Simulating Underwater Human Motions on the Ground With a Cable-Driven Robotic Platform

Human performance and body motions when submerged underwater are highly influenced by buoyancy forces. In this article, we simulate the effect of buoyancy on human motion over ground by using a cable-driven robotic system. The robotic platform was configured to apply buoyancy forces on the human torso, similar to underwater, while subjects performed reaching and assembly tasks. Previous studies have analyzed muscle activity, postural balance, and limb kinematics in aquatic enclosures. However, from these studies, it is difficult to correlate observed human physiology changes with a specific underwater feature. The goal of this article is to expand our knowledge in objectively characterizing how physical underwater features affect human performance. The results of this article could help in designing more efficient overground programs to train divers in performing submarine motor tasks. For this purpose, we investigated motion of body center of mass (COM), ground reaction forces, muscular activity with surface electromyography (sEMG), and limb coordination while participants performed reaching tasks with and without simulated underwater forces. Within the simulated underwater environment with the cable system, buoyancy force significantly displaced the COM to outside the base of support. Additionally, ground reaction forces and sEMG of back muscles were significantly reduced during this condition. The results obtained in the present study are in line with previous experiments performed underwater. The results show the potential applicability of cable-driven platforms to expand our understanding in the future about the influence of aquatics on functional tasks.