Choose rather to be strong of soul than strong of body.
As intelligent as Pythagoras was, he was almost certainly wrong in his intuitive hard-edged separation of body versus soul. It hasn’t been long since I last wrote about the wonders of physical exercise for brain and mental function. But new studies have continued in the meantime, and it’s important to stay on top of them. Scientific progress is incremental, and evidence in support of a particular theory either continues to accumulate or wavers until a few killer studies finally disprove the theory.
By keeping up to date with evidence as it appears, we can minimize the chance that we hold outdated or erroneous assumptions about how the world or our bodies work. So is there still a strong case in support of regular aerobic activity as a cognitive enhancer? And does aerobic activity beat muscle training in boosting our mental function?
When we think about cognitive function and possible activities to enhance, stimulate, or protect it, we typically consider mental exercises; this is what makes brain training and problem-solving games so popular. We feel that our cognitive ability is being challenged and that our performance is improving in the game, so we make a natural analogy to the challenges of lifting progressively heavier weights at the gym: physical exercises push the limits of our body and improve it in the process, while mental exercises push the limits of our brain and improve it in the process.
But as my previous article highlighted, it’s a mistake to think about physical and mental activity as independent domains. They are both indispensable parts of the same unified structure that we call a human. So it shouldn’t be too surprising to learn that the aerobic activity that benefits our body also benefits our mind. All of our actions, thoughts, feelings, and experiences come from the operations of our biological organs after all.
In line with this logic, it’s reasonable to expect that physical exercise should benefit the brain and mind, but we still need good evidence to demonstrate that it actually happens. A new study published at the end of January 2019 in the journal Neurology targets exactly this question.
The group of researchers from Columbia University wanted to test the cognitive effects of regular aerobic exercise for adults between the ages of 20 and 67. They recruited 132 participants with normal cognitive ability but below-average physical fitness. Then, they randomly sorted these people into two groups: an aerobic exercise group and a stretching/toning group.
Participants in the aerobic exercise group selected from a list of different activities, but all activities were organized to meet a standard heart rate intensity during the exercise. It doesn’t particularly matter whether you run, cycle, or swim. As long as it gets your heart pumping in the same way, you should achieve similar aerobic effects. The stretching/toning group instead performed exercises that enhanced physical flexibility and core strength.
Recruits in both groups individually attended a fitness center four times a week, for a total of 24 weeks. Each session lasted approximately an hour under the guidance of trainers and coaches, and heart rate was continuously monitored to make sure that the aerobic training was hitting its desired targets.
Over the course of the experiment, the researchers assessed aerobic capacity (VO2 max) and cognitive ability three times for each participant: first before the experiment started, second after 12 weeks of training, and finally after the full 24 weeks of training. This allowed the researchers to analyze the change in aerobic and cognitive ability as participants trained throughout the 6 months of the study. If physical exercise does affect cognitive ability, it’s possible that it influences each of our mental functions differently. To make sure they were able to detect this, the researchers tested several cognitive skills including language, attention, and memory.
Fortunately for us, we can unwrap the data now to learn the results rather than waiting 6 months like the diligent researchers. But first, a few sanity checks. Before the experiment started, the aerobic exercise and stretching/toning groups did not differ in age, sex, education, IQ, or any of the cognitive assessments that the researchers used. This is good news because it suggests the randomized grouping successfully removed any major bias in splitting the participants. The aerobic group had slightly more participants with hypertension, but the rarity of medical conditions overall meant that only six participants (out of the 132) were affected.
Now that the sanity checks are in order, let’s look at what happened to the measures of aerobic capacity. Unsurprisingly, the aerobic training group showed greater improvements in aerobic capacity than the stretching group. Their VO2 max was elevated to similar levels for both the 12-week and the 24-week assessments, while the stretching group showed no change. As expected, the aerobic training succeeded in improving participants’ cardiovascular fitness.
The more exciting question relates to how the cognitive outcomes changed. Most of the cognitive traits did not change with either training program, but one particular trait jumped out of the data. That trait is called executive function, which typically refers to our ability to effortfully guide our behavior toward specific goals. When you organize or prioritize your options, suppress inappropriate actions, categorize information, and focus your attention on critical aspects of a task, you are using executive function.
The researchers found that participants in the aerobic exercise condition showed a greater improvement in their executive function performance after 24 weeks of training compared to the stretching group. They also spotted an interesting interaction with participant age: older participants saw larger benefits to their executive function from the aerobic exercise.
To work out whether the executive function improvements might be linked to brain changes, they also ran some imaging scans. The scans revealed larger growth in a small area of the middle frontal cortex on the left hemisphere of the brain after aerobic training compared to stretching/toning. However, the amount of growth did not seem to correlate with improvements in executive function.
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Bodily decay is gloomy in prospect; but of all human contemplations the most abhorrent is body without mind
— Thomas Jefferson
The results of this study support the idea that aerobic exercise is good for our cognitive function. As with any study though, it has its limitations and we need to wait for even better evidence before believing that we’ve hit upon the correct answer. Better evidence means bigger studies, with more participants followed over longer time frames, that replicate these effects. Perhaps the positive effect on executive function was just a fluke? If an independent lab finds the same pattern, we can be more confident that it’s a legitimate effect.
For now, the evidence is moving in an optimistic direction that suggests if you care about your mental wellbeing, jumping on your bicycle or treadmill regularly is a good idea. And let’s face it, even if it doesn’t improve your cognitive function, you’ll almost certainly be helping out your cardiovascular health, and there’s no real sign of a downside from regular exercise.
There are, of course, mental activities that benefit our mental wellbeing too. Mindfulness is growing in popularity and the evidence to support its psychological benefits is getting stronger. And rather like the benefits of physical exercise for cognition, mindfulness may also have important benefits for physical health. Whatever way we look at it, the road between mind and body is a continuous two-way street. Our body produces our mind and our mind feeds back to affect our body. This seamless cycle is a great reason to pay equal attention to our physical and mental health.