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Study reveals that humans evolved to walk with an additional bounce in their step due to foot arch development


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A new study shows that humans may have evolved a spring-like arch to help us walk on two legs. Researchers studying the evolution of bipedalism have long hypothesized that the high arch of the foot helps us walk by acting as a lever propelling the body forward.

But now a global team of scientists has discovered that arch flexion bounces back into an upright position for more efficient walking. In running the effects are larger, suggesting that the ability to run efficiently could be a selective compression of an elastic arch that also makes walking more efficient. This discovery could help doctors improve treatments for today’s patients’ foot problems.

said Dr. Lauren Welty, first author of the study Frontiers in bioengineering and biotechnology, who conducted the research while at Queen’s University and is now affiliated with the University of Wisconsin-Madison. “It turns out that instead, the spring-like arch bounces back to help the ankle lift the object.”

Step by Step

The evolution of our feet, including the elevated medial arch that distinguishes us from great apes, is critical to bipedal walking. It is thought that the bow gives hominins greater leverage when walking upright: the mechanism is unclear, but when the movement of the bow is restricted, running requires more energy. Bow bounce can make us more efficient runners by pushing the body’s central mass forward, or by compensating for the mechanical work the muscles had to do.

To test these hypotheses, the team selected seven participants with varying arc motion, who walked and ran while their feet were filmed by high-speed X-ray motion capture cameras. Each participant’s arch height was measured, and their right feet were CT-scanned.

The scientists created rigid models and compared them to measured motion of the bones of the foot to test the effect of arch motion on adjacent joints. They also measured which joints contributed the most to arch bounce, the contribution of arch bounce to center of mass and ankle thrust.

He tends to walk on two legs

Although the scientists expected to find that bow bounce helped the rigid lever of the arch lift the body, they discovered that a rigid arch without rebound caused either the foot to leave the ground too early, reducing the efficiency of the calf muscles, or the ankle bones bent forward too much.

The forward tilt reflects the posture of a walking chimpanzee, rather than the upright stance that characterizes a human gait. The flexible arch helped bring the ankle back upright, allowing the leg to push off the ground more effectively. This effect is greatest when running, suggesting that efficient running may be an evolutionary pressure in favor of a flexible arch.

The scientists also found that the joint between two bones in the medial arch, the scaphoid and the medial cuneiform, is crucial to the flexibility of the arch. Changes in this joint can help us trace the evolution of bipedalism in the hominin fossil record.

“The motion of our feet seems to allow us to walk and run straight rather than leaning forward or swooping into the next step too soon,” said Dr. Michael Rainbow from Queen’s University, senior author.

curative capacity

These findings also point to treatment avenues for people whose arches are rigid due to injury or illness: Arch flexibility support can improve overall mobility.

“Our work indicates that allowing the arch to move during thrust makes locomotion more efficient,” Welty said. “If we restrict the movement of the arch, there will likely be corresponding changes in how other joints function.”

“At this point, our hypothesis requires further testing because we need to validate that differences in footwork across populations lead to the kinds of changes we see in our limited sample,” Rainbow said. “However, our work paves the way for an exciting new investigative avenue.”

more information:
Michael Rainbow et al., The mobility of the medial arch of the human foot enables upright bipedal locomotion, Frontiers in bioengineering and biotechnology (2023). DOI: 10.3389/fbioe.2023.1155439

the quote: Humans Evolved To Walk With Extra Spring In Our Step, Foot Arch Study Shows (2023, May 30) Retrieved May 30, 2023 from https://phys.org/news/2023-05-humans-evolved-extra-foot-arch .html

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