Low Back Forces During Load Carriage in Asymmetrical Gait.

Carrying tasks are a part of everyday life for both able-bodied individuals and those with clinical gait asymmetries. While carrying tasks and gait asymmetries have each independently been associated with low back pain, the combination of these factors has received limited attention. We addressed this gap by employing an established experimental protocol to induce gait asymmetries with a clinical walking boot in healthy able-bodied participants (n = 12). Participants carried dumbbells weighing 7.5% and 15% of body weight in 1 or 2 hands. Low back joint and muscle forces estimated from a musculoskeletal model during asymmetric and symmetric gaits were compared. Our results indicated that normalized peak low back forces were mostly not impacted by gait asymmetry except when carrying the higher 15% load alone in the hand contralateral to the walking boot. Raw peak L5/S1 intervertebral joint compression (1291-3551 N) and shear (181-604 N) forces during all carrying tasks were below spinal unit tissue injury tolerances for manual materials handling. Future work should look to examine nonbiomechanical factors, alternative sources or levels of asymmetry, or other daily tasks that could contribute to low back pain in those with gait asymmetries.