Workout pants with zippered legs let you peel off the pants without removing your shoes. This feature is ideal if you want to take off the sports pants and strip down to shorts once you get to the gym, or during your workout. You can find fitted tights with zippers also. Some zippers run the length of the pant leg, and others extend from the bottom of the pant leg to the upper calf.
Caveat: If you wear sports pants with zippers for your workout, the zippers may rub and chafe your legs. It's best to wear the athletic pants with zippered legs if you will be wearing them pre-or post-workout, or as casual wear.