by Dr. Keoni Teta
Conditions of the brain that cause, or have potential to cause, dementia-like illnesses are at epidemic proportions. Some estimates say 135 million people in the US will become afflicted with some form of dementia by the year 2050. This figure is probably on the low end considering the rapid rise in obesity and diabetes, both of which can have devastating effects on brain health.
Research on the advantages of exercise for improving brain function have finally put the kibosh on the myth of the dumb jock. Yes, it is safe to say that people who exercise regularly have better brains, and are continuously optimizing their brain function as long as they stay physically active. Physical activity is shown to give one, no matter their age, a younger and healthier brain. Exercise has many direct, positive effects on the brain, including, but not limited to, increasing cerebral blood flow, promoting neuronal growth and balancing neurochemicals. It has a multitude of indirect benefits, such as blunting the negative response to the stress hormone (cortisol) on brain atrophy and function, quelling anxiety, and promoting a strong anti-depressant effect.
Also, the dogma that existed just a few decades ago, that the brain has a finite number of neurons, and cannot grow new ones, has been shown to be absolutely false. Yes, throughout life, the brain creates and grows new neurons (known as neurogenesis), and exercise greatly potentiates this outcome.
With what we know now, exercise is clearly the best way to reduce the risk of age-related cognitive decline and neurodegeneration. No medication even comes close to what exercise does for your brain. Furthermore, exercise has been shown to prevent, and improve,
almost all neurological diseases and disorders such as:
- Parkinson’s Disease 1
- Alzheimer’s Disease 2
- Stroke recovery 3
- Depression/Anxiety 4,5,18
- ADHD 6
- Age-related Cognitive Decline 7
- Schizophrenia 17
- Multiple Sclerosis 19
The one area of the brain that has the most research in terms of how exercise affects it, is the hipoocampus. The hippocampus belongs to the limbic system and plays a major role in short and long-term memory, spatial navigation, and conflict processing. It is located in the brain under the cerebral cortex and resides in the two medial portions of the temporal lobe. This is a wonderful thing because if one side no longer functions, then the other hippocampi can take over.
Recent evidence has shed light on the mechanisms within the brain and hippocampus of how exericse improves brain function and cognition. The main mechansims are:
- Neural Plasticity
- and Neurotrophic Factors
Neural Plasticity is the brain’s ability to reorganize itself by forming new neural connections throughout life. It allows the neurons in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment. Basically, the brain is constantly reshaping itself based on the lifestyle inputs we give it. Exercise, learning new things, sleep, stress and nutrition all help mold and shape the brain throughout life.
Neurogenesis is the process by which neurons are generated from neural stem cells and progenitor cells (both of which are “parent cells”). It is basically the formation of new nerve cells.
Neurotrophic Factors are a family of biomolecules that support the growth, survival, and differentiation of developing and mature neurons. There are many types of neurotrophic factors with more, certainly, being discovered in the future. The main ones shown to optimize brain health in response to exercise are, BDNF (Brain-Derived Neurotrophic Factor), Insulin-like Growth Factor 1 (IGF-1), and Vascular Endothelial Growth Factor (VEGF).
- BDNF – acts on neurons throughout the body, especially the brain areas involved with learning and memory, like the hippocampus. It promotes neurogenesis and neuroplasticity. Exercise significantly increases the amount of BDNF in the body.
- IGF-1 – mediates many of the effects of growth hormone and helps control tissue growth and remodeling. Exercise promotes increased levels of IGF-1. The amount of IGF-1 released into the blood during exercise is positively correlated with exercise intensity and duration. Like BDNF, it promotes neural plasticity and neurogenesis. It also promotes muscle growth and strength.
- VEGF – as its name implies, Vascular Endothelial Growth Factors, promote the growth of new blood vessels. It also plays an important role in neural plasticity and neurogenesis. Hypoxia, or inadequate cellular oxygen supply, is the main stimulus for VEGF secretion, and exercise creates a relative hypoxic environment in the body. VEGF exerts a neuro-protective effect in hypoxic neurons.
Just exercising your muscles causes a surge in these brain enhancing biomolecules (BDNF, IGF-1 and VEGF). This hormonal soup helps to create a better brain and a better body.
Exercise and Learning:
Since exercise of any kind appears to prevent cognitive decline, a good question to ask is, whether it improves learning capacity. A number of studies have answered this question.
A study in the journal, Neurobiology of Learning and Memory, looked to see how quickly running improves learning ability. 10 Learning performance was assessed immediately after high impact sprints, jogging, or a period of rest in 27 healthy subjects in a randomized, cross-over design. The study found vocabulary learning was 20% faster after intense physical exercise (sprints) as compared to the other two groups. Sprinting elicited the strongest increases in BDNF and catecholamine levels. More sustained BDNF levels during learning after sprinting were related to better short-term learning success, whereas absolute dopamine and epinephrine levels were related to better intermediate (dopamine) and long-term (epinephrine) retentions of the novel vocabulary. Thus, BDNF and two of the catecholamines seem to be mediators by which physical exercise improves learning. Having students sprint in place immediately before exams may be helpful for getting better grades.
Exercise during pregnancy appears to confer tremendous benefit to offspring. Specifically, improving object memory recall. This was an animal study, and the exercise form used was running. It is amazing that even a pregnant mother who exercises has the potential to make her baby have a better brain. 11
Aerobic Exercise and Brain Optimization:
Aerobic training also has plenty of evidence showing that it attenuates brain atrophy and cognitive decline, with positive effects observed for motor function, cognitive speed, delayed memory functions and auditory and visual attention. As cardiorespiratory fitness improves, so does brain function.
Twelve weeks of aerobic exercise, performed 3 times a week, for 30 minutes on a treadmill, appears to show significant benefit in people with traumatic brain injury. 15 The cognitive benefits were strongly correlated with improvement in cardiorespiratory fitness.
In this study a training regimen of cycling improved gait and executive functions in people with Parkinson’s disease. Recumbent bicycles were used to train participants. Duration of the exercise program started at 20 min with 60% of intensity per session, and was then increased by steps of 5 min and 5% intensity every week until participants reached 40 min of training at 80% intensity. Bike speed was maintained at 60 revolutions per minute. The program lasted 12 weeks, with three training sessions per week. 16
Another study, in the elderly at risk with Alzheimers disease, done with walking as the main form of exercise, showed a 1,800% increase in memory, language ability, attention, and other cognitive parameters as compared to the non-exercisers. The exercise group only spent about 2.5 hours/week exercising. 20
Building Muscle and Brain Optimization:
Compared to aerobic exercise for brain health, resistance training has not been studied nearly as much. However, the data that we do have appears to show just as much benefit for the brain as other forms of exercise. The advantage of resistance training is that it improves strength and muscle maintenance better than aerobic exercise.
A study in the Journal of International Neuropsychological Society looked at two different forms of exercise, resistance training and toning/balance training, in order to assess the brain benefits, cognition and brain volume. 12 The study was done with older women, and was 52 weeks in duration. It compared resistance training (either once- or twice-weekly) or balance-and-toning (twice-weekly). The cognition measures were executive functioning and memory, and they were assessed before the study began, immediately after the 52 weeks of training and 1 year after the study training ceased. Brain volume was also assessed at those time points. The resistance training whether it was once or twice per week improved the brain metrics better than the toning/balance training. So older women with as little 1-2 time per week of lifting can increase their brain size and improve their memory.
A study out of Australia from the University of Sydney, showed a direct correlation between building muscle and improving one’s memory and cognitive functioning. 13 The results were part of the SMART (The Study of Mental and Resistance Training) study 14 which was a randomized, double-blind trial involving 100 older adults with Mild Cognitive Impairment (MCI), aged between 55 and 86. The participants were divided into four groups doing either:
- Resistance exercise and computerized cognitive training;
- Resistance exercise and a placebo computerized training (watching nature videos);
- Brain training and a placebo exercise program (seated stretching/calisthenics); or
- Placebo physical exercise and placebo cognitive training.
The resistance exercise prescribed was only two weight lifting sessions per week for 6 months. Besides showing a direct strength/brain benefit, the study also showed that resistance training is more beneficial than just brain games and memory training. The resistance exercise used a minimum of 80 % of their peak capacity. The benefits persisted even 12 months after the supervised exercise sessions ended.
Exercise, Genetics, and Dementia Risk:
A study in the Journal of Alzheimer’s Disease (AD) looked at the relationship between genetics, exercise and dementia risk. 8 They looked at the genotype Apolipoprotein E (APOE), in which people have increased risk of AD. This gene is partly responsible lipid transport. Specifically, carriers of the ε4 allele of the APOE gene (APOE4) as opposed to the other APOE genotypes (APOE 2 and 3) have higher levels of total cholesterol and accumulation of atherosclerotic plaques in arteries, leading to increased risks of cardiovascular disease and stroke, as well as dementia and AD. What this study found is that genetics and lifestyle independently determine dementia risk. In other words, sedentary individuals have just as much risk of AD as those in the high risk APOE genotype (APOE4).
The exercisers in this study primarily did only walking, and it showed walking, as little as three times a week, conferred brain benefits.
Considering the healthy brain effects of exercise, it would make sense for people in the highest risk genotype, APOE4, that remain active throughout life, would offset the increased genetic risk of AD. Unfortunately, the above study did not specifically find this association. However, it is a well-known fact that not all people with the APOE4 genotype get AD, and those that don’t tend to be active and have other healthy habits. It is likely true that people with the APOE4 genotype that remain active lower their risk of AD to the equivalent of non-carriers. 9
Exercise is an effective and smart strategy for brain related diseases, especially for age-related diseases that cause cognitive decline. It is also a wonderful tool for promoting learning ability and capacity. Based on this evidence, it seems Physical Education, or exercise, should be more of a requirement for learning, than academic study alone. Almost all forms of cardiovascular exercise, as well as different types of resistance training, have shown brain benefits. It does appear higher intensity exercise conveys more of an advantage for boosting BDNF, IGF-1, and VEGF. Currently, the form of exercise that is best for optimizing brain health is not known. However, it is safe to say that exercise should consist of both an aerobic and anaerobic component in order to maximize brain benefits. It is phenomenal that only as little as 15 minutes of walking per day helps your brain. And, getting stronger or putting on more muscle has a direct corresponding effect on brain health. Another, fascinating aspect, is that these brain effects have been shown to be almost immediate, and may last for up to, at least, a year after exercise is stopped. Anyway, the adage, “body fitness promotes brain fitness,” or something similar should certainly replace the “dumb jock” myth. The other thing about the evidence on exercise and brain health is that it is never too late to start exercising.