Your sweat is as unique as your fingerprint and studying it can improve your performance. Darryl Griffiths, the founder of Shotz Nutrition, has been studying sweat for more than 20 years. His research has helped athletes go faster and put an end to muscle cramping and stomach issues.
This article will explain how to use the results of a sweat test to build a custom fueling plan. To learn even more about Griffiths and his work, listen to our podcast interview.
Why You Sweat
The average human body temperature is 98.6 degrees Fahrenheit. To survive, your body has to remain between 95 and 104 degrees Fahrenheit.
Sweat is your body's built-in cooling system. When your body temperature rises, sweat forms on the surface of your skin. When air passes over your body, the sweat creates an evaporative cooling effect.
While sweat does a great job at keeping you cool, the process causes your body to lose water and minerals critical for performance.
Sweat rate is a measure of the volume of sweat your body produces in one hour. On average, humans sweat between 0.7 and 2.9 liters per hour— that's roughly two cans of soda to 3/4 of a gallon.
What's important to understand is people sweat at different rates. If two athletes exercise at the same intensity, one may produce 1.0 liter of sweat per hour, and the other 2.5 liters.
Your sweat rate will change based on intensity and temperature. For example, you'll sweat a lot more in 100-degree heat than you will in 70-degree heat.
Your sweat contains a mixture of minerals. The mineral that has the most significant effect on performance is sodium. The concentration of sodium in sweat differs between people and ranges from 311 mg/L and 3084 mg/L.
The key takeaway here is the sodium concentration of your sweat is unique to you, and never changes. Regardless of your diet, fitness level, or the environment, your sodium concentration will always be the same.
Effects On Performance
Athletes with low sweat rates and sodium concentrations typically perform better in hot weather. These same athletes often struggle to perform in cold weather because of their inability to raise their core temperature. Without a high enough core temperature, muscles do not activate properly.
Athletes with higher sweat rates and sodium concentrations often perform poorly in the heat but excel in cold weather.
You Can Thank Your Parents
Your genetics determine both your sweat rate and the sodium concentration of your sweat. These values never change and remain constant throughout your life. Knowing this, you may want to pick races with weather conditions that better suit how you sweat.
The Sweat Test
Athletes can perform a test to determine their sweat rate and the sodium concentration of their sweat.
Before the test, athletes weigh themselves in the nude with full bottles of water. A sweat collection patch is also attached to the athlete's arm to collect sweat in an absorbent pad.
During the test, athletes exercise at race intensity. The room temperature is set to mimic the temperature of their race.
When the test is over, the athlete is dried and weighed in the nude with whatever water remains in their bottles. The weight loss recorded during the test can be used to calculate the athlete's sweat rate. A machine analyzes sweat from the sweat patch and calculates sodium concentration. Watch a video of Griffiths' sweat test on YouTube
What Can You Do With This Information?
Knowing your sweat rate and the sodium concentration of your sweat will help you build a custom fueling plan. If you lose 1.1 liters of water per hour, you can develop a hydration plan to help you replace that amount of water. Knowing the sodium concentration of your sweat will help you develop an effective sodium replacement plan. To learn how to developing a fueling strategy, read our article How To Perfect Your Fueling Plan, or read Griffiths' book "Sweat. Think. Go Faster."