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I have seen several references to situps being harmful due to "high compressive lumbar load" and recommending crunches. When researching where the quote came from, it looks like every reference quotes the same paper by a Dr. Stuart M. McGill named Stability: from biomechanical concept to chiropractic practice. The author being a chiropractor pricked my ears since this is a profession which had sponsored beliefs ranging from "vertical subluxations" that can harm everything from backs to your brain to your liver to your chi (and, in the lab, any given pair of chiropractors will identify completely different "vertical subluxations" for the same patient). I don't know if Dr. McGill has a degree in any form of science-based medicine — his various biography pages are coy as to what he has other than a "PhD" — but I'm willing to give him the benefit of the doubt.

That said, has there been an supporting or opposing research on his claims? Is there any proof other than a 1999 paper?

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As a preface, although your concerns about the validity of the field of chiropractic are entirely warranted, it appears that Dr. Stuart M. McGill is indeed qualified. He was a former professor at the University of Waterloo, holding Ph.D., Masters, and Bachelors degrees in Kinesiology (Biomechanics), Kinanthropology (Biomechanics), and Physical and Health Education, respectively. So whilst there appears to be no other literature to corroborate his findings, without performing the bio-mechanical calculations ourselves, it is reasonable for us to accept his claims.

It seems fairly clear from McGill's tone that he does not support the prescription of sit-ups: “...performing sit-ups using bent knees or straight legs is probably not as important as the issue of whether to prescribe sit-ups at all!” However, he states only that “Compressive loads in excess of 3000 N [~300 kg] certainly raises questions of safety for some patients.” The same thing can be said about all exercise. Thus, the question really becomes one of degree. We might reasonably ask, prescribe to whom? And for what reason? McGill's subsequent analysis suggests strongly that he is evaluating sit-ups as an exercise for the general (unconditioned) population and as an abdominal exercise. Furthermore, he is clearly making assumptions about the way in which they are to be performed. And from his perspective, I believe, he puts forward a very good case against sit-ups.

However, that does not imply that sit-ups are inherently dangerous or harmful—only that they are potentially dangerous for a certain subsection of the population, and that there are objectively better choices of exercise for abdominal development. So in order to assess the former question, we should again examine the literature.

Virtually all of the existing data surrounding the link between sit-ups and injury come from the military. One oft-cited study, for example, revealed that 56% of the injuries recorded from a sample of 1,532 soldiers performing the biannual Army Physical Fitness Test (APFT) were from sit-ups. This evidence certainly appears rather damning, especially since running ‘only’ accounted for 32%. However, when we consider those data in their context, the danger of sit-ups becomes rather less clear. That study revealed an injury rate of 7.6%, or one in thirteen—a staggering rate of injury for a test consisting of just three disciplines (push-up, sit-up, and a 2-mile run)! But given the demands of the military, and the seasonal variation in training and conditioning that has been observed, we can safely assume that this observation represents an exception. Indeed, it is notable that the authors of the study concluded that “The push-up, sit-up, and run events of the APFT do not pose a considerable acute injury risk to active duty soldiers.” Clearly the military is willing to accept greater risks than most of us might.

Given their ubiquity in physical training, if sit-ups were inherently dangerous, we would expect a plethora of hard data demonstrating that fact in the literature. But no such data seem to exist. We can reasonably conclude, therefore, that they are not inherently harmful or dangerous.

It is certainly notable that compressive loads may exceed recommendations for the normal population. We should therefore objectively class sit-ups as a moderately difficult exercise, and one appropriate only to healthy-weight athletes with some level of conditioning. And we should further take measures to prescribe or perform technique that would minimise spinal compressive loads and consequent injury—in particular maintaining ‘neutral’ curvature of the vertebral column throughout the movement, both at the lumbar and cervical spine (that is, without ‘crunching’ or pulling the head forward).

On a final note, the sit-up should be understood to be an exercise for the hip flexors, with the abdominal muscles functioning only to support the spine isometrically. This is clear from McGill's article, which summarised the relative contribution of the different contributing muscle groups.

I hope that is helpful.

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    Thank you. That was indeed very helpful. – Sean Duggan Jul 29 at 12:54
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    Great points! The military tests encourage completion of as many situps as possible in a short period of time - a race of sorts. The 'quality' of reps is determined by rules that don't necessarily guarantee the best form. Speed and quantity are paramount. The test is fine for someone with exceptional core strength attained through a variety of core exercises over a period of time who uses proper form. It could be injurious to a novice, someone who is out-of-shape or an individual who uses poor form, which may explain the injury results from the military tests. – DSway Jul 29 at 19:48
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Yes, situps are incredibly harmful.

Why? Dr. Stuart McGill said so. Why is that important...

Stuart McGill is a respected academic on spinal mechanics, and most definitely not a chiropractor!

If you look at that his profile which you linked, he is the Director of the University of Waterloo's Spine Biomechanics Laboratory. The paper you mentioned is peer-reviewed and cited by 39 articles, and he is one of the most published and cited authors on spine biomechanics.

Out of pure interest I have read one of his more recent paper on core strength and back stability, and he is pretty methodical about his work and his paper are filled with actual statistics and descriptions scientific methods.

From a pure broscience perspective, he has been interviewed by T-Nation and Bret Contras and they are look like they lift, so you gotta trust them bro.

There are few names I trust in fitness, and when it comes to core exercises and strength Stuart McGill is one of them. If he says sit-ups are bad (which he does, and backs up with actual peer-reviewed science) then I'd believe him.

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    Bro you lumped Bret Contreras in with broscience? That hurts man. – Eric Oct 24 '14 at 1:39
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    Wow bro, do you even logic? Broscience is based on brologic, which revolves around the ultimate question - "do you even lift bro?". The key proof in Brologic is "Brost hoc ergo bropter hoc", which states that "if they look like they lift, they must know about lifting". Since Bret is huge, and looks like he lifts, he's must know about lifting. Now, just as formal logic and boolean logic are not mutually exclusive, neither is brologic, so there may be other methods of proving Brets credentials. I chose the most efficient method. – user2861 Oct 24 '14 at 1:47
  • Brost hoc ergo bropter hoc lulz – Eric Oct 24 '14 at 1:58
  • Mainly because most of his papers and books have chiropractry in their title? :) And yes, I know he's a professor. That means he has a doctorate. Said doctorate could be in anything, include a D.C. – Sean Duggan Oct 24 '14 at 2:30
  • No, they don't there is one paper (that was targeted to Chiropractors), but none of his books and very few of his papers mention "chiropractor" in the title. You have an unhealthy level of scepticism. – user2861 Oct 24 '14 at 3:04
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Well to get away from vague statements, what do you mean by harmful? Are you asking if situps are inherently bad to your health?

If situps are harmful if you have injuries to the areas involved in a situp?

My personal reasoning is that situps are not harmful. Claims to compressive loading don't make sense as you do them supine - you are under a constant compressive load when you stand. So any loading would have to add up to that level and surpass the max weight you can comfortably carry. (You don't twist do you?)

However, if you normally do a few situps and suddenly decide a 100 situps is what "strong" people do, I would say that is harmful.

Overusing your core muscles (abs) would lead to trunk instability as they would be excessively fatigued and you may injure yourself during or after the exercise as they would be unable to do their role in stability, or in a reduced fashion.

As always, just because a little is good, doesn't mean a lot is better.

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No they aren't. No exercise is harmful if performed with proper technique

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