Getty Images

The genesis of much of the ab work we do these days probably lies in the work done in an Australian physiotherapy lab during the mid-1990s. Researchers there, hoping to elucidate the underlying cause of back pain, attached electrodes to people’s midsections and directed them to rapidly raise and lower their arms, like the alarmist robot in “Lost in Space.”

In those with healthy backs, the scientists found, a deep abdominal muscle tensed several milliseconds before the arms rose. The brain apparently alerted the muscle, the transversus abdominis, to brace the spine in advance of movement. In those with back pain, however, the transversus abdominis didn’t fire early. The spine wasn’t ready for the flailing. It wobbled and ached. Perhaps, the researchers theorized, increasing abdominal strength could ease back pain. The lab worked with patients in pain to isolate and strengthen that particular deep muscle, in part by sucking in their guts during exercises. The results, though mixed, showed some promise against sore backs.

Video

From that highly technical foray into rehabilitative medicine, a booming industry of fitness classes was born. “The idea leaked” into gyms and Pilates classes that core health was “all about the transversus abdominis,” Thomas Nesser, an associate professor of physical education at Indiana State University who has studied core fitness, told me recently. Personal trainers began directing clients to pull in their belly buttons during crunches on Swiss balls or to press their backs against the floor during sit-ups, deeply hollowing their stomachs, then curl up one spinal segment at a time. “People are now spending hours trying to strengthen” their deep ab muscles, Nesser said.

But there’s growing dissent among sports scientists about whether all of this attention to the deep abdominal muscles actually gives you a more powerful core and a stronger back and whether it’s even safe. A provocative article published in the The British Journal of Sports Medicine last year asserted that some of the key findings from the first Australian study of back pain might be wrong. Moreover, even if they were true for some people in pain, the results might not apply to the generally healthy and fit, whose trunk muscles weren’t misfiring in the first place.

“There’s so much mythology out there about the core,” maintains Stuart McGill, a highly regarded professor of spine biomechanics at the University of Waterloo in Canada and a back-pain clinician who has been crusading against ab exercises that require hollowing your belly. “The idea has reached trainers and through them the public that the core means only the abs. There’s no science behind that idea.” (McGill’s website is backfitpro.com.)

The “core” remains a somewhat nebulous concept; but most researchers consider it the corset of muscles and connective tissue that encircle and hold the spine in place. If your core is stable, your spine remains upright while your body swivels around it. But, McGill says, the muscles forming the core must be balanced to allow the spine to bear large loads. If you concentrate on strengthening only one set of muscles within the core, you can destabilize your spine by pulling it out of alignment. Think of the spine as a fishing rod supported by muscular guy wires. If all of the wires are tensed equally, the rod stays straight. “If you pull the wires closer to the spine,” McGill says, as you do when you pull in your stomach while trying to isolate the transversus abdominis, “what happens?” The rod buckles. So, too, he said, can your spine if you overly focus on the deep abdominal muscles. “In research at our lab,” he went on to say, “the amount of load that the spine can bear without injury was greatly reduced when subjects pulled in their belly buttons” during crunches and other exercises.

Instead, he suggests, a core exercise program should emphasize all of the major muscles that girdle the spine, including but not concentrating on the abs. Side plank (lie on your side and raise your upper body) and the “bird dog” (in which, from all fours, you raise an alternate arm and leg) exercise the important muscles embedded along the back and sides of the core. As for the abdominals, no sit-ups, McGill said; they place devastating loads on the disks. An approved crunch begins with you lying down, one knee bent, and hands positioned beneath your lower back for support. “Do not hollow your stomach or press your back against the floor,” McGill says. Gently lift your head and shoulders, hold briefly and relax back down. These three exercises, done regularly, McGill said, can provide well-rounded, thorough core stability. And they avoid the pitfalls of the all-abs core routine. “I see too many people,” McGill told me with a sigh, “who have six-pack abs and a ruined back.”

The Phys Ed column will appear here in Well every Wednesday and also in print once a month, in the Sunday magazine. In it, Gretchen Reynolds, who is working on a book about the frontiers of fitness, will write about what the latest science can tell us about how to make ourselves stronger, more flexible, less prone to pain and generally fitter and healthier. We want to hear what you think, so stay tuned and offer your comments and questions.