A great lower back stretching exercise that that moves your back from an arch to a curl, producing spinal flexibility and abdominal strength. To perform the exercise, kneel on all fours with your hands beneath your shoulders and your knees directly below your hips. Exhale and gently arch your spine. Inhale, tighten your core muscles and round your back, like a cat. Move slowly between movements and hold in each position for 5-10 seconds. Repeat 10 times.