Distance running spent most of its history treating footwear as a minor variable. Shoes got lighter, and lighter was better, and beyond that the equipment was not where performance came from. That assumption broke when a generation of racing shoes combining a thick, highly resilient midsole with a stiff embedded plate arrived and produced improvements large enough that the sport had to decide whether footwear had become equipment in the regulatory sense.
The interesting part is not that the shoes work. It is why they work, because the mechanism is neither a spring nor a trick, and understanding it explains both why the advantage is real and why writing a rule against it turned out to be so awkward.
