There’s a common notion in existence that suggests that sit-ups can help stabilize the spine and, therefore, help prevent back pain.
In fact, I’ve had dozens of patients proudly profess that sit-ups are in their daily exercise routine as part of their own self-made back care program.
So the question is – what is the role of sit-ups in helping to prevent back pain?
It’s a good question – an important question. Fortunately, it’s a question that has been well-studied, and answered beyond any reason of doubt. One of the leaders – if not THE leader - in spinal mechanics in the world is Dr. Stuart McGill, a professor of biomechanics at the University of Waterloo.
In Dr. McGill’s studies, it was found that regular straight-legged sit-ups put approximately 3500 Newtons of force (or about 730 lbs) of compression on the spine per sit-up. (By the way, we don’t want to have excess compression on our spines as it will lead to injury). To put those figures into perspective, the National Institute of Occupational Safety and Health has set a limit of compressive force on the spine for any action in the workplace to not exceed 3300 Newtons.
In other words, a single sit-up places more (damaging) compressive force on the spine than the legally maximal limit allowed in the workplace!
In an effort to counter this, some people have recommended substituting bent-leg sit-ups for straight-legged sit-ups, with the theory essentially being that the bent leg will take pressure off of the spine, and will, thus, reduce the compressive force on the spine. Guess what? This was studied too, and the compressive forces were found to be similar to that of the straight-legged sit-ups. Not good.
In spite of these findings, some might counter by suggesting that the pay-offs of working the abdominal muscles outweighs any risk of injury. This is completely wrong for multiple reasons. Firstly, you should note that Dr. McGill and colleagues have measured the muscle usage patterns of various abdominal muscle groups in response to many different abdominal exercises. It turns out that the sit-ups (both straight-legged and bent –knee) are not any better at working the core musculature than other measured exercises. In fact, for some important abdominal muscles, the sit-up exercises are less effective. So the “pay-offs” of these exercises are not even that good anyways.
If we couple the fact that the sit-ups are not especially effective at training the important core musculature with the proven truth that they put an exceedingly high compressive force on the spine, then you understand where I am going with this – sit-ups are bad news. Under no circumstance will I recommend them.
I was recently at a seminar in which Dr. McGill spoke. He reminded the delegates that it’s not so much that the compressive forces of sit-ups on the spine MAY cause an injury, rather, it’s that they, in fact, WILL cause injury. The only question is – when.
At some point, with enough repetitive compressive force is applied to the tissues of the spine, it will give out. Guaranteed.
In future postings I will discuss real “core stability”. I will describe what it is, as well as why it is important and necessary. Further, since I have already shot down the usage of sit-ups in any exercise program, I will discuss some GOOD core exercises – exercises that have passing grades in the scientific literature. These are exercises that will help prevent injuries, rehabilitate existing conditions, help you perform daily tasks comfortably and safely, and enhance sports performance.
Stay tuned.
In good health,
Dr. Michael Carney
