My post from last week on water intake prompted this inquiry from a regular reader in the Philippines.
Thanks for the information on fluids. I run 5–10 K without water until I get back home. I guess my greater concern is under-hydrating. I bike too but usually carry a 3-li-bladder which I refill after 30K. Some of my buddies limit their fluid intake taking in as little water as possible. I always say this could be harmful to them but old-tales of low fluid intake from old-timer bikers always out-reason me. What say?
This is a very good question and observation. It indeed is a old-timers’ myth. I’ve run into the same. It may be borne from the thought that drinking fluids while working out gives you cramps. Like the myth that cold water is bad for you science has proven it all wrong. (Cold water is absorbed in the body faster than warmer water.) The keys of course are moderation in quantity so as not to cause complications and to stay hydrated both before and after workouts because it is rare that an athlete can take in all they lose in the workout.
Hydration is highly individual. So doing the weighing exercise before and after a workout is one good technique to help to determine if you need to take in more fluids on a ride/run.
Under-hydrating is by far more common than over-hydrating. Use that weighing-in test to see if you need more fluids or not. As little as 2-3% body weight loss begins to affect performance. For a 70K (154#) guy that is only 2K (4-5 pounds or so).
On a bike you can easily hydrate without the bloating or cramping possibilities that you will be more prone to in running. It is also so easy to carry more than enough fluids on a bike instead of on your person. Therefore, there is no excuse at all for not taking in adequate fluids.
“Heat” effects can begin in temps as low as 70F degrees (27C or so)! It has been shown that environmental temperatures above 65F (23C) WILL slow athletes down. And the effect is more dramatic in a non-acclimated athlete, a poorly conditioned athlete, youth and elderly. But make no mistake about it, even those who “love” the heat and “run great” in the heat slow down… most likely just not as much as others.
[By the way, if you set a PR in some race in temps above these thresholds you can guarantee that on the same course with temps 20F degrees lower you would have run even faster.]
Also individual adaptation is critical and knowing what you can handle as an athlete. I run 45 minutes or so without even a thought of stopping for fluids; even here in the desert with temps hitting well over 40C or 100F! It is NOT that I am advocating it. I’m just saying I know I easily handle it. And I’m smart enough to take fluids before and after to accommodate the effort.
In modest temps (25C/77F and less, or so) I can routinely go an hour and fifteen minutes to an hour and a half without thoughts of fluids.
[I’ve lived in the desert for 32 years and have learned about myself and heat both when I’m in shape as well as out of shape.]
Heat can build up in your body rapidly in an unprepared athlete. In as little as 10 minutes it could put you out of commission! This by the way is separate from dehydration (our main topic here). You don’t become dehydrated in 10 minutes (unless you were dehydrated already going into the effort from not drinking fluids all day). Even a well hydrated body that is not acclimated to heat will succumb to the heat MUCH faster than an acclimated person. So, very short distances can yield heat related injuries.
Certainly the longer the run or ride the more the need is for fluids… hot or not.
Bottom-line however is that to avoid fluids while working out is fool-hearty at best and stupid and dangerous at least.