Somewhere in my box of childhood knick knacks there’s a Polaroid of a boy doing a full split. He is comfortably suspended by the two chairs on either side of him, and there's a foot and a half of musty karate studio air between him and the floor. He, in his white gi, is hovering effortlessly with arms proudly akimbo and a smile on his face. That boy in the photo was me. That boy was I. Yes, I was once card-carrying member of the Full Split Club, and that Polaroid was the first and last time I ever did a split.
At some point during my teens I lost faith in karate class. I could produce a powerful "kee-ya!", but seeing as I was among the shortest and most Jewish kids in my class, it wouldn't have startled anyone. After all, what was I going to do, middle punch them in the thighs? Instead I pivoted to my strengths: video games and non-contact sports.
By the time I got to college, the most stretching I did was to wrinkle my brow. I loved thinking, I loved books, and I got curious about language, sciece, and logic. But even as my mind was being flattened, twisted, and reshaped, my body was beginning to freeze, congeal, and stiffen like stale bread. My posture became stooped, my belly sagged, and I stopped being able to sit comfortably cross-legged. And because all of this was happening to everyone around me, I just thought it was a normal part of ageing. I didn't realize what I was giving up.
Well, I quit my physics PhD -- not entirely by choice, I admit -- and if there's one thing I know from physics, is that when a pendulum swings far in one direction, it's gonna be swinging pretty darn fast the other way too. So it was with me. I decided I was not going to be a stale baguette for my entire life. I was going to take this body and do something with it that I hadn't done since people non-ironically took pictures with Polaroids. I was going to do a split. But first I needed to learn how to stretch, and what I learned about stretching surprised me.
There's a science to stretching
The way Modern Man thinks about stretching is by analogy to modern materials like plastics or taffy: you tug on them with enough force and they deform. If you keep tugging, you get more deformation. Everyone knows that people who stretch tend be stretchy. Maybe all those years of stretching have deformed (i.e. lengthened) their tendons and ligaments. But are we really stretching our connective tissue when we stretch?
When it comes to flexibility training, more stretching is not just more, it's different. The type of anatomical changes you can see depend on how long you train for: days, weeks, months, or years. In fact in the first couple months of static stretching you can expect an increase in range of motion without any anatomical changes. You just get used to the pain from stretching. That's it. We know this because scientists have measured the change in lengths of people's muscles after a stretching program and found them to be the same length as when they started.
This part alone is surprising enough, but let me point you to a disturbing detail about the state of sports science. Basically all of the studies on stretching take place over 12 weeks or less. Which means what they're studying is not tissue elongation, but "stretch tolerance" -- that's the lingo for getting used to the pain of stretching -- and so all of their conclusions can only be applied to that one endpoint. Having more ROM is better, but what if I want to actually lengthen my muscles. Is there a fast way to do that?
Studies on anesthetized patients
You might argue that if I increased my pain tolerance enough I could scissor myself right into a full split. Perhaps what's holding me back is just my poor stretch tolerance, or put differently, being a wimp, but in kind of a subtle, anatomical way.
Some scientists had the idea to study anesthetized patients as part of a study on flexibility. They took patients scheduled for surgery on one leg and tested the flexibility in the other leg before and after anesthesia. The response: essentially no difference. With the nervous system effectively cut off from the legs, the scientists couldn't find a significant effect. The tension was truly structural in nature, not neurological. And since the patients were unconscious, stretch tolerance didn't enter the equation at all, and yet they were still limited.
So while my wimpiness might not be up for debate, I can at least be confident that it's not hampering my splits.
A diversion into muscle tissue
In order to find our ideal stretching program, we'll first need to understand what happens when we stretch a muscle. A muscle is a long chain of fiber-like bundles made of tiny little units called sarcomeres. You can think about a sarcomere like a little piston that can grow or shrink. As it turns out, sarcomeres can produce the greatest tension when they're at their resting length. If you stretch them out too much, or compress them too much, they're not able to produce much tension. And because muscles are made of sarcomeres they behave the same way: strong at their resting length, weaker when stretched or compressed. (If you've ever done bicep curls, you know that the hardest part is when your arm is fully extended.)
Muscles themselves can grow or shrink in response to stress. Hypertrophy is when the muscle increases its cross section by adding sarcomeres "in parallel", but it can also increase its length by adding sarcomeres in series. (I am not, personally, a shining example of muscular hypertrophy, but because I studied hard I can at least appreciate it on some level.)
We also know, from cruel experiments on mice, that muscles can add or subtract sarcomeres in series if they're held in a fixed position for a long period of time. We have apparently been assuming that these results translate to humans who stretch for five minutes a week, which may or may not be true. The key point to take away from this diversion, though, is that if you want to get a lot more flexible, you'll need to do more than just decrease your pain tolerance. You'll need to do something to elongate your muscle tissue.
Horse stance
"In riding a horse, we borrow freedom." - Helen Thompson
I didn't want to spend ten minutes a day for a year to maybe be able to get a full split. I wanted the express ticket to splitsville. And I found that ticket in Thomas Kurtz's book Stretching Scientifically, where I first learned about horse stance.
... talk a little about what horse stance is
Let me first talk about the stretching part, before I talk about the "Scientifically" part, because it's a great example of someone being right for the wrong reasons.
Kurtz has a famous spiel about horse stance. He brings one leg up to show that he can raise it parallel (and anyone can do this.) Then he brings another leg up to show that it can be done with the other leg as well. Then the coup de grace. I'll let him say it in his own words:
Now, what have you done? You have done “half side splits” with both your legs! You have proved to yourself that both your hip joints have all the mobility (range of motion) needed for a full side split! You have also proved that the muscles of each of your legs are already long enough for a side split. You know that no muscle or ligament runs from one inner thigh to the other (or, if you don't know it, you can ask your doctor). So, what keeps you from doing the whole side split with both legs spread sideways at the same time? Your nervous system, that's what! I will not bore you here with explaining how that happens. The important thing is that with the right stretching method you will teach your nervous system to let you do side splits any time, without any warm-up.
There are two problems with this. First, the line about the boring details is giving me serious Fermat vibes. I would love to be bored with the details, but he has never published these boring details anywhere as far as I can tell, perhaps because the margins of the page were too small to contain them. Plus, as I mentioned above, experiments show that the nervous system has only a marginal effect on flexibility. Second, I don't find it entirely convincing that we have done two "half splits" because the angle of your pelvis when you do this exercise is not the same as it would be if you brought your leg out to the side while sitting down. It's slightly rotated around the vertical axis.
What Kurtz has, however, are results. He claims that with the right training you can do a split within a few months, if your anatomy allows for it. So why is horse strance training so effective, if it's not the nervous system?
Strength if flexibility, and flexibility is strength
The answer that I've come to is the following syllogism.
If a muscle is strongest at its resting length, and you train a muscle to be stronger at a longer length, then you must increase its resting length.
In the horse stance you hold yourself up using your hip adductor muscle at their maximum length. By strengthening them at their maximum length, you are increasing their resting length. And this is where the quick increase in flexibility comes from. It turns out that the combination of strengthening and stretching (which is what horse stance does) packs on the sarcomeres faster than anything else (and also dampens the pain response).