The calf muscles are also commonly involved as often are other leg muscles in the thigh and hip. (sock-doc.com)
They also recruit other leg muscles, and you can do this little circuit as a complete unit if you want — or add a couple of the moves to one of your existing workouts. (thebettyrocker.com)
They do focus mostly on your butt but also use your other leg muscles too. (rachaelattard.com)