Pain in the back of the foot from walking too much may be related to calcium deficiency. Calcium deficiency tends to cause twitching and cramping in the hands and feet and therefore, painful symptoms may occur.
Alternatively, calcium deficiency that causes osteoporosis may also cause pain in the back of the foot under exercise. However, in general, dorsal foot pain after prolonged walking usually occurs due to conditions such as plantar fasciitis caused by heavy activity and fatigue fractures caused by over-exercise.
It is advisable to wear appropriate shoes and exercise in moderation to avoid bone and joint damage.