on the range of lateral flexion (P<0.05) were observed. These results have important clinical implications in terms of using range of motion of the lumbar spine as an examination tool and suggest that studies using range of motion as an outcome measure should consider initial resting posture.