As someone who counts herself among the estimated 75 percent of Americans who will experience back pain at some point during their lifetime, I know it’s important to strengthen my core. To that end, I have done thousands of crunches over the years trying to achieve core stability. But without really understanding exactly what the core is and why it is so important to strengthen it, I was probably wasting a lot of reps—and I still get backaches. It turns out that there’s a lot more to “the core” than just abs.

Your core encompasses all of the muscle layers in your trunk and pelvis (see “What is the core?”, below). “All movement, balance, and strength emanates from your core,” says Michael Melnik, MS, OTR, an exercise physiologist in Minneapolis who coaches clients in functional movement to prevent back injuries. The goal of core-stability training is to create a solid foundation for the entire body, which can effectively transfer energy to the limbs and reduce the stress of a lifetime of walking and standing and sitting in front of computers, which can put even more stress on the body.

Most importantly, before you begin to strengthen your core, you need to learn how to feel it. “When you engage your core, you’re not just tightening the superficial abdominal muscles,” says Terri Nishimoto, PCFP, a physical therapist in Denver. “You should feel deep muscles pulling everything in. You should engage your core in any activity that loads the spine; when you do, it should feel like a corset tightening around you. I tell people to imagine pulling their belly button to their spine.”

Core strengthening is fine, in moderation, for pregnant women during the first trimester; during the second and third trimesters, however, women should avoid exercises that involve lying on their backs. Anyone with an injury, weakness, or chronic health condition should consult her doctor before starting any exercise regimen.

The next step is to strengthen it by doing a series of specific exercises that target each of the core muscles. Taking a Pilates, Vinyasa yoga, or FitBall class may be the easiest way to start. No time for classes? Try doing the following exercises at home at least three times per week. You will reap maximum results by being consistent and taking a day off between workouts.

1) Heel slides
Strengthens the transversus abdominis. Lie on your back with your legs straight out. Put your hands on your pelvis to make sure it remains still while you bend one knee and slide that foot up along the other leg toward your butt, contracting your core. Then slide it back down to the starting position. Do this several times, alternating legs.

2) Lower abs marches
If heel slides are easy, try lower abs marches. Lie on your back with your legs raised and knees bent 90 degrees, keeping your back firmly on the floor. (Your lower back should not arch at all. Visualize pulling your belly button to your back while you do these.) Put your hands on your pelvis to make sure it remains still while you slowly drop one foot until it taps the ground, and lift it back up, maintaining the 90 degree bend in your knee throughout the motion. Aim for two sets of 20 reps, alternating legs.

3) Clams
Works the hip adductors and glutes, which is probably where you will feel it. Lie on your side with your legs on the floor, bent 90 degrees in front of you and your knees together. Rotate your upper leg upward, keeping your feet together. Do 15 reps, then switch sides and repeat.

What is the core?
The key muscles that comprise or surround your core are your rectus abdominis, your “six-pack” abs at the front of the abdomen; the multifidus muscles, which lengthen and rotate the spine; the external and internal obliques, which run along the side of the abdomen; the transversus abdominis, the deepest abdominal muscle that protects and stabilizes the spine; the three muscles running along the spine from the neck to the lower back; the hip flexors, located in front of the pelvis and upper thigh; the gluteus maximus and minimus, which are actually at the side of the hip; the piriformis at the back of the hip; and the hip adductors along the middle of the thigh.

4) Plank
Strengthens, stabilizes, and builds muscle endurance in the abs and back. Lie face down resting on your forearms. Push off the floor, similar to doing a pushup, but instead of using your hands for support, your forearms remain on the floor parallel to one another. Keep your back flat and try to maintain a straight line from your head to your heels. If you feel your butt sticking up in the air, tilt your pelvis inward; if you feel it being pulled down by gravity, tuck your pelvis under while pulling your belly in Try to hold this position for 15 seconds, lower and repeat. Work up to 60 seconds.

5) Balance ball exercises
Once you’ve mastered static core exercises and feel ready for a new challenge, add a balance ball to your training toolkit. Because balance balls require that you stabilize them while doing an exercise, they force more muscles to work at once. That’s why these large inflatable balls are considered one of the best tools for core-stability training. To get the hang of incorporating a balance ball into your core-training routine, Nishimoto suggests sitting on the ball and bouncing, and also sitting on the ball and lifting one leg at a time. Once you feel comfortable with it, almost any exercise can be adapted and done on a ball for increased effectiveness. For example, if you can do a solid Plank for a minute at a time, try performing it with your lower legs (shins) on the ball.