Start in a pushup (plank) position on your hand and toes (not pictured). Lift your right foot off the floor and slide your right knee forward toward your left hand so that your knee and outer ankle rests on the floor. Slide your left leg back as far as comfortable, but keep your hips square to the floor and level.
Breathe slowly and steadily as you hold the stretch, pushing your hips toward the floor, but keeping the back long, shoulders down and chest lifted. Hold for 10-30 seconds. Switch sides.
This is an advanced stretch. Do not attempt this stretch if you are unable to maintain proper form as indicated in the instructions and photo. For a deeper stretch, fold forward and let your forearms rest on the floor in front of your leg.
Original article and pictures take http://www.sparkpeople.com/myspark/ex/exercises.asp?ID=547 site