Leg curl your way into that dress

Swiss ball leg curl

Target Muscles: hamstringsSynergist Muscles: gastrocnemius, erector spinae

Set Up: Lie supine on the ground with your knees bent and your heels on the top of an exercise ball. Lift your hips up as high as you can (A).
Action:

Roll the ball away from you until your legs are straight but your knees are not locked. Hold for a second (B) and then roll the ball back towards you by bending your knees. Repeat.

this move is great for your hamstrings as well as it takes alot of core strenght to even get into the position so your working a ton of muscles at one time.