Everyone knows you’ve got to “use it or lose it,” but what does that mean exactly? What do we lose, and why? And how does using it help?
With every passing decade, physiologists have understood even better that a person is a colony of cells, both our own and really surprising numbers of “alien” cells, everything from friendly bacteria in our gut to ancient organisms that have developed such a close working relationship with our own cells that they have become us.
All of that life inside of us, the life that makes us who we are, needs constant maintenance, a constant supply of nutrients. We have to stay active not so much because it’s good for us: we have to stay active because it’s good for them. They need nutrients, oxygen, waste removal — and they never sleep, never stop needing those services, not for one minute of our lives.
Bourne concentrated on rest and mobility. From somewhere in his forgotten past he understood that recovery depended upon both and he applied rigid discipline to both.
The Bourne Identity, by Robert Ludlum, p137
You are your stresses.
There is a reason that babies all look pretty similar: none of them have been shaped by stress yet. Oh, sure, they have some distinguishing features, but nothing like adults. They are kind of larval looking, all of them.
Much of who you are as an adult is a modified — stress-adapted — version of an original template. What would you be like if you had never had anything but extremely mild physical stresses in your life? What if you grew up in a padded, zero-G room? You would literally be fragile. Your bones would be like Styrofoam. You would look different: your skin would be a different colour and texture, your joints a different shape. You wouldn’t be able to do much of anything in normal gravity.
Most of who you are and what you are physically capable of is the result of adaptation to stress.
All of biology is organized around adaptive reactions to stimuli: immediate reflex (neurological) responses, nearly immediate hormonal and behavioural responses, tissue change responses. Every response is about improving conditions for the organism. Starting to fall down? The organism reacts to stop it. Regular pounding impact on your legs? Make the bones stronger. Etc.
Take away the stresses, and the body steadily stops investing energy in unnecessary adaptations. Adapting is “expensive.” You don’t do it if you don’t have to.
The way some tissue adaptation has been extremely well-described by science. Others, not so much. Bone adaptation is the best understood … and the most surprisingly fluid. Bone adapts well.
"There are two “laws” of tissue adaptation, one each for hard and soft tissue. Wolff’s law is that bone will change and strengthen in response to loading. This was first noticed by Julius Wolff in the 19th Century, who got the naming rights. It was greatly refined in the mid 20th century by Dr. Harold Frost, an American surgeon who studied bone biology, and published scientific papers more often than I change my socks. The full details of how bone responds to stress are described in his Mechanostat model. The corollary in soft tissue is the obscure and much less developed Davis’ law. (No one even seems to know who Davis was.)
Although there’s no question soft tissue does adapt to stress, the responses of muscles, tendons, and ligaments are much more complex and less well understood. Many treatments are based on the idea of forcing adaptation or “toughening up” tissues by stressing the tissues. It has always been a reasonable idea, but the devil is in the details: what constitutes the “right” amount and kind of stress is difficult to know, and the results of such therapies have generally been highly inconsistent.
In 2012 and 2013, it seems to have become strangely fashionable to deny the health benefits of running, and to assert that it actually makes you fatter and erodes muscle and bone! For example, these claims are actually made in John Kiefer’s popular article, Why Women Should Not Run (and shredded in this great rebuttal, Sorry, but Science Says Running is Good for You, Not Bad).
Running can be hard on bodies, but it takes mental gymnastics and abuse of the evidence to believe that “cardio above a walk or below a sprint is bad for you (especially if you are a woman).” However, even the assumption that running can be “hard on bodies” is not safe. For instance, the evidence actually shows that “running significantly reduced arthritis and hip replacement risk.”1
Say what? Running is good for joints?
Well, at least not particularly bad for them. The results are probably due in large part to the fact that runners were typically skinnier. Nevertheless, the data flies in the face of the common assumption that running is much harder on the joints. Instead, what it clearly shows is that running is either neutral or helpful …. probably because using joints is healthier than not using them, on average. Obviously overuse is another matter.
Everything — but, above all, your heart and lungs, and your brains if you want to keep sharp into old age.
The evidence is overwhelming that moderate aerobic activity is probably the single most important kind of exercise … because there isn’t a single cell in your body that doesn’t depend on a constantly blood-borne supply of oxygen and nutrients. The delivery system must be constantly challenged.There isn’t a cell in your body that doesn’t need a constant blood-borne supply of oxygen and nutrients.
But you really have to use anything that you don’t want to lose.
There is a concept in athletics called “training specificity.” It’s one of the Laws of Exercise: you get good at what you do, and only what you do. If you jump up and down on one foot, you’ll get good at jumping up and down on one foot … but not the other foot. If you lift weights slowly, you’ll get good at lifting weights slowly … but not good at lifting them quickly.
You kind of need a specific exercise for anything you want to keep in shape. Which is why so many exercise experts recommend a wide variety of exercises.
But what happens to stagnating tissue? Other than just not getting tougher? Well, it gets dysfunctional and incompetent …
Even though people are well aware that you need to stay active, few people understand just what exactly goes wrong when you don’t exercise — other than going to fat. There are at least two major concerns that are not widely understood.
First, reflex degeneration.2 We are full of reflexes, some of which are going to get exercised almost no matter what we do — like the swallowing reflex, say. But a lot of neurological responses can easily get neglected, like postural reflexes in a chair-bound office worker. If you spend many hours a day in a chair, you simply don’t have to work very hard to stay upright. It’s easy to stay upright! Not only do the core stability muscles go to pot, but so do — and more importantly — the reflexes that activate them. And we know that using those reflexes again will restore them.3If you spend many hours a day in a chair, you simply don’t have to work very hard to stay upright.
Second, muscle tissue dysfunction and painful trigger points.4 Trigger points, better known as muscle knots, are more clinically significant than most doctors understand,5 causing and complicating countless painful injuries and problems, especially back pain,6 to say nothing of an incredible amount of moderate stiffness and low-grade discomfort that limits exercise and suppresses quality of life in countless small ways. Trigger points will form in muscle tissue when that tissue is either overstimulated … or stagnant … and the combination is especially deadly.
The weekend warrior whose muscles stagnate in a chair throughout the week but are challenged on the ski hill on Saturday is pretty much doomed to an accumulation of increasingly problematic trigger points, often misinterpreted as “getting too old for this.”
That pretty clearly implies a need for some kind of in between exercise intensity, something not too easy nor too hard: but a Goldilocks “juuuust right.”
I’ll finish with a diagram:
There is “weak evidence that some types of exercise” — more challenging types, for the most part — are “moderately effective, immediately post intervention, in improving clinical balance outcomes in older people.” A very common sense conclusion! So far there is really no evidence about the balance effects of more typical exercises like walking or cycling.BACK TO TEXT
From the abstract: “Chronic exercise increased feelings of energy and lessened feelings of fatigue …”And of course there are countless other kinds of research showing an incredible variety of exercise benefits. BACK TO TEXT
This excellent radio segment discusses recent scientific evidence that debunks several exercise myths, showing that stretching isn’t as useful as you might have thought, that working out exclusively on the weekend may actually be dangerous, and response to aerobic and strength training may depend on your genes.BACK TO TEXT
It’s been in vogue in physical therapy for a long time now to “mobilize” injuries as quickly as possible — probably too much in vogue. In the zeal to get people on their feet again ASAP, serious sprains — which are worse than fractures in some ways — are almost never put in a cast. Turns out that’s a mistake. A 2009 experiment published in the Lancet presents clear evidence that a full cast for a severe ankle sprain is superior to the almost universal practice of using braces and tubular compression bandages. The editors write, “This elegant study highlights the need for trials to address common problems.”BACK TO TEXT