Underpronation is a term that also goes by the name "supination." In the fitness industry, this means your ankle does not roll inward when your heel touches the ground while walking or running. Prolonged underpronation of the foot can lead to plantar fasciitis and tendinitis in the Achilles tendon. There are several steps you can take to correct this condition.
Examine the bottom of your sneakers for definitive signs that you are underpronating. Look at the outer edges of your soles for wear marks. Also, place your sneakers on a level surface and inspect the way they are sitting. If you are underpronating, the sneakers will be tipped toward the outer edge.
Buy a new pair of running shoes that help prevent excessive supination. Get a pair that have a curved last, meaning they curve inward at the insole, and that offer good shock absorption when you run in them.
Make an appointment with a podiatrist to be fitted for orthotics, which will offer additional support. A cast will be made of your foot, the orthotic will be designed based off of this.
Stretch the back of your legs to relieve underpronation. One such stretch is a downward-facing dog yoga stretch. Lie on your stomach with your hands under your shoulders. Curl your toes under your feet and push yourself up in the air. Walk your hands back as you lift your hips up in the air and push your weight back toward your heels. Keep your knees straight the whole time. Your body should form a 90-degree angle at this point. Hold the stretch for 30 to 45 seconds, release and repeat three to four times. Do this three times a day.