In the lifting bar abs you will need, as said, a metal bar that can support the weight of your body. and then you'll have two types of lifting bar abs, the straight legs lifting bar abs and the bent legs lifting bar abs. As said one is with your legs straight and the other one is with your legs bent. And in both exercises what you'll have to do is to hold the bar with your abs and let your body be hanged, and when you are in a well balanced position you'll have to raise and lower your legs many times until you feel your abs sore. Bent legs lifting bar Abs:
Straight legs lifting bar Abs:
Details: Always stay in a well balanced position because if you don't it won't have the same effect.