1. OLYMPVS:

Olympvs specializes in technical casual wear tailored for muscular bodies. They have become popular with athletes across the world, with customers rating an average 4.9/5, with 10,000+ products sold. 

     2. Jed North:

Jed North is a workout clothing brand for many gym goers. Stretchable & affordable fitness clothes for men and women.

If you’ve ever been in or near a gym in the last 5 years. You’ve heard about GymShark. It’s the most popular athletic brand worn by bodybuilders and sells to customers in 181 countries.

     4. Young LA:

Young LA is a personal favorite for workout pants. Not only are they high quality and form fitting, you can find them on Amazon for $15-$30.  

     5. Barbell Jeans:

Founded by a team of friends and athletes, who apparently got together and launched Athletic Fit Jeans on Kickstarter.

That campaign grew to become the 2nd most funded fashion project of all time (according to their website), to bring "Athletic Fit" mainstream.