3 Things You Don't Know About Your abdominal muscles

1. You can strengthen your core without moving a muscle. Whereas most muscles propel you, your core resists movement--for instance, to protect your spine when you twist your torso. So don't be surprised by how hard it is to stay contracted when performing some of my H.I.G.T ab workouts. You're conditioning your core to do its job more effectively.

2. Slouching sabotages your six-pack. Training your core helps correct poor posture. But an hour a week of core work can't compensate for the 50 hours spent slumped over your keyboard. The fix: Stay tall through your hips and keep your head up and shoulder blades back and down all day long.

3. Core muscles contract first in every exercise. All the energy you exert originates in your torso, before being transferred to your arms and legs. So a weak core reduces the amount of force you're able to apply to a barbell. When you hit a plateau in presses, squats, or any other strength move, ask yourself if you're training your core as hard as you can. Here are two very challenging ab exercises to increase core strength.

**Plank with Diagonal Arm Lift
Assume a modified push up position with your feet shoulder-width apart, forearms on the floor. Keeping your torso steady, raise your right arm forward and to the right, so that it points to 2 o'clock. Hold for 2 seconds, then lower and repeat with your left arm, raising it to 10 o'clock. That's one rep. Your elbows should be bent 90 degrees and directly under your shoulders.

***Single-Leg Lowering
Lie on your back with your legs extended straight up. Keeping your legs straight, lower your left leg until your foot is 2 to 3 inches off the floor. Return to the starting position, then repeat with your right leg; that's one repetition. Think about pushing the bottom of your heel away from your hip as you lower your leg. Don't point your toes; keep your foot flexed toward you. Lead with your heel.