Swelling in your legs after a long run can be the result of many different factors.
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It might seem like a bad joke -- you go running for exercise to lose weight and slim down, but instead, your legs appear larger after a run than when you started. Because of the impact level and the increased blood circulation, running can cause your legs to temporarily swell as the muscles and bones in the area are put under stress. Unless the swelling is severe, prolonged or accompanied by pain, swelling legs after a run can be fairly normal and can be a result of a number of factors. Pay attention to swelling legs, but don't let it deter you from the benefits to your muscles and bones that running provides.
Fluid Retention after Running
According to MayoClinic.com, standing upright for long periods of time -- which you do during running -- can cause fluids to settle in your lower body. This is due to gravity, and fluid retention in your legs can be exacerbated as your legs, in addition to supporting the full weight of your body, also experience increased blood flow. As gravity pulls fluids down into your legs, it can cause swelling, also known as peripheral edema. Swelling due to fluid retention is more common in long-distance runs than in shorter ones.
According to the American College of Sports Medicine, weight-bearing activities, especially repetitive motion ones such as running, can cause a number of overuse injuries, inlcuding strained muscles. A strained muscle can cause your leg or joints to swell, as the muscle fiber is damaged. To reduce the risk of a muscle strain, slowly build up to more intensive running workouts, both in terms of distance, speed and duration. As well, properly warm-up and cool down your muscles to reduce the chance of injury.
Medial Tibial Stress Syndrome
Medial tibial stress syndrome, also known as shin splints, is one of the most common leg injuries, according to Runner's World. This injury occurs when the periosteum becomes inflamed. The periosteum is the membrane around your bone, between the muscle and your bone, and can become inflamed due to stress from weight-bearing or high-impact activities such as running. Symptoms of periosteum inflammation include pain and swelling, as well as a red flush in the area.
More Serious Causes
Deep vein thrombosis, also known more commonly as a blood clot, can cause your leg and ankle to swell. A severe condition, it is still relatively rare, but can be fatal if left untreated. Deep vein thrombosis symptoms include cramping in the calf -- one leg only -- and some redness. If the swelling in your leg becomes worse after exercise and your skin is red and warm when touched, seek emergency medical attention immediately.