Numbness in your feet while exercising could have a variety of different causes, including problems from expanding muscles to nerve compression. Tight shoes or restrictive foot straps also can lead to numb feet. The diagnosis is based on where the numbness occurs. If your foot numbness is making it difficult to exercise, however, you may need to have your feet examined by a specialist.
Muscle Expansion
During exercise, muscles expand by up to 20 percent, which can crowd out and compress surrounding tissues, blood vessels and nerves, according to Dr. Cathy Fieseler, sports medicine committee member of the Road Runners Club of America. As you continue exercising, the sensation can worsen and even lead to loss of muscle control. To alleviate the swelling, you should stop the activity.
Nerve Compression
Tarsal tunnel syndrome is a nerve problem that can cause numbness in the feet. The tarsal tunnel is a narrow area located on next to the ankle bones, on the inside of the foot. The tunnel contains arteries, veins, tendons and nerves and is protected by a thick ligament. People with flat feet are at higher risk of developing tarsal tunnel syndrome because the heel puts pressure on and strains the posterior tibial nerve. People with varicose veins, a swollen tendon or arthritic bone spurs also are at risk of developing the condition. If you've had a sprained ankle, the inflammation and swelling near the tarsal tunnel can compress the tibial nerve, resulting in foot numbness.
Other Causes
Numbness in the feet also can be caused by wearing tight shoes, using exercise machines with restrictive foot straps, vibration from exercise machines or biking and climbing, which places continuous pressure on the bottom of the foot. Before making a doctor's appointment, be sure your symptoms are not connected to these other causes by loosening your foot straps and wearing thinner socks. You also can try using a different brand of exercise shoe. It's possible that you need a wider shoe, or a shoe with higher arches. Weak arches and flat feet are typically hereditary, but pregnancy, wearing high heels, aging and injury can cause changes in your foot structure, according to fitness expert and author Mark Sisson.
Shoes
Ill-fitting shoes, especially when paired with thick socks, can cause numbness in your foot and toes. Replace exercise shoes every three to six months or after walking 300 to 500 miles. If you exercise daily, rotating between two pairs of exercise shoes gives each pair time to go back to the original shape. Avoid using your exercise shoes for casual activities. When you're buying new sneakers, wear your normal workout socks -- or a pair of thick socks. It's important that your shoes offer a snug fit, but that your feet have plenty of room. Shoes that are too large can lead to hot spots, which refers to friction from your foot sliding around in a large shoe. If you experience numbness on the top of the foot, sample shoes with different enclosures and don't tie the laces too tightly. If you have numb toes, avoid shoes that are too flexible.
