How much is enough for thirsty cyclists?
by Nancy Clark (Courtesy of Adventure Cycling Association)
If you are a serious cyclist who works up a good sweat, or a touring cyclist who will be enduring
extended days of hot weather, you might have wondered how much you should drink before, during,
and after a hard ride. According to the latest recommendations from the American College of Sports Medicine (ACSM), only you can determine that answer because fluid needs vary greatly from person to person. Here’s what ACSM has to say about fluids for thirsty cyclists:
• Sweat rates commonly range between 1 to 4 pounds (0.5 to 2 quarts) per hour, depending on your sport and environmental conditions. For example, sweat rates for a 110-pound fitness exerciser might be one pound (16 ounces) of sweat per hour, while a 200- pound intense athlete might lose about four pounds (a half gallon) per hour. Football players might lose more than 16 pounds (2 gallons) of sweat in a day. Even fast swimmers sweat — almost a pound per hour of training.
• Few cyclists actually make the effort to learn their sweat rates; they simply drink according to thirst throughout their ride. This can be okay if you are exercising gently for less than an hour. But if you’ll be sweating bullets during an extended hard ride, you really should know your sweat rate. Otherwise, you are likely to become chronically dehydrated, underhydrate repeatedly, ride slower, feel needlessly fatigued, and have less fun.
To learn your sweat rate, weigh yourself nude before and after a 1-hour ride at your standard pace in hot weather. If you lose 1 pound, that equates to 16 ounces of sweat loss. Two pounds is 32 ounces — or a quart. Plan to replace these losses with programmed drinking, such as 8 ounces every 15 minutes, or one 24-ounce water bottle every 45 minutes.
• The best way to determine adequate hydration while “on the road” is to monitor your urine. You should need to urinate every 2 to 4 hours, and the urine should be pale in color and of significant volume. If you can last from 8:00 a.m. until 4:00 p.m. without having to urinate, you are dehydrated. Start drinking!
• There’s no need to try to superhydrate before a ride; your body can absorb just so much fluid. If you overdrink, you then may have to inconveniently urinate during the ride; the kidneys can only make about 1 quart of urine per hour. A wise tactic is to tank up 2 or more hours before your ride; this allows time for your kidneys to process and eliminate the excess. Then drink again 5 to 15 minutes before heading off.
• Some cyclists can tolerate exercise while they are dehydrated better than others. But most cyclists who lose more than 2 percent of their body weight in sweat lose both their mental edge and their physical ability to ride well, especially if the weather is hot. Yet, during cold weather, you are less likely to experience reduced performance even at 3 percent dehydration (4.5 pounds of sweat loss for a 150 pound cyclist). Dehydration (3 to 5 percent) does not seem to affect either muscle strength or anaerobic performance. Yet, a sweat loss of 9 to 12 percent body weight can lead to death!
• If you become more than 7 percent dehydrated (either by sweat loss, diarrhea, or vomiting), you will likely end up with a doctor introducing intravenous fluid replacement. In most cases, there is no advantage to taking fluids by IV, unless it’s for medical necessity. But please stay out of the emergency room or medical tent by knowing your sweat rate and drinking accordingly!
• If you become significantly dehydrated and have to bike again within 12 hours, such as during a hard tour in the summer heat, you need to aggressively rehydrate. This means drinking 50 percent more fluid than your sweat loss (to account for the water you lose via urine). Sipping fluids for several hours after you exercise maximizes fluid retention and is preferable to gulping one big drink.
• Sweat contains more than just water; it has electrically charged particles that help keep water in the right balance inside and outside of cells. Most cyclists can replace electrolytes via the foods they typically eat throughout the day. The key is to choose a few salty foods (such as a ham and cheese sandwich with mustard or some pickles or pretzels). Bananas or orange juice for potassium is also a fine choice.
• Dehydration is more common than overhydration, but overhydration to the point of hyponatremia (low blood sodium) is very dangerous and can escalate into seizures, coma, and death. Don’t drink more than you sweat; learn your sweat rate. If your stomach is sloshing, stop drinking! Pay attention to your riding buddy. If he or she is drinking lots of plain water and starts complaining about headache, vomiting, swollen hands and feet, undue fatigue, confusion (which is caused by progressive swelling of water in the brain), and wheezing (caused by water in the lungs), stop riding and insist that your buddy eat some salty foods.
• In general, hyponatremia that occurs in events that last for less than 4 hours is from overdrinking water before, during, and even after the event. Hyponatremia that occurs in ultra-endurance events that last for more than 4 hours is often related to extreme sodium losses. So, with extended rides, be sure to replace sodium losses with more than just sports drinks, which generally contain too little sodium to balance sweat loss. Choose endurance sports drinks and salty snacks such as pretzels, V-8 juice, soup, olives, and salt sprinkled on foods.
• When you are pedaling hard for more than 1 hour (or doing less intense, longer riding), adding 120 to 240 calories of carbohydrates (30 to 60 grams) per hour to your diet can help you perform better. These carbs help maintain normal blood glucose levels so you are able to enjoy sustained energy. Sports drinks are an easy way to get carbs plus water, but orange juice, bananas plus water, or granola bar plus water will also do the job.
• You are likely to maintain better hydration if you have easy access to good-tasting beverages before, during, and after the ride. “Good-tasting” generally means:
– a cool temperature (most athletes prefer between 60 to 70° F).
– a little sodium.
– an appealing flavor (varies greatly between cyclists and cultures).
If you are touring in a part of the country that has yucky-tasting tap water, you might want to add flavoring to plain water, such as a wedge of lemon, some Crystal Light, or Kool Aid.
• Muscle cramps are believed to be associated with dehydration, electrolyte deficits, and muscle fatigue. If you sweat profusely, become caked with salt, and experience cramps, take extra care to drink plenty of sodium-containing fluids while exercising. Because of the high salt content of the average American diet, you can probably replace sodium losses during meals without sodium supplements. But consuming extra salt on your food if you have had high sweat losses can be a smart way to enhance recovery, retain fluid, stimulate thirst, and just plain feel better.
• If you like to enhance your performance with a caffeine boost before or during the ride, rest assured caffeine in moderation, such as a 12-ounce mug of coffee, is unlikely to increase your 24-hour urine output or cause you to become dehydrated. Enjoy it if you like it!
• Alcohol, on the other hand, does have a diuretic effect, particularly in large amounts. After exercise, consume alcohol only in moderation — if at all — with lots of extra water (plus some carbs to buffer the alcohol and refuel the muscles).
The Bottom Line
For long-distance cyclists, the saying “drink responsibly” holds true for all fluids (whether they contain alcohol or not). Don’t let dehydration — or overhydration — affect your enjoyment of the ride and finish your day feeling great.
Reference: American College of Sports Medicine Position Stand: Exercise and Fluid Replacement. Medicine and Science in Sports and Exercise, 39 (2):377-390, February 2007.
Former TransAmerica tour leader Nancy Clark, M.S., R.D., C.S.S.D. (Board-certified specialist
in sports dietetics) counsels casual and competitive athletes in her private practice at Healthworks,
the premier fitness center in Chestnut Hill, Massachusetts (617-383-6100). Her Sports Nutrition Guidebook ($24) and Cyclist’s Food Guide ($20) are available by sending a check to
P.O. Box 650124, West Newton, Massachusetts 02465 or via www.nancyclarkrd.com.
© 2010 - 2012 Bob Beach
