robert landy

Most are familiar with doing rollouts using a basic ten dollar ab wheel, but rollouts can and should at times be done with a barbell. Using an empty bar allows you to work through slightly more range of motion than an ab wheel does. The bar sits a little lower to the ground which means your body can fall flatter. This will also place the points of contact (the bar and your knees, or feet if you're doing them standing) further apart. The further the distance between these contact points, the harder your abs must work to keep your lumbo-pelvic region positioned correctly. – Drew Murphy

Doing rollouts with a landmine attachment is very unique because only one end of the bar will roll while the other end remains fixed in place. This makes the bar travel in an arc, and places a lot of stretch on your distal lats and obliques. – Drew Murphy