Workout Attire: Why Sweat Changes Everything

Athletic wear gets its own article because the conditions during exercise are different from just wearing clothes around. Sweat is the key variable. When you sweat heavily, your pores open, your skin surface temperature increases, and skin permeability goes up. This means chemicals in tight-fitting, skin-contact athletic clothing have substantially more access to your body during a workout.

The vast majority of athletic clothing sold today is made from polyester, nylon, spandex, or blends of these petroleum-derived synthetic fibers. These materials are excellent at moisture wicking and stretch performance. But they require significant chemical processing and are often treated with additional finishes.

Antimicrobial Treatments and Finishes

Antimicrobial treatments are standard on most athletic wear because synthetic fabrics harbor odor-causing bacteria. The most common antimicrobial agents used are silver-based (silver ions, silver nanoparticles) or triclosan, though triclosan use has declined following FDA concerns about it. Silver nanoparticle treatments are effective at reducing odor but research has raised questions about their effects on the skin microbiome and their environmental persistence when they wash off.

Moisture-wicking finishes, anti-pilling treatments, UV-protective coatings, and durable water repellent treatments (often PFAS-based) are all additional chemical layers that may be applied to athletic fabric. A piece of activewear could easily have four or five different chemical treatments on top of the base synthetic fiber.

Better Workout Wear

For lower-intensity workouts like yoga, Pilates, walking, or light gym work, natural fibers like organic cotton, hemp blends, and Tencel actually perform well and have excellent breathability. For higher-intensity cardio or competitive sports, the performance properties of synthetics are harder to replicate, but cleaner synthetic options exist.