Recent Studies
Most commercial sports drinks
contain too little sodium (salt).
Higher concentrations of sodium
(40+ milliequivalents per liter; or
1,000 milligrams per quart, liter) are mo
re effective for rehydration.
A solution containing sodium 75
milliequivalents per liter (1,875
milligrams per liter or quart) enhan
ces fluid retention more than a
solution containing 20 milliequiva
lents per liter (500 milligrams per
liter or quart). Bottom Line
The mouth and the gut are different. Although the gut absorbs
sodium-rich fluids better, many athletes cannot get them past the mouth because the mix tastes revolting. Salty snacks may be a better way to replace your sodium.
How Much Water Can You Lose?
Sweat rates have been reported higher than 3.5 quarts (liters) per
hour with heavy exertion in the heat.
More typically, athletes sweat about 16 ounces (½ quart, 500
milliliters, 1 standard water bottle
) per hour when exercising
moderately in cool or temperate conditions.
Athletes sweat about 32 ounces (1 quart, 1 liter, 2 standard
waterbottles) per hour when exercisi
ng moderately in hot conditions.
I sometimes ride from Del Mar to San Clemente, California, and
back—about 85 miles. On the way, I drink from my two large water bottles. In San Clemente, I buy two or three bottles of fluid. I drink one there and use the rest to refill
my water bottles. On the average, I
leave at 147 pounds and come back at about 142 pounds. If I am 5 pounds lighter at the end of the ride, it means I am still down more than 2 quarts of fluid.
Once I rode a 40-K time trial in 90°+ heat and high humidity. I
drank 2 gallons within an hour of
the end of the ride—and I still was
not tanked up.
Once I went on a desert trip with my wife and rode a century.
Both of us needed to replace almost one-third of our weight in fluids that day. I drank 45 pounds—almos
t 5 gallons. That is 20 quarts.
That is eighty 8-ounce glasses of fluid!
It is easy for the body to use a lot of fluid quickly.
How Much Should You Drink?
It is generally recommended that
athletes consume enough fluids
to replace sweat and urine losses during training and events.
Few athletes do. Since not all that is drunk is retained (about 60% is eliminated by
the kidneys as urine), some advocate rehydrating with 150% of lost fluids. Studies show that 50% to 100% more fluid is required, depending upon simultaneous
sodium ingestion.
Single-Day Training/Events
Aim to drink 16 ounces (500 millilite
rs, 1 standard waterbottle)
per hour while exercising moderately or in temperate conditions.
Aim to drink up to 32 ounces (1 quart, 1 liter, 2 standard
waterbottles) per hour when exercising at high intensity or in the heat.
Most athletes cannot drink more than 32 ounces per hour and so
get dehydrated during training or events in the heat. For many events, modest dehydration is not a problem. Ultraendurance and Multiple-Day Training/Events
For ultraendurance events that last more than a single day, or
athletes repeatedly competing ov
er several days, athletes cannot
afford to get behind. They must keep up with fluid losses.
Athletes can learn to tolerate up to 48 ounces per hour. Replace fluids lost, up to 48 ounces (1.5 quarts, 1.5 liters, 3
standard waterbottles) per hour when exercising in the heat.
Nutrition for Sports, Essentials of 30
