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Thursday, April 22, 2021

Review: Exercised

 Exercised is an evolutionary biologist's view of the modern invention of exercise. It turns out that Dan Lieberman was the person whose paper inspired the book, Born to Run, which described a tribe of Tarahumara runners in Mexico who run barefoot. But when Lieberman actually visits that tribe, when he interviews everyone, he discovered that most people would say that they didn't race, and definitely did not exercise. When he finally found a racer, he asked the racer about training, and the racer looked nonplused and had to have the concept of training explained to him. It turned out that the Tarahumara race was actually a social ritual, involving kicking a ball, following it, and then kicking it again. The race involved 2 teams, and the team that lapped another team won, so races could go on all night. Lieberman speculates later on in the book that this sport probably evolved out of the need to track animals over long distances while doing persistence hunting.

Lieberman delves into many myths about exercise. The big one (which is the subtitle of the book) is that we were never born to exercise. The hunter-gather tribes live on such an edge of caloric sufficiency that humans who unnecessarily expended energy would have to give up reproduction or other important activities of life, so instead, the human body (and brain!) evolved to do everything as efficiently as possible while expending as little energy as possible. In fact, the average hunter gatherer walks about 20,000 steps a day, which while a lot compared to modern Westernized societies, is only about 10 miles. From this insight, many other aspects of modern ailments and attitudes towards exercise can be deduced. For instance, one reason walking doesn't really result in weight loss is that walking is so efficient that you'd have to well exceed the minimum typically prescribed by health authorities --- you pretty much have to run (an hour or so) or walk tremendous amounts to achieve weight loss.

From this, Lieberman goes on to attack other myths, such as the one about "sitting is the new smoking." It turns out that traditional hunter-gathers do sit a lot. But it's rarely more than 15 minutes at a stretch, and obviously, they're still getting lots of walking in. It's not the sitting that's bad, it's that the time spent sitting in front of a TV or computer monitor is time that isn't spent exercising. Lieberman then explains why exercise is so good for you --- it creates inflammation and then the body hyper-compensates, basically overdoing the repair and eliminating the damaged caused by the exercise and then some. What's important here is that the lack of activity actually induces a mild form of inflammation, which is repaired during recovery from exercise. Because humans evolved in a state where exercise was required to survive, the recovery system never evolved to activate outside of exercise, which is why exercise is so important.

Similarly, Lieberman dismisses the paleo-fitness regime. He points out that the traditional hunter gatherer male is 5'5" and 115 pounds, and that modern gym rats with access to weight machines and dumb-bells and access to all the food they want, have exceeded the strength of most hunter gatherers (not to mention weight!). The metabolic requirements of excess muscle would never have been tolerated in a state of caloric scarcity. He does point out that traditional human society do participate in rituals that look a bit like training: dancing and sports, some of which last long enough to evoke endorphin high and other experiences that athletes have experienced,.

The exploration of aging is also excellent. Lieberman points out that hunter gatherers do live to the traditional 4 score and 10 years, but also have much reduced morbidity compared to modern Westerners. The advances in medicine mostly means that people who might otherwise have died earlier, live about as long as hunter gatherers, but in a state of requiring constant medical support in the form of medicine, surgery, and therapy. He points out that even people who never exercise (e.g., Donald Trump) frequently do live long lives --- it's just that they might have to be on medication, and obviously they're not performing optimally, mentally or physically.

The book is well written and I read it compellingly for not just the health nuggets and advice, but also for the stories about the research on the topic. After I finished I wanted to go back and start it again, and wish I'd waited for the ebook version from the library so I could have highlighted the important passages. Highly recommended.

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