The act of sweating doesn’t get a whole lot of attention.
But by understanding how our bodies lose liquids and salts during exercise, we can craft a hydration and electrolyte replacement strategy that can help ensure we optimize not only race performance, but recovery and general health as well.
Perspiration is our body’s primary cooling system. The process involves moving sweat (water, sodium, and electrolytes) to our skin’s surface via sweat glands. On our skin, the water in our sweat vaporizes, leaving (mainly) salt behind.
Heat moves away from our bodies as the water vaporizes into the air. Unfortunately, there is neither an unlimited amount of water nor sodium in our bodies. Thus, there is a limited capacity for our bodies to perspire, unless we continue to replenish the fluid and electrolytes that we lose.
This is particularly important for athletes, and even more so for athletes training and competing in hot temperatures. That’s because of the integral role that water and sodium play in so many physiological processes.
We need water for countless body functions, including a few that are specific to athletics:
- The amount of water in our bodies establishes our blood volume. Therefore, our blood volume will fall if our body water content drops. Because blood is responsible for carrying oxygen, our ability to supply oxygen to our working muscles will deteriorate if we are dehydrated; we will have to slow down.
- Blood also transports nutrients, including energy from food, vitamins, and minerals, to areas of need. However, with low blood volume, our ability to transport nutrients to our working muscles will also decrease. More slowing down!
- We need water to cool our bodies. Our bodies operate best in a concise temperature range. (This is one of the most well-known homeostatic balances.) We naturally slow down when we feel overheated from heat stress. If our body temperature rises too high, we may become dizzy, nauseous, weak, confused, and possibly unconscious; these are symptoms of heat stroke.
Furthermore, athletes need sodium for water absorption, retention, fluid balance, and muscle contraction.
- Water follows sodium. So, if sodium is low in our periphery, we won’t effectively absorb the fluid into our blood or around our cells. Instead, the liquid will bloat our gut.
- Sodium is essential for nerve impulse transmission and muscle contractions. Therefore, when sodium balance is off, our muscles may contract involuntarily.
- Sodium helps to maintain the fluid balance between the inside and outside of our cells. Suppose we have too little sodium and too much fluid. In that case, too much water will go from outside to inside the cells where there is a higher sodium concentration. This extreme condition, called hyponatremia, can cause grogginess, nausea, loss of balance, seizures, coma, and even death.
Not everyone sweats in the same way and, therefore, there are various considerations based on an athlete’s sweat rate, sweat composition, and fluid balance.
For example, someone whose sweat contains little sodium may try to compensate and consume too much sodium. This can lead to fluid retention, blood pressure increases, kidney stress, and a higher risk of kidney stones.
More commonly, someone whose sweat contains a high sodium concentration will fail to take in enough electrolytes. In this case, the athlete is at risk of dehydration, muscle cramps, fluid dysregulation, edema, hyponatremia, and overheating.
What should you do? The most straightforward (and perhaps oversimplified) answer is to drink fluids with electrolytes when exercising intensely or in hot environments for extended periods of time. However, understanding your sweat rate and sodium concentration will help you best meet your fluid and sodium needs.
Sweat Composition Assessment
In our laboratory, the Sweat Analysis includes:
- Sweat rate and sodium concentration analysis
- Personal hydration and electrolyte replacement plan
Alternatively, determining sweat rate at home is reasonably straightforward. Simply subtract your post-workout weight from your pre-workout weight and add the weight of any drink or food consumed during the exercise. Then, calculate sweat loss per hour by dividing fluid weight lost by the workout time.
You will want to perform this test for various workout intensities and climates to understand your sweating tendencies more completely. From here, you can develop a hydration plan matching your sweat loss. If you lose over 3% of your body weight during a workout, you are not drinking enough and will experience a performance decline.
Then there’s sweat sodium concentration. Our sweat analysis test will evaluate the sodium lost in your sweat. A low-sodium sweater may sweat 500 milligrams per hour or less, while a high-sodium sweater may lose 2,000 milligrams of sweat per hour or more. Fast Talk Labs uses a sodium analysis tool calibrated before every assessment.
Consumer-level sweat analyzer tools are available. These tools can be helpful, especially if you validate them against a laboratory sweat analyzer. If you do not have access to sweat analysis tools or services, you can do reasonably well by observing if you are a low-, medium-, or high-sodium sweater. Do you have lots of salty deposits on your jersey, shorts, or skin after a workout? How do you compare to other athletes you know?
Notably, sweat rates and composition will vary among individuals and at different times of the season. Additionally, sweat rate and composition will change in response to different diets, exercise intensities, and climates.
Ultimately, understanding your sweat rate and composition can improve your performance, recovery, and health.
