Work-related musculoskeletal disorders are causing occupational diseases. While allowing them to control the execution of their picking task, one solution to physically relieve workers performing trunk flexions is to assist them with an exoskeleton. This preliminary study focuses on the determination of the appropriate measurements systems (motion capture and electromyography) to characterize dedicated trajectories of movements responsible of lower back pathologies. Three tests have been realized with and without a back-assisting exoskeleton for loaded box picking. The results of the study help us to understand which body strategies were used to perform the same task from one individual to another under different conditions. This preliminary study validates this multimodal approach to show the use of a back-assisting exoskeleton for posture harness in dynamic conditions.