(This article has been reprinted from the USTA High Performance Coaching Newsletter, Vol. 2, No. 2/2000)
By Michael F. Bergeron, Ph.D., FACSM
No doubt, many of you reading this feel that you’ve heard enough regarding the importance of drinking plenty of fluids and the benefits of staying well hydrated. After all, your players seem to drink a lot of water during play and most tend to avoid severe problems such as cramping or having to retire due to overheating.
Yet, many well-trained and “informed” tennis players continue to have hydration-related problems. From being a little “off” and not quite playing your best to painful heat cramps or heat exhaustion, there is a wide spectrum of symptoms related to inadequate or inappropriate hydration management that are commonly observed at many tennis tournaments, especially when it’s hot.
The three primary nutritional factors, related to keeping your players hydrated, are Water, Electrolytes, and Carbohydrates.
These are also the nutrients that have the most immediate effect on performance – positive or negative, depending if their intakes are managed well or not.
• Many players begin play dehydrated.
• On-court sweat losses can be extensive – 1-2.5 liters (~35-88 ounces) per hour is typical.
• Any water deficit can have a negative effect on a player’s performance and well being. The effects of a progressive water deficit due to inadequate fluid intake and/or excessive sweat losses include
• Increased cardiovascular strain – your heart has to work harder.
• Decreased capacity for temperature regulation – you heat up more.
• Decreased strength, endurance, and mental capacity – your intensity is lower, you tend to lose control, and you make inappropriate shot selections.
• Increased rate of carbohydrate metabolism – you fatigue faster.
• Many players to not adequately rehydrate after play.
What you can do:
• Drink plenty of fluids (water, juice, milk, sport drinks) throughout the day.
• Don’t forget to drink regularly during all practice and warm-up sessions.
• Have another 12-16 ounces about 1 hour before you play.
• Drink at each changeover – typically, older adolescents and adults can comfortably drink up to 48 ounces or so per hour. This rate of fluid intake can prevent large fluid deficits from developing for most players.
• After play, drink about 150% of any fluid deficit that still remains. For example, if your weight is down 1 pound at the end of play, you still need to drink another 24 ounces.
• Players lose far more sodium and chloride (salt) from sweating than any other electrolyte.
• Sodium and chloride losses are greater with higher sweating rates.
• Sodium and chloride losses tend to be less with players who are used to (acclimatized to) the heat.
• Sodium deficits can lead to incomplete rehydration and muscle cramps.
• If you don’t replace the salt, you can’t completely rehydrate.
• Excessive water consumption, combined with a large sweat-induced sodium deficit, can lead to severe hyponatremia (low blood sodium) – a very dangerous situation. Even mild hyponatremia can give a player a sense of fatigue, apathy, nausea, or a headache.
What you can do:
• When you play in a hot environment (or any time you sweat a lot), add some salt to your diet (or eat certain high-salt foods) before and after you play. Good sodium and chloride sources include
• salt: ¼ teaspoon (or 1.5 grams) has 590 mg of sodium
• salted pretzels
• many types of soups
• salted sport drinks (or Pedialyte)
• tomato sauce (pizza!)
• tomato juice
• Adequate carbohydrate intake is crucial to optimal tennis performance.
• Consuming carbohydrates before and after exercise can help restore some of your body water reserves.
• Playing tennis in the heat causes the body to use carbohydrates faster. So, even if you eat well prior to playing, after 60 to 90 minutes of intense singles, chances are you’ll need some supplemental carbohydrate to continue playing your best.
• Ingesting too much carbohydrate or too much of an inappropriate carbohydrate (e.g., fructose) can delay carbohydrate and fluid absorption and may cause gastrointestinal distress.
What you can do:
• Generally, 7-10 grams of carbohydrate per kilogram of body weight (~500-700 grams per day for a 155-lb player) is recommended for periods of intense training or competition.
• During play, 30-60 grams per hour is most effective. Choose a sport drink whose primary carbohydrate is sucrose, glucose, or a glucose polymer (e.g., maltodextrin).
Adequate and well-timed water, electrolyte, and carbohydrate intake should be priorities for any player looking to play well and safely. Yet their importance is still often overlooked or underestimated.
Dr. Bergeron is a member of the USTA Sport Science Committee.
If you would like to submit a question that may be answered by our Health & Fitness team or want to share an idea for a future column, please click here.