Most folks think abs come from crunches. In truth, "abs" are primarily a function of what/how much you eat. If you burn enough body fat they will become visible. But whether you want a six-pack or you just want a strong core for optimal health, consider replacing crunches and sit ups (which can damage your lumbar discs) with these three core stabilizing plank variations which are favorites among my JJFit Challenge crew. Try them in a circuit for 30-60s each for 2-3 sets.

1. Extended Planks – have your feet a little wider than usual and walk your hands out to a comfortable plank and then walk them out even further past your comfort level, screw your hands into the ground and hold your body parallel with the ground for about 3 seconds and repeat.
2. Rainbow Planks – start in a forearm plank and slowly drop your hips side to side (as far as you can, ideally tapping the floor). Keep your forearms glued to the ground (don't let your elbows pop up). This is a good one because it strengthens the obliques but also gives the muscles of your hips and lower back a nice stretch.
3. Plank Birddogs – start in a forearm plank and extend the opposite arm and leg and hold for 1-2 seconds. Alternate. Try to reach your heel as far behind you as possible (keep your foot flexed so your toe points toward the ground). When reaching your hand try to extend as far as possible and keep your thumb up/pinky down on that hand (so your arm is externally rotated). Try not to let your heel go too far above your butt.

For a visual of how to perform these moves check out this video. And for tips and ideas for staying fit and active while at home check out this recent Law.com column.