Should You Stretch Your Hamstrings?

Should you stretch your hamstrings?

Generally, I say “probably not”.

In this post, I am going to explain why stretching the hamstrings is often not advisable.  I’m going to focus on the left hamstring and approach the matter from the perspective of Postural Restoration®.

What does the hamstring do?

Three hamstring muscles labeled with blue arrows.

Three hamstring muscles labeled with blue arrows.

What is little appreciated about the hamstrings, and muscles in general, is that they play multiple roles.

What most everyone is familiar with is the “prime mover” role. Muscles move us by contracting and pulling bones closer together. The hamstrings main role as a prime mover is to move the legs back and extend the hip forward. These are sagittal plane movements and comprise most leg based training.

  • Hip extension. This is the motion your hips do when you get up out of a chair or come out of the bottom of a squat. Your hips move forward as your legs move backwards. It’s the movement that pushes you forward as you walk and run.
  • Knee flexion. Think leg curl. Your calf moves closer to the back of your leg.

That’s what everyone learns.

What is less appreciated, but hugely important, is the hamstrings role as movers and stabilizers of the pelvis and internal and external rotators of the femurs.

These vitally important functions are usually an afterthought, yet without them you will have a non-functioning pelvis. These movements are frontal and transverse plane movements. When you lose frontal and transverse plane movement at the pelvis, bad things will happen: back pain, knee pain, shoulder pain. The list is endless.

Acetabulum/Femur Anatomy

Your upper leg bone, called the femur, attaches to the ilium at a location called the acetabulum. Remember, the acetabulums are part of the pelvis. The left and right iliums comprise the two biggest bones of the four-boned pelvis (picture is in the next section).

You can’t say pelvis, or iliums, without implying acetabulum and vice versa. They are the same bones.

The alignment of femur in the acetabulum and the alignment of the acetabulum on the femur are central to Postural Restoration Institute’s® approach to restoring proper movement patterns in the human body. At first glance, you might wonder why I differentiate between femur/acetabulum alignment and acetabulum/femur alignment. Aren’t they the same thing?

picture of an acetabulum and femur. Essential for Postural Restoration exercises

The femur attaches to the pelvis at the acetabulum

No. They aren’t. A femur moves in an acetabulum, but an acetabulum also moves on a femur. These two motions are happening all the time. Unfortunately, the movement of the femur in the acetabulum is what most rehabilitation and performance professionals look at and completely overlook how the acetabulum moves on a femur. Both are important.

The inside portions of the hamstring, the semimembranosus and semitendinosus, rotate the femur internally on the acetabulum. The outside portion, the biceps femoris, externally rotates the femur on the acetabulum.

On the other end (remember that muscles exert influence on both ends) the hamstrings move the acetabulum internally on the femur. Understanding this concept was the key to me restoring my lower back health.

When the hamstrings no longer internally rotate the acetabulum on the femur, we stop moving correctly. You need proper “acetabulum movement on the femur” at the same time you get proper “femur movement in the acetabulum”.

You can’t have a one-sided relationship. The femur and the acetabulum/pelvis are married together. Both must be dynamic and moving. If one stops playing its proper role, a dysfunctional relationship will follow that will affect the rest of the body.

Stabilization of the Pelvis

Not only do hamstrings move our femurs, they also act as stabilizers.

Very rarely do we think about the stabilization factor.

The hamstrings stabilize both the knee and the pelvis, and it’s the hamstring’s stabilization role of the pelvis that is of most concern.

The pelvis consists of four bones: the left ilium, the sacrum (between the iliums in back, not labeled), the right ilium, and the pubis (between iliums in front, not labeled). All four bones move independently of each other and on each other.

The human pelvis.

The word pelvis indicates some sort of solidity. But the pelvis is not solid. If it were, we would not move. Importantly, the pelvis moves in three planes of motion: sagittal (forward and back), frontal (side to side), and transverse (rotation).

Your pelvis is what connects your upper body and lower body. So it’s very important that it moves correctly and is stable enough to allow powerful leg and torso movements. If you have ever heard of the phrase “you can’t fire a cannon out of a canoe”, it’s a good analogy.

If your pelvis isn’t stable, it’s like you are trying to build a house on an unstable foundation. Problems will undoubtedly arise.

And a pelvis can’t be stable unless the hamstrings can internally rotate the acetabulum on the femur. If you have weak and stretched out hamstrings, your pelvis will be unstable.

The pelvis runs the show for humans. What goes on at the pelvis: the position it is in and how it moves, affects every other area of the body.

The reason is simple: everything from your head down to your feet, not to mention the way you breathe, is connected to the pelvis. As I’ve mentioned, your legs sit inside the part of the ilium called the acetabulum.

Because the human body is better thought of as a linked chain than a collection of separate parts, what happens at the illium will affect what happens below:

Illium => acetabulum => femur => knee => tibia=> ankle => foot.

It also directly affects what sits above it via the sacrum:

Ilium=> sacrum => spine=> rib cage => shoulder blade => neck => head

If there is a limitation of movement, weakness, or instability anywhere along the chain, compensation will have to occur.

  • If there is a limitation of movement somewhere, that movement will have to be found somewhere else.
  • If there is instability somewhere, other areas will have to stabilize more to make up for the lack of stability. Too much stability in a joint is not desirable as the joint can not adapt quickly to an ever changing environment
  • Weakness somewhere will force other muscles to work harder.

Put all of this together, and make it go on for too long, and you’ll likely end up with some injury or pain.

Now that we can see that pelvic stability and movement is important, where do the hamstrings fit in?

The Left AIC Pattern

In the typical Left AIC pattern as identified by the Postural Restoration Institute®, the left pelvis is forwardly rotated compared to the right. The overall orientation of the pelvis is to the right. To better visualize this, stand up and push the left side of your pelvis forward. Your body will now orient to the right.

Virtually all humans will be in this asymmetric pelvic alignment to one degree or another, so don’t think this doesn’t apply to you.

This is what the pelvis looks like in the Left AIC pattern.

Left AIC pattern effect on the pelvis.

Left AIC pattern. Left ilium (left side of pelvis) is rotated forward (flexed) compared to the right.

In this position, the left hamstring is lengthened and weak.

This is because when you rotate an ilium forward, the attachments of the hamstring–at the underside of the pelvis and below the knee, move further apart.

Due to the increased distance between attachment sites, both the lateral hamstring and the medial hamstrings will both be in a permanently stretched, and thus weakened position.

From this perspective, we have an unstable left side of the pelvis and the left femur is often unstable as well. Stretching your left hamstring will only serve to destabilize the pelvis and left leg even more.

This is not a desirable state of affairs.

What if your hamstring feels tight?

There are cases where someone who has very stretched out hamstrings feels like their hamstring is tight. So they stretch it more. The fact is that if you get more than 90 degrees on a straight leg raise, your left hamstring is not tight. In fact, it is stretched out and rather useless, especially on a pelvis that is in a Left AIC pattern.

What these types of people are likely feeling is increased neural drive to the hamstring. This is when the central nervous system’s signals to the hamstring are in overdrive.

The CNS senses the instability in the pelvis and is telling the left hamstring to work harder to stabilize the pelvis. But the left hamstring is in no position to do so. It can’t overcome the flexed state of the left pelvis and overactive hip flexors.

It is likely that this increased neural drive is being interpreted by someone as “tightness”. So they keep stretching, further weakening the left hamstring and destabilizing the left pelvis. It becomes a vicious cycle of stretching and destabilization.

What’s the Solution?

First, stop stretching. If the straight leg raise is at 90 degrees or more, you don’t have a tight hamstring.

Second, ideally you would reposition your left pelvis to get it into a more neutral resting position. This would immediately put the left hamstring into a position so that it can now start stabilizing the pelvis effectively. The constant feeling of tightness might then cease. I say “might” because what two people sense or feel, and how they personally interpret these sensations, is not always the same.

Third, we would want to strengthen the left hamstring to start providing stability to a better positioned left pelvis. Trying to strengthen the left hamstring when the pelvis is in the Left AIC pattern will not actually help. It may just serve to neurologically strengthen the aberrant pelvic position and recruit more compensatory muscle strategies.

Just doing these three things can have a dramatic impact upon our ability to move, develop power, and stay injury free.



  1. Pam Heimann says

    I am very interested in your website. You do a very good job explaining the complicated positioning of bones and muscles. If possible, I’d like your opinion on my poorly aligned pelvis! I have scoliosis (believed to be from birth) that never gave me trouble until my late 40’s. I am now 55 and working very hard at eliminating the pain in my hips. My twisted spine is causing my left pelvis to hike up and slightly BACK, my left shoulder is high. I first sought help because of extreme lower back pain. PT did wonders and eliminated the back pain but the hip pain remained. A chiropractor’s help greatly reduced the hip pain (mostly left side) and has given me consecutive pain free days. Most recently, weekly yoga has also helped. I’m not sure if the resetting movement that you show is right for me since my left pelvis is pulled back – not pushed forward. Does this make a difference? Thanks for your helpful information.
    My goal is to be pain free by the time I retire!

    • admin says

      Hello Pam, yes the repositioning exercise is generally correct as is. Often times people think their right side is forward compared to the left but upon testing it shows that the left is forward compared to the right. It’s very rare that a right side is forward compared to the left simply because of how our body is arranged internally. It goes back to the fact that the right diaphragm is much bigger and stronger than the left diaphragm, and hence pulls us to the right.
      My recommendation would be to see a PRI certified PT. They are listed on the PRI website. They’d definitely be able to help.

  2. Jaji says

    Hello Neil,

    I’m not sure if I had these issues I’m experiencing prior to an injury sustained doing Brazilian Jiu Jitsu or after. Nevertheless it looks like a partial calf tear on the inside area I’ve had for many years now. All problems I’m experiencing is on left side of body..heel doesn’t feel like it contacting ground, calf, hamstring, hip area, basically all the way up to jaw is tight, hip is rotated and spine twisted.
    I’ve tried Gonstead Chiro and A.R.T and still having issues.
    My question is if I’ve sustained an injury to calf, would any of these exercises/technique bring Balance to my body?
    As you mentioned in one of your posts..the compensation is definitely at hip, L5 area, neck etc.
    Do you think continuing Active Release Technique and Gonstead (cause they did help somewhat) and maybe focusing on specific areas would be good idea?
    The area between lower back in left side and lower rib cage feels caves in specially while I sit I’m guessing do to rotation and twisting of spine.
    Any thought would help..I’m at a lose, cause I know I’m trying things that should help as it has others I know..but the calf situation is really throwing things off I think and last thing I want is to go under the knife for calf.

    • admin says

      Almost all PRI exercises work to restore strength and movement on our left-side. PRI recognizes that we tend to overuse the right side of our body, and in a very real sense we become disconnected from the ground on the left side. Being able to sense your left heel on the ground is a really big deal. If you are in the US, your best bet is to find a PRI provider listed on the PRI website.

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