Numbness is a loss of sensation in a body part usually caused by nerve compression. It feels very similar to when a limb "falls asleep" if you've held it in the same position for too long. It is rarely life threatening, but can be annoying, especially when you're exercising.
Diseases
There are some illnesses that cause numbness in the feet, although they usually have other symptoms, too. Some of the more serious causes of numbness include diabetes, multiple sclerosis, Lyme disease, a herniated disc, Guillain-Barre syndrome and a brain tumor. See your doctor if you experience numbness most of the time, if the numbness occurs in other parts of your body, or if it is accompanied by pain, blurred vision or nausea.
Other Causes
Numbness in the feet during or after workouts can also be caused by more benign or treatable disorders. These include a Vitamin B deficiency, improper or tight shoes, improper exercise technique or even the type of exercise you're doing. An article in the "Providence Journal" reports that many people who use elliptical trainers experience numbness and tingling because their feet maintain constant contact with the pedals, causing pressure to build in the feet and cause them to increase as much as a full size. This swelling presses on the nerves in the feet, causing numbness.
Diagnosis
If your numbness doesn't resolve once you've given your feet a rest or if it spreads to other parts of the body, your physician might run some tests to determine the cause. Blood tests can diagnose a Vitamin B-12 deficiency while nerve conduction tests can diagnose more serious problems of nerve damage. An MRI can diagnose conditions such as tumors or multiple sclerosis.
Treatment
After ruling out a serious illness, treating numbness in the feet is usually devoted to decompressing nerves and improving circulation in the feet. Your health care provider or a trainer at your gym might suggest taking a break to flex your feet during exercises that cause numbness, or loosening the laces on your shoes to allow for foot swelling. A vitamin B-12 deficiency will be treated with supplements.
