Did you know that the human body is mostly made up of water? In fact, up to 60 percent of our body weight is water.
As you can imagine, dehydration decreases athletic performance. During exercise, water is lost through the lungs as water vapor and through skin as we sweat. Even a two percent loss of water has significant negative effects on athletic performance. A five percent loss of water drops work capacity by around 30 percent.
The loss of water from the body can mean a sprinter's performance is reduced by up to 50 percent, and maximum aerobic power is reduced by up to five percent.
When water loss during exercise is not replaced, blood volume decreases. Decreased blood volume results in a decrease in performance, an increase in body temperature and muscle cramping. Drinking water is the key to preventing dehydration, reducing the risk of heat injury and maintaining performance.
Exercising outside is a great way to enjoy a workout. However, you must pay attention to hydration. When it's warm outside our body perspires to cool down. Temperature, humidity and the intensity and duration of your activity can determine how efficient one loses water through sweating and breathing. Depending on the conditions, you may not even realize how much you are perspiring.
The environment affects the perception of sweating. Swimmers may not feel or see any sweat on their bodies. Athletes performing in a very dry climate visibly see much less sweat than those in a humid environment. So, don't rely on visible appearance or on thirst alone to tell you how much you need to drink. If you are thirsty, you are probably dehydrated. To keep our muscles working effectively and to avoid fatigue, you must drink plenty of water before, during and after an activity.
Drink water in advance of physical activity
A guideline when preparing for a workout is to pre-hydrate by drinking two cups of fluid two hours before the activity. Pre-hydration, much like filling up the gas tank before a long drive, helps to make sure you are well-hydrated before exercise.
During the activity, drink at least 4 ounces of water every 15 minutes to keep your body and muscles well-hydrated. Be sure to hydrate after the activity, too. A good option is to weigh yourself before and after exercise and drink at least 20 ounces of water or replacement fluid for every pound of weight loss.
Even though sweat on your skin tastes salty and may burn your eyes, the body is very efficient at holding on to salt. The actual sweat as it leaves your skin pores is mostly water. The salty taste of sweat on the skin is a result of evaporation of the water out of the sweat as part of the body’s cooling process.
Tap water is generally the best fluid for hydration before, during and after exercise. If the exercise activity lasts more than an hour, diluted fruit juice or a diluted sports drink will provide carbohydrates for energy, plus minerals to replace lost salt from your sweat.
Sports drinks vary in the amount of sugar and salt in the drink. Be sure to read the labels. Generally, an 8-ounce serving of many sports drinks contain more than the replacement needs of carbohydrates and sodium. Therefore, my general rule of thumb is to add an equal amount of water to the sports drink.
Chocolate milk is a newly touted recovery drink after exercise to replenish sugar, electrolytes and to provide some fat calories for the recovery process. Fitness waters are also good, but the vitamin replacement is not needed during exercise but may help recovery.
One of the main benefits of consuming sports drinks and designer waters are the good taste. If the taste equates to drinking during exercise, then hydrate with the sports drink.
So, drink water often, and add a little salt and sugar to the water if you exercise for longer than an hour. Alternatively, dilute your favorite sports drink with an equal amount of water.
Have fun and enjoy the outdoors or indoors while exercising. Drink water to perform your best!
For more articles from James Slauterbeck, M.D., visit the USA Jags Sports Medicine Blog.
