Low back three-dimensional joint forces, kinematics, and kinetics during walking

Objective. The purpose of this study was to examine the three-dimensional l ow back loads, spinal motions, and trunk muscular activity during gait. Spe cific objectives involved assessment of the effects of walking speed, and a rm swing on spinal loads, lumbar spine motion, and muscular activation. Design. An in vivo modeling experiment using five male participants. Thirty walking trials were performed by each participant yielding five repeats of each condition (3 walking cadences x 2 arm swing conditions). Background. Walking is often prescribed as a rehabilitation task for indivi duals with low back injuries. However, there are few studies which have exa mined the joint loading, spinal motions, and muscular activity present when walking. Additionally, the majority of studies examining spine loading dur ing gait have used an inverse dynamics model, commencing at the cranial asp ect of the body, approach which does not include the impulsive phases of ga it (i.e. heel strikes and toe offs). Methods. Low back joint forces (bone on bone) and moments were determined u sing an anatomically complex three dimensional model (detailing 54 muscles and the passive structures acting at the low back) during three walking cad ences and with free arm swing or restricted arm swing. In order to assess t he influence of the transient factors such as heel contact on the joint for ces a bottom up (from the feet to the lumbar spine) rigid link segment anal yses approach was used as one input to the three-dimensional anatomic model . Lumbar spine motion and trunk muscle activation levels were also recorded to assist in partitioning forces amongst the active and passive tissues of the low back. Results. Net joint anterior-posterior shear loading was the only variable s ignificantly affected by walking cadence (fast versus slow P < 0.0003). No variable was significantly affected by the arm swing condition. Trends demo nstrated an increase in all variables with increased walking cadence. Simil arly, most variables, with the exception of axial twist and lateral bend lu mbar spine motion and lateral joint shear, demonstrated increasing trends c aused by the restriction of normal arm swing. Conclusions. Tissue loading during walking appears to be below levels cause d by many specific rehabilitation tasks, suggesting that walking is a wise choice for general back exercise and rehabilitation programs. Slow walking with restricted arm swing produced more 'static' lumbar spine loading and m otion patterns, which could be detrimental for certain injuries and tissues . Fast walking produced a more cyclic loading pattern.