How to strengthen foot muscles to treat plantar fasciitis permanently. Weakness of foot muscles or poor motor control is a major cause of a lot of foot problems and injuries. Plantar fasciitis is such a common problem for a lot of runners and athletes. In order to treat plantar fascitiitis you need to work on improving the strength of various foot muscles and specially your big toe muscles – flexor hallucis brevis and flexor hallucis longus to support your arch. This video shows you how to strengthen foot muscles, improve motor control and awareness of your foot.