A search through endurance-related forums will reveal hand-swelling is a common malady, with posts complaining that hands look like “a rubber glove that's been blown up” or fingers that “feel very tight and hard to bend.” Although the condition is most common to ultra runners, hand-swelling can affect hikers, walkers and triathletes as well -- pretty much anyone who is part of the endurance community. But does it mean anything? All smart endurance athletes know it is important to pay attention to their bodies, and it’s natural to wonder if sausage-like fingers are the symptoms of something gone wrong. This article focuses only on edema (swelling) due to exercise. There are other causes of edema that may require medical intervention: see your doctor if in doubt. The answer, as with many biological systems, is complicated. At the very least, hand-swelling is nothing more than an annoying response to exercise, but at the worst, it’s a signal for a dangerous condition called “hyponatremia,” which occurs when the body’s electrolyte levels become dangerously low.

 

Common Cause Number 1: Hand-swelling as a response to increase blood circulation

Why it’s happening: Essentially, hand-swelling is part of the body’s response to exercise. It’s likely occurring for one of three reasons:

1. Increase blood flow to the working muscles: During a hard workout, like a long endurance run or hike, the legs, heart and lungs are working so hard, that the body redirects blood away from parts it considers less essential, such as the hands. Unfortunately, the hands are not always happy to oblige, and the redirection of blood flow may cause the blood vessels in the hands to expand, in an effort to maintain the original level of blood flow. This can potentially cause swelling.
2. Increased blood flow to the surface of the skin: During exercise in hot temperatures, the body redirects blood to the surface of the skin in order to help release excess heat. This causes blood vessels to expand, including those in the hands, which may cause swelling. This is why hand-swelling tends to be worse during the heat.
3. Blood pooling: Medically known as “edema,” blood pooling can occur for a variety of reasons, including, simply, gravity (something to which any pregnant woman will attest). After walking for an extended period of time, during which the arms are at the sides, gravity will simply pull blood into the hands, causing swelling. The effect can be exaggerated during hiking, especially if a person is carrying a heavy backpack that restricts blood flow from the arms back to the body. As a side note, this is the same reason the feet swell when running, and it’s why running shoe experts will often fit runners with ½ a size larger than their normal shoes.

Cause for concern: Although hand-swelling due to increased blood flow may be annoying, it’s not a cause for concern. In fact, it’s a sign that the body is doing exactly what it is supposed to do: releasing excess heat or redirecting blood to working muscles. The swelling will usually go away an hour after exercise is completed. If, however, the swelling does not go down after an hour or two, you may want to consult a health professional to ensure the swelling is not a symptom of a more significant issue, such as congestive heart failure. Steps for prevention: To prevent blood from pooling in the hands, it may help to move the arms periodically -- raise them over the head, make fists with the hands, or bring weights along during the walk to perform a few sets of bicep curls. During hiking, it may help to lighten the load in carried on the back to prevent too much reduction in blood flow to the arms in general. Lastly, it may help to remove rings that would cause discomfort if the fingers swell.

 

(Less) Common Cause Number 2: Hand-swelling as a symptom of imbalanced sodium levels

Why it’s happening: To understand why hand-swelling is a response to imbalanced electrolyte levels, it is important to know that the body’s fluid levels are in flux, constantly changing in order to maintain correct concentration of fluid and electrolytes. When electrolyte levels in the bloodstream are too low, the body can respond by shifting fluid out of the blood vessels into the surrounding tissue (attempting to reduce fluid levels relative to salt levels to restore the correct concentration). Since any change in size is clearly noticeable on usually-thin fingers, the skin on hands and feet is usually first to present with edema. How often does hyponatremia occur? A study of Boston Marathon runners, published in the New England Journal of Medicine, found that only 13 percent of runners exhibited symptoms of hyponatremia after the marathon, and only 0.6 percent exhibited “extreme” symptoms. Still, this condition is extremely serious, so take note if you experience the symptoms listed in “Cause for concern” (below). Cause for concern: Low electrolyte levels can cause hyponatremia, which is very dangerous, and can even be fatal. However, hyponatremia rarely (if ever) manifests itself in hand-swelling only. If hyponatremia truly is the cause, it will very likely be accompanied by confusion, irritability, headaches that won’t go away, nausea or extreme weakness. If you display any of these symptoms, it’s critical to take immediate steps to restore the proper ratio of electrolytes in the body. Steps for prevention: The U.S. National Institute of Health considers hyponatremia as one of the main complications of endurance events, and a 2001 review of the condition found that it usually occurs when athletes exercise for more than four hours or when fluid intake is abnormally high. Hyponatremia also affects females more than males. Based on the scientific literature, hyponatremia can likely be alleviated in two ways: 1) Don’t underconsume electrolytes and 2) Don’t overconsume water. Make sure electrolyte-replacement is a part of your workout nutrition, as opposed to simply water. Consider taking salt supplementation for an easy way to ensure you’re replacing electrolytes. SaltStick, for example, is specially designed to mimic the body’s loss of key electrolytes by including sodium, potassium, calcium and magnesium in the same ratio that exists in the average person’s sweat. Sports drinks can be helpful as well.

 

Bottom Line:

Hand-swelling on its own is probably the result of the body’s attempts to reduce excess heat and is not cause for concern. Moving the arms around during exercise could help alleviate the swelling. If, however, hand-swelling accompanies symptoms of hyponatremia, such as confusion, weakness, headaches or nausea, immediate steps should be taken to counteract what is likely low electrolyte levels. Persistent edema should be considered a significant medical symptom and should be discussed with your physician. Disclaimer: Contact your physician before starting any exercise program or if you are taking any medication. Individuals with high blood pressure should also consult their physician prior to taking an electrolyte supplement. Overdose of electrolytes is possible, with symptoms such as vomiting and feeling ill, and care should be taken not to overdose on any electrolyte supplement.