The barbell rollout is one of the best anti-extension and anti-flexion exercises for your trunk. The exercise becomes increasingly more difficult the further you roll out due to the longer lever. Therefore, the fully extended end position is the most difficult position for your trunk, as well as for your shoulders.

One common flaw is using a grip that's too wide. The correct grip width should be shoulder width or slightly narrower.

Sometimes you see one and a half times shoulder width or double shoulder width, which might look impressive, but a grip that's wider than shoulder width puts you shoulder in a vulnerable position. So always choose a grip that's shoulder width or less to save your shoulders.

Related:  More on the Barbell Ab Rollout

Related:  4 Great Ab Exercises Nobody Does Right