Unilateral ankle immobilization alters the kinematics and kinetics of lifting

Theoretical and empirical data support the notion that distal lower extremity joint dysfunction could influence the low-back injury potential of workers, but the impact of unilateral ankle immobilization on low-back loading during lifting has yet to be examined.

To examine the influence of unilateral ankle immobilization on the kinematics and kinetics of lifting.

With and without their right ankle immobilized, 10 men performed laboratory-simulated occupational lifting tasks. Together with force platform data, three-dimensional kinematics of the lumbar spine, pelvis, and lower extremities were collected, and a dynamic biomechanical model was used to calculate peak compressive and shear loads imposed on the L4/L5 intervertebral joint.

In comparison to the unaffected conditions, ankle immobilization generally resulted in less knee (0.001 ≤ p ≤ 0.07) and greater lumbar spine (0.001 ≤ p ≤ 0.35) sagittal motion when lifting. Associated with this compensatory movement strategy were greater L4/L5 anterior/posterior reaction shear forces (0.001 ≤ p ≤ 0.25). However, there were cases when individual compensatory movement strategies differed from the "group" response (i.e., subjects increased their sagittal knee motion on the affected side about 8% of the time); this resulted in increased peak L4/L5 joint compression forces without changing the peak L4/L5 anterior-posterior shear forces.

Ankle dysfunction can alter the way in which individuals move and load their low-backs when lifting. The different ways in which individuals compensate for personal movement constraints could alter the potential site and mechanism of occupational low-back injury.