What Is Sweat Testing? 

It doesn’t take very much of an effort for somebody to start sweating during an activity. Excreting fluid out of our skin has given humans a huge endurance advantage due to temperature regulation. Sweat (moisture) is the key ingredient for Evaporative Cooling, which wicks heat away from our bodies and allows us to continue working at a decent rate. 

While sweating has played a role in our evolution, there is a huge range in how people sweat. The average person loses about 950 mg of sodium per Liter of sweat, with a range of 200mg to 2000mg+ per Liter of sweat.  That’s a range of 10 times between different people! 

Whatever marketing you have seen from sports nutrition companies about the benefits of their products - the truth is that no product is going to work for everyone all of the time. Riders of similar abilities can have drastically different hydration needs in the same event. There is no magic bullet for everyone except a basic grasp of their individual needs. 

The Advanced Sweat Test from Precision Hydration gives you the precise amount of sodium that you are losing in your sweat. Combine that together with some data on the rate that you sweat in different conditions, and we have a pretty good idea of what and how much you need to be consuming in various events. 

Here is an example of two riders of similar ability and bodyweight in the same event. Both riders have sweat rate data in conditions similar to the race they are competing in. One of them is me, since I am pretty average in terms of my sweat. Steve is on the high end of his sodium concentration, and is a heavier sweater as well. Despite being fictional, Steve’s sweat data is common amongst endurance athletes that have problems in the heat.

Jacob: 

Sweat Concentration: 960mg per Liter

Sweat Rate: ~1.4 Liters per hour

78 Kilograms

Steve:

Sweat Concentration: 1720mg per Liter

Sweat Rate: ~1.9 Liters per Hour

75 Kilograms. 

Let’s Break down the losses for each rider:

Sweat Concentration X Sweat Rate x Time  = Total Loss 

Jacob: 960mg/L x 1.4 L/H x 6hr = ~8000 mg Sodium

Steve: 1720mg/L x 1.9 L/H x 6hr = 19,600 mg Sodium

Given Steve’s sweat rate and concentration, he is losing 2x+ more sodium per hour than Jacob! Over 1, 2, or even 3 hours, it is possible that Steve and Jacob could consume the exact same drink and quantity and both will be performing at a similar level. As the effort gets longer, conditions more extreme, or the effort more intense, Steve could will get in trouble when his fluid and sodium losses get too big and he performance plummets.

The trick for each of these athletes is to determine how much fluid and sodium they each need throughout the event to keep the losses at a manageable level, and how to fit in carbohydrates into the plan to sustain energy levels. There is no one right way to do this, and it is not set in stone. A good plan starts with the right ingredients, and using those ingredients at the right quantity, the right time, and room to adapt by the athlete.

FAQS

Q: How many times do I need to do the Advanced Sweat Test?  Don’t my sodium levels change?

A: You only need to do the sweat test one time. Your sodium concentration does vary slightly, but not enough to change any of the recommendations. 

Q: Isn’t sodium bad for you?

A: Anything can be bad for you in the right amounts. Your body tightly regulates the sodium concentration in your body, so either too much or too little can be a problem. With the data from this test, you can ensure that you keep your sodium levels in balance. For athletes exercising in hot conditions for long durations, low sodium in the blood can be a deadly condition known as Hyponatremia.

Q: What about the other electrolytes lost in sweat?

A: There are 4 other electrolytes lost in sweat, including: Potassium, magnesium, calcium and chloride. These other electrolytes are not lost in significantly less quantity and more consistently between individuals.

Q: How much does the Advanced Sweat Test cost?

A: The basic test that you can book here is $150. If you want a home visit or a group discount, please reach out.

Sources:

Precision Hydration ltd

Empirical Cycling Podcast