Three-dimensional kinematics of the lumbar spine during treadmill walking at different speeds.

The lumbar spine is of primary importance in gait and its development is influenced by the upright posture adopted in human locomotion. However, little is known about the kinematic behavior of the lumbar spine during walking. The aim of this study was to examine (1) lumbar spine kinematics during walking, (2) the effect of walking velocity on lumbar motion patterns and (3) the coupling characteristics of rotation and bending. In 22 volunteers aged 15-57 years, the three-dimensional displacements of T12 to the sacrum were sampled during elementary movements of the trunk and during walking on a treadmill at four walking velocities. A three-dimensional electrogoniometer (CA 6000 Spine Motion Analyzer) sampling at 100 Hz was used. We analyzed maximal primary and coupled motion ranges (ROM) and velocities in each plane. Lumbar ROM during walking did not exceed 40% of maximal active ROM. Transverse plane ROM and frontal and transverse velocities increased with walking velocity. Coupling of rotation and bending during walking was individually variable and dependent on walking velocity. Moreover, the smoothness of the bending-rotation path varied with walking velocity. A simplified envelope of lumbar coupling characteristics during walking is presented, and the existence of an individually variable walking speed that is characterized by a more harmonic lumbar contribution is hypothesized.