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Water Retention & Exercise

Jun 14, 2011 | By Lyn Michaud
Water Retention & Exercise
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Water retention causes weight gain during exercise, indicating too much fluid replacement. Increasing fluid intake before prolonged physical activity, also called hyperhydration, may prevent dehydration from likely fluid loss in hot conditions. According to Gatorade Sports Science Institute, exercise reduces the ability to eliminate excess water and inappropriate fluid retention may dilute the sodium concentration in the body and lead to additional health complications.

Fluid Absorption

The small intestine absorbs water from drinking water, beverages and food. According to an article in the journal "Sports Medicine," published in August 2007, fluid distribution throughout the body requires 20 to 30 minutes and depends on the rate that the stomach empties its contents into the small intestine, the rate of intestinal absorption and water retention inside and outside the body's cells.

Water Loss

The body removes water in urine, feces and sweat. According to the Gatorade Sports Science Institute, exercise leads to a 20 to 60 percent decrease in urine production because the body regulates removal of excess heat from exercise by stimulating the sweat glands. In addition to water loss, sodium chloride, potassium, calcium and magnesium may be lost in sweat.

Dehydration

Excess fluid loss slows the rate of stomach emptying and may lead to decreased performance with an increasing inability to regulate body temperature, putting stress on the cardiovascular system. According to researchers at the Nutrition and Technology Research Institute Maastricht in the Netherlands published in "Sports Medicine" in August 2007, fluid replacement cannot wait for thirst, because the stimulus to drink occurs after the body's water deficit reaches 2 percent of body mass.

Fluid Regulation

To regulate blood pressure, the kidneys eliminate water and salts from the blood under the hormonal control of vasopressin, atrial natriuretic peptide, aldosterone and the renin-angiotensin system working in combination. According to the Gatorade Sports Science Institute, exercise decreases blood flow to the kidneys. Vasopressin increases water permeability of the kidney collecting tubules and increases solute re-absorption, leading to decreased urine output resulting in a net increase in water retention.

Optimal Fluid Replacement

Fluid replacement should equal fluid lost. A study published in "Research Quarterly for Exercise and Sport" shows that glycerol added to water increases fluid retention with only mild side effects of increased blood pressure and cramping. In hot conditions, glycerol extended average exercise time by 21 percent compared to plain water. According to an August 2007 "Sports Medicine" review article, fluid replacement containing 7 percent carbohydrates increases intestinal absorption of water and at least 50 millimols-per-liter of sodium improves water retention. However, guidelines published in "Sports Medicine" in 2004 don't support sodium tablet supplementation.

Inappropriate Water Retention

Hyponatremia, results from a rare though dangerous decrease in blood sodium levels increasing water into the brain leading to seizure, respiratory arrest, coma or brain damage. The Gatorade Sports Science Institute suggests that hyponatremia may occur with drinking more than 3 qts. of plain water per hour. Warning signs of hyponatremia include puffy fingers and ankles, headache, confusion and stomach bloating. According to researcher Margaret Hsieh's "Sports Medicine" article, because the symptoms of hyponatremia can be similar to hypoglycemia, gastroenteritis, heat stroke, exercise exhaustion and exercise induced collapse, diagnoses requires lab testing for sodium levels.

References

Article reviewed by David Fisher Last updated on: Jun 14, 2011

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