  Low back pain is one of the most common musculoskeletal disorder. To reduce
its incidences, some back exoskeletons have been designed and already
commercialized. However, there is a gap between the phases of device and
testing on subjects. In fact, the main unsolved problem is the lack of
realistic simulation of human-device interaction. Consequently, the objective
of this paper is to design a 3D multibody model of the human body that includes
the full thoracic and lumbar spine combined with a low back exoskeleton,
enabling to analyze the interactions between them. The results highlight that
the use of the exoskeleton reduces the net torque in the lower lumbar spine but
creates normal forces transmitted through the thighs and the pelvis, which
should also be considered for low back pain. As a perspective, this model would
enable to redesign low back exoskeletons reducing both torques and forces in
the human joints in a realistic dynamic context.
