An Underwater Lower-Extremity Soft Exoskeleton for Breaststroke Assistance

This paper presents an underwater lower-extremity soft exoskeleton which could provide assistance to swimming motions. With this motivation, we designed an exoskeleton called Powered Swimsuit to assist the wearer in breaststroke with fins. The actuation system was embedded inside of a portable waterproof cabin fabricated on the back of the swimsuit. The assistive force was applied to the bottom of the fins via soft cables. During the propelling period of the stroke cycle, the cables pulled the ankle joints to provide assistance to plantar flexion. Three competitive swimmers participated the experiments to evaluate the proposed soft exoskeleton. Several kinematic parameters including joint angles and muscle activities of the lower extremities were recorded simultaneously. Compared with breaststroke without assistance, the peak of surface electromyography in the sweep phase with the exoskeleton assistance decreased by 49.13% (gastrocnemius) and 74.51% (soleus) on an average. The results showed the feasibility of the proposed Powered Swimsuit in underwater motion assistance.