Sweat Facilitated Amino Acid Losses in Athletes — Research Summary

The following is a summary of peer-reviewed research by Dunstan R. Hugh et al. (2016), published in PLoS One. Read the full article

Précis: Sweat Facilitated Amino Acid Losses in Male Athletes during Exercise at 32-34°C

• Bimodal Excretory Mechanism: Exercise-induced sweat initially leaches free amino acids from the stratum corneum's natural moisturizing factor (NMF), transitioning after 35 minutes to direct eccrine excretion characterized by high concentrations of serine, histidine, and ornithine that significantly exceed plasma levels, alongside active conservation (reabsorption) of glutamine and proline.

• Phenotypic Stratification of Nitrogen Loss: Diagnostic clustering separates endurance athletes into Low, Intermediate, and High sweat-facilitated amino acid loss (SFLAA) phenotypes. The "High" SFLAA cohort exhibits severe excretion rates up to 22.8 mmol/h, depleting up to 40% of the daily recommended histidine allowance within a single hour of exercise.

• Clinical Implications for Recovery: Pronounced dermal nitrogen clearance triggers skeletal muscle proteolysis to maintain plasma homeostasis, driving myofibrillar catabolism that compromises athletic performance and induces peripheral muscle fatigue. This identifies a critical clinical window for targeted, pre-digested free amino acid supplementation to avert overtraining syndrome and accelerate tissue repair.

Clinical Endpoint:

The primary clinical endpoint is the quantification of net hourly dermal nitrogen clearance (specifically via sweat-facilitated amino acid loss) to identify athletes at high risk for exercise-induced skeletal muscle catabolism and peripheral fatigue.