Hydration for Athletes: When Water Is Not Enough (...and When It Is)
With the influx of "hydration enhancers" on the market, it's easy enough to think that electrolytes are needed simply on the basis of working out. The reality is that for some, electrolytes truly are needed to replace losses from sweating and restore fluid balances, as even slight dehydration (eg. a 2% loss of body weight) can adversely affect performance and focus. For others, however, water alone is enough to stay hydrated and support performance. Whether or not you need to add electrolytes to your workout routine is based on individual factors such as workout intensity, environment, sweat rate, and sweat sodium concentration.
Hydration Basics
Hydration simply refers to maintaining a proper amount of fluid in the body. Fluids are lost daily, primarily through sweat, urine, and evaporation (like breathing hard during a workout). Hydration status may also be influenced by sickness and certain medications, which may cause your body to expel even more fluids. Athlete or not, all individuals need to make sure they are replenishing water losses by drinking fluids. Water of course is the most hydrating option, however other drinks such as milk, smoothies, juice, tea, coffee, and even some foods, like fruits and vegetables, all support hydration.
Our bodies are made of anywhere from 50 to 75% water, comprising various organs and tissues such as the brain, heart, lungs, skin, muscles, kidneys, and bones. It may come as no surprise that hydration status directly impacts many aspects of our health. For instance, adequate hydration helps the heart pump blood more efficiently, which in turn supports the delivery of oxygen to the brain and may assist in improving memory, mood, concentration, reaction time, and energy.
Where Electrolytes Come In
Electrolytes are minerals that carry an electrical charge, including sodium, potassium, calcium, and magnesium, and are lost through sweat and urine. The body tightly regulates electrolyte concentrations to ensure cells function properly. While potassium, calcium, and magnesium are present in sweat, their concentrations are relatively low and remain fairly consistent. In contrast, sodium is lost in much larger and more variable amounts. Because sodium losses are substantially greater than those of other electrolytes, most hydration strategies and electrolyte supplements are designed to replace sodium.
Hydration and Performance
Athletes and individuals who partake in especially long, hot, and sweaty exercise may need to replenish electrolytes lost through sweat, particularly sodium. Along with potassium, sodium plays a key role in fluid regulation by balancing fluids inside and outside of the cells. If sweat losses are high or an athlete is a "salty sweater," such as someone who notices white salt crystals or rings on their clothing after exercise, replacing sodium with sports drinks or electrolyte supplements may be beneficial. In some cases, drinking only plain water during extra sweaty and prolonged workouts can increase the risk of hyponatremia, a condition characterized by abnormally low blood sodium levels. Symptoms of hyponatremia range from mild to severe and may include muscle fatigue, dizziness, nausea, seizures, and even coma in rare cases.
Do I Need Electrolytes?
There is no single sodium replacement recommendation that applies to everyone, as both sweat rate and sweat sodium concentration are highly variable between individuals. The most effective hydration and electrolyte strategies are personalized based on sweat rate and sweat sodium testing. Athletes can test their sweat sodium concentration using at-home sweat patches (like this one from Gatorade), and use online hydration calculators (like this one from Precision Fuel&Hydration) to develop a personalized hydration plan.
When sweat testing is not available, electrolyte replacement can be viewed on a spectrum. For most workouts lasting less than an hour with minimal sweat loss, rehydrating with plain water is generally sufficient. However, athletes exercising in high heat for a prolonged period of time and with heavy sweat losses may benefit from sodium replacement.
Electrolytes can be a valuable tool for supporting performance and hydration, but they are not necessary for every workout. Pay attention to your individual needs and adjust your strategy based on your sweat losses, training demands, and environment.
References:
Buck, E., McAllister, R., & Schroeder, J. D. (2023). Exercise-associated hyponatremia. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK572128/.
Karpinski, C., & Rosenbloom, C. (Eds.). (2017). Sports nutrition: A handbook for professionals (6th ed.). Academy of Nutrition and Dietetics.
McDermott, B. P., Anderson, S. A., Armstrong, L. E., Casa, D. J., Cheuvront, S. N., Cooper, L., Kenney, W. L., O'Connor, F. G., & Roberts, W. O. (2017). National Athletic Trainers' Association position statement: Fluid replacement for the physically active. Journal of Athletic Training, 52(9), 877–895. https://doi.org/10.4085/1062-6050-52.9.02.
U.S. Geological Survey. (n.d.). Water: You, water, and the human body. U.S. Department of the Interior. https://www.usgs.gov/water-science-school/science/water-you-water-and-human-body.
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