Why the push up? What can it really do? When you're ready to build strength and develop a tight and toned upper body and core, look no further than the push-up. his fantastic body weight exercise not only defines, strengthens and tones your body, but, it also builds strength and is a complex compound move that works your chest, biceps and core. So, if you struggle to get to the gym, or the dude over the other side took the your weights, then drop to the floor and smash out your own body weight!