When the design team at inov-8™ wanted to increase the structural stability of the arch area and the propulsive efficiency of our shoes, we looked to the human foot for inspiration. The foot’s plantar fascia ligament structure acts like a large strong bow string, creating tension along its length from the front of the heel to the ball of the foot in order to maintain the structure of the arch and help convert the foot to a rigid propulsive lever.

When we take a step, our foot impacts on the ground and the tension along the plantar fascia ligament increases as the heel lifts from the ground. As the toes begin to extend and the heel rises further, tension on the plantar fascia increases until it carries the entire body weight of the runner. This increase in tension along the plantar fascia ligament from the movement of the foot is often referred to the “Windlass effect”.

The “fascia band” is a feature of the outsole of inov-8 footwear (Roclite & f-lite outsoles), designed to utilize the “windlass effect” in achieving a high level of structural integrity to the arch of the foot during the propulsive phase of the running step cycle. The inov-8 fascia band replicates the anatomical position of the plantar fascia ligament and duplicates the function of the human foot’s ability to utilize the “windlass effect”. The inov-8 fascia band also replicates the benefits of the windlass effect of the human plantar fascia structure. Originating at the front of the heel’s outsole the inov-8 fascia band extends forward along the outsole and divides, just as the human fascia divides, into five bands that terminate anterior to the metatarsal heads. As body weight moves forward onto the metatarsal heads and the toes begin to extend, tension on the inov-8 fascia band increases. When the heel leaves the ground, the inov-8 fascia band resists elongation of the medial arch and carries the entire body weight of the runner converting the shoe into a rigid propulsive lever.