You won’t find “core muscles” on a chart of human anatomy as you will “pectoralis major” and “gluteus maximus.” Core muscles are simply those that girdle your trunk and pelvis. But even though you won’t find them, they’re especially important for maintaining the stability of your body as you reach, stretch, and bend. Building core strength also could improve your posture and may protect you from lower back pain.

The method of exercise known as Pilates, which emphasizes slow, sustained movements that often involve lying on a large inflated ball, certainly works the core muscles. But resistance training provides a more focused and challenging workout that will build muscle mass as well as core strength.

The problem with Pilates

“My reservation is that Pilates may be good for the untrained, but I don’t think the exercises offer the ability to increase strength,” says Gary R. Hunter, PhD, director of the physiology lab at the University of Alabama. “One of the major advantages to resistance training is that you can increase the resistance. You can progress in very small increments and allow the body to adapt. That way you can keep the resistance high."

The disadvantage of Pilates, Hunter says, is that the exercises are based on moving your body mass and weight. “So there’s no way you can increase the resistance unless you change the exercise,” he says. “As soon as you can handle the body weight, you’ll cease to have increases in strength and size of your muscles.”

Exercises to build core strength

Because there are so many muscle groups involved, several exercises are necessary to build core strength. Let’s start with a few exercises for your abs and then move onto exercises for your back muscles. The goal is to repeat the exercises until your muscles are fatigued.

• Sit-ups are the classic exercise for strengthening the abdominals, but some people find that they strain the neck muscles. Correct form is very important. You should start sit-ups with your knees bent and your lower back against the floor. Crossing your arms on your chest produces less strain than locking your hands behind your head. Make sure you bend at the waist as you sit up, not at your neck.
• Most gyms now have a sit-up machine that allows people to perform sit-ups while sitting upright — a position that does not strain the neck. You should first choose a weight that allows you to do 8 to 12 repetitions comfortably and then push the padded bar that is against your chest toward your thighs.
• A back extension machine works the lower back muscles — a difficult group to exercise safely. The movement on this machine is the opposite of that on the sit-up machine: There is a padded bar against your back, which you push backward.
• Back extensions provide another safe way to exercise lower back muscles. Lie on the floor face down with your arms at your side and lift your chest off the floor. If this is too difficult, begin with your arms parallel under your chest, forearms on the floor, and hands pointing forward. Try to use your back to lift your chest off your forearms, but let your arms do some of the work if necessary.
• Leg lifts gently exercise lower back muscles and abdominals. Lie on your back, arms at your side, and lift your legs about 12 inches off the ground. If that is too stressful, lift one leg at a time, and lift it only as high as is comfortable for you.