Millions of Americans are taking up core-strengthening exercises including yoga and Pilates. Many are enthusiastic but inexperienced novices who fail to protect their spine while learning these practices.

In fact, in a recent national poll conducted by Harris Interactive, more than half of all Americans suffered from back pain within the past month, with nearly 16 percent blaming exercise.

In addition, one out of four people were unable to engage in vigorous physical exercise due to back pain.

"Our physician members are certainly seeing an influx of back pain cases and injuries stemming from the popularity of yoga, Pilates and martial arts," said Thomas Errico, MD, President of the North American Spine Society (NASS).

"Core-strength exercises are a fantastic way to improve posture and balance, increase flexibility and overall physical fitness and reduce stress," Errico said. "Core strengthening is often a component in back-rehabilitation programs and, when properly performed, may help prevent back injury.

"However, it is important for people practicing these types of exercises to understand how improper technique or even simple mistakes can result in back pain and possible spine injury."

Finding a good instructor for your core-strength program is time well spent. According to Andrea Ferretti, yoga instructor and health and wellness editor at the nation's leading yoga publication, Yoga Journal, reputable instructors should always ask new class participants if they have had injuries, surgery or special needs.

"Many yoga poses can be modified to accommodate individuals who suffer from back injuries. But there are certain poses that should be avoided too, depending on the severity and type of injury. In many cases, yoga can ease and even alleviate back-pain symptoms."

Many NASS members are experts in the field of exercise and rehabilitation. SpineLine medical editor and NASS board member Stuart M. Weinstein, MD, says: "Any patient, regardless of age, can participate in some form of exercise. The benefits of core strengthening include improvement in function, whether at home, work or on the playing field.

"For patients with chronic low-back pain, functional gains are more important than just focusing on strength and flexibility. Successful core-strengthening programs emphasize practical performance of strength and flexibility exercises."

To help those interested in improving core strength to protect their spines while becoming physically fit, the society developed simple tips and suggestions:

* Always get proper instruction on the correct poses from a certified instructor. Says Yoga Journal, it's perfectly fine to ask your instructor where he or she received training and how many hours of education was received to become a certified instructor. In class, speak up, ask questions! It is better to learn proper technique than risk an injury.

* Always keep proper head, shoulder and pelvis alignment. Exercises that focus solely on abdominal crunches ignore many of the other supporting muscles of the spine, pelvis and hips.

* Individuals beginning a new exercise program should check with their doctor first -- especially if they had back or neck pain. Ask about ways to protect your spine and tell him of any recent and all past injuries.

* Commit a modest amount of time and energy. The most challenging and physically demanding core exercises should be reserved for advanced and experienced exercisers and athletes whose activities require maximal physical output.

* Back pain sufferers should avoid exercises that place the spine in extreme forward bending or combined bending and twisting. These place excessive stress on the intervertebral disks.

It may take some time to reap the full benefits of a yoga, Pilates or other core-strength exercise program. Learning to use one's muscles to support -- not stress -- the back takes time, patience and commitment, too.

NASS is the nation's leading nonprofit, multidisciplinary medical society dedicated to advancing spine care. Basic instructions for home exercises are on the For Spine Patients section of www.spine.org, or purchase the patient education books Know Your Spine and The Spine Owner's Manual at Amazon.com.