The stiff human foot enables an efficient push upward when walking or running, and was critical in the evolution of the upright gait of humans. An international research team now explains how humans evolved two unique arches in the foot that help this uprightness1. The findings will be useful in improving the design of artificial limbs and robotic feet.
Unlike primates such as chimpanzees and gorillas, who have flexible flat feet, humans have stiff, arched feet. Researchers have mostly studied the medial longitudinal arch (MLA), which runs from the heel to the ball of the foot, ignoring the role of the transverse tarsal arch (TTA), which runs across the foot.
Studying mechanical mimics of the midfoot, human cadaveric feet and fossil foot bones, the researchers tried to find out the TTA’s contribution to stiffness of the human feet. The scientists, including a researcher from the Jawaharlal Nehru Centre for Advanced Scientific Research in Bangalore, India, performed three-point bending tests on these models. They found that the TTA is responsible for more than 40% of the stiffness in our feet.
Tracking the growth and evolution of primate feet, including that of extinct human ancestors, the researchers found that only the genus Homo had fully developed arches (MLA and TTA). Together, these arches contribute to the stiffness of human foot, they report.
This renewed understanding of the human foot may improve the treatment of flatfoot disorders and the study of foot function in human motion, the researchers say.
References: 1. Venkadesan, M. et al. Stiffness. Source: https://www.natureasia.com/
