Hydration For Athletes

Hydration is key for both nutritional status and athletic performance. While humans are able to maintain a balanced hydration state on a regular basis in the absence of exercise with minimal forethought, athletes require much more detailed planning and preparation to ensure they stay properly hydrated. A hydrated state can be defined as having adequate amounts of fluid within the body’s tissues, while, conversely, a dehydrated state is when the body is lacking sufficient amounts of fluid. With the human body being composed of ~50-70% water, it comes as no surprise that dehydration can have a dramatic impact on athletic performance.

An athlete that is dehydrated can experience a variety of issues including, but not limited to, overheating, cramping, hyperventilation, nausea, and poor appetite after exercise. If an athlete is experiencing such symptoms, there will almost certainly be a decrease in performance.

Additionally, there are a variety of outside factors that affect an athlete’s sweat rate and likelihood of becoming dehydrated. Some of the factors to look out for include:

  • Weather – One of the more important factors to consider when it comes to preparing an athlete for competition in regards to hydration status. The temperature, air pressure, altitude, and humidity all play a role in determining how and when to hydrate.
  • Clothing/uniform/sports equipment – Required uniforms or sporting equipment that the athletes wear may contribute to the body having to work harder to cool down.
  • Duration and intensity of the sport, availability of fluids – The nature of the activity and access to hydration products can help determine protocols and bring awareness to how many water breaks athletes are getting, and what types of products athletes are drinking (water, sports drink, concentrated electrolytes, etc.). It is especially important to monitor athletes with high volume outputs to make sure they are hydrated both prior to and during play.

The two most practical ways to monitor and assess hydration status in athletes are looking at urine color and estimating sweat loss through the measurement of body weight before and after exercise. Both of these tried and tested assessments are non-invasive and capable of being done in a relatively quick and reliable manner when consistent protocols and practitioners are used. Below, additional information on these hydration assessment tools is provided:

  • Urine Color:
    • Have the athlete keep track of their urine color, with the goal to have their urine be a pale, light yellow color.
    • Overhydration color: almost clear yellow
    • Hydrated color: light/pale yellow
    • Dehydrated color: bright to darker yellow
    • Very dehydrated color: orange to brown
  • Sweat Loss:
    • Weigh the athlete before exercise.
    • Weigh the athlete after exercise. This is to be done in the same dry clothing as when the prior weight was taken.
    • Assess any potential body weight changes. Most weight that is lost during exercise is water weight. For every pound lost, rehydrate with 20 oz of fluid. Studies have shown that a loss of more than 1% body weight during exercise has a negative effect on performance depending on the sport.

There are several strategies that athletes seeking to focus on their hydration can adopt to get them pointed in the right direction prior to more targeted, sport-specific, recommendations. While athletes should carry a water bottle and be intentional about drinking throughout the day, it is important to note that there are other beverages besides water that can also be used for hydration. Juices, milk, and shakes or smoothies all contribute to baseline daily fluid needs of about 120 ounces for men and 90 ounces for women. Studies have shown that beverages containing caffeine up to ~400 mg per day can still be considered hydrating; beyond that amount, caffeine-based products may lead to diuretic effects. Every athlete’s body will metabolize caffeine at different rates, so educating athletes on how much caffeine is tolerable is a topic that staff can discuss with athletes they work with. Note that at certain levels caffeine is also an NCAA banned substance.

It is important to recognize that hydration is not just affected by water loss, but also electrolyte loss. Sweating causes a loss of electrolytes like potassium, magnesium, sodium, and calcium. Potassium and sodium work together in the body to maintain fluid balance, while magnesium and calcium aid in energy metabolism along with muscle function. Fluid balance, energy metabolism and muscle function are all important factors to understand why it is important to replenish with electrolytes before, during and after exercise. Easy sources of potassium could be dark leafy greens, citrus fruits, and potatoes. Magnesium can be found in peanut butter, beans or nuts. Calcium is found in dairy foods along with broccoli and almonds. Lastly, sodium is found in various salty snack foods, but can be found in sports drinks as well. Today’s sports nutrition market has made it easier for athletes to rehydrate, by creating electrolyte packets that can be mixed into water. Below is a table that compares food sources, a sports drink and an example electrolyte packet and their sources of potassium, magnesium, sodium and calcium.

ElectrolyteAmount in FoodsAmount in Sports Drink (20 fl oz)Electrolyte PacketDietary Reference Intake
Potassium926 mg (1 baked potato)80 mg200 mg3,400mg
Magnesium49 mg (2 tbsp peanut butter)0 mg60 mg400 mg
Sodium359 mg (1 oz pretzels)270 mg1000 mg1,500 mg
Calcium187 mg (1 cup Greek yogurt)0 mg0 mg1,000-1,300 mg

In addition to daily fluid needs, athletes should make sure they are drinking before, during and after exercise. A good routine would include drinking 16-20 oz of water or sports beverage at least 4 hours before exercise and 8-12 oz of water 10-15 minutes before exercise. During exercise, try to have a sip or two of water or sports drink every 15-20 minutes. After exercise, 16-24 oz of water or sports drink is a good start if unable to gauge sweat loss replacement needs. Fueling your body with the foods or drinks containing the electrolytes listed above can help combat the negative effects that dehydration can have on nutritional status and athletic performance.

Here are some questions to ask athletes to get them thinking about hydration:

  • Do you carry a water bottle with you?
  • What drinks besides water do you have during the day?
  • How often do you have a water break during exercise?

This article was written by Shannon Kelly, RD, a Collegiate and Professional Sports Dietitians Association Registered Dietitian (RD). To learn more about sports nutrition and CPSDA, go to www.sportsrd.org.


Appendix J dietary reference intakes summary tables – NCBI bookshelf. (n.d.). Retrieved September 19, 2022, from https://www.ncbi.nlm.nih.gov/books/NBK545442/ 

Barley, O. R., Chapman, D. W., & Abbiss, C. R. (2020). Reviewing the current methods of assessing hydration in athletes. Journal of the International Society of Sports Nutrition, 17(1), 52. https://doi.org/10.1186/s12970-020-00381-6

Belval, L. N., Hosokawa, Y., Casa, D. J., Adams, W. M., Armstrong, L. E., Baker, L. B., Burke, L., Cheuvront, S., Chiampas, G., González-Alonso, J., Huggins, R. A., Kavouras, S. A., Lee, E. C., McDermott, B. P., Miller, K., Schlader, Z., Sims, S., Stearns, R. L., Troyanos, C., & Wingo, J. (2019). Practical Hydration Solutions for Sports. Nutrients, 11(7), 1550. https://doi.org/10.3390/nu11071550

Downloadable resources. Downloadable Resources – CPSDA | SportsRd.org | Collegiate & Professional Sports Dietitians Association. (n.d.). Retrieved September 8, 2022, from https://sportsrd.org/downloadable-resources/ 

Fluids and hydration. U.S. Anti-Doping Agency (USADA). (2022, July 7). Retrieved September 8, 2022, from https://www.usada.org/athletes/substances/nutrition/fluids-and-hydration/ 

Killer, S. C., Blannin, A. K., & Jeukendrup, A. E. (2014). No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PloS one, 9(1), e84154. https://doi.org/10.1371/journal.pone.0084154

Lohsiriwat, S., Hirunsai, M., & Chaiyaprasithi, B. (2011). Effect of caffeine on bladder function in patients with overactive bladder symptoms. Urology annals, 3(1), 14–18. https://doi.org/10.4103/0974-7796.75862

Trangmar, S. J., & González-Alonso, J. (2019). Heat, Hydration and the Human Brain, Heart and Skeletal Muscles. Sports medicine (Auckland, N.Z.), 49(Suppl 1), 69–85. https://doi.org/10.1007/s40279-018-1033-y