I bought these for yoga, weight lifting, and running. The fabric is SUPER compressive, so my regular size S is pretty tight. The fabric is also a little too thick, so that I can feel bunching at the back of my knees, which is annoying. That said, 2 wonderful things about these leggings: 1) they stay put (the waist doesn't roll down), and 2) I look fantastic in them.
Sharon recommended this style