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Sunday, 8 June 2014

Hydration Fundamentals for Optimal Sport Performance


Proper hydration is an important factor for sustaining a high level of athletic performance. Improper hydration can lead to disappointing results for even the most elite athletes. Though there are a number of factors (including weather, metabolic rate, and type of sport) that can impact the hydration of athletes and negatively affect performance, this article discusses effective strategies and recommendations for maintaining optimal fluid balance.

Learning Objectives:

  1. Understand the basics of hydration and the role of electrolytes in the body.
  2. Comprehend the mechanics of fluid replacement protocols.
  3. Proficiently identify the suggested intake requirements before and during sport to ensure proper hydration. 
One of the biggest challenges athletes face, especially in warmer weather, is maintaining proper hydration. Unfortunately, determining appropriate intake can be overwhelming and confusing for athletes to follow. As personal trainer, it’s critical to keep hydration at the top of your clients’ minds with concise steps and easy guidelines. You can help your clients realize the importance of staying hydrated with some simple tips and tricks for before, during and after sport.

Hydration Regulation within the Body

The main component of blood is water, which delivers a number of substances including oxygen, nutrients, and hormones to the cells and removes waste from the cells. It is also a vital component to your body’s temperature regulating mechanism (Benardot, 2012). Water, along with electrolyte components, controls the osmotic pressure in our body, essentially dictating the amount of intercellular and extracellular fluid.
Fluid levels are regulated by several hormones in our body. These hormones, known as ADH (antidiuretic hormone) and aldosterone, monitor the osmolality of the blood and volume of extracellular water. It’s ADH and aldosterone which stimulate kidney function, adjusting the volume of water and electrolytes either excreted or retained by your body (Rolfes, Pinna & Whitney, 2009). 

The Power of Electrolytes for Athletes

Electrolytes are minerals contained in foods and beverages, which dissolve in the fluids in our body and break into electrically charged ions. There are five chief electrolytes—sodium, potassium, calcium, magnesium and chloride—which play a role in many body functions including fluid balance, blood pH, heart, nerve and muscle function.
These minerals are electrically charged, which means that they have the ability to conduct electrical impulses. These electrical impulses are essential for physical activity as they are what makes muscles contract. In order to keep muscular, cardiac, nervous, and digestive systems all firing correctly, an adequate supply of all these minerals is required (Rolfes, Pinna & Whitney, 2009).
Sweat rate, through exercise, can induce high levels of water and electrolyte loss. Exact levels depend on both the individual and the environment. Genetically, some people have a predisposition to be heavier and saltier sweaters. Sweat contains electrolytes, with the make-up primarily being sodium in addition to lower levels of potassium, magnesium and calcium (Sawka, 2007). Even endurance athletes who are not heavy sweaters will require more than the upper limit (UL) for sodium (2300mg). Potassium is a mineral important for both electrolyte and fluid balance, and while during sport plasma potassium levels decline at a rate lower than sodium it is recommended that endurance athletes hydrate with a drink that includes both (American Dietetic Association, 2009).

Dehydration and the Athlete

Dehydration is classified as water deficit in excess of 2% to 3% body mass (Benardot, 2012). Low levels of hydration lead to low blood volume. With low blood volume, your body compromises circulation and has poor nutrient exchange, hormone balance and waste removal. When your body’s hydration level drops below 2%, exercise performance is decreased (Sawka, 2007). Therefore, adequate fluid intake both before and during sport is essential for optimal performance and health.
When dehydrated, sodium levels in the blood decrease, resulting in hyponatremia (low sodium). The first signs of hyponatremia include fatigue, headache, weakness and nausea. Additional manifestations include cramping, disorientation and confusion, swelling of extremities, and in extreme cases, swelling of the brain. Cramping can be common in athletes and is a good key indicator that the body has depleted its electrolytes (American Dietetic Association, 2009).

Fluid Replacement for Maintaining Fluid Balance

The goal of hydration before and during sport is to prevent excessive dehydration and changes in electrolyte balance, to ensure that athletic performance is not compromised.

Before an Event

To ensure your athletes go into an event hydrated, they should drink plenty of fluids the day before and morning of an event. It is recommended that 400 to 700 ml (≈2  to 3 cups) of electrolyte or carbohydrate –containing fluid should be ingested 60 to 90 minutes prior to sport. In an event lasting longer than one hour an additional 300 to 600 ml (≈1 to2cups) may be beneficial to the athlete (International Olympic Committee, 2010).

During an event

During exercise, appropriate fluid balance helps sustain athletic performance and replenish losses. The consumption of beverages including electrolytes and carbohydrates can provide benefits beyond pure water alone by helping to sustain electrolyte balance and endurance performance by replenishing glycogen stores.
Planning a hydration schedule helps people remember to continue to drink. A tip for athletes is to hydrate before dehydration levels occur, with recommended drinking rate of two to four ounces every fifteen minutes. Endurance athletes participating a training session or event lasting one hour or more are advised to use a combination of electrolytes and carbohydrates. Beverages containing 4 to 8% (4 to 8g / 100mL or approximately 16 grams per cup of fluid) of carbohydrate are advised in order to provide rapid delivery of fluid and fuel and minimize gastric intolerance (International Olympic Committee, 2010).
The type of carbohydrate recommended is a rapidly digested form of sugar, primarily glucose and fructose, avoiding maltodextrin, which can cause gastric distress to the athlete. The use of a commercial sports drink with electrolytes as well as sucrose or syrups containing no more than 50% glucose or fructose is recommended (American Dietetic Association, 2009).

Replenishing Losses Post-event

After sport it is recommended to measure losses and replenish appropriately. This is an essential part of the recovery process and both water and electrolytes should be replenished. Losses will vary from person to person and a simple at-home assessment of fluid loss can be done to determine exact levels of rehydration that should be met.
A sweat test is an easy way to assess how much fluid should be replaced, and can be done by athletes at their gym or home. To perform a sweat test:
  1. Measure body weight before and after a workout.
  2. Sweat loss (ounces) is equal to body weight (pounds) before exercise minus body weight after exercise. 16 ounces (2 cups) of water should be consumed for every pound that has been lost.
  3. Additionally electrolytes should be replenished. The athlete should consume a minimum of 500mg of sodium per liter of sweat lost.
  4. To convert to a sweat rate per hour, the athlete can divide sweat loss by the exercise time in minutes and multiply by 60 (International Olympic Committee, 2010). 
Hydration is fundamental to athletic performance and the correct electrolyte balance is needed for maximizing results. However, it is important to remember that because the rate of fluid loss is influence so many variables, rehydration is not one-size-fits-all formula, and therefore careful analysis of the individual’s losses is an integral first step in creating a hydration plan. As personal trainers, reminding your client of the importance of hydration will also help build best-practice hydration habits.


Benardot, D. (2012). Advanced Sports Nutrition. Human Kinetics. 2nd ed.
Rolfes, S., Pinna, K., Whitney, E. (2009). Understanding Normal and Clinical Nutrition. Cengage Learning. 8th ed.
Sawka, M. H. (2007). Exercise and Fluid Replacement Position Stand. American College of Sports Medicine. 39 (2). 377-390. Accessed on 3/10/14 from:
American Dietetic Association, Dietitians of Canada and American College of Sports Medicine (2009). Joint Position Statement: Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise.41(3):709-31Accessed 5/20/13 from
International Olympic Committee (2010). Nutrition for Athletes. Accessed on 3/12/14 from

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