Start seated side by side with both knees bent to the outside. Hook elbows to help balance each other and practice posture lifting chest and spine. Lift the back leg and lower. Try for 12 to 15 repetitions on each side, then turn around and repeat on the other leg. This exercise builds a better bottom side and strengthens the core and spinal muscles. Use your partner for stability and balance, and keep those elbows lifted to work the shoulders.