Of course some people tend to have really tight hamstrings, and 90 degrees of flexion (assuming the knee is straight) seems like a fanciful idea.

Next we have to define this general term stretching.  When someone does their usual home stretching routine it’s a combination of passive stretching (putting a muscle in a lengthened position without engaging nearby muscles to do so) and active stretching (moving a body part into position with your own muscle contraction).  It’s not intentional about which one they’re using on which muscle group.  It just works out that way based on where gravity is relative to their body.

So, what I gather from the arguments about whether stretching is increasing our range of motion is that people are talking about this, mainly passive, form of stretching.

But before we dive into the mechanics of active stretching, let’s first answer; why would you care?  

One effect of stretching is pain relief.  This is why it feels good.  Passive stretching is actually pretty good for pain relief. Maybe you wouldn’t call it pain because it’s not that intense, but how about discomfort relief?

I think there are two really plausible mechanisms for this relief effect.  The first is that the movement of tissue while stretching reduces ischemia…which is uncomfortable for tissue. (I’ll show you what ischemia is: take your thumb and press it into your opposite forearm with moderate pressure for 5 seconds.  Now take your thumb away.  Do you see the pale mark you made? That’s from lack of fluid movement.  That’s ischemia.)  The second plausible mechanism is that lengthening the tissue could be reducing micro-contractions in the muscle.  You know how if you get a cramp in your calf the most immediate relief comes from doing a calf stretch?  Well it’s like that. Lengthening tissue makes cramps go way.

The other (at least hoped for) effect of stretching is to increase our elastic range and lengthen our tissue.  Lengthened tissue is good because the nerves  and the joints have more freedom.  Which keeps them from getting compressed or torqued out of their desirable alignment, reducing wear and irritation. Increased elastic range is good because if your tissue is more like a rubber band and less like a sheet of drywall it can release absorbed impact through motion.  Also, if your tissue is like a sheet of drywall then it is ischemic and will be prone to injury and degeneration … coupled with an inability to release absorbed impact that could lead to damage.

So, that’s why we care about stretching, and why we care about doing it effectively.

Now, lets talk about the difference between passive stretching and the various forms of active stretching.  I’ll use the hamstrings as an example throughout. I’ve got Leon Chaitow’s book on Muscle Energy Techniques open in front of me and on pages 46 and 47 there’s a table of 32 studies that were done between 1982 and 2011 on the effect that different stretching techniques had on increasing hamstrings range of motion.  The gist of all these studies is that all the active techniques increased range of motion more than passive stretching, but passive stretching did increase length more than those that did nothing.

The first active technique was to passively lengthen the hamstrings to a comfortable end of range and then contract the hamstrings against an unyielding surface then passively lengthen them again.

it’s okay if you didn’t get that.  Go ahead and keep reading.  I’ll explain in more detail below.

The next most effective active stretch was to contract the quadriceps to move the hamstrings into a stretched position, rest (without returning to a shortened position) and then contract the quads again to increase the stretch to the hamstrings.

Now, the best stretch.  

It’s a combination of the previous two stretches.  First you lengthen the hamstrings to their end range of motion.  Next you contract the hamstrings against something solid without shortening them from the achieved range.  Then you engage the quads to increase the hamstrings length.  Shift your stable resistance to account for any increased range of motion and contract your hamstrings against it again.  You can google this as either “PNF stretching” or “contract-relax agonist contract” stretching, or even “contract-relax antagonist contract”.  You’ll get dozen of youtube videos of people confidently telling you how it’s done and every one will vary slightly on the details.  Don’t get bogged down!  It doesn’t really matter that much and it’s okay to experiment.  The main point is this cycle through engaging the agonist (hamstrings) and engaging the antagonist (quadriceps).  It’s causing two important things to happen that don’t happen with passive stretching.  Those two things are reciprocal inhibition  (when the contracting muscle makes its opposite relax) and post isometric relaxation (when the contracting muscle temporarily relaxes afterward).

Despite all the youtube video that show a therapist assisting a client you can actually do this quite well yourself.  Here’s how:

I’ll describe the standing variation of the home hamstrings stretch.  You could do it laying on your back, but the standing variation is nice because you can do it anywhere, which means you’ll do it more often.

1.  Pick a solid object to use for resistance.  The seat of a chair or the back of the sofa work well.  You’ll want an object that is as high as you can lift your leg straight out in front keeping both knees straight.  So go ahead and lift your leg straight out in front of you and look around for a piece of furniture that will fit under your heel.

2.  Stand with your solid object in front of you.  You may want to hang onto something for balance.  Stand facing the object with your pelvis square-on.

3. Lift your leg straight out in front with your knees straight and place your heel on the chair, etc.

4.  Press your heel into the object that’s providing resistance for 10 seconds with 20% of your strength.  You’ll feel your hamstrings contract when you do this.

5.  Rest for a couple seconds. Take a breath.

6.  Contract your quads to lift your leg up off the object.  You may be able to lift it two inches or it may not go up at all.  That’s all okay. The important part is that your quads are contracting.

7.  Have your 12 year old daughter slide a book in the gap between your heel and the chair.  Something that fills the gap that developed between your heel and the chair, etc.  (If you’re 12 year old daughter isn’t handy you could also adjust your relationship to the object providing resistance by tilting forward with your back straight or squatting … which is hard to do on one leg.)  The idea is to maintain any length you gained in the muscle as you start your next round.

8.  Press into the resistance again.

Do steps 4 through 7, 4 or more times. Don’t try to stretch much past 90 degrees.

You can finesse this stretch by either sticking your rear out a bit (this moves the bone your hamstrings attach to farther away) or by focusing on straightening your knee.  Some people can actually flex there hip pretty well, but the knee starts to bend quite early on.  You can also do both of these at the same time, straighten your knee and stick your rear out.  It doesn’t take much of that to make it a much deeper stretch.

How often do you need to do it to benefit?

Good question.  As with most of this stuff, more evidence is needed.  Chaitow cites two studies that deal with frequency of the first active technique I mentioned.  It looks like doing that one once a week will maintain flexibility while doing it 3 or more times a week will result in further increases of range of motion.

I hope that’s useful, not confusing, and not mind-numbingly technical.  As always, if it brings up more questions for you I want to hear them.