Athletes need a healthy, balanced diet to perform at their best, but nothing is more important than staying well-hydrated.
Athletes who are searching for ways to gain a competitive edge often don’t pay enough attention to this simple fact: fluids are one of the best performance enhancers around. Even slight dehydration – the loss of about 1% of your body weight from sweating (that’s less than 2 pounds in a 150-pound person) – can impair athletic performance.
What is dehydration and how does it happen?
Simply put, dehydration is an imbalance in the body’s fluids, such that fluid intake doesn’t replace fluid losses. When your body’s fluid level is low, it cannot properly carry out its normal functions.
When you exercise, heat is produced by the activity – not just the activity of your working muscles, but all the metabolic activity that’s needed to keep your body’s engine running. As the body heats up, heat is transferred from the body core to the skin, where it can be dissipated.
Some heat can simply radiate from the skin, especially if it’s cool outside. But most heat is lost through evaporation – we begin to sweat and then the water evaporates off the skin surface, helping to keep us cool. Additional water losses happen naturally from the breath as well as the digestive system and urinary tract.
But the body only has so much fluid on reserve, and the rate at which we lose water can be affected by a number of factors – losses increase as exercise intensity increases, and when conditions are especially hot and humid.
What happens when you get dehydrated?
When you get dehydrated, the volume of fluid in your blood vessels drops, which can affect your circulatory system. With less blood flow to the skin, the evaporation process is impacted. The heart rate rises as the body works harder to keep you cool, which makes it physically more difficult to continue exercising and mentally difficult to keep your motivation. Furthermore, sweating causes you lose more than just water. You lose important body salts – notably sodium and chloride, but also magnesium, potassium and calcium.
With a loss of just 1-2% of your body weight from sweating, your performance will be impacted negatively. By the time you reach losses of 3%, you’re at an increased risk of heat cramps, heat exhaustion and heatstroke. The early warning signs of dehydration include dry mouth, thirst, headache and fatigue. As dehydration progresses, muscle spasms (heat cramping) can occur from sodium loss; further heat stress can bring on symptoms of heat exhaustion which include weakness, dizziness and nausea. Left unchecked, dehydration can lead to heatstroke, a potentially life-threatening breakdown of the body’s heat-regulating mechanisms.
How can athletes prevent dehydration?
Athletes lose between 1-2 liters of sweat per hour of continuous exercise. You can tell you’re getting dry because you’ll get thirsty; however, by that time, you’re probably already more than a little dehydrated. Urine color and volume can also provide an estimate of your hydration status (if you’re not putting out much, and the color is dark, you should probably step up your intake) but this doesn’t really help you know how much fluid your body needs to bring yourself back into balance.
This is why athletes are advised to drink on a schedule. It’s one of the best ways to ensure they are meeting their needs and replacing fluid losses. Athletes who don’t drink on a schedule tend to replace only about half of the water that they lose during exercise.
How to hydrate before, during and after a workout
Before exercise: Start out well-hydrated. Drink fluids freely for 24 hours prior, then have 2-3 cups of fluid 2-3 hours before the event. Then, about 30 minutes before starting out, have at least 5-10 ounces of additional water or up to 20 ounces if exercise will be especially strenuous or if it is unusually hot or humid.
During exercise: Sweat (and urine) losses may be as much as 1-2 liters per hour. Aim to replace them. You may not be able to replace all your losses, but most athletes can manage about 0.5-1 liter per hour, which is best done by drinking every 10-20 minutes. Sports drinks that also contain salts (sodium, chloride, potassium and magnesium) as well as some carbohydrates will help maintain blood sugar and keep body salts in balance.
After exercise: The goal is to replace losses, which is why athletes are often advised to weigh themselves before and after an event or workout to estimate how much they need. For every pound lost, 2-3 cups of fluid should be taken in. While plain water quenches thirst, beverages that also contain salts and carbohydrates can replenish the body’s carbohydrate stores and facilitate water absorption. Specially designed sports drinks are great for this, especially when coupled with a balanced post-workout snack or meal.
Here’s how athletes can stay hydrated: