The hidden spring in your step

Researchers reveal the way our legs adapt to fast movements. When people hop at high speeds, key muscle fibers in the calf shorten rather than lengthen as forces increase, which they call 'negative stiffness.' This counterintuitive process helps the leg become stiffer, allowing for faster motion. The findings could improve training, rehabilitation, and even the design of prosthetic limbs or robotic exoskeletons.