Do the hanging knee raise. It targets the obliques, a pair of
muscles that run diagonally along the sides of your torso & are
responsible for its ability to flex. It also works the lower
portion of the rectus abdominis, the large muscle that flexes the
torso forwards & backwards. This muscle is responsible for the
rippled 'six-pack' or 'shredded' abs look so many guys covet.
Crunches alone won't deliver that six-pack - although this much
appreciated exercise does assist mightily in abs development &
definition. Only aerobic exercise & a fat-burning diet will
reveal those much-desired bulges that yearn for development.