Practical Applications: Exercise-Associated Hyponatremia
Many athletes may be unaware of the risks of hyponatremia, and so endurance athletes especially should be educated on this medical condition. Technically, what athletes experience is exercise-associated hyponatremia, defined as symptomatic hyponatremia with plasma sodium levels less than 130 mEq/L. This hyponatremia usually occurs in individuals engaging in endurance events lasting longer than 5 hours. These individuals sweat for long periods of time and are losing sodium in their sweat. If they replace their fluid losses with water without consuming foods or beverages containing sodium, extracellular fluids in the body become low in sodium. This causes a shift of water into the cells, and if happening rapidly or severely enough, this can cause congestion in the lungs, swelling of the brain, altered CNS functioning, and ultimately could result in death.
The best way to avoid hyponatremia is to avoid overdrinking. Individuals should be encouraged not to drink more than the amount that they lose, acknowledging that a mild fluid deficit (less than 2 percent body weight loss) will most likely not result in performance impairments. Additionally, individuals who are “salty sweaters” as evidenced by the white salt rings around their forehead and on their shirt (wearing darker shirts can help to identify this), or if they are exercising for more than 4 to 5 hours, should consider electrolyte replacement, particularly sodium. In general, hyponatremia can be avoided by consuming sports drink instead of plain water during prolonged exercise.
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The recommended intake of sodium is approximately 20 to 30 mEg/L, though this may need to be customized according to individual sweat rates and sodium content of sweat. This is the sodium amount found in most sports drinks and sport nutrition products. Typically a salt tablet is not warranted, unless the individual is only consuming water and is not consuming sodium-containing foods. In addition, thiazide diuretics and use of nonsteroidal anti-inflammatory drugs (NSAIDs) can increase one’s risk for hyponatremia due to interference with the antidiuretic hormone (ADH) that helps regulate fluid balance. Individuals consuming these medications should pay particular attention to appropriate fluid and electrolyte consumption. While this is a very small segment of the athletic population, it is a condition that could be quite serious and athletes in these sports should precautions to avoid.
Glycogenesis the process of adding glucose molecules to glycogen for storage in the liver or in muscle cells, commonly stimulated by insulin.
Muscle cell hypertrophy an increase in muscle cell size. Hyperaminoacidemia having excess amino acids in the blood. Gluconeogenesis the production of glucose from noncarbohydrates carbon sources including pyruvate, lactate, glycerol, and glucogenic amino acids.