A new exercise program changes the chemical makeup of your muscles as an adaptive response to increased activity. The changes that take place in your muscles after exercise prepare them for more of the same by storing additional fuel for energy. Muscles replenish glycogen stores after a workout, and extra water in the muscles is a natural side effect of this process. Consult with your doctor before you start a new exercise program if you have a history of health problems.
Glycogen is hydrophilic, which means that it attracts water, says personal trainer William Sukala. For every gram of glycogen you store, 2.7 g of water is also retained in the muscle. This happens not only as a result of new exercise programs but also takes place after workouts in an established exercise regimen. Glycogen stores are needed to fuel muscles during physical activity. When exercise depletes glycogen stores, more carbohydrates get converted to glycogen, and water retention results.
Although replenished glycogen stores continue to attract water after exercise even in established routines, the process may be more noticeable in a new exercise program if you're trying to lose weight. You may see temporary weight gain, for example, or not lose as much weight as you expect initially. However, if you consistently burn more calories than you consume, water retained by your muscles after exercise will have little or no effect on your weight goals. Weigh in once a week rather than daily to avoid frustration with temporary weight fluctuations resulting from exercise.
On average, men need 13 cups of fluid a day and women need about nine cups. The Human performance Resource Center recommends drinking 3 to 8 oz of water every 15 minutes during exercise. If you exercise longer than an hour, you need even more liquid -- at least enough to replace fluids lost through sweat. If you don't meet your body's need for fluid, including water demanded by taxed muscles, you risk dehydration.
Your workouts affect your glycogen and water stores. If you consistently challenge your muscles with tougher workouts, the amount of energy you burn increases. This, in turn, creates a larger demand for glycogen. To ensure that you have sufficient carbohydrate stores to fuel your workouts, aim to get 45 to 65 percent of your calories from carbohydrates, with an emphasis on complex varieties such as whole grains, fruits and vegetables.