Look. Don't stretch. I know your doctor told you to. Your physical therapist told you to. All your friends tell you to. Every magazine published in America has told you to, in articles richly illustrated with indecently radiant fifteen-year-olds, dressed (sort of) as twenty-year-olds, in graceful yoga poses. The implication being, not that you can stretch this way if you're fifteen, but that if you stretch this way you'll look fifteen.
We'll leave aside for the moment why you'd want to look like you were stuck in the most unhappy, self-absorbed and useless stage of your life. You do: so do I. We're stupid. But that's not what I want to talk about. I want to talk about stretching, and why you shouldn't do it.
Here's the story as most people hear it: because you're stressed out, you tense your muscles, which makes them (as we learned in eighth grade science class) short. And in a process vaguely but devoutly believed in, your muscles somehow stick that way. As your mother told you your face would stick that way when you took to making horrible faces. So now you have tight muscles, and they're prone to injury, causing you pain, and making it hard to move.
Presented that way, the solution looks obvious. The muscles are too short: well, we'll just stretch them out. Make them longer. Problem solved. Maybe it will hurt a little, but you deserve to hurt, because you inflicted this tightness on yourself by not being radiantly, serenely fifteen. After you've expiated all that sinful stress, and atoned for this self-abuse, you'll be blessed, your body will be fifteen, everybody will love you, and your body will no longer hurt.
Now, unfortunately, it's precisely people who are prone to abuse themselves to whom this story will sound most convincing, and they will swing with gusto into abusing themselves by stretching out painfully, trying to force their muscles into a relaxed state. And they will injure themselves, over and over.
Let's back off a little and look at what really happens when your muscles are "tight," and why stretching is often the very worst thing you can do when they are.
Muscles are essentially long, parallel microscopic threads, which are arranged in parallel bundles, which are themselves arranged in parallel bundles. We talk of a whole muscle contracting, but that's not usually what happens. Usually a few of the bundles contract at a time. Then they run out of oxygen, and they let go while other bundles step in. It's not often that the whole muscle is working at once -- when it does, it will also become completely exhausted at once, and that's when you can't hold on any longer and fall from Mt Rushmore. It's all about fuel supply. The amount of oxygen the muscle strands can store is suprisingly small. They run out in a few seconds, at most minutes, if they're not spelled by their buddy strands.
So what happens when a muscle is "tight," or "knotted"? Well, one thing we can be sure of -- it's not steadily contracting and burning oxygen. It doesn't have enough fuel stored to do that for five minutes, let alone days. No: something quite different is happening. It is, in fact, "sticking," more or less as your mother warned your face would. When a muscle strand contracts it hooks itself chemically into a shorter strand, in a very ingenious way. Once it's hooked this way, it actually requires no energy at all to stay contracted. In fact it needs more energy to unhook itself. And sometimes, apparently, the strands hook themselves in such as to cut off their own fuel supply. Some of the muscle is contracted and can't let go. Now we've got a real problem. Now we've got those tight muscles you want to stretch out.
Okay, so you conscientiously stretch the muscle out, even though it hurts. What happens? Most of the muscle is nowhere near the limit of its motion. But the contracted fibrils are very close to their limit. What happens is precisely what you would expect: the stuck ones simply snap.
Now, a little of this is fine. Tiny muscle strands snap all the time. The system is built with massive redundancy. But there's a limit, and by the time you're in enough pain, and restricted enough in movement, to notice, you're probably past the limit of reasonable tearing. You're looking at seriously damaging a muscle that's already in trouble. Don't do it.
Your job at this point is to do whatever you can to encourage fluid exchange in the muscle. Fresh, nicely oxygenated blood has to get in there. When it does, those strands of muscle will release all by themselves. That's what they want to do. So you do three things:
1) Relax the whole area as much as you can. Take the stress off the surrounding muscles. Make room there.
2) Alternate cold and heat. Cold causes the blood vessels and capillaries to contract, which forces fluid out; then the heat opens them again, and fresh blood, full of oxygen, rushes in. That's what we want.
3) Squeeze the muscle where it's "knotted," deliberately, so as to push the old fluid out of it.
4) And then move it a few times, gently, as far as it wants to go, but not farther.
Movement is wonderful. Moving is what muscles want to do. They love it. What they don't like is holding without moving. They hate that, in fact. It's not the active people who move around a lot who have serious muscle trouble. It's people who sit still, working at a computer, or reading, or doing fine work with their hands. Muscles aren't designed for that. They hate it.
I was surprised to learn that there is actually nothing to pump blood back to the heart and lungs. I had vaguely thought that the pressure from the heart pushes the blood all the way out and back, but of course it doesn't. It can't: it disperses too widely, down to the single-cell level, before it enters the venous system and heads back. Blood makes its return journey solely under the impetus of gravity and the movement of the skeletal muscles (above all, of the inner calf muscles). There are nifty little valves in the veins that keep the blood from moving backwards, but the forward movement is all up to you. If you don't move, the old, blue, de-oxygenated blood doesn't, either.
So I want you to move. I just don't want you to "stretch," with the intent of lengthening your muscles and tendons. Your muscles and tendons are a fine length. When the body wants them longer it will lengthen them itself, effortlessly; it needs no help from you. What it does need you to do is to move through your whole range of motion. Call it stretching if you like, but it should be easy. It should feel good. "Stretching" that hurts should properly be called "tearing" -- because that's what it is. Travell & Simon use a phrase repeatedly, in describing what they follow trigger-point work with, that I like a lot: "taking up the slack." That's all that needs to be done, and all that should be done.