# Do you sweat when you swim? **URL:** \ **Category:** Factual Questions\ **Created:** [June 26, 2003, 1:07am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411 "2003-06-26T01:07:43Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![OxyMoron](https://avatars.discourse-cdn.com/v4/letter/o/e9a140/32.png) [@OxyMoron](https://boards.straightdope.com/u/OxyMoron)\ **Post date:** [June 26, 2003, 1:07am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/1 "2003-06-26T01:07:43Z")
Not _you_, although that’s at least part of an answer. Does _one_ sweat when swimming, if the temperature is, say, below 80 degrees (F) or so? I don’t swim very well, certainly not well enough to make it real exercise, and I have no idea. It just occurred to me on this disgusting 90+ NYC day as I was watching people swim at the Y - _they’re getting a great workout and they’re probably not sweating at all_. That’s a reason to learn (again). ---
**Author:** ![TisDun](https://avatars.discourse-cdn.com/v4/letter/t/a87d85/32.png) [@TisDun](https://boards.straightdope.com/u/TisDun)\ **Post date:** [June 26, 2003, 2:15am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/2 "2003-06-26T02:15:12Z")
Yes, indeed, you can sweat while swimming. Swimming is supposed to be one of the two best full body workouts, the other being cross-country skiing. I do not know the biomechanics of sweating and how it is related to aerobic workouts but I do know from experience that you lose a lot of fluids after swimming for long durations, which I’ve always assumed is because of sweating. Think of it this way, do you sweat when you go running on a cold winter day? I’ve found that I do even when wearing a light warm up suit after only about 10 or 15 minutes. ---
**Author:** ![Geek\_Mecha](https://avatars.discourse-cdn.com/v4/letter/g/ecae2f/32.png) [@Geek\_Mecha](https://boards.straightdope.com/u/Geek_Mecha)\ **Post date:** [June 26, 2003, 3:41am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/3 "2003-06-26T03:41:19Z")
> [@](#): > > \*Originally posted by TisDun \* > \*\*Think of it this way, do you sweat when you go running on a cold winter day? I’ve found that I do even when wearing a light warm up suit after only about 10 or 15 minutes. \*\* Since you don’t have liquid against your skin, that doesn’t seem a good analogy to swimming. Correct me if I’m wrong, but shouldn’t the water make some difference? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [June 26, 2003, 3:59am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/4 "2003-06-26T03:59:50Z")
The water will make a huge differnce. The thermal conductance of water is orders of magnitude higher than in air. This is why it is possible to die of hypothermia in 20oC water, but feel perfectly comfortable in 20oC air. The water carries away heat much faster than air ever could. But to answer your question, I know that I lose alot of fluid while swimming. I assume this is due to sweating. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 26, 2003, 4:00am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/5 "2003-06-26T04:00:18Z")
> [@](#): > > \*Originally posted by TisDun \* > **…I do know from experience that you lose a lot of fluids after swimming for long durations, which I’ve always assumed is because of sweating.** Some of it could be from breathing though. There must be a fair amount of evaporation going on in your lungs. Anybody know how much? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [June 26, 2003, 4:11am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/6 "2003-06-26T04:11:04Z")
Not very much at all in the saturated atmosphere just above a body of water. You can only possibly lose as much as the exhaled volume will hold, and the inhaled volume will recover the same amount. Total loss can only possibly be the difference between saturation at 37oC and air temperature, usually 20oC+ if you are swimming. So it would be negligible. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 26, 2003, 5:25am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/7 "2003-06-26T05:25:57Z")
> [@](#): > > \*Originally posted by Blake \* > \*\*Not very much at all in the saturated atmosphere just above a body of water. You can only possibly lose as much as the exhaled volume will hold, and the inhaled volume will recover the same amount. \*\* You are neglecting the fact that exhaled air is at a higher temperature. Even if both are at 100% relative humidity, the higher temperature air has higher water content. According to [this interactive page](http://www.screensound.gov.au/glossary.nsf/Pages/Relative+Humidity+(RH)?OpenDocument), 100% RH air at body temperature contains 41 g/m[sup]2[/sup] of air, while air at 15[sup]o[/sup]C contains 12 g/m[sup]2[/sup]. At 30 litre/min of breathing you get 52 grams/hour, or about 1/4 of a cup per hour of water loss. Seems like non-negligible amount, but maybe small compared to what you lose through sweating. How would one measure perspiration during swimming? The only way I can think of is to swim in very pure water and measure the salinity of the water afterwards. I wonder if anyone has done measurements… ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [June 26, 2003, 5:59am UTC](https://boards.straightdope.com/t/do-you-sweat-when-you-swim/184411/8 "2003-06-26T05:59:12Z")
> [@](#): > > You are neglecting the fact that exhaled air is at a higher temperature. Umm, no. you are neglecting to read my posts. “Total loss can only possibly be the difference between saturation at 37oC and air temperature” How much clearer can I make it that exhaled air is at a higher temperature, and that this produces a difference? And the 1/4 of a cup per hour is clearly neglible. Normal air at 15oC (which seems to chilly for swimming to me) only contains 2.5g/m2 water. At even 15 l/min breathing you lose 34.65 grams an hour lying down sleeping. That is only 18 mL difference between swimming solid for an hour. A person sleeping for an hour will lose only 3 teaspoons of water more than a person swimming non-stop for an hour. Clearly a negligible aount. Then you fail to take into account that the nasal sinuses have an ability t reclaim moisture form the air being exhaled. I don’t have figures to hand, but I wouldn’t be surprised if the amount exceeds the three teaspoons. Great webpage there BTW.