3rd
Sweat Rate Test Protocol
If you don’t stay properly hydrated on a long ride, then you won’t likely get to finish the ride. Even if you do finish, you will feel terrible and won’t perform to your maximum potential.
Proper hydration is simple - just take in enough liquid nutrition to replace the water and minerals that you lose through your sweat. There are two keys to meeting this goal.
First, you need to find a good sports drink that carries a strong metabolic payload. Most of of the sports drinks that you find are absolute junk. A mix of food-dye and sugar and fancy marketing intended to convince you that it will make you faster, stronger and more competitive. They do no such thing. Don’t expect to get good performance from any sports drink that costs you $6 a cannister in powdered form. Look for a reliable brand with a good balance of minerals and electrolytes along with a good sustainable form of energy. Hammer Nutrition makes some good products and I rely on Endurance made by Amino Vital.
Second, you need to know how much to drink. You can’t know how much fluid to replace if you don’t know how much you are losing.
To understand your sweat rate, you will need to do a sweat rate test. It isn’t highly scientific, but it will get you in the right ball park and get you started on the road to better understanding your fluid requirements. Since I started regularly testing my sweat rate, I’ve been riding stronger and more evenly because I’m no longer letting my body hit fluid depletion on these long rides.
The most notable sign that I’m on to something with these tests is that I no longer come home with a huge headache after spending the day in the sun. I used to think my helmet was too tight or poorly adjusted. When I started hydrating properly, the headaches instantly went away.
The sweat rate test protocol is pretty simple. I’m presuming that you will do this test on a stationary bike of some sort. First, weigh yourself without any clothes on. Get dressed and record this number as your starting weight.
Then, ride your bike for at least 45 minutes in a high aerobic zone. I usually shoot for 70%-75% of my maximum heart rate. Throughout the test, keep track of how much fluid you are drinking. I try to drink complete bottles to keep the math easier.
When you are done, remove your cycling gear, towel yourself off as completely as you can and then weigh yourself. Put on a robe and record this number as your end weight.
Now we’ve got all of our data:
Starting Weight = SW
End Weight = EW
Fluid Consumed = FC
Duration of Test = D
We will probably need to do some conversions before we can do the math. You need to convert your fluid consumption into liters. There are .7 liters in a regular 24 ounce bottle. If you drank a different amount of fluid, just go to Google and type the following into their search tool “X ounces in liters” where “X” equals the size of your bottle.
Also, if you weighed yourself in pounds, you will need to convert this to kilograms as well. Just go to Google again and type in “X pounds in kilograms” where X equals your weight. Do this once each for your starting weight and your finishing weight.
Now that you have the amount of fluid you consumed in liters, convert that number to kilograms. 1 liter of fluid equals 1 kilogram of mass. So, a 24 ounce bottle, will weigh approximately .7 kilograms.
Now from here, the math is simple, just plug your variables into the following equations:
(SW-EW-FC) /D=SRM
i.e. Joe had a starting weight of 78.92kg, and end weight of 78.45kg and drank .7 liters over a 45 minute test. His math would look like this:
(78.92-77.45-.7)/45= .017 liters per minute
To make this number more relevant, just multiply it by 60 to get your sweat rate per hour. In Joe’s case, this would be 1.02 liters per hour. That works out to 34 ounces per hour, or 1.5 bottles.
So for Joe to stay properly hydrated, he knows he has to drink approximately 1.5 bottles per hour when he is out on the course. Of course, on a hot day, this will be slightly more, and on a cooler day, slightly less. If you are training for a specific event where you know what the approximate temperatures are, it makes sense for you to do the test under conditions similar to the race so you have more precise information to make decisions with.
I hope this information is helpful for you. I’m not the originator of this test, but it has served me well over the years. If you have questions, feel free to drop me a note at ross@ultrarider.ca
Posted at 17:47 - Comments (View)
