March 15, 2009
Herniated Discs and Bending
Here's an email I received a few weeks back on the subject of bending and herniated discs. (I've paraphrased it for the sake of brevity.)
I heard years ago that you should never bend backwards because it puts too much strain on the spine. Then just the other day I read that you should never bend forwards because it can cause herniated discs. So now I'm confused.
Is it true that you can damage your spine just by bending in a certain direction?
Thanks for your email. I have also read similar advice and I understand how this could cause you some confusion.
Should You Avoid Bending?
I believe that the human body is designed to bend in all directions. And what's more, I also believe that the goal of rehabilitation is to ultimately restore full function.
So naturally what we're trying to achieve is for you to reach the point where you can safely bend and twist in all directions without fear of injury.
I have heard some people suggest that bending backwards places undue stress on the spine. However, I believe that to be a myth. I have seen no scientific data to support such a notion.
Bending forward is a slightly different story.
For a 100% healthy spine, bending forwards should be perfectly safe. However, if you have degenerative disc disease, bending forwards requires a certain level of caution.
For example, since herniated discs tend to protrude towards the rear of the spinal column, some therapists advise that you avoid forward bending exercises during the initial stages of recovery. This makes sense and it won't hurt you to follow that advice as long as you keep in mind that eventually you will need to revise that policy and begin a balanced exercise program.
Otherwise, you risk developing muscle imbalances that can cause an entirely different set of problems.
What the Research Shows
Based on McGill's findings, even with a less than perfect spine, slowly and gently bending forward should not pose much of a risk factor. He demonstrated that under moderate pressure (260 N) that even with 85,000 flexion cycles (forward bends) discs in test specimens did not become herniated.
This would seem to indicate that, if you have relatively healthy discs, normal everyday activities such as bending and stooping should not cause you problems.
McGill does, however, point out one very important finding...
"Damage to the annulus of the disc (herniation) appears to be associated with fully flexing the spine for a repeated or prolonged period of time. In fact, herniation of the disc seems almost impossible without full flexion. This has implications for exercise prescription particularly for flexion stretching and sit-ups or for activities such as prolonged sitting, all of which are characterized by a flexed spine…"
And elsewhere he states...
"It would appear that the disc must be bent to the full end range of motion in order to herniate (Adams and Hutton, 1982)." 
So, as far as bending forward is concerned, the only danger zone appears to be at the full end range of motion.
All Things In Moderation
I maintain that gentle rehabilitation techniques should be utilized at all times. With that in mind here is a partial list of movement guidelines I suggest:
Never attempt any strenuous activity without warming up first.
Never use force in your stretching routine. Instead, stretch slowly and gently. Use deep breathing and relax into the stretch one-degree at a time. Don't push or force your muscles and ligaments to stretch.
Avoid sudden, high velocity exercises like fast sit-ups and crunches. Instead, always exercise in a slow, controlled fashion.
My opinion is that the best plan is to start out with a balanced exercise program right from the beginning and only alter it if you encounter a special problem. This means a variety of exercises that work the body in all directions.
There will always be exceptions to every rule, but I am not yet ready to accept the idea that bending is somehow harmful or something that should be avoided. I believe that the body was designed to bend in all directions and that there is no reason to fear normal everyday activities.
With all of the above, be sure to check with your doctor or physical therapist before proceeding on your own. There may be extenuating circumstances that require you to modify your particular exercise program.
1. McGill, S. Low Back Disorders, Evidence-Based Prevention and Rehabilitation, 2nd Edition. (p. 44-47) Human Kinetics (2007)
2. Nelson, B. The Herniated Disc: New Concepts and Treatments. Physicians Neck & Back Clinics  http://www.pnbconline.com/research/herinated_disc.htm
3. Nelson, B. Disc Syndromes. Physicians Neck & Back Clinics  http://www.pnbconline.com/research/disc_syndrome.htm
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