Sweat Rate & Fluid Replenishment
Hoping for some feedback regarding the sweat tests that are described in the "Sweat Trial" and "Monitoring Hydration Status by Kitima" wiki links.
I did a trial this a.m. in the pain cave. So with steady temperature, humidity and weather conditions I rode for an hour at HIM/Z3. Lost 1.8 lbs and drank 17 oz.
"Sweat Trial" method applied (see the wiki for an explanation of the formula): 1.8 x 16 oz = 28.8 oz at the cool/low end; 1.8 x 24 oz = 43.2 oz at the warmer/high end. The wiki also instructs to add the fluids (although this does not seem to have been done in the example provided) to its 45.8 oz/60.2 oz.
Using the method prescribed in the "Monitoring Hydration Status" (see the wiki for an explanation of the formula): 17oz of fluid replaced = 1.0625 lbs (17 divide by 16); 1.8 + 1.0625 = 2.8625 lbs lost in an hour; 2.8625 lbs x 16 oz/lbs = 45.8 oz/hr (so dead on to the cool/low end as calculated using the Sweat Trial method).
I know that I don't take in enough fluids on my rides so I expected to see a number that was higher than I've been taking in. I also realize that sweat rate is highly personalized and will fluctuate by weather conditions and once the numbers are determined they may need to be tweaked, but it seems like a lot of fluids to take in per hour (45.8 oz!), especially under the conditions used in testing (under different conditions, I expect the numbers to change but I would guess that they would still seems really high). I'd love some feedback from those who have conducted the tests and then put the resulting information to use. I want to be a believer, but the numbers seem so big that I'm skeptical. Thanks!
Comments
My numbers were very similar to yours when I last tested, with a range from mid 40's to 53oz/hr. I too thought this sounded impossibly high. But, I used this this strategy at Austin 70.3 and it worked well. It was not a hot day, so it made it a little hard to drink that much, but I did it. I felt great on the run....a little bloated the first few miles, but nothing major.
I'm planning to retest a couple of months before IMTX, and then make sure I use these for all my RR and long rides/runs.
So, your numbers do not sound "out there", at least they're similar to mine. For what that's worth.
Thanks Jeff. Its helpful to know that others have had similar thoughts but also good results.
Gerry - Here's some of my historical data for both some of my bikes. NOTE - these were all outdoor. I track Relative Humidity as I find it is somewhat determinate as to my sweat rate.
Bottom line - I dont' think your numbers are at all out of the norm.
You can only drink these volumes if you're riding in Z2/3. If you're in Z4, you will have trouble keeping it down! Goal is to come off the bike not dehydrated (tanked up), cuz it's also much harder to drink much volume while running. I find that in Z2 (and low Z3), it's not really all that hard to drink 50oz/hr. It's harder to remember to drink regularly for me. I use the auto lap feature on my Garmin to remind me. Some people set reminders on devices for every 5-10 minutes, etc. Just have to figure out what works for you, and then do THAT on race day and not something different or that you haven't tried.