This is an exercise geared toward working both your butt and back muscles. You will need a Swiss ball to perform this one. You will lie down on your back and place your feet on top of the ball. Push against the ball with your heels and lift your butt as far upward off the ground as you can. When you lift enough that your knees and shoulders form a straight line, hold your position for at least 60 seconds. Then slowly lower yourself back to the starting position. Repeat the process for ten reps, remember not to overdo this one or you will be very sore.