Why does the water make me tired?

May 29, 2011 6:33 PM

Why do I get so tired after going in the water?

When I go to a pool or beach and hang out in the water for a while, I usually feel pretty drained afterwards. It's happened for as long as I remember. I don't know if it happens every single time, but it's often.

I don't usually swim or do anything particularly athletic in the water, and it feels different from post-workout fatigue. And I'm never tired in the water; it usually hits five to ten minutes after I'm out. I don't think it's related to being in the sun, since I don't get the same feeling just being outside on a sunny or hot day.

Is this normal? Is it preventable? What causes it?

posted by Metroid Baby to health & fitness (10 answers total)

Breathing takes more effort because of the pressure of the water on your body.
posted by phunniemee at 6:49 PM on May 29, 2011

I get water-related fatigue. My theory is that even if the water is pretty warm, say 80 degrees, your body still uses a lot of energy keeping warm. Enough, I believe, to make you tired.
posted by Specklet at 6:50 PM on May 29, 2011 [1 favorite]

I asked this a while ago!
posted by oflinkey at 6:55 PM on May 29, 2011

Not only are all of those things true, but the body also works to keep cell fluids and salts in balance.

If you're in salty water, your body will out out a bit of water to try to correct the perceived imbalance. If you're in fresh water, the water comes in, and your sodium/potassium etc levels are no longer balanced for your body.

hot damn. Two human biology questions in one week. It's been 12 years since I took that class.
posted by bilabial at 7:02 PM on May 29, 2011

Water is 1000 times denser than air. Literally every move you make requires much more muscle power than you expect. Moreover, it literally takes energy to hold still. Just treading water is more of a core workout than you expect.

Because water is dense, it also conducts heat better -- much, much better than air. Even in 80 degree water, your body is working hard just keeping itself warm -- even a small difference in temp is more significant when the heat is getting whipped away from your skin.

In other words, there's a reason people exhaust themselves, get hypothermia and drown. ;-)
posted by Cool Papa Bell at 7:47 PM on May 29, 2011 [5 favorites]

I get the same, and I get it worst when I am in the surf so I always thought it was to do with the extra work of moving my limbs through the water or fighting to stay on my feet.

If I swim laps or anything I find I get ravenously hungry which I've never worked out because I usually only swim a lap or too so it can't be that I've burnt so many calories.
posted by wwax at 7:50 PM on May 29, 2011

Cool Papa Bell has it. I taught swimming lessons for many years, and would always feel exhausted after a couple hours in the pool. Even something as simple as treading water uses most of your muscles, and you are constantly facing resistance. It's deceptive, but it is also the reason that swimming is great for exercise.
posted by Nightman at 7:54 PM on May 29, 2011

Just a thought - it might be the sun, not the water. Sun will wipe a person OUT, especially at this time of year where everyone is just now getting those loooooong days in the sun. I frankly am not affected by it, but that's why I'm sitting here typing on AskMe while all my friends are sleeeeeeeeeping.
posted by deep thought sunstar at 1:04 AM on May 30, 2011

Or, I could read the question. I still think sun has something to to with it, though...
posted by deep thought sunstar at 1:08 AM on May 30, 2011

I believe the answer is related mostly to the cooling effect of the water. Your body has to maintain a certain body temperature and even water doesn't feel too cold, can remove heat from your body at a high rate. There's a reason why michael phelps eats 12,000 calories a day while training while tour de france bikers eat 6000-9000 calories a day. These riders are probably pushing their metabolism to the very limit all day long, while phelps probably doesn't train at peak intensity all day long, yet he still burns many more calories and I bet he trains in heated pools.
posted by jefftang at 9:09 AM on May 31, 2011