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This paper proposes a close-fitting assistive suit, called e.z.UP®, with a passive actuation mechanism composed of an adjustable structure. The suit can adequately assist the back and arm muscles of a user with the proposed layout of an arm assistive belt and a two-layer structure, respectively. With its lightweight characteristic (i.e., weighing 0.75 kg only), the proposed suit is portable and easy to wear without additional burden. By using the averaged Japanese body data, a simulation was conducted based on a human body model wearing our proposed suit to evaluate the layout of the arm assistive belt. The simulation results prove that the proposed suit can adequately assist the user’s arm muscles based on the user’s motion. An experiment involving the measurement of muscle activities is also implemented with seven young subjects and seven middle-aged subjects to evaluate the arm assistive belt and the two-layer structure. The experimental results reveal that the proposed suit can successfully and appropriately assist both the arm and back muscles simultaneously.

The muscle injuries of manual handling workers, caused by the repeated motion and heavy load in the daily tasks, strongly influence their quality of life. To prevent muscle injuries in many occupations, a close-fitting assistive suit weighing 0.75 [kg] with the passive actuation mechanism and adjustable structures is proposed to assist not only the back muscle but the arm muscle of manual handling workers according to the user intention. An experiment with electromyography for measuring the muscle activities is conducted with six subjects to practically confirm the effectiveness of the suit. The experimental results revealed and proved that the proposed suit can successfully and appropriately assist not only the arm but also the back muscle with a lifting-up motion, simultaneously.

Due to worker injuries in industries such as nursing and construction, we have developed a tunable and concealable worker-wear assistance suit that consists of elastic belts to prevent arm muscle fatigue and injury in workers whose arms repeatedly perform motions upon their shoulders. According to the layout and the material of the belts, the suits may assist the user's arm without any electrical resources. To verify the feasibility and functionality of the layout and the structure of our proposed suits, simulations and experiments were employed. The simulation was conducted based on the average body dimensions of young Japanese people, and its results showed that the proposed suits may effectively assist the user's arm muscles. By measuring the muscles activities of six subjects wearing these suits and lifting a load of 10 kg, practically and concretely verifying the functionality of the suits, the results showed a 45% improvement ratio for their arm muscles. The proposed assistance suit can not only directly support and assist the elbow and shoulder j oint but also indirectly prevent lower back injury.