Hydration in 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, health conditions, metabolic rate, and type of sport) that can impact the hydration of athletes and negatively affect performance, we discuss strategies and recommendations for maintaining optimal fluid balance.
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. 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.
Dehydration and the Body
Your body needs adequate water for all activities and cannot adapt to dehydration. Internally, you’re about 65% water. Without water, you can only survive a few days. Dehydration makes your blood thicker, increasing your heart rate and decreasing the amount of blood your heart can pump with one beat and causing your blood pressure to fall. Dehydration makes it harder for fat to get into your muscles to be used for fuel, so your muscles burn the limited sugars (glycogen) already there. Since your brain is about 85% water, even mild dehydration can bring on changes in your mood and a decline in your concentration and alertness.
From a sports perspective, losing as little as 2% of your body weight in fluids – for example, 1.4kilograms (representing about 1.3 litres of water) in a 65kg marathoner – can cause measurable decreases in performance. Dehydration of more than 3% of your body weight is serious, increasing the possibility of heat exhaustion and heat stroke in warm and/or humid conditions. Since athletes can sweat out 6% to 10% of their body weight during competition, you can see the importance of rehydrating.
And thirst is not a reliable indicator of dehydration. If you wait to drink until you are thirsty and stop drinking when your thirst is satisfied, you’ll remain 25% to 50% dehydrated.
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).
- After an 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:
- Measure body weight before and after a workout.
- 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.
- Additionally electrolytes should be replenished. The athlete should consume a minimum of 500mg of sodium per liter of sweat lost.
- 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.
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Special thanks to http://www.ptonthenet.com/articles/Hydration-Fundamentals-for-Optimal-Sport-Performance-3875 and https://www.livestrong.com/article/531789-dehydration-in-sports-performance/ for the great