THE ATHLETE'S KITCHEN

Fluid Tips for Active People

When it comes to preventing dehydration, you have undoubtedly heard the nagging advice "Be sure to drink enough fluids!" But how much does adequate hydration really matter, you may wonder, especially if you're working out for only an hour? The answer: a significant amount! In a study with cyclists who biked hard for 50 minutes and then sprinted as hard as they could for 10 minutes (similar to the end of many competitive basketball, soccer and cycling events), the cyclists performed 6% better (compared to when they drank nothing) in the final 10 minutes when they drank enough water to match their sweat rate, and 12% better when they consumed energy (carbohydrates) along with the water; that is, when they consumed a sports drink. Given many athletic events are won or lost by 1 point or 1 second, a 6 to 12% improvement can give you the winning edge.

Perhaps that information will inspire you to maintain better hydration during training and competition. The following tips can answer your questions and concerns about what, how much, and when should you drink.

The more calories you burn, the more fluids you need. The popular rule of thumb "drink 8 glasses of water per day" is appropriate for the person who expends about 2,000 calories per day. Exercisers need more fluids.

Copious urine -- a significant volume of every urine 2 to 4 hours -- signifies you have had enough to drink. The urine should be a pale yellow color, like lemonade -- unless you take vitamins supplements, in which case the urine will be bright yellow. Dark colored urine that is concentrated with metabolic wastes indicates dehydration. Drink more fluids routinely throughout the day.

If you sweat a lot, you should pay careful attention to your fluid intake. Do not rely upon thirst alone to tell you how much to drink; your thirst mechanism may poorly reflect your actual fluid needs. Athletes tend to voluntarily replace only half their water losses To determine your sweat rate and guide your fluid intake, weigh yourself before and after you exercise. Weight changes reflect sweat losses. Given that one pound of lost sweat equals two cups of fluid, you should plan to replace the losses accordingly. For example, if you drop two pounds of sweat during an hour of exercise, you should target drinking two pounds (32 ounces) of fluids per hour in future bouts. This comes to 8 ounces every 15 minutes.

Throughout the day, be sure to routinely consume plenty of fluids. If necessary, carry a water bottle with you -- especially if water is not readily available. At home, keep an inviting supply of water, juice or sports drinks in the refrigerator. If you enjoy the fluid, you'll drink more.

Plain water is one source of water. Juice, lemonade, soft drinks, sports drinks, juicy fruits, vegetables, soups, yogurt, milk and other watery foods are other sources. Coffee or tea count less because caffeine's diuretic effect may negate water intake if you are unaccustomed to caffeine.

Before exercise, tank up on 1 to 2 cups of water within fifteen minutes of working out. During exercise, drink about 6 to 8 ounces every 20 minutes. Water is a popular choice and is appropriate for casual exercise that lasts less than an hour. But for intense exercise, or for endurance exercise that lasts more than an hour, you should try to consume 120-240 carbohydrate-calories per hour along with the water. The energy from the carbohydrates enhances stamina and endurance.

Beverages that offer up to up to 80 calories per 8 ounces are absorbed more quickly than stronger solutions such as soft drinks or juices that offer about 100 calories/8 ounces. Some easily absorbed fluids include sports drinks, diluted juices, tea with honey, and diluted (defizzed) soft drinks.

Many athletes train with water (because it is readily available) but then choose a sports drink during competition. Unfortunately, some athletes discover the unfamiliar sports drink gives them an upset stomach. Be sure you have experimented during training with consuming several sports drink to learn which brands settle well.

Don't worry about replacing sweat losses of sodium, potassium and other electrolytes; you are unlikely to deplete your body's stores of these minerals except under extreme conditions such as >6 hours of an Ironman triathlon.

The main purpose of the sodium in sports drinks is to enhance water absorption and retention. If you are exercising under strenuous conditions that require rapid fluid replacement (such as a rugby game), your best bet is to choose a sports drink that contains some sodium.

After exercise, choose carbohydrate-rich fluids such as juices that replace both water losses and muscle glycogen--and enhance recovery. Note: most commercial fluid replacers contain fewer carbohydrates than do juices. Hence, they may less effectively replace depleted glycogen stores unless you consume large quantities of them.

Beer is a popular postexercise "recovery fluid" but the alcohol in beer has a dehydrating effect that causes you to lose valuable fluids at a time you should be replacing them. If you intend to drink beer: 1) quench your thirst with 2 or 3 large glasses of water, 2) have something to eat so that you aren't drinking on an empty stomach, and then 3) enjoy a beer or two in moderation.

Nancy Clark, MS, RD, nutritionist at SportsMedicine Brookline, designs personal food plans for active people. For a copy of her popular books Nancy Clark's Sports Nutrition Guidebook ($20) and The NYC Marathon Cookbook ($23), send a check to Sports Nutrition Materials, 830 Boylston, Brookline MA 02167.