Sweat Rate question

jhpiii

 So I calculated my sweat rate per the guidance in the Wiki. My results demonstrate a rate of 45 ounces per hour, in cool temps. (Yes, I sweat a lot) My question: Should my goal be to replenish all 45 ounces of water lost, or is there an acceptable amount of loss that does not need to be replenished?

zildgen

John, I'm not sure if you have look at the following links but they will provide some additional information.
http://members.endurancenation.us/Resources/Wiki/tabid/108/Default.aspx?topic=Monitoring+Hydration+Status
http://members.endurancenation.us/Training/TrainingForums/tabid/101/aft/7904/Default.aspx

I think that if you try to completely replace all that is lost you will get into GI trouble, or worse, it's just to much. But we each vary on our ability to absorb while racing and training. So it becomes a big experiment to see how much and how often you need to take in fluids and nutrients to be successful. Also the amount that can be taken in varies between discipline.

The type of fluid that you take in is also important. I think that you should take in a replacement fluid ie one with electrolytes, since you are losing them with your sweat and taking in that much water might lead to hyponatremia ( see http://www.slowtwitch.com/Training/General_Physiology/The_Math_of_salt_loss_1093.html ). You can also look over the Hammer nutrition web site for additional and different insight in racing and training hydration.

As for me I also sweat a lot (> 50-60 oz/hr) and live in South Florida. While on the bike I have water in a PD aero bottle and try to take in 30-40 oz/hr . I also have a feed bottle on the seat tube with a concentrated mix of Heed, Perpeteum , and Endurolytes that adds 6-8 oz/hr and I take 1 Salt Stick capsule every 20-30 min.. On the run I can not drink as much and will take in 20-30 oz of fluid/hr. That fluid is mostly water so I will increase my Salt Stick intake to 1 cap every 15 -20 min and use gels to get the calories up to 200-300/hr, That has worked for me at the HIM distance. We will see if that works as I bump up to IM. Anyway YMMV. Sorry for the long post, was looking to get you a few more sites to read over and got carried away.

mgraffeo

Sweat test gives you an estimate.

Then, you test drive that estimate during a race rehearsal, and see how it goes. Tweak based on results.

Then, go and race it.

Overall, I prefer to focus on 'what's the minimum I need' vs. 'how much should I be getting'. The RR is a great opportunity to test that.

Matt Samojeden

2x on Mike's comment of the value of the race rehearsals for dialing in hydration and nutrition.

I check my fluid loss for all long runs and rides during my IM build phase. I also capture temp and humidity data. This set of multiple data points allows me to know what I should expect to see give race day temps and humidity. Also I can see changes that are due to heat adaption.

Plan to be able to drink more on the bike than on the run where digestion is more of a challenge.

penlynwilson

John: Most people can take in 24 - 48 oz of fluid. You shoudl practice and see how much you can take in - probably more than you think you can. You want to be as hydrated as possible. Performance begins to suffer with even a 2% loss of body weight from water.

Paul Hough

@ John - like Dewey I'm in South Florida and I wish I could sweat ONLY 48 oz per hour. The key is that your sodium intake has to be in proportion to your fluid intake. If you you take in too much sodium but don't hit the fluid goal then you can have problems. Listen to Penny!

@ Penny - several years ago I was suffering from significant cramps on the run in 70.3s. I finally consulted a RD, Sports Nutritionist, etc through TriSmarter.com. I worked with them for 6 months and my assigned target fluid intake in hot weather is 50 oz per hour on the bike and 54 oz on the run. It is doable and trainable. That and other adjustments got rid of about 90% of my problem although I'm about to put it to the test this weekend.