‘Mens Sana in Corpore Sano’, the Latin phrase meaning a rational mind in a healthy body is known to most of us. Indeed there is this rumour that aerobic exercise and more specifically running, benefits not just our body but our brain too. But what is the evidence exactly and how does aerobic exercise affect our brain?
Most studies conducted so far support that running affects the area of the brain called hippocampus.
The hippocampus (two of which exist in each side of the brain), derived from the Greek ‘ιππὀκαμπος’ meaning seahorse due to its resemblance to one, plays important roles in acquisition of new memories as well as in spatial memory and navigation. The hippocampus shrinks in late adulthood and this leads to impaired memory and dementia. It is one of the first regions of the brain to be affected in age related neurodegenerative diseases such as Alzheimer’s disease. The suggestion that exercise can protect against hippocampal degeneration is attracting a lot of attention as it is a cheap and side effect-free way to protect our ageing society against dementia.
OF MICE (AND RATS)
The plethora of studies that exist in rodents show that running can improve learning and memory and that this is correlated with changes in the hippocampus.
If you are interested in some of the biology of how running affects the hippocampus, please read on!
Rodent studies have shown that running leads to increased proliferation, survival and cellular differentiation, changes in the morphology of the cells as well as changes in synaptic function, that is in the way that messages are passed from one neuronal cell to the other. Furthermore, these changes are accompanied by changes in neurotrophic factor expression (neurotrophic factors are proteins that mediate the growth, survival and differentiation of neuron cells). Brain-derived neurotrophic factor (BDNF) plays a role in neuronal plasticity, neurogenesis and learning and is the neurotransmitter most highly upregulated by exercise. Vascular endothelial growth factor (VEGF) is also regulated by exercise and has been linked to neurogenesis and hippocampal angiogenesis (generation of new blood vessels) (Vivar et al., 2013). Finally, running affects the expression of several neurotransmitter systems (neurotransmitters are the body’s chemicals that transmit signals from neuron to neuron or neuron to muscle cells) such as the glutamatergic, GABAergic and cholinergic that play a role in hippocampal neurogenesis (Vivar and van Praag 2017).
How much exercise in rodents
Some very interested results came from a recent study where the investigators tested whether high intensity interval training (HIT) or resistance training give comparable results to endurance running with respect to the hippocampus. The results showed that HIT causes a small increase in hippocampus neurogenesis, while resistance training had no effect. The conclusion was that sustained aerobic exercise is the most effective form with regards to positively affecting the hippocampus (Nokia et al., 2016).
Another study showed that moderate amounts of long-term exercise can stimulate neurogenesis with greatest doses of exercise having little effect (Nguemeni et al., 2018).
Quite convincingly, studies in rodents show that moderate amounts of running positively affect the hippocampus, memory and learning of our little friends.
This is all very good, but what do we actually know about the effects of running and aerobic exercise in humans?
The results do not appear to be as clear-cut as in rodents. This is due to interindividual variability such as underlying diseases, stress, genetic differences. Furthermore, the different exercise protocols used in human studies such as walking, running and cycling, as well as the differences in the intensity and duration of these studies, also complicate things. Importantly, there is no direct and non-invasive way to measure neurogenesis in humans (that is we can’t cut sections through a human brain). Despite the above, there is strong evidence to suggest that our favourite sport has indeed positive effects on our brain too.
- A recent review of studies investigating the relationship between aerobic exercise and hippocampal volume has shown that various types of aerobic exercise (including cycling, walking and running) lead to increased volume of parts of the hippocampus in individuals that exercise compared to controls and this is due to prevention of volume loss that naturally occurs due to ageing (Firth et al., 2018).
- In a study to test the effect of aerobic exercise on the memory and hippocampus volume of healthy older individuals, the aerobic exercise protocol used was in the form of walking. The results showed that 1 year of aerobic exercise leads to increased hippocampal volume, which translates to improved memory and levels of BDNF (Erickson et al., 2011).
- Older healthy individuals that exercised aerobically for 6 months, showed significant increases in their brain volume (Colcombe et al., 2006).
- In healthy young adults, a high intensity interval training protocol of running (HIT) was used to test whether exercise would affect their performance in a visual pattern separation task (used as a means of indirectly measuring hippocampal neurogenesis). Indeed, an increase in fitness (VO2max) correlated with better performance in the test (Dery et al., 2013).
- In a study of young healthy individuals that were subjected 3 times per week to moderate/intense aerobic exercise interval training (70-90% of maximum heart rate) it was shown that the increase in fitness correlated with an increase in the muscle secretory factor Cathepsin B and hippocampus-dependent memory function (Moon et al., 2016).
How much exercise will do the job?
The effect of running on learning a new language was tested in healthy young adults and it was shown that subjects in the intense physical exercise group (2 sprints, 3 minutes each) were 20% faster in learning new vocabulary compared to the group of low impact aerobic running (40 minutes of low impact running) or rest, while their data also suggested that BDNF, dopamine and epinephrine are mediators of the improvement in learning (Winter et al., 2007).
On the other hand, in a study of older healthy adults it was shown that low to medium intensity exercising (such as gymnastics and Nordic walking) was enough to enhance memory performance (Ruscheweyh et al., 2011).
At the moment there are no official guidelines regarding how much and what type of exercise we should engage to in order to protect our brains against ageing. Obviously, not all people can take to the track for some high intensity interval training, especially older individuals with cardiorespiratory problems. However, from everything I have read so far it seems that moderate aerobic exercise may really protect runners from the onset of dementia in older age and may also enhance the memory and learning ability on younger individuals.
FOOD FOR THOUGHT
From all the studies about aerobic exercise and brain function I have realised that there are two issues to be considered. The first is exercise as a means of protecting the ageing brain from dementia. The second is using aerobic exercise as a means for enhancing the ability of individuals to learn (for example a new language). It may be that moderate amounts of exercise are enough to prevent against dementia but harder sessions may be needed to enhance learning in young individuals. Further studies will give us the evidence we need.
Would university students benefit from a hard session at the track before attending lectures or taking exams? Perhaps I should put this to the test! As I am trying to expand my vocabulary in Italian, I shall try to memorise a few new words after my next track session, after going for a long run and after and sitting on my lovely sofa. Will keep you posted!
Physical activity guidelines UK:
Vivar C., Potter M. C., Henriette van Praag H. (2013). All About Running: Synaptic Plasticity, Growth Factors and Adult Hippocampal Neurogenesis. Curr Top Behav Neurosci 15: 189–210.
Vivar C. and van Praag H. (2017). Running Changes the Brain: the Long and the Short of It. Physiology (Bethesda). 32: 410-424.
Nokia M. S., Lensu S., Ahtiainen J. P., Johansson P. P. Koch L. G., Britton S. L., Kainulainen H. (2016). Physical exercise increases adult hippocampal neurogenesis in male rats provided it is aerobic and sustained. J Physiol 594: 1855-1873.
Nguemeni C., McDonald M. W., Jeffers M. S., Livingston-Thomas J., Lagace D., Corbett D. (2018). Short- and Long-term Exposure to Low and High Dose Running Produce Differential Effects on Hippocampal Neurogenesis. Neuroscience 369: 202-211.
Firth J., Stubbs B., Vancampfort D., Schuch F., Lagopoulos J., Rosenbaum S., Ward P. B. (2018) Effect of aerobic exercise on hippocampal volume in humans: A systematic review and meta-analysis. Neuroimage 166: 230-238.
Erickson K. I., Voss M. W., Prakash R. S., Basak C., Szabo A., Chaddock L., Kim J. S., Heo S., Alves H., White S. M., Wojcicki T. R., Mailey E., Vieira V. J., Martin S. A., Pence B. D., Woods J. A., McAuley E., Kramer A. F. (2011). Exercise training increases size of hippocampus and improves memory. Proc Natl Acad Sci U S A 108: 3017-3022.
Colcombe S. J., Erickson K. I., Scalf P. E., Kim J. S., Prakash R., McAuley E., Elavsky S., Marquez D. X., Hu L., Kramer A. F. (2006). Aerobic exercise training increases brain volume in aging humans. J Gerontol A Biol Sci Med Sci 61: 1166-1170.
Déry N., Pilgrim M., Gibala M., Gillen J., Wojtowicz J. M., Macqueen G., Becker S. (2013). Adult hippocampal neurogenesis reduces memory interference in humans: opposing effects of aerobic exercise and depression. Front Neurosci 7: 66.
Moon H. Y., Becke A., Berron D., Becker B., Sah N1, Benoni G., Janke E., Lubejko S. T., Greig N. H., Mattison J. A., Duzel E., van Praag H. (2016). Running-Induced Systemic Cathepsin B Secretion Is Associated with Memory Function. Cell Metab 24: 332-340.
Winter B., Breitenstein C., Mooren F. C., Voelker K., Fobker M., Lechtermann A., Krueger K., Fromme A., Korsukewitz C., Floel A., Knecht S. (2007). High impact running improves learning. Neurobiol Learn Mem 87: 597-609.
Ruscheweyh R., Willemer C., Krüger K., Duning T., Warnecke T., Sommer J., Völker K., Ho H. V., Mooren F., Knecht S., Flöel A. (2011). Physical activity and memory functions: an interventional study. Neurobiol Aging 32: 1304-1319.