If your going to read anything about fluid intake, please start here. There is a lot of information on the web offering their opinion about how much is recommended. It’s all controversial; how can a fluid intake be given without knowing your height, weight, sweat rate or even intensity?! Plus the ranges of fluid intake are so wide that it could leave someone either bloated or with hyponatremia. There is a simple way to figure out how much you need, but it does require a little work on your behalf.
Tools your going to need
Process
- This test is going to measure your sweat rate at a given intensity. Three “zones” should be selected before starting the test.
- Zone 1 or your recovery zone will be your first. This is typically <75% of your max heart rate. Also know as your fat burning zone.
- Zone 2 is your aerobic zone. This is 75-85% of your max heart rate. For feel, this would be half Iron pace to low Olympic pace.
- Zone 3 is your anaerobic zone. This is 85%+. This is where you will have the highest sweat rate.
- Before starting the test, use the bathroom.
- There are a couple ways to approach the test, first is to have no warm up and begin, the second is to warm up (see below). Both require the “Measuring Step”.
- Do a 15min warm up if your doing Zone 2-3 testing. Zone 1 test could probably be started from the get go. If you do a warmup, you may have to change out of your clothes to get an accurate assessment.
- The Measuring Step requires you to stand on the scale to get an inital measurement. Taking a reading in the nude is the most accurate but if you choose to use clothes (not the ones from the warm up as they will hold sweat therefore adding weight to the final reading) then make sure to wear them at the end of the test. Write the number down. Re-measure yourself 3 times for a more accurate result.
- Begin test.
The Test
Testing is very simple. Stay at your recommended zone for 20 minutes with no fluids. Measure your zone with the Garmin 305 heart rate monitor. Pedal, run or even swim (if you choose to swim make sure to dry yourself before going on the scale). After the 20 minutes is done, measure yourself in the same dry clothes you did at the beginning (or nude). Write this number down. Re-measure yourself 3 times for a more accurate result.
Testing could all be done in 1 day but not in succession as your body can treat the given stimulus differently (ie. less sweat because of repeated test).
Understanding the Results
Download the data from the Garmin. This should give you a clear plot of what your effort looked like. If it’s a flat line at your goal intensity, then you’ve nailed the test. The numbers that are important are: calories burned and the average heart rate. If the AHR is a realistic number that you see yourself working at for a race then the calories can be extrapolated for the entire duration.
For example, if my AHR for a sprint triathlon bike is 180 and my test HR is 183 then this is an accurate assessment. If the sprint ride takes you 20mins then double the calorie numbers and that will be about your expenditure.
How to Use This
Here is an example on how to use the above information:
Athlete results were: during 20min high intensity test on a stationary bike, the subject lost 1 pound. The initial weight was measured to be 150 pounds Dehydration is measured at 2% loss of total body weight. So, 150 pds x 0.02 onset of dehydration = 3 pds before onset of dehydration will cause the athlete to slow down. So, this athlete if they had no other fluids could last about an hour before performance was compromised.***
The hydration strategy is meant to give you an idea how much fluid you need to take in to avoid dehydration. Combine this with the calorie expenditure, and you have two powerful ways to measure your quantitave state during exercise. Use these numbers to help better prepare yourself for practicing and racing.
***There are many other factors invloved besides just sweat loss (water plays a primairy role in the body and those sources also need to be replenished hourly). Also note, rarely can an athlete who is working at high intensities to come out in a positive or even a neutral hydration weight (drink more or as much as they sweat). This can cause many problems such as gastric distress, urinanry issues, and a “hammock” for a stomach.
