2026 年 21 巻 2 号 p. 26-00078
This study developed a passive exoskeleton designed to alleviate the physical burden of heavy backpacks by establishing an external load path that bypasses the body. Inspired by traditional load-resting methods, the device employs rigid structural rods to transfer the weight directly from the backpack to the ground. The exoskeleton is composed of three sections: (1) Loading section that receives the backpack load, (2) Joint section that transmits the force vertically, and (3) Grounding section integrated with torsion springs to assist ankle motion. Experiments were conducted with ten healthy participants to compare "Backpack Only" and "With Device" conditions. Due to signal quality control, electromyography (EMG) analysis was performed on seven participants (n = 7), while subjective evaluations included ten participants (n = 10). The results confirmed that the load-bypass structure significantly reduced the integrated EMG of the trapezius by an average of 45.4% (p < 0.05). This objective reduction was consistent with a dramatic improvement in subjective scores for perceived shoulder strain and backpack weight (p < 0.001). Furthermore, the torsion springs successfully assisted ankle movement during the initial swing phase, leading to a 36.1% average reduction in gastrocnemius activity (p < 0.05) without disrupting natural gait patterns. However, the prototype exhibited challenges regarding gait interference; subjective walkability and stability scores significantly decreased, and unnatural muscle activity timings were observed in the tibialis anterior and rectus femoris. These issues were attributed to two mechanical limitations: the Joint section’s lack of degrees of freedom in the frontal plane, which hindered individual variations in step width, and insufficient axial compliance in the rods, which restricted the range of leg lifting during the swing phase. Future research will focus on achieving dynamic compatibility by introducing frontal plane degrees of freedom and optimizing vertical compliance to enhance the ease of leg lifting while maintaining efficient load-support performance.
