Lie on your back, either on a cushy carpet or an exercise mat. Bend your knees so your feet are flat on the floor. Keep your arms at your sides and your eyes on the ceiling. Slowly lower both knees to the right -- trying to keep your knees together as you do this -- until you feel a gentle stretch in your thighs and lower back. Hold the stretch for 5 seconds, and then slowly lift your knees back to center. Then, lower your knees to the left side, hold, and return to center. Repeat 10 times on each side, with short rests in between.