"If you're thirsty, you're already…

“If you’re thirsty, you’re already dehydrated” is a popular sports adage. It’s often recommended to drink water before, during and after a workout. The origin of the adage is unknown, but it became popular in the 1980s and 1990s. “If you are exercising for longer than an hour and reach a point where you feel thirsty, you already are dehydrated,” a fitness expert was quoted in a 1984 newspaper.

However, some people in sports medicine believe that the adage is somewhat of a myth. If a person is thirsty, a glass of water will help and it’s not too late to rehydrate.

10 July 1984, Daily Herald (Arlington Heights, IL), “Exercise in summer requires caution,” sec. 3, pg. 1, col. 2:
Drink plenty of water to prevent dehydration, which, if unchecked, can lead to heat exhaustion. Fitness experts recommend a minimum of one glass of water before, during and after exercise. “If you are exercising for longer than an hour and reach a point where you feel thirsty, you already are dehydrated,” said fitness expert Holly Jamison of the Mount Prospect Park District.

9 July 1987, Walla Walla (WA) Union-Bulletin, “Physical activity and health maintenance,” Supplement, pg. 3, col. 1:
Do not wait until you are thirsty! By this time you are already significantly dehydrated, and it will be very difficult to rehydrate yourself.

28 May 1989, Daily Herald (Arlington Heights, IL), “Sports Medicine” by Dr. Stephen A. Baker, sec. 5, pg. 1, col. 2:
Remember that when you become aware of a sensation of thirst, you are already 50 percent dehydrated!

Google Books
Play Healthy, Stay Healthy
By Gary N. Guten
Champaign, IL: Leisure Press
1991
Pg. 38:
9, Fluids
Proper hydration (drinking enough water) is one of the few areas in sports medicine where listening to your body does not work. If you wait until you are thirsty, it is probably too late. You are already dehydrated.

12 June 1991, Frederick (MD) News-Post, “Breakfast (and lunch and dinner) of champions” by Harper’s Bazaar (for The Associated Press), pg. D-1, col. 5:
Dr. Peter J. Bruno, internist for the New York Knicks and the New York Rangers, said:

“We recommend two glasses of water before you start working out, half a glass every 15 minutes during a workout, and a couple of glasses afterward. Don’t wait until you get dehydrated. If you feel thirsty, you’re already dehydrated.”

Google Groups: rec.martial-arts
Heat
Mary Malmros
7/15/92
(...)
A break at 30 minutes is a good idea, both to rest and drink water. Note that if someone really feels thirsty at the 30 minute mark, it’s not a good sign…I remember reading that, by the time you feel thirsty, you’re already dehydrated somewhat. So I do drink a good bit of water during the break, but it’s in the interest of staying hydrated…I don’t feel parched, and I shouldn’t.

Google Groups: rec.scuba
Nausea while diving
Brian Gilbert
8/2/93
(...)
I experimented the next day by drinking about the same amount of fluids as I had the day before, then diving. Sure enough I got ‘sick’. Upon exiting the water I drank some water and felt better after a couple of minutes. I never felt thirsty before going into the water, but as they say, by the time you feel thirsty you’re already dehydrated.

Google Books
The Contenders
By Richard Dale and Colin Cameron
London: Boxtree
1994
Pg. 72:
Does your body now when it is lacking in water?
No. One of the big problems is that you don’t become thirsty until after you’re already dehydrated, and, from a performance point of view, that’s too late. Your performance is already down before you’re thirsty.

Google Books
Living Lean
By Larry North
New York, NY: Fireside
1997
Pg. 85:
Additionally, when you feel a need to drink water because you’re thirsty, it is already too late: You’re already dehydrated.

Google Books
Coping with Diabetes:
Sound, Compassionate Advice to Alleviate the Challenges of Type I and Type II Diabetes
By Robert H. Phillips
New York, NY: Avery
2000
Pg. 107:
And don’t wait until you’re thirsty to take a drink — thirst is often a sign that you’re already dehydrated

The Huffington Post
Dehydration Myths: 7 Things You Should Know About Staying Hydrated
By Sarah Klein
Posted: 06/27/2013 8:41 am EDT Updated: 01/23/2014 6:58 pm EST
)...)
Myth: If you’re thirsty, you’re already dehydrated.

Fact: It’s not too late. In fact, thirst is the body’s way of telling you to drink water, and you’re not at risk of becoming dangerously dehydrated the minute you feel a little parched. “When you get thirsty, the deficit of water in your body is trivial—it’s a very sensitive gauge,” Dr. Stanley Goldfarb, professor of medicine at the University of Pennsylvania, told HuffPost in January. “It might be only a 1 percent reduction in your overall water. And it just requires drinking some fluid.”

In fact, drinking when you’re thirsty (sounds pretty basic, right?) is a pretty fail-proof method of staying hydrated, says Dr. Timothy Noakes, professor of exercise and sports science at the University of Cape Town in South Africa and author of Waterlogged. “You don’t tell your dog or your cat when to drink, they’ve got a thirst mechanism,” he tells HuffPost. “Why should it be that humans should be the unique animal in the world who have to be told when to drink?”

GoodtoKnow
Could dehydration be as dangerous as being DRUNK?!
Vicky Woollaston
16th February 2015
(...)
If you’re feeling thirsty you’re already dehydrated so don’t wait until you need a drink, sip small amounts throughout the day to keep yourself hydrated.

Google Books
Effortless Healing:
9 Simple Ways to Sidestep Illness, Shed Excess Weight, and Help Your Body Fix Itself
By Dr. Joseph Mercola
New York, NY: Harmony Books
2015
Pg. ?:
A common myth is that if you’re thirsty, you’re already dehydrated. The reality is that it’s not too late, and in fact, thirst is your body’s way of telling you to drink water