Basically scientists are pretty sure exercise causes an endogenous antioxidant response in the human body to respond to oxidative stress generated during exercise.
There’s a hypothesis out there that exogenous antioxidants such as vitamin C or vitamin E can actually negate the physiological adaptions to exercise because the oxidants are being countered by the exogenous antioxidants sort of as a first choice rather than your endogenous antioxidants.
Big confounding caveats here but I’m Just giving the simple idea here.
Here’s some lit to look at
Best insurance is to stick with great nutrition as the first cornerstone of health, as the first paper recommends.
With supplementation, it is impossible to map out the benefits and risks properly since it’s so hard to actually measure nutrition inside the body. My strategy is to stick with “well proven” ones in terms of their longevity, multiple studies and people’s personal experiences all converging to positive conclusions.
Chronically high intakes of antioxidants may impair hypertrophy, since inflammation is a critical part of muscular repair and antioxidants interfere with the inflammatory process. Antioxidants don’t appear to negatively affect muscular strength though.