Even for non-professional athletes, for everyday gym goers, sports apparel is relentlessly marketed, aiming to convince consumers that you're not actually working out unless you pay upwards of $100 to sweat in some kind of high-tech "performance" wear. Of course this is nonsense, and it's perfectly possible to effectively exercise to exercise in any sort apparel -- physiologically speaking, you could be wearing a tuxedo, a full Victorian gown, or a powdered wig, and still partake in the process known as "exercise."
However, many still believe that sportswear is a necessity, and maybe to a certain degree it could be convenient to own a few items of it. But, recent studies have shown alarming amounts of potentially hazardous chemicals in sportswear, such as phthalates, PFCs, dimethylformamide, and nanoparticle silver (used as a anti-odor/anti-microbial agent). A Greenpeace report found unsafe levels of unsafe chemicals in the sports uniforms and far merchandise for the 2014 World Cup. In order to cope with this situation in the sportswear apparel market, in Shape, Jessica Teas includes the recommendations of buying organic fabrics, avoiding screenprinting/plastic prints (these often have phthalates), and "avoiding trademarked technical fabrics."