This exercise is a mobility training and this exercise is good for when you want to start the training because it is very good and simple for your back. The first thing you need to do is lift up your legs and bend your legs like in the video. Your arms, head and back on the floor. OK? It is important as well to flex your feet because when you do this, you are going to work your hamstring as well. You’re going to stretch your hamstring a little bit so it is important. It is important that you keep your hands on the floor. Don’t bring your hand up, like I am doing in the video now. You can check here.