Mark Twain once said that he got all the exercise he needed acting as a pallbearer at the funerals of his friends who exercised regularly. Similarly, Donald Trump reportedly thinks the human body is like a battery with a limited store of energy, and so chooses not to use up any of it on exercise. This may be the only thing the two men have in common.
Suspicion of exercise, though, is entirely natural, as the evolutionary biologist Daniel Lieberman points out in this entertaining and informative book. When interviewed, modern hunter-gatherer peoples are mystified as to why westerners should be obsessed with running long distances and lifting heavy weights when they don’t have to.
The difference, of course, is that we don’t automatically get enough physical activity in an ordinary day – but learning from modern hunter-gatherers, along with facts about the evolution of the human skeleton, can give us some clues as to how to do so in a healthier and perhaps even fun way. Lieberman himself is an expert in the evolution of running, for example, and his research helped inspire the barefoot-running movement based on solid evidence that striking the ground with the ball of the foot (rather than the heel, as highly cushioned shoes encourage) is more ergonomically efficient and leads to fewer injuries.
It’s not the case, though, that even if you run “normally”, you’ll eventually wreck your knees. That is one of the many “myths” about exercise that Lieberman helpfully punctures by carefully assessing all the evidence from studies. (Inactive older people are much more likely to develop osteoarthritis of the joints than lifelong exercisers.)
Nor is it true that simply walking would be insufficient exercise: it’s just that you need to do much more of it than most people (at least five hours’ brisk walking a week). You often hear these days that exercise doesn’t help people to lose weight. It turns out, argues Lieberman, that isn’t true either, and for the same reason: most people trying don’t do enough of it.
The book is full of helpful tips – you’ll build muscle faster by extending muscles under load rather than contracting them; the kind of chair you sit on doesn’t matter as long as you strengthen your back muscles and move regularly – conveyed in a humorous and sympathetic style. The notion of exercise, Lieberman keeps repeating, is modern, weird and unpleasant, so the best way to do more is to find something you actually enjoy, and perhaps build in some social motivation by doing it with other people. By the end of the book I was exhausted at the very thought, but there is always tomorrow.
• Exercised: The Science of Physical Activity, Rest and Health by Daniel Lieberman is published by Allen Lane (RRP £25). To order a copy go to guardianbookshop.com. Delivery charges may apply.