Abstract
BACKGROUND: Lower limb muscle bionic devices have attracted significant attention in rehabilitation and assistive sports technology. Despite advancements in mimicking human movement, current devices still face challenges in enhancing strength and movement capabilities. These devices often focus on monoarticular muscles, overlooking the synergistic effects of biarticular muscles and their role in energy transfer, which limits the overall improvement in movement performance. METHODS: This study presents an enhanced gastrocnemius-mimicking exoskeleton robot (EGME), leveraging the biarticular characteristics of the muscle. The device delivers force spanning both the knee and ankle joints to provide vertical support and forward propulsion in an underactuated manner during locomotion. Its effectiveness was evaluated through experimental trials involving five volunteers performing level walking and squat holding tasks. RESULTS: Experimental results showed that the EGME significantly reduced gastrocnemius activation, improved exercise endurance, and enhanced ankle stability. Activation decreased by up to 46.4% during walking and by an average of 59.8% during the short-duration squat holding task, while endurance time in the long-duration squat holding task increased by a factor of 7.79 with the exoskeleton. CONCLUSION: This study demonstrates the strong potential of biarticular exoskeletons to enhance muscle function and movement performance, offering new insights into bionic device design. These findings suggest broad applicability in performance enhancement and rehabilitation. Future research should further explore their effects on inter-joint coordination and kinematic coupling to refine the design and functionality of such systems.