How Much Amino Acid Do You Lose in Sweat During a Long Run?

If you've ever finished a long run feeling flat, foggy, or slower than your fitness should allow, the answer might not be in your training plan. It could be in your sweat.

Most runners know sweat contains water and electrolytes. Fewer know it also carries away a specific group of amino acids — and that the losses are larger than most nutrition strategies account for.

What sweat actually contains

Eccrine sweat is not simply diluted plasma. Research shows that six amino acids — histidine, glycine, serine, lysine, aspartic acid, and ornithine — are excreted in sweat at concentrations that can significantly exceed their levels in blood plasma. These are what InnovAAte's research team identified as High-Demand Amino Acids (HDAA).

During a single hour of vigorous running, sweat losses of these amino acids can clear the equivalent of 343% of the total HDAA available in your entire circulating blood volume. That's not a rounding error — it's a meaningful physiological drain.

Why this matters for runners

These amino acids aren't just building blocks for muscle protein. They underpin energy transport (glycine is essential for haemoglobin and cytochrome construction), acid-base buffering (histidine is a key component of carnosine), and structural repair of connective tissue. When circulating levels fall, the body activates proteolysis — breaking down skeletal muscle to restore plasma balance.

For endurance runners, this creates a compounding problem: the longer the run, the greater the loss, and the more muscle tissue is sacrificed to compensate. Recovery slows. The next session feels harder. Over a training block, the cumulative deficit adds up.

What most hydration strategies miss

Standard electrolyte drinks replace sodium, potassium, and magnesium. Some add carbohydrates. Almost none address HDAA losses — because until recently, the research identifying them as a distinct category simply wasn't widely known.

Replacing fluids and electrolytes without replacing HDAA is like refilling a car's water and oil but ignoring the fuel. The system runs, but not as it should.

The practical implication

For runners training more than 45–60 minutes per session, targeted HDAA replenishment — before, during, or immediately after runs — can help maintain plasma amino acid availability, reduce the proteolytic response, and support faster recovery between sessions.

The peer-reviewed science behind sweat-facilitated amino acid losses is detailed in our research précis: Sweat Facilitated Amino Acid Losses in Male Athletes.

Learn more about InnovAAte's HDAA formulations at innovaate.com.au.