Exercise increases blood flow to your heart and lungs, as well as to the muscles you're working. This can reduce blood flow to your hands, making them cooler. In turn, the blood vessels in your hands may react by opening wider — which could lead to hand swelling. As you continue to exercise, your muscles generate heat that makes your system push blood to the vessels closest to the surface of your body, to dissipate heat. This response triggers perspiration
and may also contribute to hand swelling. Sometimes, endurance athletes develop hyponatremia
(hi-poe-nuh-TREE-me-uh) — an abnormally low level of sodium
concentration. Swollen fingers and hands may be a sign of hyponatremia, but other signs, such as confusion and vomiting, are more prominent than is swelling. Drinking too much water, particularly during a marathon
or similar long, strenuous event, may cause your body's sodium to become so diluted that you become hyponatremic. Hyponatremia requires immediate medical attention. There's no proven way to prevent or reduce most exercise-related hand swelling, but these tips may help ease discomfort: Remove your rings and loosen your watchband before exercise. , Perform occasional forward and backward arm circles during exercise. , Stretch your fingers wide and then make fists several times during exercise.