Device and Method for Alerting a Runner When a New Pair of Shoes is Needed

The life of a pair of running shoes—unlike their casual counterparts—is largely determined by the amount of cushion they provide. As they are used, the foam midsole gradually is compacted. The midsole is made of a synthetic polymer with elastic properties to provide cushion. When this cushioning body has worn down, runners are subject to more injuries, which can become chronic. The average pair of running shoes last between 300 and 500 miles, but their life varies based on the runner’s style and weight. The only way to determine whether a pair of shoes is worn out is to keep a mileage log or to guess based on feel. This invention provides a method and device that quantitatively measure wear on the midsole of a running shoe. Two impact sensors are placed in the heel of the shoe; one at the base, between the midsole and outsole, and one at the top, between the midsole and the upper. When the runner’s foot strikes the ground, the lower sensor receives the full force of the impact, while the force on the upper sensor is reduced by the cushioning midsole. As the midsole wears down, the difference in force measured by the two sensors decreases. A control circuit measures the difference, and when it falls below a predetermined threshold, the circuit activates a visual alert in the form of an LED.