Calculating Sweat Rate

  • SwimNP

    Posts: 50

    May 16, 2009 4:40 PM GMT
    Has anyone else ever done this? I did it yesterday and was very surprised by how much I sweat in an hour.

    What I did was weigh myself before an hour intense stairclimb workout with just a dry towel, worked out, dried completely off, then weighed myself again with a new dry towel.

    During the workout, I drank 1.5 Liters of water. This was used in my calculation as well.

    ***Given: 1Liter=1kg=2.2Lbs*****

    Here were my results:

    Beginning Weight: 187.4Lbs (85.2kg)
    Ending Weight: 184Lbs (83.6kg)
    Weight Loss during workout: 3.4Lbs (1.5kg)

    Additional weight consumed in water: 3.3Lbs (1.5kg)
    Total weight loss (Weight loss during workout + water drank): 3.4Lbs+3.3Lbs= 6.7Lbs (3.0kg)

    Sweat rate (Total Weight loss * 1Liter/1kg/time worked out): 3.0kg * 1Liter/1kg/hour = 3.0Liters/Hour.

    So I sweat roughly 3 Liters per hour O____________o . Unfortunately I couldn't add in the weight loss by just working out (Carbs/Fat/Protein) because I didn't know what ratio to use. I did ask the trainers and they honestly couldn't tell me that either. I did burn 975 calories though!

    What this means is I need to actually consume an additional 1.5 Liters perferably 1-2 hours before working out (your body can only absorb around 1 Liter of water an hour), and start replacing some minerals (mainly sodium) during the workout.

    Here's a nice link with mineral loss per liter of sweat. The next link you can put in your weight and it will tell you at what lvl of water loss will you fall under what condition. Stay hydrated guys! icon_wink.gif

    [url]http://www.arniebakercycling.com/pubs/Free/NS%20Sweat.pdf[/url]

    http://www.watertribe.com/Magazine/Y2002/M12/SteveIsaacHydrateOrDie.aspx

  • Posted by a hidden member.
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    May 16, 2009 9:30 PM GMT
    Don't forget that 5-10% of the attributable change in mass in loss of water is from breathing as well. *pant*pant*pant*

  • SwimNP

    Posts: 50

    May 17, 2009 1:05 AM GMT
    Oooh yeah, added the breath sweat in there too lol. I got interested in this based of a class lecture. If I remember correctly we were told you breath out 400 milliliters or so of perspiration per day (the average person) .
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    May 17, 2009 1:52 AM GMT
    Oh yeah, I don't know how much in weight, but you're going to lose carbon mass in the form of CO2 from beta-oxidation of lipids while exercising... I want to say that I'm remembering 2-5% of weight loss will be in CO2, but I honestly don't recall well.
  • Posted by a hidden member.
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    May 17, 2009 1:59 AM GMT
    dat stuff is not accurate bro...never weigh after sweating, u will be all da way officon_eek.gif
  • SwimNP

    Posts: 50

    May 20, 2009 1:41 AM GMT
    I know it can't be completely accurate, there's alot of other things to take into consideration. The measurements were done with towels though. Hehe if I weighed myself the cloths that I worked out in, I probably would have weighed like 190+ pounds.

    Oooh on a side note, what's with all the sweat topics lately lol
  • Posted by a hidden member.
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    May 20, 2009 12:15 PM GMT
    Why measure sweat? Really? I don't understand.
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    May 20, 2009 12:49 PM GMT
    The reason to measure your sweat rate is for endurance sports, such as cycling, where you need to hydrate while performing.

    My nutritionist recommends not drinking any liquids while conducting the test. In my case, I lost 4 lbs.
  • SwimNP

    Posts: 50

    May 20, 2009 2:22 PM GMT
    Thanks Frank, you're right =). It's not only a fun thing to do but it does have a purpose. You lose so much more in sweat than just water. There are electrolytes that are lost too. The big one being sodium and a few other minerals would be calcium, iron, magnesium, potassium, etc. Not many people would worry about this if they are doing an hour of cardio or less. Electrolytes are lost, but really you're not great danger of throwing your body out of whack for short time spans.

    Endurance athletes that don't have an understanding of sweat and electrolyte replacements can run into some serious problems. There was a post before somewhere on this site on hyponatremia (low blood sodium levels). Up to 1,400 milligrams or more of sodium is lost per liter of sweat. If all these athletes just drank water to hydrate during a race, they would just further dilute their body of sodium. This could result in some severe symptoms like coma, seizures, muscle weakness and cramps, and possibly death. These aren't fairytale symptoms, they have actually happened to people (from endurance athletes to a lady that did nothing drink and drink but never pee'd in hopes of winning a radio contest).

    Some sources to back things up (I used my med/surg book too):

    http://www.realjock.com/article/75/

    http://www.nlm.nih.gov/medlineplus/ency/article/000394.htm