Traditionally, exercise is seen as ‘for the body’, while thinking and mental activity is seen as exercise ‘for the mind’. That divide suits many academics fine. We enjoy inhabiting our mental world! Bodies? Who needs them! But this apparent divide between body and mind is rapidly crumbling. Research suggests that exercise boosts cognitive capacity and flexibility, as well as improves focus and motivation. It also offsets any negative effects of stress, which in itself is a sufficient reason to make exercise a habit.

The link between physical exercise and brain health was first established in patients who suffered a stroke or an accident that resulted in brain damage. Physical exercise proved to be an essential component of regaining brain functionality. Elderly patients suffering from mild dementia, or other brain-related disorders such as Alzheimer’s also improved significantly once they started a fitness regime (see for example: Erickson and Kramer 2011). Their brains rejuvenated.

But until recently, very little research had been done into how exercise benefited ‘healthy’ people. A couple of recent studies suggest that exercise has similar brain-boosting effects no matter health status. People who exercise have larger brains, and perform better academically. It’s extraordinary.

One of these studies looked into the link between children’s physical fitness, their brain volume, and their academic performance (Chaddock 2010). The study showed that children who were fit and exercised regularly tended to have larger hippocampal volume, important for learning and memory, and better cognitive skills than the children who were not fit. The study looked at the impact of exercise on the structure of the brain, by using MRI imaging. It found that fit children on average had a 12% larger hippocampal volume compared to unfit children, after controlling for known confounds. The scientists then used cognitive tests to check whether increased hippocampal volume indeed led to increased cognitive ability. And indeed it did.

This was one of the first studies to confirm the finding that exercise leads to an increase of hippocampal volume, that was previously detected in rodents. Rhodes et. al. (2012) for example show that the brain volume and brainpower of mice increases dramatically when they are allowed to run in a wheel. The experiment was an intricate one, in which mice were divided into four different groups, with different stimuli that were thought to affect cognition. In the end, only exercise mattered. The only group of mice that became smarter and improved their performance on cognitively challenging tests were those who got on the treadmill.

Exercise has short-term benefits for academic performance, as well as long-term ones. A study of young Irishmen showed they performed better on memory tests following a burst of physical exercise. They were asked to take a memory test, then cycle to get their heart rate up, and then take the test again. The second time they took the test, just after coming off the bike, their scores improved significantly. The scores of the control group, who got to relax between the two tests remained the same. Blood tests showed that the men who were asked to cycle had higher levels of BDNF, a protein that promotes neuron health, in their blood compared to the control group. Higher levels of BDNF serum are associated with better cognitive performance. The radical news: exercise immediately produces an increase of BDNF serum, which leads to better mental performance not only in the long run, but also immediately after exercising.  

To sum up: the benefits of exercise on brain functioning are long-term (due to the increased volume of the hippocampus) as well as short-term (due to the increase of BDNF, which boosts brain power).

And exercise has a number of other benefits:

• Exercise breaks the stress cycle. This is an important one. As we saw last week when we were discussing the stress cycle, thinking can switch on the stress response. Exercise is one of the best ways to switch it off. The stress response prepares you for a sudden explosion of muscular activity (even though we are sitting at our desks, thinking about a theoretical problem and staring at our computer screens). Exercise provides that burst of activity and metabolises the stress hormones you released. It signals to the mind and body that the coast is clear. The threat has passed. As such it is an excellent way to re-set your body and mind to a calmer, more relaxed state, after hard mental work that has triggered the stress response.
• Exercise protects your brain against brain damage due to stress. The hippocampus is the area of the brain most vulnerable to stress. It shrinks in a very literal way when you’re under chronic stress. This may be one of the reasons mental health issues are so prevalent in academia. Exercise boosts hippocampal volume and protects your brain against such damage.
• Exercise makes you feel good. When you exercise you release endorphins. It feels so good (afterwards) and wards off PhD blues.
• Exercise makes you look good. Appealing to your vanity here…so superficial.
• Finally, exercise is good for your health, overall. We knew this already too!

It is difficult to name anything exercise is not good for. The only caveat with exercise is that it should be reasonably enjoyable for you to be able to reap all the benefits. Back to our mice: when they were allowed to run in a running wheel their health and brainpower improved significantly, but when they were forced to run, they didn’t do as well. Take a cue from the mice: make sure you do something you enjoy. If you over-exercise (if you are still tired the next day) it becomes an additional stressor to the body, and it loses many of its benefits.

References

The elderly:

K. Erickson, M. Voss, R. Prakash, A. Kramer et.al. (2011) Exercise training increases size of hippocampus and improves memory. PNAS USA 108: 3017 – 3022

The mice:

J. Rhodes, M. Mustroph, S. Chen, S. Desai, E. Cay, and E. DeYoung (2012), Aerobic exercise is the critical variable in an enriched environment that increases hippocampal neurogenesis and water maze learning in male C57BL/6J mice. Neuroscience. 219:62-71

The kids:

L. Chaddock, K. Erickson, R. Prakash, J. Kim, A. Kramer et al. (2010) A neuroimaging investigation of the association between aerobic fitness, hippocampal volume, and memory performance in preadolescent children. Brain Research 1358; 172-183

The young Irishmen:

E. Griffin, S. Mullally, C. Foley, S. Warmington, S. O’Mara, A. Kelly (2011) Aerobic exercise improves hippocampal function and increases BDNF in the serum of young adult males. Physiol. Behaviour 104(5):934-41