The Influence of Foot Posture and Load on Lumbar Biomechanics During Trunk Bending

Low back pain imposed huge expenditures to the industry with many days away from work. Despite industrialization, statistics show the number of work injuries, work transfer, work restriction and absenteeism in recent years is still high. Various factors are involved in low back injuries, which make it complicated to deal with. In many industries (such as construction, transportation, and healthcare) low back pain is highly prevalent.;In the current study, we recruited 14 participants to investigate the effect of staggered foot posture on lifting biomechanics and to understand if maintaining a staggered foot posture could reduce spinal tissue loading and its influence on the spinal active and passive tissue interaction. The study involved a total of 24 trunk flexion and extension motions (3 different foot postures, two levels of load and four repetitions). Each trial involved seven seconds to move from an upright standing posture to reach to a fully flexed trunk posture, to stay six seconds in full flexion trunk posture and then use another seven seconds to move back to upright standing with and without holding an external weight of 15 lb. Results of this study showed that during performing trunk bending motions with staggered foot posture, unbalanced cumulative electromyography (CEMG) would be observed among the two sides of lumbar extensor muscles and with the increase of foot distance, trunk kinematics would change, and the flexion-relaxation phenomenon (FRP) of lumbar muscle would alter