The term "Muscle fit" is a type of clothing fit that aims to be tighter around the muscular areas of the body but in many cases the shoulders, chest and arms. The Muscle Fit isn't intended to be super tight or restrictive, it aims to be the perfect fit for those that take pride in their appearance. You can typically buy "muscle fit" clothing, and in rare cases "athletic fit" clothing in t-shirts, polo's, joggers and various other clothing types.