What kind of athletic tight shorts (long to the thigh) are worn at the gym called pants?

Called bodybuilding shorts, they are generally black, blue, or green in color, made of a silky material and an appropriate rayon blend with a lot of stretch, similar to dance pants, wide at the top and narrow at the bottom, with a belt around the waist or designed to be looped straight through.

Here's exactly what bodybuilding shorts look like: