Exercise’s Instant Brain Boost

How long and hard should you exercise to maximise post-workout cognitive gains?

We hear a lot about the links between exercise and brain health. Getting regular exercise seems to boost cognitive performance, ward off age-related cognitive decline, fight depression, and so on.

These are all good long-term reasons to stick with an exercise routine. What’s less well appreciated is that exercise also has some more or less instant brain benefits. Aside from making you feel energized and lifting your mood, going for a run will boost your performance on certain cognitive tests.

So how much exercise do you need to maximize this effect? A study I blogged about a couple of years ago suggested that there was a sweet spot, with 30 minutes of moderate cycling (including warm-up and cool-down) providing a bigger boost than 55 minutes.

Now a new study by researchers at Ritsumeikan University in Japan (which, as an aside, has one of the dominant teams on Japan’s fiercely contested Ekiden running circuit) takes a more detailed look at this question, exploring how both duration and intensity affect the cognitive boost, and how long the boost lasts.

The cognitive test used in the study was the Stroop Task, which involves a screen flashing colour words like RED, YELLOW, and GREEN with the letters in different colours that either match or don’t match the word they spell. You have to press a button corresponding to the spelled word, rather than the colour of the letters, which is considered a good test of cognitive functions like response inhibition.

Here are some of the results, comparing cognitive performance after cycling for 20 minutes at a low intensity (triangles), 20 minutes at a moderate intensity (circles), or 40 minutes at a low intensity (squares). A lower “interference score” indicates a better cognitive performance:

Exercise’s Instant Brain Boost
Medicine and Science in Sports and Exercise

Comparing the two low-intensity bouts, the improvements are pretty similar right after the workout, but they seem to last a bit longer after the longer workout. It’s not a big difference, though, so hard to know if that’s a real effect.

At the higher intensity, the improvement is much greater and lasts longer. (Again, on this chart, the lowest result, indicated by circles, is the best.) It’s worth noting that the intensities (30 per cent or 60 per cent of VO2max) were chosen so that the subjects performed exactly the same amount of work in 40 minutes of easy cycling or 20 minutes of moderate cycling. Despite this fact, the moderate cycling produced a better result.

In a separate part of the study, the researchers zeroed in on moderate-intensity cycling and compared three durations: 10, 20, or 40 minutes. In this case, 20 and 40 minutes were initially very similar (and both superior to 10 minutes). But by the time half an hour had passed after the exercise, the cognitive benefits appeared to persist in the 40-minute group more than the 20-minute group.

The good news, in some ways, is that it doesn’t take much to get a boost. Cycling at 30 percent of VO2max really is very easy, equivalent to a brisk walk. Going a little harder or longer enhances the benefits, at least for the range of workouts studied here. But the basic message is: Get up, get outside, and move around a bit, and you will be measurably sharper when you return to your desk.


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