Modeling and Evaluation of an Energy-Saving Backpack with Adjustable Stiffness.

Backpacks are widely used as an efficient and convenient means for manual load transportation. However, carrying heavy loads for a long time can significantly increase the risk of health issues. In response to the growing demand for relieving muscle fatigue, this paper proposes an energy-saving backpack that can adapt effectively to variable walking speeds and load masses. Inspired by the traditional bamboo pole commonly used for transporting goods, an energy-saving theory based on its mechanical characteristics is proposed. Guided by the theory, the backpack is designed with adjustable stiffness to enhance adaptability across different usage scenarios. Under the experimental conditions of a load of 12 kg and variable walking speeds, the backpack achieves a minimum reduction of 8.6% in the root mean square (RMS) value of gastrocnemius muscle activation. Furthermore, when the load increases from 9 kg to 12 kg, the net metabolic rate is reduced by an average of at least 14.3% compared to conventional backpacks. The experimental results confirm the effectiveness of the proposed backpack under variable conditions, demonstrating the high adaptability and flexibility that the energy-saving backpack provides.