When you exercise, blood flow is directed to the working muscles to ensure they receive the oxygen and nutrients they need to function at an increased intensity. As a result, circulation to other parts of your body -- especially your extremities -- is reduced, which can cause numbness. This usually is not serious and your symptoms tend to subside soon after you stop working out.
Symptoms of Reduced Circulation
Numbness in your fingers is quite common during exercise because fingers rarely are the body parts that require extra blood flow during a workout, says Edward R. Laskowski, MD, of Mayo Clinic. As well as numbness, your hands and fingers may feel stiff and appear red and puffy as the blood vessels in your hands expand to get as much blood as possible. These symptoms may be slightly uncomfortable, but they are not usually cause for concern. However, see a doctor if they persist.
Having numb fingers when exercising could be due to gravity, says Dr. Carl Lavie in "Fitness" magazine. When you run or bicycle, for example, your hands usually hang below the level of your heart. This means the blood must travel against the force of gravity -- and from the farthest point on your body -- to return to your heart. This factor alone can cause numbness in your fingers. However, it can be worsened because you are not actually using your arm and hand muscles to perform these activities, so they're doing very little to help pump the blood away from your fingers.
Extra blood pumping around your body during a workout means your body has extra fluid. When this fluid is trapped in your muscles, it causes swelling -- a condition called edema, says Christian Nordqvist on Medical News Today. Your working muscles can prevent this fluid from pooling by pumping it back to your heart, but your smaller muscles may not be as effective. For example, your arm muscles don’t produce as strong a pumping action as your legs and buttocks do, Lavie says. This is especially the case when performing exercises -- like running -- that don’t target your arm muscles. Without a strong pump, blood that does make it to your fingers must travel back to your heart against gravity. The quantity left to pool in your extremities can cause your fingers to go numb and appear swollen.
In most cases, the symptoms and reasons behind numb fingers during exercise are not cause for concern, according to Lavie. However, numbness can be unpleasant and detract from the enjoyment of your workout. Still, you can prevent numbness; to promote blood flow to your fingers, remove rings and snug watches or wrist jewelry before exercising, says Laskowski. At regular intervals throughout your workout, squeeze your fingers and shake your hands to encourage pumping action in your arms.