Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: BOB ZIETARSKI on 19/10/2008 13:21:20

Title: Why does swimming make me dehydrated?
Post by: BOB ZIETARSKI on 19/10/2008 13:21:20

BOB ZIETARSKI  asked the Naked Scientists:

Good evening, here i am in Altea, on the beach, people watching (mostly semi-naked!) when i can't understand why i'm de-hydrated after a couple of swims a day. Is this to do with the attractive girls or is the magnetic pull of a larger mass of water on a smaller (me) mass ??

a good programme. (http://www.thenakedscientists.com/HTML/podcasts/)
 
regards,

bob zed
camping cap blanche (non prime loan caravan owner)

What do you think?

Title: Why does swimming make me dehydrated?
Post by: RD on 19/10/2008 14:32:39

Quote

Yes, swimmers sweat. Biochemists estimate that active adult swimmers sweat about 1 to 1 1/2 quarts per hour.
Medical texts support this estimate. Further evidence of this rate of sweating comes from the fact that competitive swimmers,
especially distance racers, report losing 2 to 3 pounds in an average meet. Much of this weight loss is sweat.

http://www.stranco-leisure.co.uk/pdf/Chlorination_a_Matter_of_Demand_and_Dosage.pdf

Title: Why does swimming make me dehydrated?
Post by: Don_1 on 20/10/2008 17:05:40

Sweating will dehydrate you and when swimming in. After a good hard swim, get out of the water and try to dry yourself, you will notice the sweating then. As for the sea, any small amount of sea water in your mouth will have a drying effect due to the high saline concentration.

Title: Why does swimming make me dehydrated?
Post by: Make it Lady on 20/10/2008 21:34:16

Swimming always makes me wee buckets after I have finished. Does anyone think that this has something to do with it?

Title: Why does swimming make me dehydrated?
Post by: Bored chemist on 21/10/2008 19:29:31

Quote from: Make it  Lady on 20/10/2008 21:34:16

Swimming always makes me wee buckets after I have finished. Does anyone think that this has something to do with it?

Glad to hear that bit.
When the body is cold ( and it often was when I was swiming) the blood vessels near the skin contract to keep the warm blood away from the skin. This saves losing heat to the water. However it also raises the blood pressure in the body. The body senses this and does something about it- it causes the excretion of some water to drop the blood volume.