The Press Up exercise is to improve spinal mobility. If you can lie comfortably on your stomach, propped up on your forearms, this is the next progression. Place your palms on the floor under your shoulders and press up as if you were going to do a push up - but in this case you leave your hips down and only lift your upper body. Only go through a comfortable range, don't force it! Hold the position only briefly - a second or two, then lie back down. Repeat as instructed by your coach. You should never feel pain with this.