An Upper Limb Exoskeleton for Pinpointed Muscular Exercises With Overextension Injury Prevention

Over-automated equipments and modern city life style lead to the diminishing opportunities for muscle using; however, the comfortable life is not always good for human health, and appropriate muscle training can not only enhance muscular strength and endurance but improve the health and fitness. Different kinds of ideas have been proposed for muscle training by exercise machines, which control direction of resistance for safety sake but isolate specific muscle groups to be trained. Compared with machines, free-weight exercise is a whole-body training in which human limbs can be moved on different planes to train more muscle groups. In this study, an upper limb exoskeleton design is proposed for free-weight exercise to strengthen the principal muscles of upper limb and shoulder. The upper limb exoskeleton is constituted of 3-DOF shoulder joint and 1-DOF elbow joint. The joint torques of shoulder and elbow joint of the exoskeleton match the objective joint torques from a model of free-weight exercise. The principal muscles of human arm and shoulder are training by dumbbell lateral raise, dumbbell frontal raise, dumbbell curl motion, and overhead triceps extension motion. With the arrangement of small-inertia springs, the exoskeleton is capable of preventing the muscle from injuries caused by the huge inertia change. The evaluation of the model was conducted by using isokinetic dynamometer to measure shoulder abduction-adduction, shoulder flexion-extension, and elbow flexion-extension for the male and female adults, and the results matched with the data obtained from the derived model.