Martial arts inspires a new method for modeling ankles and knees

Researchers in Japan have developed a new way to simulate the forces acting on the ankle, which could improve the care of ankles, feet and knees in medicine, occupational health, sports and everyday life. Hajime Shiraishi of the Kurume Institute of Technology and Haruhiro Shiraishi of the University of Tokyo describe their method in an article in the open access journal Forces in mechanics.

Some sophisticated techniques already exist to simulate the forces acting on the body to aid in medical rehabilitation and the design of prostheses and footwear. The authors of this article attempted to overcome the limitations of these techniques and reduce their complexity when applied to the ankle by focusing on the mechanical forces in the tibia.

In addition to its relative simplicity, this approach has significant advantages in terms of versatility. It can be applied to different body types in different ethnic groups and in any gender by adjusting key numerical variables.

The method begins by calculating a physical characteristic known as the “moment of inertia” around the ankle and determining the center of gravity on the sole of the foot. The resultant force on the center of gravity improves the understanding of the behavior of the lower leg from the knee to the ankle and to the foot.

The authors drew inspiration from the movements used in Japanese Kobudo – traditional and ancient forms martial arts— designed to minimize effort during movements.

One of the key findings of the study is that the most important factor affecting ankle loading is not so much its ability to generate force, but speed strength is generated and how quickly shocks can be absorbed. Time is very important.

The researchers anticipate that the most immediate application is likely to be in guiding the development of more effective wearable devices to support the knee and ankles, either after injury or to prevent injury.