The posterior oblique sling helps maintain core stability and facilitates the generation of strength & speed; particularly when it comes to rotational movement (especially important for golfers, tennis players & hockey players, for example).

In the following video, Dr. Jason Lemieux of Physiomed Oakville demonstrates a variation of the standard bridge exercise for targeting the muscles of the posterior oblique sling:

 

 

Here, Dr. Lemieux targets this same muscle group with a half-kneeling row/pulling exercise: