Exercise and Mental Health, Part 4 - Cognition

Welcome to the penultimate blog post of this series! You can find the previous posts here:

  1. Exercise and depression
  2. Exercise and self-esteem
  3. Exercise and happiness

This post will look at exercise and its effects on cognition, or brain power. While exercise isn't going to turn any of us into Einstein, it can have significant benefits for the brain, both acutely and chronically. I wish that exercise made me better able to understand the papers referenced within this post because it was hard work reading them, but well worth the effort.

This was perhaps the easiest post to write so far in this series, as I was able to find a review paper on acute effects of exercise and another paper on how regularly exercising helps the grey matter. They both neatly summarised a ton of research and both deliver good news!

The first paper I read covered the acute benefits of exercise on cognition (Chang et al.). This lengthy review looked at 79 studies that examined the effects exercise had on cognitive performance. The studies assessed looked at subjects' performance on tasks during and after bouts of aerobic exercise. Why aerobic? It seems that aerobic exercise (going for a jog) has been studied much more than anaerobic exercise (lifting weights) for its impact on cognition. This is good news for the average person - aerobic exercise takes many forms, and a lot of them don't require expensive gear, gym memberships or specialist knowledge. Nearly anyone can get outdoors and go for a jog.

Thanks to the fact that they analysed a whopping 79 studies, they could confidently draw some interesting conclusions. Some studies looked at what happens if you challenge someone with a cognitive task whilst they're exercising. This...doesn't really make sense to me. If you're exercising, you're exercising. The idea of doing work while exercising seems a bit odd. Anyway - they found that unfit people performed worse mentally while exercising and fit people didn't. This makes sense; the fitter you are, the less mental energy you'll need to use focusing on exercise, meaning you can challenge your brain at the same time. I guess if you're unfit, you'll be too busy fighting for breath and this will hamper your cognitive performance. This is interesting to know but perhaps irrelevant for most people!

Luckily, if you're unfit, testing your mental performance after exercising seems to show a benefit. It also shows a benefit for fit people. For maximum benefits for all, the researchers found that moderate to high intensity exercise seems to work best, and that 20 minutes of exercise is necessary to get an improvement above baseline on any mental task. Very light intensity exercise actually seems to make performance worse. 

This raises the question: can something as simple as going for a 30 minute run before work or at lunch make you productive? It's definitely something worth experimenting with if you so desire!  

The other paper I read looked beyond the acute effects of exercise and examined the results of regular aerobic exercise on working memory, selective attention (which Google defines as "the capacity for or process of reacting to certain stimuli selectively when several occur simultaneously") and task-switching. The authors define task switching as:

"responding to similar target stimuli, but on the basis of one of two different rules. For example, a participant might be instructed as follows: If the target digit is green, indicate whether the digit is greater or less than 5; if the target digit is red, indicate whether the digit is even or odd."

They go on to say:

"On nonswitch trials, the response rule remains the same as on the previous trial; on switch trials, the response rule changes. The difference in reaction times between rule switch and nonswitch trials is referred to as the switching cost, because it reflects the degree of slowing arising from the need to mentally change task goals before responding. Such mental-set-shifting requires executive control, including volitional inhibition, working memory, and mental flexibility; thus, smaller switching costs can be interpreted as reflecting more efficient executive functioning."

I must admit that it took me several reads to understand that second quote. All of the things the studies reviewed here give great insight into someone's overall cognitive health and abilities. Regular aerobic exercise improves improve all of them but, and here's the catch(!), only in older adults. 

It remains unclear if there's much benefit for younger adults when it comes to cognition but from my reading, I wonder simply if that is due to a lack of research on younger populations. Indeed, the authors of the second paper I looked at said there is a "scarcity of data" on the topic of young adults, aerobic exercise and cognition. There are a few studies they looked at that suggested modest improvements in certain tasks, but the benefits aren't as significant as they are for older adults.

This suggests that aerobic exercise should be a central part of anyone's life as they age. You might, if you've read the previous posts in this series, be able to guess what my advice is here for anyone looking to see if exercise improves their brain power.

  1. Keep the cost to entry low: getting a good aerobic workout could be as simple as walking briskly for 30 minutes or rediscovering a love for a sport you once played
  2. Make sure you're doing something you love and do it regularly
  3. Monitor how you feel: if you feel benefits from exercising then keep going. If not, there's likely some tweaks you can make to intensity, activity, duration or another variable that'll make a difference

The last post will hit your screens next week - if you've enjoyed this one or any other in the series so far then feel free to share!