Classical Chaturanga builds on the alignment and prop work you practiced in the previous postures. Begin in Plank Pose with your shoulders slightly ahead of your wrists. Plug into the floor with your big-toe mounds to activate your quadriceps, lift the tops of your thighs, and keep your tailbone heavy. Exhale into Chaturanga. Think more about pulling your chest forward than lowering. This will help keep the heads of your upper arms in line with the sides of your body, rather than collapsing toward the floor. Catch yourself at elbow height. Again, Tadasana shoulders!