Saturday, June 26, 2021

How Much Exercise Is Good For Your Brain?

I rode 105 km before work this morning. No prizes for guessing I was thirsty, hungry (despite eating before I started work) and needless to say, tired. 

There are days when after a run or ride I feel alive, my mind is laser clear, and all my synapses are firing. Today's ride was definitely not a ride where I felt clarity afterwards. 

There's plenty of evidence that short bouts of moderate exercise improves your performance in the ability to perceive, react, process and understand, store and retrieve information, or do cognitive tasks afterwards. You may not feel it, but the finding is highly repeatable.

However, we do not know how much exercise is enough to trigger this effect. Or whether how fit you are or what type of cognitive task you're doing matters.

I found an article where researchers in Australia tested 21 trained cyclists and triathletes (11 male, 10 female). These athletes did 15 minutes of moderate cycling followed by a pair of cognitive tests lasting 4 minutes. They rode another 30 minutes moderately before repeating the same cognitive tests. This was followed by an incremental ride to exhaustion (taking about 11 to 12 minutes on average) before doing a final round of cognitive tests (McCartney et al, 2021). Three different timepoints were measured, after 15 minutes, 45 minutes and exhaustion.

Moderate cycling was done at 50 to 55 percent of peak power from a previous test and this got them to average 75 percent of max heart rate (HR) after 15 minutes and 80 percent of max HR after 45 minutes.

Results showed that 45 minutes of exercise trumped 15 minutes. For these trained endurance subjects, their cognitive performance decline definitely did not happen after 45 minutes of moderate exercise.

Contrary to what the researchers expected, the decline did not happen after complete exhaustion as well, being better than after 15 minutes. Note that there was a 2 minute delay from the moment of exhaustion until the start of the cognitive tests so this delay may just be enough to recover.

Bear in mind that exercising for longer does not always mean better since there will be a point for everyone where if you exercise long enough your cognitive performance will start to drop. 

These subjects were also not allowed to drink during the testing. Male subjects lost 2.3 percent of their starting weight while the females lost 1.7 percent. This is well above the threshold suggested to cause cognitive impairment. 

The subjects repeated the testing twice. In one testing, they were given 2 capsules and told that the capsules were "designed to enhance cognitive function" during exercise. 

The capsules were just placebos, as the researchers wanted to test whether the subjects were influenced by this. The placebos did not have any significant effect which supports the case that this is a physiological effect - a result of enhanced blood flow to the brain or elevated levels of neurotransmitters.

There was another study done in 2015 where researchers from Taiwan found that 20 minutes of moderate exercise produced the biggest cognitive boost, compared to 45 minutes. The biggest difference between the two studies is that this Taiwanese study used healthy but non athletic university students (Chang et al, 2015).

Since the 2021 study used trained endurance athletes, it makes sense that they will probably benefit from a longer exercise duration compared to the university students.

There you have it, exercise does makes you improve your brain function. However, we cannot always go out for a run or ride before an important meeting, deadline or decision. It can also be shooting hoops or lifting some weights or any other exercise if running or cycling ain't your thing. Just do it when you have the opportunity.


Chang YK, Chu CH, Wang CC et al (2015). Dose-Response Relation Between Exercise Duration And Cognition. Med Sci Sp Ex. 47(1): 159-165. DOI: 10.1249/MSS.0000000000000383

McCartney D, Desbrow B and Irwin C (2021). Cognitive Effects Of Acute Aerobic Exercise: Exploring The Influence Of Exercise Duration, Exhaustion, Task Complexity And Expectancies In Endurance-Trained Individuals. J Sp Sci. 29(2): 183-191. DOI: 10.1080/02640414.2020.1809976.

Our Sat ride before Covid-19

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