Proper fluid consumption is essential before, during and after exercise to prevent dehydration. Too little fluid consumption may cause an imbalance in the body's electrolyte levels and allow the core temperature to rise above normal levels. Excessive water retention may signal difficulties with controlling fluid levels. High-intensity exercise such as running can encourage water retention in the body, particularly running over long distances or in extreme heat.
Running at high speeds over long periods of time causes your body to lose fluid primarily through sweat. You also excrete water through urine and even breathing. Extreme fluid loss can lead to dehydration, or a body water deficit. A body water deficit of greater than 2 percent of body weight may decrease your athletic performance, as well as cause significant health problems. Dehydration prompts you to take in more fluids; it can also prompt your body to retain water.
Dehydration and Hormones
Prolonged running, especially at elevated temperatures, may lead to water loss and increased sodium in the blood. Your body produces hormones that act on certain organs to maintain fluid balance. One of the most important hormones, the antidiuretic hormone, acts on the kidneys to increase water retention. Another hormone, aldosterone, prevents sodium excretion by the kidneys, which encourages fluid retention in the body. Therefore, a lack of fluid in the body during and after running may lead to increased water levels in the body as these hormones attempt to correct your fluid balance.
In addition to being retained between cells, water can also be stored in the liver and muscles bound with carbohydrate in the form of glycogen. According to the American Council on Exercise, 1 gram of glycogen can have as much as 2.7 grams of water bound to it, causing body weight to increase by 3 to 5 pounds. Runners often consume larger amounts of carbohydrate, particularly before a long-distance event, resulting in greater water storage in muscles. In addition, some muscle-building supplements, such as creatine, can increase the risk of dehydration or muscle cramps.
Consuming adequate amounts of fluid before, during and after running can prevent dehydration and subsequent water retention. Avoiding high-sodium foods that promote water retention will also help prevent weight gain from excessive fluid. Finally, exercising in temperature-controlled environments will limit extreme sweating and fluid loss that leads to increased water retention.