The windlass is that apparatus that are used by the sailors on yachts to wind the rope about to make it easier to move the boom. In the foot there is a mechanism that is known as the windlass mechanism that gets its name from this apparatus used on boats. There is a ligament like structure beneath the foot called the plantar fascia which is at one end attached to the underside of the heel and at the other end to the great toe or hallux. When we are walking and the rearfoot comes off the floor, the foot moves around the great toe where this ligament is connected, tightening up the ligament as it winds around the windlass of the first metatarsal head. This is the windlass mechanism of the foot. It is a vital functionality as the plantar fascia is what supports the arch of the foot, therefore it really should function effectively and quickly for normal biomechanics. This is the foots natural arch support mechanism.
There are a number of conditions associated with the windlass mechanism not functioning correctly. When the windlass does not work, then the arch of the foot will fail from this lack of support and a number of disorders may develop because of that for example hallux valgus and heel pain. The cause of the windlass mechanism not functioning correctly can be multiple such as the force needed to establish it simply being too much, so the body needs to work harder to help make the windlass function. If that effort does make it function, then that is an increased energy expenditure that may be very fatiguing. Clinicians use different design characteristics in foot supports to enhance the windlass mechanism and to make walking easier and more efficient. If the windlass can be established easily when walking will not need so much and the foot could naturally support its own arch.