Some foot problems are perpetuated by weak foot muscles. The foot can be supported with arch supports while tendons, ligaments or muscles are healing but the arch support does not help the foot become stronger. As such, I encourage my patients to try and strengthen their feet. They may find at some point they no longer feel the need to wear foot orthotics or that they do not need them as much as they used to need them.
Foot strength can be improved by strengthening the muscles that begin in the leg and continue into the foot as a tendon, or by strengthening the muscles that are completely incorporated within the foot itself. Two groups of muscles, the intrinsics and the lumbricals are a good example of the latter. These small muscles exist around the metatarsal bones and extend to and help stabilize the toes. Maintaining these muscles in top condition can help improve foot strength and specifically toe strength.
Below are a couple of links of videos that do a very good job of demonstrating exercises you can do at home to help strengthen your feet.
Below is a technique to strengthen the small muscles in the foot:
Below are a series of exercises for general foot and ankle strengthening.
The video below demonstrates a specific stretching exercise to address achilles tendonitis.