Acute exercise in men transiently increases plasma concentrations of homocysteine, cystathionine, cysteine, glutathione, and taurine, indicating an immediate activation of the transsulfuration pathway and glutathione biosynthesis as part of the oxidative stress response.

When a man exercises intensely, his muscles produce more reactive molecules that damage cells. In response, his body breaks down a specific amino acid to make another one that builds a powerful antioxidant. This antioxidant soaks up the damaging molecules, and the body also produces a related compound that helps manage the process. All these substances rise quickly in the blood right after exercise, then return to normal.