Hamstring Flexibility Does Not Prevent Back Pain

Hamstring flexibility is not correlated with back pain (with standing activities, running, and most sitting).

An interesting question is why do some people feel better with bending over forward - even if it doesn't affect flexibility. Or bending forward for what are called core strengthening exercises - even if strength does not change.

Usually pain returns when they go back to standing and walking and activities. Even when they do get more flexible and strong. Why? Where did the confusion come from that mistakenly led to popular practice of hamstring stretching and core exercises for back pain?

 

The Quick Story

I am a research scientist in physical ability in all kinds of environments: heat, cold, altitude, undersea, acceleration, injury states, and more.

I did initial work (pilot studies) that found no relation between amount of hamstring flexibility and incidence of lower back pain.

My results were not well received. I was boo'ed at a prestigious sports medicine conference.

I quietly put my results on the shelf and continued for years to re-check existing studies, collect data, and see what else might be involved.

In the meantime, respected names in spine research found the same results in their studies - no relation between hamstring flexibility and incidence of back pain.

 

I had already conducted years of studies that found that standing with a posture that allows too much inward curve of the lower back (hyperlordosis/ swayback) causes pain, usually during standing activities. The overly angled lower spine physically compresses, pinches, and shortens the area making it ache, and eventually damages the spine joints called facets. More about this is on my Back Pain With Standing page.

 

Middle and right show two kinds of swayback. Both angle the lower spine and can make the area ache with standing activities. Left is neutral spine.

 

In continuing work, I found that during the act of bending over forward to stretch or exercise, the too-large inward curve of the lower back reduces during those few seconds of the move. The brief reversal of symptoms became mistaken for cure or healthy treatment. Hamstring stretching became further confused with hamstring flexibility. Like "whispering down the lane" it next changed into hamstring flexibility prescriptions for any kind of back pain.

Instead of knowing to stop the poor posture that causes the pain in the first place, people continue damaging their back with swayback, getting pain, and pursuing various treatments.

When people go for various treatments, they lie down with knees bent. Of course the pain will lessen. They are reducing the lower back curve (for that moment). It does not matter if they get needles, or oils, or massage, it was lying down and reducing the lower back curve that stopped the cause temporarily. Then claims are made that the treatment must work, because pain comes back, and people feel better to go to their repeated treatments. However they are not stopping the real cause when it matters - during the rest of their day.

When people stand up and go back to standing swaybacked, the same lumbar compression and shortening brings back the same pain. Bending over to stretch, or lie with knees bent either relaxing or exercising, are not cures or prevention.

 

It was mistaken identity.

The resulting myth of fixing back pain with hamstring stretching, treatments, or core exercise would be harmless (except for taking time and money), except that without stopping the painful posture of swayback, pain and damage from swayback accumulates.

Another problem is that the same forward-rounding and forward bending (flexion) during conventional hamstring stretches and core exercise puts herniating forces on discs. It is one of several reasons that hamstring stretches and "hip hinges" are more commonly a cause of lower back and disc pain, not a fix. They are not even healthy ways for temporary relief.

 

Other smaller factors too.

If you injure a hamstring, it may hurt at the place it attaches to your "sit" bones. That pain gets mistaken for sciatic pain. Stretching the hamstring can help the injured hamstring and the pain, depending how the stretch is done. More on this on my Stretching Smarter page and Fix Lower Back Pain page. Bending over (or forward) to stretch the hamstrings gets mistaken for relieving sciatica, when too much bending over forward is usually one of the key causes of hurting discs enough to cause true sciatica. Other times, tightness in the posterior hip and upper leg makes pain. Hamstring stretches can, incidentally, stretch those areas and take away that separate cause of pain, leaving people to wrongly credit the hamstrings. Seems harmless, except that true causes go unexamined and un-prevented, leaving people to take much time and money to do "cures" of stretches and core exercises hoping something will work, accidentally or not, when they are not preventing the cause, dooming them to have repeat pain and accumulation of damage.

 

What To Do Instead?

If you get lower back pain after long standing, walking & running, and feel that bending over forward, or sitting, or raising legs brings relief and stretches out the ache, you probably stand with too much lumbar arch (swayback / hyperlordosis).

Swayback is a poor posture, not a structural condition. Prevent the entire problem with neutral spine which is a smaller inward curve. Then you don't compress the lumbar spine and don't cause back pain in the first place.

Neutral spine is a more comfortable position that you keep all the time instead of sagging into swayback. Neutral does not mean to push the hips forward, or to tighten, or compress your abdomen. Those things make more stiffness and discomfort. If you feel pain trying to move to neutral you are doing it wrong. Check this page on Fixing Back Pain With Standing - What Abs Really Do for pictures and movies so you can see the differences. Make sure to understand, not just force a strange stiff new posture.

Then, to get a healthy lower back stretch built into your regular day, use good bending, explained on the Fix Lower Back Pain page and in my books. For effective and functional hamstring stretches without flexion, see my book Stretching Smarter Stretching Healthier, with one helpful stretch in my web site Stretching Smarter article. It is a whole world of healthier smarter movement mechanics and daily habits. You won't get the pain and will also move and stretch in healthier way to stop future damage.

 

 

Do Tight Hamstrings Change Hip Tilt?

Not when you are standing. It is easy to see this for yourself.

Hamstrings attach to your "sit bones" which are the "bumps" on the bottom of your pelvis. There are claims that tight hamstrings pull the sit bones downward and/or inward so that the pelvis tilts posteriorly. To see if this really happens, you can easily check people with tight hamstrings. Some allow (or intentionally produce) a poor posture called anterior pelvic tilt - shown by the yellow lines on the model in the photo below. If tight hamstrings did pull the pelvis down in back, then people with tight hamstrings (most people) would not (and could not) tilt the pelvis anteriorly (the front tilts downward), producing this poor posture in the photo below:

 

 

If it were true that tight hamstrings pull the pelvis down in back, it would prevent anterior tilt, show in yellow lines of photo above. You can see that the pelvis is UP in back, not pulled downward. Many people stand with this anterior tilt whether they have tight hamstrings or not. My page with information to fix an anterior tilt is: Back Pain With Standing. 

Consider all the people who do have tight hamstrings and also a too large lumbar angle (tilt their hip forward / swayback) - maybe even yourself. Why didn't tightness prevent the swayback or even pull to neutral spine? Because hamstrings don't work that way, and swayback can occur from tightness in the front of the hip, not the back. It can also occur from tightness in other places, and even without any tightness (when it's just slouching).

 

When Do Tight Hamstrings Change Hip Tilt?

When you sit on the floor with legs straight out in front of you. In that position, tight hamstrings can't lengthen enough to let the pelvis sit level. The pelvis tilts posteriorly and the lower back rounds, as in my drawing of Backman! below:

 

Sitting with your back rounded for long periods presses discs outwards and makes muscles ache. In this case, you could blame tight hamstrings for the ache, but it is the bad sitting. Most people don't sit on the floor with legs straight out, they sit in chairs with knees bent. Hamstrings are not involved if you sit with your back rounded when your knees are bent. In that case, it doesn't matter if your hamstrings are tight not not, you are just slouching and that is what hurts.

 

Tight hamstrings can also restrict kicks when standing. When people stand and kick one leg high up in front, if their hamstring is tight, they will usually round their back to compensate - the movement has to come from somewhere, and since it is not coming from the leg, it comes from the back. In this case, high hard repeated kicks, repeatedly forcibly rounding the spine could potentially make pain. In that case, tight hamstrings would be involved. However it is not the case as a generality, when sitting in chairs, or cross legged on the floor, or standing, or for most exercises, and so on.

 

When Hamstring Pain Is Confused For Back Pain And Disc Pain

Another possible reason hamstrings are thought related to back pain is when an injured hamstring is confused for injury somewhere else nearby in the back or posterior hip. A hurt disc commonly hurts deep in the posterior hip - in the buttock cheek - even if the disc itself is physically located higher up.

A hamstring "pull"can also be confused for sciatica. If a "pull" (strain or tear) occurs where the hamstring attaches to the hip - on the "sit bumps," the pain of a hurt or tight hamstring can wrongly be thought to be disc or lower back pain, even S.I. pain. The term "lower back pain" usually encompasses the posterior of the hip, so that records of pain may say "lower back" pain and would be accurate for the general location, but not the cause.

A tight or shortened hamstring or a spasm may yank at the attachment  (on that sore sit bone) when extended, as when taking long or high steps, kicks, or even during a "straight leg raise test" for disc, and felt in posterior hip / buttock cheek, making a sore lower back. Disc herniation also hurts with the spine flexion that often occurs with these same moves.

Pain that goes down the back of the leg from a hurt hamstring may be confused for pain down the back of the leg from a disc impinging the nerve. ( It should not be confused when you know what you are doing, but often is).

A good differential is needed to identify a hamstring component from all the other reasons. Also, several different injuries can occur at the same time. That is sometimes why a scattershot (but wrong) approach of stretching sometimes helps for one reason, even if the main cause is something else. Then "pain comes and goes" or "it helps a little." Identifying and fixing all the contributors is needed. It's better to understand and use direct correct fixes to stop damage quickly, than let time pass in pain trying random things.

 

 

Disclosure and Conflict of Interest Disclaimer

This study was not funded by anyone or any agency, and has no financial relation or obligation to anyone. Funding agencies have gone out of their way to meticulously ignore me.  I have no financial relationship with any manufacturer, vendor, service or product provider discussed in this study. These studies were done before I wrote the book The Ab Revolution. The training manual that became the book was the result of the findings of my work, not the other way around. The book is also not commercially funded or related to any product sales. The story is here  - look for "A Short Story of My Work Developing These Methods."

 

 

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The Exciting Details

To get to the more exciting part, skip this and scroll down to "What Does This All Mean?"

 

The Hamstring Studies

1. My Pilot Study - I Found No Relation Between Hamstring Flexibility and Lower Back Pain:

It was so often repeated that you have to stretch your hamstrings to prevent or fix back pain, but why? I set out to find if there were any relation between the two. People often repeat the mistaken idea that tight hamstrings tilt your hip that reduces the lumbar angle, making back pain, but hamstrings don't work that way and if they were that tight, you couldn't take a step forward. (Plus if that were true, the prescription would be to make hamstrings tighter to reduce the too large angle, called hyperlordosis, which causes much lower back pain). Many years ago, I looked at 167 of my patients and students. I carefully measured hamstring flexibility and noted if they had back pain at the time, or at any time in the past. Running the data comparing flexibility to incidence of any lower back pain, resulted in no relation, no correlation, nothing that linked the two.

Quick overview of flexibility measurement (continuous data measures):
For these purposes, zero degrees is lying flat on your back with both legs down on the floor together,
45 degrees is one leg lifted to diagonal, 90 degrees is leg able to stretch to perpendicular - pointing to ceiling, and so on.
I collected flexibility in degrees - continuous numbers from zero to 180 if they lifted leg all the way back to their ear in a lying down split.
I measured flexibility in the dominant leg, non-dominant leg, and both legs together to make it more like a "sit and reach test" but preventing the lower back from flexing or rounding, to better isolate hamstrings.

 

I presented my work at scientific conferences and they practically threw tomatoes at me, saying my work could not be true because "everyone knew" that hamstring tightness meant you would have back pain and therefore stretching would fix it and that meant that hamstring flexibility was a  predictor of back pain. There were so many inductive leaps and faulty premises in those statements that it was hard to address them in ways that would appease or enlighten them. These were doctors who were even keeping people out of jobs if they had tight hamstrings. They said that tight hamstrings necessarily meant the people would get back pain, and employers didn't want to pay Workmen's Compensation claims. That's how bad this myth had gotten.

 

2. Then What Happened?

In subsequent years, highly respected researchers did their own studies - and found no relation between hamstring flexibility and back pain.

During that time, I did more work on separating if hamstring flexibility itself, or something in the act or motion of hamstring stretching brought relief. With no correlation between hamstring flexibility and lower back pain, what else might hamstring stretching do or include?

Not a lot of my work is published in journals. I am busy trying to get work done and don't present or publish all (or even much of) my work Publish?? I'm trying to accomplish something here!

For the many who have been asking, I put some of the results of my studies of my patients with knee pain on my Lower Body page and a few of my lower back pain studies on my Ab Workshop syllabus. Here are the results of this study on hamstrings:

 

3. The Next Work - Comparison of Neutral Spine and Hamstring Stretch for Relief of Hyperlordotic Lumbar Pain

PURPOSE
A widespread prescription for lower back pain (LBP) is hamstring stretching. Some patients report relief from hamstring stretching, others, no effect or worsening. A pilot study of 167 subjects found no relation between hamstring flexibility and LBP. Subsequent independent studies confirm no relation between hamstring flexibility and LBP (1,2,3). Disc injury (4) and osteoporotic fracture (5) can be caused and worsened flexion, such as that involved in conventional hamstring stretch.

Previous work determined that hyperlordosis (swayback) results in one form of lower back pain (LBP) by compression of facets and soft tissue, and shortening lumbar height (6,7). Neutral spine (NS) lengthens and unloads, directly stopping LBP(8,9). Momentary incidental lumbar lengthening during hamstring stretch briefly stops symptoms. Spinal stenosis symptoms also often reduce with flexion (7). It is proposed that temporarily reversing swayback with hamstring stretching became confused with the separate entity of flexibility. The purpose of this study is to compare a neutral spine method, Ab Revolution (AR) with conventional hamstring stretching (HS) for LBP from hyperlordosis.

METHODS / ANALYSIS
Pilot study of 167 subjects measured degrees hamstring flexibility using straight leg raise test, compared to nominal measures of active LBP, previous LBP, or never LBP. Of initial 167 N, 113 had active LBP. Of these 113, 92 reported wanting to bend forward, lift one leg, sit, or bring knees to chest to relieve symptoms.

Following the pilot study, a new study group was formed from original subjects. Of the initial Pilot study, four had been lost to follow up. The remaining 88 were divided into two groups: Neutral spine training group called Ab Revolution (AR) N=44, and a group receiving daily conventional hamstring stretching (HS) N=44. Hamstring stretch group (HS) performed hamstring stretches of their choosing or prescribed by their physical therapist twice daily.

Nominal outcome measures of ability to employ neutral spine (NS), flexibility (increase, decrease, no change), and LBP were assessed at day 1, 6 weeks, and 6 months, analyzed using Chi-Square.

RESULTS
Of the Hamstring Stretch (HS) group, 41 of 44 increased hamstring flexibility, and there was no significant lasting reduction in LBP, 39 had brief symptom relief during hamstring stretching but return of pain with upright stance and activities of daily living, 43 of 44 were measured as not using neutral spine when standing or ambulating (no NS). 18 of 44 had increase in LBP.

Subjects using neutral spine training (Ab Revolution or AR) showed significant reduction of LBP during daily activities at day 1, 6 weeks, and 6 months. At 6 months 40 of 44 had no LBP. LBP was not correlated to change in hamstring flexibility in either group.

CONCLUSIONS

1. Incidental lumbar flexion from hamstring stretching, not hamstring flexibility, reduces LBP by reversing swayback - at the time of stretching.

2. Temporary reversal of symptoms from swayback (hyperlordotic lower back pain) occurring during hamstring stretching, became mistaken for relief from the hamstring stretch itself. Hamstring stretching became further confused and combined in practice with hamstring flexibility. Hamstring flexibility prescriptions became further derivative to include any kind of hamstring stretches for any kind of back pain.

3. The temporary bending forward during crunches and other flexion based "core" exercise does not cure back pain through strengthening. The temporary reversal of the original problem of slouching with too much inward lumbar curve provides temporary relief that is mistaken for real change or cure. The pain from hyperlordosis comes back as soon as the person stands and resumes the real cause - not weakness, but standing in hyperlordosis. Crunches and core exercises do not change that. This is why there is only temporary relief from conventional exercises, or chronic pain that "has to be managed through recurring flexion" or intermittent pain that is confusing and "no one understands why it comes and goes." No amount of strengthening or core exercise makes you prevent the hyperlordosis which is the root of this one kind of pain.

4. Hamstring stretching is not curative for lower back pain

5. Hamstring stretching and flexion based core exercises may aggravate specific lower back pain, and over time, create new lower back injury.

6. Lumbar lengthening and restoring neutral vertebral angle through neutral spine technique (AB Revolution AR) gives sustainable pain relief by directly stopping cause of LBP from swayback (hyperlordosis).

7. Using neutral spine through AR is functional; stopping cause of LBP and integrating needed resting and active length of lumbar spine during activities of daily living.

REFERENCES
1 Jones MA, Stratton G, Reilly T, Unnithan VB. Biological risk indicators for recurrent non-specific low back pain in adolescents. Br J Sports Med. 2005 Mar;39(3):137-40.
2. Grenier SG, Russell C, McGill SM. Relationships between lumbar flexibility, sit-and-reach test, and a previous history of low back discomfort in industrial workers. Can J Appl Physiol. 2003 Apr;28(2):165-77.
3. Jackson AW, Morrow JR Jr, Brill PA, Kohl HW 3rd, Gordon NF, Blair SN. Relations of sit-up and sit-and-reach tests to low back pain in adults. J Orthop Sports Phys Ther. 1998 Jan;27(1):22-6.
4. Veres SP, Robertson PA, Broom ND. The morphology of acute disc herniation: a clinically relevant model defining the role of flexion. Spine (Phila Pa 1976). 2009 Oct 1;34(21):2288-96.
5. Tzermiadianos MN, Renner SM, Phillips FM, Hadjipavlou AG, Zindrick MR, Havey RM, Voronov M, Patwardhan AG. Altered disc pressure profile after an osteoporotic vertebral fracture is a risk factor for adjacent vertebral body fracture. Eur Spine J. 2008 Nov;17(11):1522-30. Epub 2008 Sep 16.
6. Bookspan, J. Identifying and Reversing Hyperlordosis as a Factor in Lower Back Pain. Medicine and Science in Sports and Exercise, 39:5 May 2007.
7. Bookspan, J. Hyperlordosis Retraining Method Relieves Lumbar Disc and Stenosis Pain—An Unexpected Finding. Medicine and Science in Sports and Exercise, 41:5, 2009.
8. Bookspan, J. Ab Revolution functional core retraining relieves low back pain more effectively than conventional physical therapy. Medicine and Science in Sports and Exercise, 38:5, 2006.
9. Bookspan, J. Functional Core Retraining Superior To Conventional And Pilates Core Training In Remediating Low Back Pain. Med Sci in Sports and Exercise, 37:5. 2005.

In these references - respected names in spine research found the same results in their studies - no relation between hamstring flexibility and incidence of back pain.

 

 

"Even historians fail to learn from history."
- Professor John Gill - Star Trek episode 52 Stardate unknown, Patterns of Force

 

 

• Study publication (abstract): Bookspan, Comparison of Neutral Spine and Hamstring Stretch for Relief of Hyperlordotic Lumbar Pain J. Medicine and Science in Sports and Exercise, Volume 44:5 Supplement. 2012.
• Study presentation at the 59th Annual Meeting and 2nd World Congress on Exercise is Medicine of the American College of Sports Medicine at the Moscone Convention Center in San Francisco, CA, 1 June, 2012.

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Above, my students Karen and Annie demonstrate the standing hamstring stretch.
Can you spot two positioning mistakes that they (deliberately) are demonstrating for your benefit?

 

1. Karen (left) demonstrates keeping the standing foot turned outward (incorrect) while Annie (on right) demonstrates keeping the standing foot facing straight forward (better stretch).

2. Annie demonstrates curling the pelvis under too much. Karen keeps the hip and pelvis vertical as needed. Make sure you can spot these easy things for yourself, so that you are are stretching what you think you are stretching.

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