After three decades of ﬁguring how out the spine works, Stuart McGill has come to loathe sit-ups. It doesn’t matter whether they are the full sit-ups beloved by military trainers or the crunch versions so ubiquitous in gyms. “What happens when you perform a sit-up?” he asks. “The spine is ﬂexed into the position at which it damages sooner.”
The professor of spine biomechanics at the University of Waterloo knows a thing or two about snapping spines. In his lab, McGill proudly shows off a machine that’s probably created more disc herniations than any other in the world. “We get real [pig] spines from the butcher and we compress them, shear them and bend them to simulate activities such as golf swings and sit-ups, and watch as unique patterns of injury emerge.” A disc has a ring around it, and the middle, the nucleus, is ﬁlled with a mucus-like liquid. Do a sit-up and the spine’s compression will squeeze the nucleus. On his computer, McGill shows how the nucleus can work its way out of the disc, hit a nerve root and cause that oh-so-familiar back pain. “From observing the way your total gym routine is performed, we can predict the type of disc damage you’re eventually going to have.”
While there are lots of ways to injure a back, the sit-up is an easily preventable one. According to his research, a crunch or traditional sit-up generates at least 3,350 newtons (the equivalent of 340 kg) of compressive force on the spine. The U.S. National Institute for Occupational Safety and Health states that anything above 3,300 newtons is unsafe.
So McGill suggests replacing sit-ups with exercises to strengthen the core while not bending the spine:
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Want more awesome McGill resources? Visit Craig Liebenson's site for a complete list of audio, video, and written articles outlining the most up-to-date research on athletic performance and core development.
Learn why crunches are hurting your back and why your traditional core exercises are missing the mark when it comes to improving athletic performance at the 2013 BSMPG Summer Seminar featuring Professor Stuart McGill as keynote speaker!
Hurry - this seminar will sell out again this year. Discounted prices end December 31st, 2012!