Causes. Running is one of the most common causes of plantar fasciitis, but there are many other reasons it might occur. Those who flex their foot and stretch it too vigorously and too often might find it’s a problem for them. Those who put a lot of stress on their feet might notice it happens to them. For example, someone who gains a large amount of weight at one time can put a lot of stress on their feet and cause swelling and inflammation that doesn’t subside. Pregnancy is one great example of this happening to a person who normally doesn’t feel any stress in their foot. It can happen to either foot or both at the same time. It’s also important to note that some people develop this pain without an obvious reason they can think of.
