Hydration & Endurance Athletes
Hydration is crucial for health and performing your best in training and competition.
By Scott Wrigley, MSc, CSCS, CPT, FNS, PN1, USAT Level 1 Coach, USA Cycling Level 3 Coach, US Masters Swimming Level 2 Coach
Hydration is essential for life and optimal functioning. Water plays a key role in digestion and absorption, metabolic processes such as the electron transport chain (ETC), temperature regulation, nutrient and waste transport, oxygen delivery, joint lubrication, pH balance, and more (1).
Hydration is also essential for optimal endurance performance. Losses of ~2-3% of total body weight have been shown to impact performance negatively. Some impacts of dehydration include (2, 3, 4):
Reduced stroke volume
Increased heart rate
Increased rating of perceived exertion (RPE)
Impaired temperature regulation
Impaired blood flow to the muscle
Impaired aerobic performance
Impaired cognitive performance (decision-making)
It is clear that in order to optimize health and performance, athletes should prioritize hydration. In this article, we cover: how much fluids we need per day; tips for staying hydrated throughout the day; hydrating prior to, within, and post-training/racing; electrolytes; and monitoring your hydration status.
Fluids: how much do you need a day?
On average, the total amount of water required per day is approximately 11.5 cups for women and 15.5 for men. However, we get approximately 20% of the water we need from the foods we eat, reducing the total water we need to consume from beverages (5). After adjusting for 20% of fluids coming from foods, women need approximately 9 cups/day and men ~13 cups/day. However, it should be noted that fluid needs vary based on factors such as environment, activity level, age, and health status.
Tips for staying hydrated throughout the day
Carry a bottle of fluids with you.
The bottle will act as a constant reminder of your intention to stay hydrated. Additionally, you will have fluids with you in case you find yourself in a situation where there are no fluids, such as a water fountain or vending machine, available.
Drink fluids prior to and with your meals.
Drink more than just water.
Drink tea, carbonated water, water with electrolyte powders, fruit-infused water, etc.
Make sure that you are consuming the recommended daily intake of fruits and vegetables.
For adults, the recommended daily intake levels are 1.5-2 cups of fruits per day and 2-3 cups of vegetables per day (6).
In addition to being sources of vitamins, minerals, phytonutrients, fiber, and electrolytes, fruits and vegetables are primarily composed of water (7).
Fluids and Training/Competition
In addition to drinking plenty of fluids over the course of the day, athletes should maintain hydration by drinking adequate fluids prior to, during, and after training or competition.
Prior to training/competition:
3-4 hours prior to training or competition, individuals should drink approximately 5-7 mL/kg of body weight (∼2-3 mL/lb) (3). 15-30 minutes prior, athletes should consume another 200-350 mL (7-12 oz) of fluid (4).
During training/competition:
During training/competition, a solid starting target is to drink ~400-800 mL/hour (~13-27 oz/hour) (8). How much you take in will vary based on factors such as exercise intensity, duration, environment, sweat rate, etc.
Post-training/competition:
Post-training/competition, athletes should aim to replace ~100-150% of fluid lost (4, 8). For example, if an athlete lost .5kg (~1lb) during training or competition, they would aim to take in approximately 16-24oz of fluids (3, 4, 8).
Electrolytes
Electrolytes play a critical role in many physiologic processes, including digestion and absorption, maintaining fluid balance, nerve signaling, muscle contraction, temperature regulation, and more.
When we sweat, in addition to water, we also lose electrolytes. Depending on factors such as exercise intensity, duration, and environmental conditions, endurance athletes may need to supplement with electrolytes either within or in addition to their hydration beverage.
A 2015 study comparing the performance of athletes consuming a sports drink + additional electrolytes (pill form) vs a sports drink + placebo (cellulose pills) found that athletes who consumed the additional electrolytes finished a 70.3 distance triathlon ~26 minutes faster compared to the placebo group (9).
However, electrolyte losses differ from athlete to athlete. A 2016 study examining the sweat electrolyte concentration of marathon runners found electrolyte losses in sweat "varied significantly among runners" (10). As such, I recommend that athletes measure electrolyte concentrations of their sweat and sweat rate to optimize electrolyte intake in training or competition in order to improve performance.
A few examples include an at-home sweat test and a non-exercise sweat test.
At-home sweat test: the GX Sweat Patch by Gatorade Sports Science *
Non-exercise sweat test: the Advanced Sweat Test from Precision Fuel & Hydration *
*Endurance Forge has no affiliation with either Gatorade Sports Science or Precision Fuel & Hydration.
How do you know if you're hydrated?
There are many tests that can be used for assessing hydration status. However, urine color remains the most cost-effective replacement for these and provides valuable insights into acute hydration status (4).
Takeaways
Water is essential for digestion and absorption, metabolic processes such as the ETC, regulating body temperature, transporting nutrients, waste products, and oxygen, and lubricating joints.
Losses as little as ~2-3% of total body weight can negatively impact performance.
Hydration needs are met through both food and beverage intake.
Women need approximately 9 cups per day, and men 13 cups.
In addition to daily hydration, athletes should drink adequate fluids prior to, during, and post-training/competition.
Electrolytes are crucial for many physiologic processes, including muscle contraction, and electrolyte needs vary greatly from athlete to athlete.
Urine color provides a valid marker of hydration status.
References:
Rowlands DS, Kopetschny BH, Badenhorst CE. The Hydrating Effects of Hypertonic, Isotonic and Hypotonic Sports Drinks and Waters on Central Hydration During Continuous Exercise: A Systematic Meta-Analysis and Perspective. Sports Med. 2022 Feb;52(2):349-375. doi: 10.1007/s40279-021-01558-y. Epub 2021 Oct 30. PMID: 34716905; PMCID: PMC8803723.
American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007 Feb;39(2):377-90. doi: 10.1249/mss.0b013e31802ca597. PMID: 17277604.
American Dietetic Association; Dietitians of Canada; American College of Sports Medicine; Rodriguez NR, Di Marco NM, Langley S. American College of Sports Medicine position stand. Nutrition and athletic performance. Med Sci Sports Exerc. 2009 Mar;41(3):709-31. doi: 10.1249/MSS.0b013e31890eb86. PMID: 19225360.
United States Anti-Doping Agency (USADA). (2018). TrueSport Nutrition Guide. Retrieved from https://www.usada.org/wp-content/uploads/TS-Nutrition-Guide.pdf
Gordon, B. (2022, June 23). How much water do you need? eatright.org. Retrieved April 5, 2023, from https://www.eatright.org/health/essential-nutrients/water/how-much-water-do-you-need
Current dietary guidelines. Dietary Guidelines for Americans, 2020-2025 and Online Materials | Dietary Guidelines for Americans. https://www.dietaryguidelines.gov/resources/2020-2025-dietary-guidelines-online-materials
Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration, and health. Nutr Rev. 2010 Aug;68(8):439-58. doi: 10.1111/j.1753-4887.2010.00304.x. PMID: 20646222; PMCID: PMC2908954.
Vitale K, Getzin A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients. 2019 Jun 7;11(6):1289. doi: 10.3390/nu11061289. PMID: 31181616; PMCID: PMC6628334.
Del Coso J, González-Millán C, Salinero JJ, Abián-Vicén J, Areces F, Lledó M, Lara B, Gallo-Salazar C, Ruiz-Vicente D. Effects of oral salt supplementation on physical performance during a half-ironman: A randomized controlled trial. Scand J Med Sci Sports. 2016 Feb;26(2):156-64. doi: 10.1111/sms.12427. Epub 2015 Feb 14. PMID: 25683094.
Lara B, Gallo-Salazar C, Puente C, Areces F, Salinero JJ, Del Coso J. Interindividual variability in sweat electrolyte concentration in marathoners. J Int Soc Sports Nutr. 2016 Jul 29;13:31. doi: 10.1186/s12970-016-0141-z. PMID: 27478425; PMCID: PMC4966593.