if you're a skinny guy, rather than hitting abs exclusively, try aiming for big-muscle exercises that don't target the abs directly. what do i mean?
as an example, while most guys normally think of a standing overhead press as a shoulder exercise, it actually places great resistance on the spine - what's called
"axial loading." when the spine is under stress, the muscles of your abs & lower back contract in order to keep you safely balanced & erect. since supporting a load overhead can cause your body to bend, twist, turn, or sway, your entire core must work to prevent that movement & instability. this makes axial-loading exercises far better ab builders than crunches. that isn't to say that isolated ab-training is useless, but to build the most overall muscle while keeping your abs sharp, you're simply better off performing compound exercises such as squats, dead-lifts & overhead presses
(all of which are axial-loading, working the abs).
