Effects of Foot Placements on Lumbar Loads in Patient Transfer Motion: Comparison between Anteroposterior and Mediolateral Placements

Many caregivers experienced lower back injuries by patient transfer motion. Patient transfer motion causes lumbar load since this task requires lifting and twisting. For this problem, previous studies explored the suitable posture such as trunk angle to reduce lumbar load in patient transfer motion. However, it is difficult to adjust these postures for caregivers because these postures should be dynamically adjusted in patient transfer motion. Thus, we focus on initial foot placement to reduce lumbar load, because initial foot placement is adjustable before starting transfer. Therefore, the objective of this study is to find suitable initial foot placement for patient transfer motion. In the experiment, 10 healthy males performed simulated patient transfer motion with anteroposterior (AP) and mediolateral (ML) foot placement. Erector spinae muscle activity was measured during patient transfer by the surface electromyography (sEMG). Furthermore, compressive force of L4-L5 was calculated by the computational musculoskeletal simulator. The results showed that AP foot placement provided smaller compressive force of L4-L5 than ML. On the other hand, there was no significant difference for erector spinae muscle activity between AP and ML foot placement. These findings will contribute to determining suitable initial posture to prevent lower back injuries in patient transfer motion.