Lower back kinetic demands during induced lower limb gait asymmetries

Gait asymmetries are common in many clinical populations (e.g., amputation, injury, or deformities) and are associated with a high incidence of lower back pain. Despite this high incidence, the impact of gait asymmetries on lower back kinetic demands are not well characterized due to experimental limitations in these clinical populations. Therefore, we artificially and safely induced gait asymmetry during walking in healthy able-bodied participants to examine lower back kinetic demands compared to their normal gait. Are lower back kinetic demands different during artificially induced asymmetries than those during normal gait? L5/S1 vertebral joint kinetics and trunk muscle forces were estimated during gait in twelve healthy men and women with a musculoskeletal lower back model that uniquely incorporated participant-specific responses using an EMG optimization approach. Five walking conditions were conducted on a force-measuring treadmill, including normal unperturbed "symmetrical" gait, and asymmetrical gait induced by unilaterally altering leg mass, leg length, and ankle joint motion in various combinations. Gait symmetry index and lower back kinetics were compared with repeated-measures ANOVAs and post hoc tests (α = .05). The perturbations were successful in producing different degrees of step length and stance time gait asymmetries (p