Help! Am trying to decide if I should buy GS legs. I do a lot of racewalking, and tend to not go for really heavy weight workouts with my legs, as I find it bothers my knees. So I focus mostly on alternating PS legs and ME, sometimes (but not very often at all) throwing in S&H legs or PLB. *But* I recently bought both GS upper body DVDs and love them--so I'm wondering if it's worth it to go for GS legs, too. Opinions?