Fluids and Sports

You’re scheduled for a tough match tomorrow and it might be a very hot day. What drink do you put in your tennis bag?

A fluorescent-colored sports drinks? Electrolyte beverage? A high-caffeine soft drink? Sugar water? Glucose polymer? Fruit juice? Or just plain water? What about a few glasses of beer after the match to rehydrate or, at least, relieve the many aches and pains?

High intensity exercise in hot weather can easily make you sweat away two to four pounds (one to two quarts) in an hour. Body temperature rises and performance declines. Fluid replacement is critical. If fluids are not consumed at regular intervals, the result may be heat stroke, organ damage, dehydration—and possibly death.

To avoid the health hazards and maintain peak performance during a tennis match, you should drink before, during, and after a grueling workout. Ideally, weigh yourself before and after a practice match to give yourself a good idea of how much water weight is lost, then consume at least two cups of water for each pound lost. The body is made up of about 60% water and needs to be fully hydrated to perform optimally. When the outside temperature or humidity is especially high, the body requires even more water because it must work harder to cool itself.

Studies show that at least half of all recreational tennis players do not drink enough water to perform well. Inadequate fluid replacement may be at the bottom of recurrent or chronic injuries as well as poor match play results. A sub-optimal water intake will affect your speed, endurance, and strength. It can also cause dizziness, nausea, and muscle cramps. Even a slight water deficit—about one quart—slows blood circulation and reduces concentration.

Never depend on your thirst to decide on when to drink fluids. Thirst is a poor indicator of dehydration because you may already be dehydrated before the body’s thirst mechanism kicks in. It’s best to start drinking well before you feel thirsty and keep drinking even after your thirst is quenched.

The best beverage is pure spring water. It’s the quickest fix for preventing or reversing dehydration and the beverage that is the easiest for the body to absorb. Sweetened sport drinks are more slowly absorbed and are only of value to elite athletes who push themselves well beyond the activity levels of the average tennis player.

Long matches over 90 minutes played day after day (as in tournaments) will require replacement of not only water but carbohydrates and the electrolytes sodium, magnesium, and potassium. Although the average North American diet will contain adequate amounts of these electrolytes, sport drinks or diluted fruit juices are acceptable beverages in addition to plain water between matches.

How do you know if you’re drinking enough? Spot-check your urine often to see how much fluid you really need. Urine should be as light or pale colored as possible and more frequent than when sedentary, to be on the safe side. The darker or more yellow the urine, the more water you need to replenish your fluid reserves.

Basic guidelines

The American College of Sports Medicine has made the following general guidelines for vigorous exercise as experienced during a very competitive tennis match:

• Drink plenty of water (1–2 cups) at least 15 minutes before a tennis match, even if you are not thirsty. Never restrict fluids during exercise.

• During the match, drink 8–12 ounces of water every 15 to 20 minutes regardless of thirst. Cold drinks are best because they are absorbed most rapidly.

• If your match, usually categorized by exercise physiologists as “vigorous exercise,” lasts under one and a half hours, the only fluid replacement beverage you are likely to need is water. Add a squeeze of lime or a splash of juice for variety.

• Beyond an hour and a half, you can benefit from one of the many sport drinks on the market. The drink should not exceed 8% carbohydrate by weight because more than that will slow absorption and may cause stomach cramps or nausea. To play it safe, dilute the sports drink by an equal amount of water.

• If you are an elite athlete and feel the need to replace both water and electrolytes, make your own sports drink by diluting any natural fruit juice beverage with an equal amount of water. Orange juice, grapefruit juice, and apple cider are excellent choices. Fruit juices, even freshly squeezed, are less expensive and equally effective as just about any commercial sports drink.

• Do not drink anything with caffeine (coffee, tea, chocolate, cola drinks) or alcohol, both of which are thought to have a dehydrating effect.

• Carbonated drinks of any kind should be avoided since these tend to make you feel full, making it difficult to drink enough.

• Drink 2 cups of water for every pound lost during the match. After exercise, choose carbohydrate-rich fluids such as juices that replace both water losses and muscle glycogen (stored carbohydrate) to enhance recovery.

Beer after tennis?

You may have seen the odd tennis player drinking beer after a match. Is this really a good way to replenish water and electrolytes lost during vigorous exercise?

Beer’s alcohol content has a dehydrating effect that causes you to lose even more valuable fluids at a time you should be replacing them. If you simply must drink beer, first quench your thirst with 2–3 large glasses of water. Ideally, have something to eat so that you aren't drinking on an empty stomach. Enjoying a beer or two in moderation in this fashion will at least help you wind down from the stress of a hard-fought match.

Dr. Zoltan Rona