Exercised: The Science of Physical Activity, Rest and Health By Professor Daniel Lieberman

Michael Preedy, Queen Mary University of London, UK

---

https://doi.org/10.36866/122.12

“Now what?”

Having hauled itself away, the train no longer shields them from the wind. Standing on the platform, their shivering eyes follow the grim heath beyond them. In the distance, a rocky prominence, solitary beneath a silvery Scottish sky.

“We go for a walk,” says Tommy casually. “What?” asks Spud.

“A walk,” Tommy says again. “There.” And pointing across the rugged scene, he sets off to tread the land, to climb the hill.

His friends follow, hesitant. But no sooner have they crossed the tracks than they stop, shaking their heads.

“Well, what are you waiting for?”

Spud swigs his Special Brew. “Tommy.” How to put it? “This is not natural, man.”

Bewildered, Tommy gasps, “It’s the great outdoors! It’s fresh air!”

No use. Spud, Renton, and Sick Boy are not convinced. Turning, they go back the way they came, accompanied by a disappointed Tommy.

An amusing moment. One among many in Danny Boyle’s Trainspotting. And one, I

suspect, that another Daniel would have little difficulty comprehending.

Professor Daniel Lieberman reveals a lot about himself in his intriguing new book. Making my way through Exercised (I read every page, a courtesy rarely shown to writers by their readers, not to mention their reviewers) gave me the sense of becoming better acquainted with its author. I’m confident, therefore, that Professor Lieberman would empathise with the boys in Trainspotting. Professor Lieberman is an enthusiastic exerciser – he’s run marathons (plural), for fun. So, it’s easy to imagine him hiking the Scottish Highlands with Tommy. An eminent biologist, Professor Lieberman would disagree with Spud’s judgement of the great outdoors as “not natural.” But he would regard Spud’s reluctance to walk in it as perfectly normal.

Why? Because he thinks humans didn’t evolve to exercise.

At the outset, Professor Lieberman distinguishes “exercise” from “physical activity.” Since few people read novels, let alone dictionaries, he generously gives definitions.

Physical activity (noun): any bodily movement produced by skeletal muscles that expends energy

Exercise (noun): voluntary physical activity that is planned, structured, repetitive, and undertaken to sustain or improve health and fitness

In his view, “we never evolved to exercise – that is, do optional physical activity for the sake of health and fitness.” Rather, humans evolved “to be physically active when necessary.”

While it’s true that the word “exercise” is a noun, it’s also a verb. I assume, since no evidence is offered to the contrary, that the biology of exercising muscles, process and outcome, is the same regardless of whether the action is voluntary or involuntary.

Professor Lieberman seems willing to ignore this, however, as he shifts ground throughout his book. On the one hand, he makes the persuasive case that the ancestors of Homo sapiens were naturally selected for their ability to travel over great distances, walking and running across Africa and beyond. That is to say: they, and hence we, evolved the anatomy and physiology needed to exercise their muscles and move their bodies.

On the other hand, Professor Lieberman rigidly affirms that we didn’t evolve to exercise. Savanna, yes. Spin class, no. Insisting upon a distinction between “physical activity” and “exercise” seems to me to be as helpful as asserting that our ears evolved to hear gorillas but not to listen to Gorillaz (I refrain from opining upon which is more grating). It’s a not-so-slight sleight of hand that, at best, disorientates the reader and, at worst, confuses what is otherwise clear writing.

Professor Lieberman is most comfortable (find me an academic who isn’t) when explaining his own research. At the book’s core is the juxtaposition of so-called WEIRD societies (Western, educated, industrialised, rich, democratic) with traditional hunter-gatherer populations. Synthesising knowledge from years of fieldwork in Africa and Mexico, he contrasts how people in disparate cultures engage in exercise (or should that be physical activity?), the effects this has on their bodies, and the consequences for health and disease. The comparisons are revealing.

“Sedentary Westerners spend as much daily energy walking as chimpanzees, but hunter-gatherers like the Hadza walk about three times more than an average Westerner, spending nearly twice as many calories despite weighing much less… hunter-gatherers spend about 10 percent of their total energy budget trudging about, but Westerners spend only 4 percent… if average industrialized people walked as much as the Hadza, they would spend approximately 350 calories a day walking. If they didn’t compensate for all those spent calories by eating more, they would slowly but surely shed pounds.”

Whether or not one agrees that the separation of “exercise” from “physical activity” is redundant, Professor Lieberman’s concern that we don’t do enough of either is valid. Obesity, for instance, continues to attain new epidemic heights, supplementing other chronic diseases. (I would offer WEIRDO as a more suitable acronym, but it’s becoming increasingly visible that obesity is the one trait the West is willing to share with the developing world.)

I found Professor Lieberman’s blend of anthropology, evolutionary biology, and physiology pleasing enough. There is a fair amount of popular science writing intended, I would imagine, for the general curious reader. Mitochondria are introduced as the “tiny power plants in cells,” a marginal improvement on the ubiquitous and tiresome use of “powerhouse.” The inelegant word “behooves” is invoked too readily, and Professor Lieberman possesses that American peculiarity of placing question marks where they have no business being. Yet in other respects, the prose is coherent if conventional.

Professor Lieberman would like to avoid having Exercised branded a support manual: “this is not a self-help book.” And yet, part of the book’s charm comes from the sensitive manner with which he encourages his reader: “we should treat exercise the way we treat education by making it fun, social, emotionally worthwhile, and something that we willingly commit ourselves to do.” My fear, though, is that the audience most likely to read this amicable book (young, educated, well-off, healthy) is least likely to require its recommendations. Then again, one could do worse than to reacquaint oneself with decent advice.

Make exercise necessary and fun. Do mostly cardio, but also some weights. Some is better than none. Keep it up as you age.

Now what? We go for a walk.