Electrolyte Replacement, Explained
Do you need to sweat the small stuff?
By Emily Brown
As featured in the November 2009 issue of Running Times Magazine
Runners have talked about electrolytes for decades. Now the general public is getting in on the act, thanks to widespread marketing for not just sport drinks, but electrolyte-enhanced waters, teas and other beverages. Amid the claims of improved performance and recovery, the most basic questions are seldom asked: What exactly are electrolytes? And do runners, let alone the general population, really need to be concerned about replenishing them?
Chemically, an electrolyte is a substance that, when in fluid, dissociates into electrically charged ions. The positive or negative charge carried by these ions is what allows our body's cells to use electrolytes to carry electrical impulses throughout the body. When you're running, electrolytes are crucial in maintaining your body's ability to transmit nerve impulses and contract muscles. Electrolytes serve other biological functions, too, including water balance and distribution to working cells as well as acid-base balance.
The electrolytes required by our bodies to perform these functions include sodium, chloride, potassium, magnesium and calcium.
The typical American diet contains an abundance of each of these, which exist at normal levels in most healthy individuals. However, certain medical conditions, especially diseases involving the kidneys, can result in severe imbalances. In addition, any illness causing profuse vomiting or diarrhea can leave an individual with depleted levels of certain electrolytes. That said, most healthy individuals with a good diet consisting of a wide variety of foods don't need to be concerned with electrolyte replacement through the use of electrolyte-enhanced beverages.
For athletes, however, certain situations may contribute to electrolyte losses, in which case proper replacement becomes important. The main reason athletes need to think about replacing electrolytes is because electrolytes are lost from the body through sweat. Sodium and potassium are lost in the greatest amounts via sweat, while magnesium and chloride are lost in only small amounts.
For the most part, the more you sweat, the more electrolytes you'll lose while running. If you sweat a lot and/or you seem to be caked with salt after runs, you can probably assume that you're losing a fair amount of electrolytes during your runs and need to pay special attention to replacing them. Sweat rates can range from 0.3 to 2.4L per hour (roughly a half pound to 5 pounds per hour). To determine your sweat rate, weigh yourself before and after running; each pound lost equates to ~2 cups of fluid. Although individual concentrations will vary widely, one pound of sweat contains approximately 80-100mg of potassium and 400-700mg of sodium.
The symptoms of electrolyte imbalance are often the same as those of dehydration, since the two tend to go hand in hand. A common symptom is muscle and/or abdominal cramping. Other symptoms include light-headedness, nausea, confusion and muscle spasms.
If you are a candidate for focusing on electrolyte replacement, when and how should you do so?
Again, our diets typically provide more than enough of the electrolytes we need to perform the biological functions that require them. Therefore, we don't really need to be concerned with restoring electrolytes before exercise.