Exercise under lockdown

Harvard University human evolution expert Dan Lieberman tells Chris Smith about the origins of exercise...
15 September 2020

Interview with 

Dan Lieberman, Harvard University; Katie Mack, North Carolina State University; Richard Hollingham, Boffin Media


Person running, jogging and stretching


Chris Smith is joined by human evolution expert Dan Lieberman to talk exercise, de-conditioning and what we mean by fitness...

Well back down here on Earth, and putting his feet on the ground very much. Excuse me. Dan Lieberman, professor of human evolution at Harvard University. I hope you'll excuse those terrible puns, but you're celebrating too. You've got a new book out, it's called Exercised. That's Exercised with an E not an O, although we are feeling rather exercised in the present climate aren't we? Tell us about your book.

Dan - It's basically a natural history of physical activity, and the punchline really is that although we evolved to be very physically active, we never evolved to exercise, which I define as voluntary physical activity for health and fitness. And so I use, in the book an evolutionary and anthropological approach to, kind of demystify and debunk all kinds of myths about physical activity that make people feel confused, and embarrassed, and shamed, and blamed, and basically irritated by people like me who try to get them to exercise.

Chris - Well, I did ask you when we were doing a sound check before the program, what did you have for breakfast? And you said a run.

Dan - No, I said I like two breakfasts. So yeah, I like to have sometimes a little bit to nibble before I head out, go for a run and then come back, and then I like to have a second breakfast, just like Bilbo Baggins. So I think he had the right idea.

Chris - Katie, are you a fitness freak or couch potato?

Katie - I am somewhere in the middle, I think. I do exercise a lot, and since the whole pandemic thing started, I've been doing a lot of running. Before the pandemic I was into rock climbing in rock climbing gyms, which all closed for a while. I was running for a couple of months and now it's a little bit less than that, but just to be outside, I think I'm much more sane when I'm moving and, you know, getting regular exercise. So, I do something a few times a week, at least.

Chris - Same for you, Richard?

Richard - I think I'm one of the few people in the world who's lost weight since lockdown, because similarly I started running, ignoring the pain in my knees and there's an exhilaration to running. I'm not sure I enjoy running. I enjoy having run. And I had a question to Dan about this. What point in history do we think we realised we weren't doing enough physical exercise in our daily lives, or we were eating too much and we had to actually discipline ourselves to take exercise, to actually do something separate on top of our normal day to day lives.

Dan - I mean, your observation is absolutely correct. It's a very recent phenomenon, because until recently people had to be very physically active in order to survive. I mean, until 600 generations ago, all our ancestors were hunter-gatherers. They didn't even have anything they grew in a field, right. And then from many hundreds more generations, our ancestors were simple farmers. And it's only recently with the rise of, you know, different social classes, and machines, really the industrial revolution, that large numbers of people could live without being physically active. And now we have this very strange inversion whereby people who are wealthier actually, are more likely to be physically active than people who have a lower socioeconomic status, because they actually now have the time and money to pay for gyms and, you know, don't have to take long commutes and stuff like that. So exercise is really, you know, for most people, really an industrial, post-industrial phenomenon.

Chris - Indeed, because parkrun has come back. This is the organisation that encouraged people to just go out and not do competitive, aggressively fast running, go and have sort of, fun running. And you can't really, they say, underpin, or underline, or underscore, strongly enough, the health benefits of exercise. Is running actually that good for us though? Because there must be a cost to this repetitive impact on your joints?

Dan - Well look, everything has cost and benefits. And when people try to advertise exercise as a magic bullet with no negative potential, you know, I think that's part of the reason that people have a kind of a BS-meter, and they realise that they're being sold a bit of an overly optimistic prescription. But we evolved to run millions of years ago. And I believe that running is a skill, and that many running injuries, not all, but many running injuries are caused by the fact that people don't know how to run properly. You know, we teach people how to swim properly and how to throw properly. But we just tell them to lace on a pair of shoes and go running and surprise, surprise, a fair number of them get injured.

Chris - I wanted to raise the point that was made to me by one of my colleagues the other day, saying that during lockdown, we've got this situation now where a lot of old people haven't been out much. They haven't been taking the same sort of exercise that they naturally would have done just going shopping, which is a form of exercise. If you take yourself out, down the street, up and down the stairs a few times it builds muscle mass. She made the point to me that we're probably going to see another wave of people who die this winter. Not because they die of coronavirus, but because of coronavirus, because they've become so deconditioned, their muscles have wasted. They're less steady on their feet. They're more likely to fall over, more prone to things like hypothermia.

Dan - You're absolutely right. I mean, people evolved to be physically active, right. Again, we should distinguish between physical activity, which is just the activity, any activity that you do, any kind of moving. With exercise, which is sort of, planned voluntary physical activity for health and fitness. So we know that for most people, this is a worldwide average. And of course it depends on your age, but 150 minutes a week of moderate physical activity. So a brisk walk for example, reduces your relative risk of dying by about 50%. But it doesn't happen immediately, those negative effects accrue very slowly.

So there's no question. We know that the lockdown has decreased people's physical activity by approximately 40%. And it's happening because they're not going anywhere. They're not going to the stores. They're not doing all the things that they used to do. And the end result is we're going to have more hypertension. We're going to have more metabolic syndrome. We're going to have more cancers. We're going to have more heart disease. Those negative effects are going to accrue very, very, very slowly over decades, actually. So they should also be added to the toll of this pandemic. Absolutely.

Chris - Couple of very quick questions for you if I may please, Dan. Kevin asks, as we get older we can't seem to achieve the same level of fitness that we did when we were younger. So what actually, he asks, is fitness?

Dan - Well, of course, fitness is defined differently by all kinds of different folks. And people in the physiology sort of exercise world define fitness as basically how much oxygen you can get in and use, just basically your aerobic capacity. So a common measure of fitness is your VO2 max, the sort of the maximum level of oxygen you can suck in and use in your muscles. And it is true that as we age our VO2 max inevitably declines, and there are a number of reasons for that. You know, we lose mitochondria in our cells. Things stiffen, you know, ageing takes its effect. But we also know that people who are even moderately physically active slow the rate at which their fitness declines enormously. So one of the most important arguments that I make in my book is that it's actually kind of a chicken and egg question, which is that humans are one of the few species that evolved to live past reproductive age, and we become grandparents. And we know that for thousands of generations, the grandparents were important because they would forage and hunt for their children and grandchildren. But in turn that physical activity turns on repair and maintenance mechanisms that keep us from ageing and keep us fit. And so in a way we evolved to be physically active, but physical activity also evolves to help us live long. And so as we age, keeping up activity becomes ever more important in order to slow the rate at which we lose fitness, slow the rate at which we lose functional capacity, slow the rate at which we accrue various kinds of chronic diseases like diabetes and heart disease and even cancers. And the good news is you don't need to do a lot, just a moderate amount has an enormous benefit. You don't need to run marathons.

Chris - Someone once said to me that if you could turn exercise into a pill, it would be impossibly powerful compared to all the other drugs that we've ever invented. Ross is wondering, though, what can sometimes cause nausea after exercise, I've had this myself, if you go and have a fierce bout of exercise and then you feel pretty sick and you think, well, why did I do that? Clearly exercise is not good for my health.

Dan - Well, I mean, nausea can be caused by so many different things. I mean, sometimes it can be caused by dehydration. It could be caused by you know, muscle contractions, it can be caused by electrolyte imbalances. But you know, most people when they go out and go for a run or a walk or climb a mountain for fun, or go for a bike ride, nausea is not really normal. I mean nausea tends to occur from intense physical activity, intense exercise. And again, I think we have by commodifying and medicalising exercise, people think they have to go to extremes in order to get benefits to the point that they get nausea or they get cramps or various other kinds of problems. And I think that's part of the problem. Exercise is a kind of 'virtue', you know you line up on one line and run 26 miles to another line. And somehow that makes you virtuous about it. It might be fun. And I like to do that, but you don't need to do that to get the benefits of physical activity.

Chris - There you go, Katie, you're on good form with your climbing and your running.

Katie - That's great to hear!



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