How evolution keeps you on the couch


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Mark Fenske, a neuroscientist at the University of Guelph, has an interesting article in the Globe and Mail about how evolutionary forces on our brains affect our motivation to exercise. His basic argument is that we’re wired to avoid wasting energy, since our ancestors needed to make sure they’d have enough energy to find food or flee from danger. And recent neuroimaging studies (he’s not specific about which studies, by whom, and under what conditions) offer some support for this idea:

When subjects were considering whether to perform a given action, neural activity within one part of the striatum, the putamen, was found to decrease with the amount of physical effort the action would require… By helping to produce an aversion to unnecessary physical activity, the striatum may be partly to blame for the growing number of couch potatoes in Western societies.

Seems fairly intuitive — it would be surprising if we hadn’t evolved some such mechanism. But does this mean we’re incapable of overcoming this barrier to exercise? Of course not:

A number of studies indicate that increasing the reward associated with an effortful action can lead to its being chosen over an easier option. And brain scans show that the size of such a reward is associated with activity in the nucleus accumbens, which is another part of the striatum linked to motivation.

Again, this is quite painfully obvious on an intuitive level, though it’s interesting that scientists are zeroing in on which specific parts of the brain are responsible for these drives. The real pay-off, and the reason I’m linking to the article, comes in Fenske’s conclusion. We can trick the brain and tip the balance in favour of exercise, he says, by reminding ourselves of the well-established mental and physical benefits of exercise:

[B]y learning and thinking about exercise-related rewards we can strategically increase the incentive value of physical activity. This may explain why being reminded of such benefits, and how I always feel better after running than before, is so effective at getting me out the door.

To some extent, that’s what this blog is all about! The more we learn about all the different ways exercise benefits us, the easier it is to get out the door.

(And there’s a postscript too: exercise leads to physical changes in parts of the basal ganglia related to cognitive control. So the more you exercise, the better you get at overcoming your ancient brain’s aversion to “needless” effort.)

5 Replies to “How evolution keeps you on the couch”

  1. @RH
    Neat study — thanks for posting the link. Certainly reinforces the idea that our “conscious” decisions are constantly being primed by unconscious factors. I guess that’s (part of) what researchers mean when they talk about the modern “obesogenic environment” — we see a lot more commercials for fast food than for exercise equipment!

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