The application of stress, the recovery from that stress, and the subsequent adaptation that results from the process is the central organizing principle of everything that has to do with physical improvement. From physical and occupational therapy to preparation for the Olympic Games, the stress/recovery/adaptation cycle is not just a good idea, it’s the law.

It is May 15, and you decide that this year you are going to get a suntan — a glorious, beautiful, tropical suntan. So you decide to catch some rays outside at lunchtime. You lie on your back for 15 minutes and flip over to lie on your belly for 15 minutes. Then you come in and eat lunch, and go back to work. That night, your skin is a little pink, so the next day you just eat lunch, but the following day you’re back outside for your 15 minutes-per-side sunbath.

You are faithful to your schedule, spending 30 minutes outside every day that week. At the end of the week, you have turned a more pleasant shade of brown, and — heartened by your results — resolve to maintain your schedule for the rest of the month.

The critical question: what color is your skin at the end of the month?

If you ask a hundred people this question, ninety five will tell you that it will be really, really dark. But in fact it will be exactly the same color it was at the end of the first week. Why would it be any darker?

“Stress” is that which causes a perturbation of the steady state of a system — in this case, your physiology. If the stress is mild, it causes no response. It doesn’t disrupt the situation enough to be noticed. If the stress is too great, it can kill you. This is what happens when you fall off a building or get mauled by a bear.



But if the stress is just right, it will cause “adaptation,” a response that restores the state of your physiology to what it was before, plus a little more, so that if the stress is applied again your body is ready for it. The stress/adaptation/recovery cycle operates in all living things, and it is an integral part of existence in whatever environment an organism lives.

Your skin adapts to the stress of the sun exposure by becoming dark enough to prevent itself from burning again. That’s the only reason it gets dark, and it adapts exactly and specifically to the stress that burned it. Your skin does not “know” that you want it to get darker. It only “knows” what the sun tells it, and the sun only talked to it for 15 minutes.

It can’t get any darker than the 15 minutes makes it, because the 15 minutes is what it is adapting to. If you got darker every time you were exposed to the sun, and the darkness just accumulated, we’d all be dark — but only the parts exposed to the sun. Most of us would only have tanned faces and arms, because the skin under our clothes received no stress.

Stress can be varied in a couple of ways. It can vary with the total amount of stress, like jogging two miles vs. six miles. This type of stress variation is called volume. Or it can vary in intensity, like jogging two miles in 18 minutes vs. running two miles in ten minutes.

So if you want your skin to get darker, you have to either stay out longer or go to a place with more intense UV in order to give the skin more stress than it has already adapted to.

The widespread failure to comprehend this pivotal aspect of adaptation is why so few people actually understand the concept of training. (We’ll explore the important differences between exercise and training in a future article.)

The idea that your tan should get progressively darker is not a terribly strange idea to wrap your head around. Getting in better physical shape is the same thing — exactly the same thing. You apply a stress that is appropriate for you, a stress you can recover from. The process of recovering from the stress results in adaptation to the stress, then you apply a little more stress to your now-adapted self, and the process proceeds in an upward direction, each step resulting in more adaptation to the stress.

You get stronger by starting with the weights you can do now, and then adding a little bit more next time, and every time you work out, until progress stops. This will be quite a while, many months for most people, and when that happens we’ll get more fancy about programming.

But not until then — as long as this simple process works to improve your strength, anything more complicated is a waste of time.

Complexity doesn’t speed up a process that is already proceeding as fast at it can, it just dilutes the stress and thus the adaptation.

Just like the untanned skin under your clothes, the parts of your physical system that you do not stress cannot adapt, because adaptation to the stress is specific to that stress. If you want to be a better runner, you have to run, either progressively longer, progressively faster, or both depending on your sport. If you want to be stronger, you have to lift weights, because producing muscular force against a resistance develops strength — strength is defined as the ability to produce force against a resistance.

Jogging will not make you stronger, because jogging is not about producing higher amounts of force. It’s about putting one foot in front of the other, generating enough force to propel you forward for a period of time sufficient to complete a prescribed distance. But jogging does not produce the kind of stress that improves your overall strength, because strength is not the limiting factor when you jog.

But the funny thing about getting stronger — the thing that makes it better than jogging — is that strength is such a basic and widely applied adaptation that it benefits every other physical characteristic regardless of specificity.

Strength is the only physical characteristic that benefits all the others. If you get stronger, you run better, throw better, dance better, do everything better, because strength is the most general physical adaptation, the physical basis of all the others. In other words: strength benefits running, but running doesn’t benefit strength. Like wealth, strength trickles down.

If you want to get stronger, you have to do things that require strength — things that cannot be done without strength and things that will be limited by a lack of strength — so that the production of force during the activity becomes a stress to which you can adapt. The most productive way to do this is with barbells, because they work large amounts of muscle mass while requiring you to balance the load. This stresses both your strength and your ability to balance, causing both to adapt at the same time. Since both strength and balance are necessary for effective functioning as a physical human being, this seems like a pretty good approach to the problem of getting better at it.

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images courtesy shutterstock – haveseen – Kzenon / instagram – lanaleony