This is an excerpt from Bodybuilding by Peter Fitschen & Cliff Wilson.
After you complete the side mandatory poses, the judges will have you quarter turn toward the back of the stage. Typically, they will call out rear double biceps pose, sometimes called the back double biceps pose. Place one foot behind you and spike your calf. Sometimes the judges specify which calf you should spike. If they do not specify which foot to place behind, then pick the one you feel most comfortable with. Place your foot behind your other foot approximately 10 to 15 inches (25-38 cm). Your knees should be turned outward slightly and bent just a little. Flex both hamstrings by digging your feet against the floor, as if you were trying to perform a leg curl. Flex and squeeze your glutes tightly. Bring your arms out to your sides and flex your biceps and the entire muscularity of your back. You should not pinch your shoulder blades together. Instead, keep them open so that your back stays wide. Lean your torso back ever so slightly toward the judges.