Plantar Fasciitis is an inflammation of the plantar fascia, a thick slab of connective tissue that runs along the bottom of the foot. Heel pain in the morning is pretty much a smoking gun diagnosis of plantar fasciitis.
Exercise, particularly impact activities such as running and jumping, may cause plantar fasciitis. So may a number of other things, such as overpronation, which occurs when the foot rolls inward while walking. Being overweight can put extra pressure on the foot that can lead to plantar fasciitis.
Sometimes the condition resolves quickly or it may take months to heal. You can help the process along with self-care methods, but see your doctor if it is not improving. Use nonprescription pain remedies, if necessary, and ice the foot. You may need to rest it for a couple of weeks, reducing your exercise level or switching to something that does not impact the heel as much, such as biking or swimming.
Learn specific stretches for the foot and lower leg and practice them frequently. When you get back to exercising, make sure to warm up properly, stretch gently beforehand and more intensely afterwards. Stretch the foot while you are still lying in bed, before you swing your feet over to stand up. Wear shoes with thick, well-cushioned soles and good support. Try using those heel pads or heel cups that you get at the drugstore, but these do not help everybody — sole pads work better for some. Custom orthotic inserts should not be necessary.