The windlass is that device that are used by the mariners on yachts to wind the rope around to make it less difficult to move the sails. Within the foot there is a mechanism that is called the windlass mechanism that gets its name from this equipment used on yachts. There is a ligament like structure beneath the foot called the plantar fascia that is at one end connected to the bottom of the heel bone and at the other end to the great toe. When we're walking and the heel comes off the ground, the foot rotates around the great toe where this ligament is connected, tightening the ligament as it winds around the windlass of the first metatarsal head. This is the windlass mechanism of the foot. It is a crucial functionality as that ligament is what supports the arch of the foot, therefore it really should function adequately and quickly for normal biomechanics. This is the foots own natural arch support mechanism.
There are a number of conditions related to the windlass mechanism not functioning properly. When the windlass does not work, then the arch of the foot will fail from this lack of support and a range of disorders may develop as a result of that such as bunions and plantar fasciitis. The reason for the windlass not working properly can be multiple such as the force required to establish it just being way too high, so the body has to work harder to make the windlass work. If that hard work does make it function, then that is an increased energy expenditure that could be very fatiguing. Clinicians use different design characteristics in foot orthoses to enhance the windlass mechanism and to make walking easier and more effective. If the windlass can be established easily during walking or running is not going to need so much and the foot will naturally support its own arch.