PURPOSE: Improving strength and stability of your core. The core is your powerhouse - all movement relies on it. The back extensor muscles - erector spinae and multifidus muscles - function mainly to provide posterior stability for the vertebral column and to oppose the force of gravity for maintaining erect posture and controlling forward flexion. Don't confuse core work with six-pack training. Having the visibly appealing six-pack has almost nothing to do with training abs and everything to do with the quality and quantity of calories you're eating. The key to seeing your abs is low body fat. Someone with very muscular abs who has high body fat will not see any definition, and someone who has not trained their abs at all with low body fat might see definition. Men will have to reach at least 10 percent body fat or lower, and women will need to be at 14 percent or lower to reveal the six-pack.

GOAL: Your core muscles run the length of your trunk and torso. When they contract they stabilize your spine, pelvis and shoulder girdle and create a solid base of support. The goal of abdominal training is to maintain a firm foundation and to transfer energy from the center of the body out to your limbs. A conditioned core is able to generate power from the extremities with less risk of injury to the back.

TOOLS: Abdominal crunch resistance machine, bodyweight, stability ball, medicine ball, bosu ball. You can use a variety of tools to train the core. The stability ball is great because, in addition to increasing range of motion for crunches and other abdominal exercises, it improves your balance and coordination. Planks are a great abdominal exercise that uses your own bodyweight. (Lie face down on mat resting on the forearms, palms flat on the floor. Push off the floor, raising up onto toes and resting on the elbows. Keep your back flat and a straight line from head to heels. Tilt your pelvis and contract your abdominals to keep body parallel to floor. Hold for 20 to 60 seconds, lower and repeat.)

FORM: You must successfully engage your rectus abdominis while reducing the involvement of your hip flexors. To do a traditional crunch on the floor or on a stability ball, engage your abdominal muscles by curling your shoulders slowly toward your hips. Imagine peeling each vertebra from the mat one at a time. Keep your head neutrally aligned, with your chin off your chest. This relaxed posture allows you to concentrate on contracting the abdominal muscles with maximum intensity. Place your hands lightly just behind your head; don't apply any pressure. Exhale on the way up and inhale on the way down. Strive for quality of movement with each contraction. Slow and controlled movement is best. You should never pull on your neck when doing a crunch. Aim to keep a fist's distance between your chin and chest when doing a crunch. When doing a hanging knee raise, there should be no swinging whatsoever. Rather, the torso will remain still and movement will be only around your pelvic area and legs.

LEVELS:

Light: Beginners. The ab crunch resistance machine or basic floor-based crunch are ideal ways to begin.

Moderate: Regular exercisers. Time to try a stability ball.

Intense: Athletes and avid exercisers who strength train. Hanging leg raise; adding rotation for oblique work should be commonplace in your program.

DURATION:

This is the amount of time to spend on your entire strength training workout, not just the targeted here.

Beginner: 10 to 30 minutes

Intermediate: 30 to 45 minutes

Advanced: 45 to 60 minutes

FREQUENCY:

Two to four times a week. Depending on your strength-training regimen, you might need to concentrate on your core only one or two days a week. Here's why: If your program is primarily free weights, you are simultaneously working the core through stabilization. If your program is founded in resistance machines, you will need two to four times a week. Design your abdominal workout by choosing a variety of exercises, combining spinal flexion, rotation and lateral flexion exercises.

Target muscles: Abdominals and low back

MODES:

The resistance machine pictured here is a safe and effective way to perform guided ab crunches; the hanging leg raise uses your own bodyweight to challenge your low back and abs; doing crunches on a stability ball (aka balance ball, exercise ball, Swiss ball) intensifies the crunch while supporting the low back; training with a medicine ball (slamming it to the floor or into a wall forces the core to contract and produce power); bosu ball is an unstable piece of equipment that demands stability from your core to stay balanced.

How will this help me?

Abdominal conditioning will benefit you in many ways. The muscles of the core make it possible to stand upright and walk, run and play. These muscles help you control movement, transfer energy, shift your body weight and move in any direction. A strong core distributes the stresses of weight-bearing movement and protects your back.

Defining fitness

Find meanings of these fitness terms at www.cindysays.com and www.ymcawv.org: powerhouse/core, core strength, six pack, multifidus bracing, stability ball, erector spinae, rectus abdominis, shoulder girdle, bosu ball.

NEXT WEEK: Heart-smart exercise

Cindy Boggs, fitness presenter, author and Activate America director, has been an ACE-certified coordinator/instructor since 1989.

Send your questions about fitness, training or health to YMCA of Kanawha Valley, 100 YMCA Drive, Charleston, WV 25311, or e-mail cindys...@aol.com.

Look for Cindy's fitness advice book, "CindySays ... You Can Find Health in Your Hectic World" on her Web site www.cindysays.com or contact the YMCA, at 304-340-3527.