Squats are one of the most versatile exercises that work the legs and butt muscles. This simple exercise can be done at any time (except in the office with witnesses). Try adding an exercise ball to your simple squat routine. Using an exercise ball requires your body using a variety of muscles to establish balance. Grab an exercise ball (or purchase one for $20-25 at your local sporting goods store). Be sure the exercise ball is sized for your height.

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Stand near a wall and place the exercise ball between your lower back and the wall. Your posture should be straight, hands at the sides, head facing forward and shoulders relaxed. Focus on tightening your abdomen. Bend your knees until parallel to the floor, keeping your weight on your heels.

As you bend, the stability ball will roll up your back. Return to your starting position, letting the ball return to your lower back. Complete three sets of 20 repetitions.

Lunges

You can use the stability ball for lunges, too, but it's not a requirement. Lunges are an excellent way to elongate and shape the butt muscles. If you choose to use an exercise ball, hold the ball over your head at your starting position. As you take a step forward to bend into your lunge, lower the ball with outstretched arms directly in front on your. Continue to raise and lower the ball with each repetition. You'll feel the engagement in your abdomen.