Last month we discussed how important your core is for many bodily functions. In order to exercise your core properly, it takes a little more than sit-ups and crunches. As a reminder, your core is everything minus your arms, legs, and head. Any exercise that forces you to stabilize your body is a core exercise.
If you only had time for one core exercise, doing planks would be the winner. To do a plank, place yourself in a push-up position, except with your forearms on the ground instead of your palms. Your body should be completely straight – from the back of your head all the way down to your heels. While in this position, look at the floor just a few inches in front of you and tighten your buttocks. The tendency is to raise your butt slightly up in the air, thereby making the exercise too easy on your core. Try to hold this position for 30 seconds. As your core improves, advance to 60 seconds or more, with multiple sets.
An entire book could be written on core exercises. One of the most efficient ways to work your core is to incorporate some moves into your regular routine. Remember that the primary role of your core is to stabilize your body. Try performing dumbbell curls on one leg or with both feet on a slightly unstable surface (such as a 4-inch-thick foam pad). Working one side of your body at a time will also stress your core (e.g. alternating dumbbell curls).
I hope this keeps you straight!