THE IMPORTANCE OF EXERCISE FOR THE BRAIN AND NERVOUS SYSTEM

As a species, we have spent millions of years evolving in such a way that robust physical activity has almost always been a large part of life for all humans on every continent.[1]

In today’s world, it is often forgotten that the body is an extension of the mind. Disciplines of thought, such as psychology, have endeavored to separate the body from the mind. This mentality is further perpetuated by the effects of technology, which promote leading a sedentary lifestyle. In spite of improving certain aspects of life, technological living has undermined one of the greatest tools we have for optimizing the ways in which our mind works: physical activity.

The following article reveals the interconnectedness of the brain and body, emphasizing the importance of regular exercise for developing and maintaining the health of the nervous system.

Exercise Occurs in the Brain First, Body Second

Recent research findings have shown there is no separation between the brain and body. In fact, the brain responds in advance before we are consciously aware of our own choices and resultant actions. It takes anywhere between 6 and 10 seconds[2], depending on the brain’s response and the type of processing required. This extends towards any physical activity, thoughts, feelings, sensations and perceptions – i.e. our entire lived experience.

With regard to exercise, all physical actions take place first in the brain and then in the body. For a physical action to occur, the brain needs to instruct the muscles that will be used to function via nerve transmission. This then causes the muscles to contract and sends back a signal to the brain. It is only after this that the brain can then process for us that the contraction has occurred and we can then become aware that we have performed a physical action.

In this sense, the part of brain processing that allows us to experience ourselves as having an experience is the last to fall in place and therefore we are the last to know what is truly going on inside our brains and bodies!

This also highlights just how interwoven the brain and body are and is something to keep in mind when considering the below benefits of exercise for mental health.

11 Benefits of Exercise for the Brain and Nervous System

The following benefits illustrate the importance of exercise for maintaining optimal mental health and well-being.

1. Required for Neurological Development

It has been known for a very long time that exercise enhances the development of the nervous system and is, as such, very important for children[3] [4] [5]. The majority of schools include physical education as a part of the curriculum and children are encouraged to participate in plenty of physical activity, including physical play, sports, gymnastics and dance.

A very surprising set of studies even reveal that pregnant women that exercise improve the neurological development of the fetus in utero[6].

Exercise is also required for neurological development in teenagers. However, many teens become less and less active as they grow older. As seen in children, this has been shown to impact their cognitive and academic performance detrimentally and is as much a requirement.[7]

The minimal requirement for childhood and adolescent health tends to be an hour of moderate to vigorous physical activity per day, whereas the recommendation is half that at a lesser intensity for adults.

Later research has begun to disprove that exercise is only important to the development of the growing nervous system, as it is now understood that the nervous system does not stop growing, even in adulthood. In fact, just like all other cell types, the cells comprising our nerves undergo constant turnover and renewal. Exercise helps to promote this process, improving neurogenesis (neuronal regeneration) and growth in both the developing and adult nervous systems.[8]

2. Cognition, Mental Alertness and Neurogenesis

The way in which exercise improves neurogenesis has a profound impact on cognitive function and mental alertness. This is because it tends to increase the level of neurotrophic factors, such as BDNF, and regulate neurotransmitter release in most brain areas. The effects are especially pertinent in the hippocampus, regarded as one of the main areas relevant to learning.

It is also well-known that excessive stress detracts from cognitive function when the level of cortisol (a primary stress hormone) exceeds the level of BDNF in various brain regions. Other adrenergic hormones, such as norepinephrine, also interact with this pathway to facilitate focus, attention, and other factors of mental alertness that pertain to cognition. Exercise has been shown to lower as well as regulate stress hormone signaling in the brain - some further evidence that working out can make one smarter!

Exercises that elevate the heart rate (cardio exercise), such as running, have been shown in animal studies to enhance the growth, survival and differentiation of neurons. New nerves grow alongside new blood vessels, and therefore it is not surprising that exercise also promotes the process of blood vessel growth and regeneration (angiogenesis). In these ways and more, moderate intensity exercise that elevates the heart rate can facilitate optimal neurogenesis.

The above processes also describe the neurological component of muscle building. In a similar sense, muscle memory and ordinary memory are similar processes that function in different regions of the central nervous system. Exercise has a beneficial impact on both types of memory and learning through the same mechanisms pertaining to BDNF and other neurotrophic factors.

The act of learning itself can promote neurogenesis. Training exercises can promote skill learning, which biologically translates into new neuronal growth in the brain and body.

3. Neuroplasticity

Exercise promotes neuroplasticity which is the ability of neurons to be flexible in the way they adapt, wire and fire together. If you have ever found it difficult to stop thinking a certain thought or feeling a certain feeling, you might benefit from exercising in order to boost your neuroplasticity and help your neurons to fire along a different connection!

Research highlights that there are several ways in which exercise enhances the ability of neurons to be plastic. One of them pertains to neuroplasticity of the sympathetic nervous system[9], which generally regulates bodily stress and tension. Deficits in sympathetic neuroplasticity may contribute towards chronic anxiety and promote negative stress-induced changes to digestion, cardiovascular function, sleep quality, wakefulness and immune performance. Moderate exercise may help to lower over-excitability of the sympathetic nervous system, which is a component of many states of disease.

4. Coordination and Spatial Orientation

Coordination, balance and spatial orientation depend upon the nerve communication between the brain and body. Exercise improves all three of these factors by enhancing both sides of the equation.

During exercise, the brain is stimulated in the specific regions associated with balance, spatial orientation and coordination. Furthermore, muscles are strengthened, as is the wiring and firing of neurons both inside and outside the brain. This lends itself to better posture, faster automatic (autonomic) reactions and an improved sense of balance.[10]

5. Mood Regulation and Self Confidence

An extensive study that tested the effects of wheel running on lab rats demonstrated that exercise tends to stabilize neurotransmitter release in core brain areas, including the brainstem and hypothalamus.[11]

These core brain areas control basic involuntary actions necessary for survival, such as breathing and maintaining the heartbeat. However, many of them have neuronal extensions that connect to other areas of the brain, some of which are related to emotional regulation, self-identity, reflection and higher-order cognition. It was shown that exercise helped to regulate these brain areas indirectly through promoting better function in the core brain areas, particularly by reducing stress hormone release and regulating neuronal-excitability in these areas.

Along similar lines of observation, other studies indicate that exercise also helps to promote or maintain positive self-esteem in some individuals[12].

6. Improves Sleep and Brain Toxin Removal

Exercise improves the depth and quality of sleep that can be achieved[13], especially in those who battle to get good sleep as a result of aging or neurodegenerative diseases. It appears that there are multiple ways in which exercise affects sleep that are still being researched more thoroughly.

The way in which moderate exercise may lower neurologic inflammation, promote enhanced metabolism, tire out nerve cells and increase neurotrophic factors can all also contribute toward the benefits of exercise with regard to sleep. Exercise also boosts inhibitory neurotransmitters and tones down neuronal-excitability, which would prevent anyone from having a good night’s sleep. Temperature regulation and the beneficial effects of exercise on core brain areas that help to regulate sleep, such as the hypothalamus, are other reasons exercise promotes better sleep.[14]

Furthermore, exercise dramatically improves cardiovascular and respiratory functions as well as promoting waste product removal. This alone can improve waste product removal from the deeper compartments of the brain, which only typically occurs during deep sleep. Less waste products in the brain and body may also improve sleep quality. In this way, exercise promotes better sleep as well as improved toxin removal from the brain.

Sleep aside, sweating is another mechanism by which toxins can be quickly removed from the body, many of which have a detrimental effect on neurological health. A prime example would be heavy metals, of which we are exposed to on a regular basis. Several studies have looked at arsenic, cadmium, lead and mercury in isolation and have found that sweating through either exercise or saunas greatly reduced bodily levels of these metals.[15]

Lastly, exercise promotes better sleep, and with better sleep, there is better memory consolidation. In this sense, the improvements in neurotrophic factors and cellular metabolism brought about by exercise work synergistically with an improved quality of sleep in order to enhance cognition, memory and learning.

7. Enhances Immune Function

Regular exercise at a moderate intensity has been shown to improve various aspects of immune function. These benefits extend towards increasing immune efficiency, white blood cell count, and the release of both pro- and anti-inflammatory immune chemicals (cytokines). When the immune releases both these types of cytokines in healthy ratios, immune function remains in balance.

The above aspects of immunity work closely with the nervous system[16]. Immune cells are involved in destroying faulty nerve cells and ensuring healthy growth and turnover are maintained. In this way, exercise improves neurogenesis, learning and cognition through boosting immune function, specifically white blood cell count.

This correlates with scientific observations that physically fit individuals that partake in regular exercise tend to contract infections less often than those who do no exercise or those who do too much exercise (like athletes). A recent review highlights how exercising regularly may strengthen the immune system and provide a preventative benefit for contracting COVID-19[17] – provided the individual is not already dealing with an active infection.

8. Lowers and Improves Resilience Towards Stress, Tension and Anxiety

As mentioned above, exercise promotes neuroplasticity of the sympathetic nervous system and tends to lower its activity. This part of the nervous system pertains to stress, alertness and wakefulness, and is largely governed by adrenergic signaling in the HPA axis (Hypothalamic-Pituitary-Adrenal axis).

One of the ways exercise helps to lower activity in this part of the nervous system is through activating the system[18]. Through a negative feedback loop, the system eventually dials down and stress chemicals are lowered in the body. Those who exercise regularly at a moderate intensity are better able to deal with stress from other areas of their lives and it has been proven that the stress response in these individuals is lower than in those who do not exercise. [19]

Another factor pertaining to the effects of exercise on stress would be the increase in the release of galanin coupled with the lowering of stress hormones. Galanin is a major inhibitory neuropeptide, which means it serves to inhibit neuronal excitability and down-regulate the firing of the nerves when present. Faulty regulation of galanin gene expression is a key risk factor for depression, maladaptive stress responses and chronic anxiety[20], making exercise an attractive option for those predisposed to these conditions.

Studies reveal however that exercise does little to help those who have an under-functioning sympathetic nervous system[21]. In these cases, the lack of stress hormones makes these individuals highly susceptible to stress. Exercise may help after correcting the neurotransmitter imbalance in this system for these patients.

9. Improves Cerebrovascular Health and Respiratory Efficiency

Respiration is vital for the health of the nervous system, both at the respiratory level and at the cellular level. Exercise impacts both types of respiration beneficially if done at a moderate intensity.

The peak in activity helps to regulate autonomic nervous system function[22], which in turn promotes improved respiratory and cardiovascular function. When one exercises, it promotes deeper breathing, strengthening of the heart for better circulation, increased oxygen levels in the blood stream and a greater capacity for oxygen intake. The increase in oxygen uptake goes on to increase the ability to do more exercise or physical activity as it increases cellular energy production.

The brain is one of the most vulnerable organs with respect to oxygen deprivation. As a result, its well-being relies very much on the health of the pulmonary system and the cardiovascular system. The circulation of cerebral spinal fluid moves in tandem with cardiovascular circulation and thus affects the movement of nutrients, cell-signaling chemicals and waste products. Exercising helps to promote increased brain oxygen levels and increases the turnover of waste products, which helps to keep the neurons therein functioning optimally.

Since many waste products are only truly drained from the deep compartments of the brain during deep sleep, the cerebrovascular system is vital in ensuring that the brain can sustain its activity during the day and does not get clogged, per se.

10. Reduces the Risk of Acquiring Neurodegenerative Diseases

Research is currently accumulating to reveal that exercise has major benefits for the aging brain and for reducing the risk of acquiring neurodegenerative disorders. These include dementias (especially Alzheimer’s disease[23]), Parkinson's disorder, cerebrovascular diseases, traumatic brain injury[24], epilepsy and demyelinating diseases.[25] [26]

Out of all the benefits exercise poses for mental health, lowering neuroinflammation is perhaps number one in terms of preventing neurodegenerative diseases. Older adults that were placed on exercise training programs had improved mental health and cognition compared to the control group[27].

Improving sleep quality, enhancing metabolism, reducing toxic load in the brain and improving the growth and regeneration of neurons are other key factors that make exercise a vital component of neurologic disease prevention. For the same reasons, it is equally invaluable as a complementary intervention for patients suffering from such conditions and has been shown to improve the quality of life in many cases.

11. Enhances Metabolism

Increased respiration as a result of exercise begins to increase and improve cellular respiration and energy output. When there is more energy available to our cells, they can achieve more. This generally translates into improvements in growth, repair mechanisms and cellular turnover. In the nervous system, the increased cellular metabolism helps promote neurogenesis (neuronal repair) and neuroplasticity (neuronal adaptation and synapse formation).

An interesting side note on this matter would be the fact that muscle and fat release lactic acid after exercising. If the lactic acid builds up too much, we experience muscle stiffness and fatigue. For many years, this was perceived as a bad thing, but research has been revealing that this lactic acid gets transported to the liver and transformed into lactate before re-entering circulation to serve as a fuel for energy production. Just like glucose, lactate can be converted into ATP (energy) by the mitochondria in neurons and muscle tissue in order to further enhance their growth and turnover.[28] Lactate has also proven to be a fuel source for the growth and expansion of new neurons, further showing how exercise improves neurogenesis, cognition and metabolism in the nervous system.

The fatigue experienced in this regard is more the lag time between lactic acid conversion into ATP and the decline in ATP levels as a result of the increased activity.

Exercise Tips for Enhancing Mental Health

• Get a Good Mix of Exercise Types

What type of exercise works best? Different types of exercise confer different benefits to both brain and body. In general, aerobic exercise tends to yield the most benefit for the nervous system due to the cardiovascular-respiratory enhancements.

However, stretching and weight-bearing exercise is equally as important for maintaining other aspects of health which may have secondary impacts on neurological health. For example, stretching and loosening up the muscles and joints may help improve the benefits gained from aerobic exercise (potentially offering additional fuel substrates such as lactic acid) and tends to lower the risk of exertion-related injury.

Weight-bearing exercise is good for bone health and ensuring that calcium and other minerals remain in the bones. Without this component, these minerals may begin to move the wrong way, weakening the bone matrix and compromising the vascular system. This, in turn, might contribute towards reduced circulation, lower cognition and increased body stiffness.

• Exercise as Regularly as Possible, For as Long as Possible

How much exercise is considered healthy? The answer to this question is unique to the individual asking it. A healthy level of exercise depends on your physical ability and fitness level. One ought to exercise regularly, every day if possible, and for as long as their body can allow without over-exerting themselves too much. It is important to use our muscles and break a sweat, but if one hurts or over-exerts themselves, the result is not nearly as beneficial.

In the modern context, time is another constraint for many in terms of how much exercise one can do. It is generally recommended that adults partake in at least 30 minutes of moderate-intensity exercise for a minimum of 5 days a week. For children, this amount is increased up to an hour a day. In spite of this, adults that do more exercise tend to benefit if the exercise is kept at a moderate intensity.

Athletes and military personal tend to do a lot more exercise every day, at much higher intensities, in order to purposefully over-exert their bodies. This level of physical activity is not advised for the general population.

While the evidence is promising, it is very difficult to ascertain what a beneficial level of exercise would be in the elderly population. However, the same advice applies to all. One needs to work with their level of physical aptness and make progress from there.

• Try Not To Overdo It

Too much exercise can cause too much tissue to break down and increase cerebral ammonia levels. Ammonia is a waste product of most cells and, at detrimentally high concentrations, can cause neurologic toxicity. Ammonia toxicity tends to result in a temporary reduction in cognition and a loss of coordination.[29]

Further research reveals that irregular binge exercising, particularly at high intensities, can suppress immune function, increase inflammation and over-activate the sympathetic nervous system, which is associated with stress[30]. This may be related to the increase in bodily toxicity observed for the same phenomenon.

Some data highlights how athletes are more susceptible towards upper respiratory tract infections during intensive training[31], while other sources are challenging that notion as infection tends to be brought about by multiple factors that also affect athletes[32]. Therefore, it is not clear whether extreme exercise is a direct cause of infection or if it merely suppresses immune function and may increase the risk. Nevertheless, it is a bad idea to exercise while one has an active infection, as many systems of the body become compromised under such conditions.

On this note, it is easy to overdo it if your body has trouble getting rid of waste products. Those with thyroid conditions, autoimmune conditions, chronic viral infections, liver problems or metabolic diseases should be more cautious when approaching exercise than other individuals as a result.

• Avoid Exercise 1 Hour Before Bed Time

Studies reveal that exercising improves the quality of sleep but not if done in the hour before bedtime.[33] Exercising right before bed may keep one awake for longer and interfere with the depth and quality of sleep. However, exercising at any other time of the day at a moderate intensity appears to improve sleeping parameters, especially in those that suffer from insomnia or who have limited sleep quality.

Conclusion

Regular exercise is vital for health and well-being. This is especially true of the cardiovascular system and the nervous system, which are enhanced the most by the benefits of exercise. Consistent physical activity at a moderate intensity can serve to improve cognition, learning, memory, emotional regulation, adaptability and all forms of neurological processing in general. Furthermore, the benefits of exercising regularly extend into all phases of life, helping to prevent the onset of neurodegenerative diseases and improve mental functions well into senescence.

Exercise should occur at a moderate intensity, for at least 30-60 mins a day, 5 days a week. Over-exertion negates the benefits of exercise and is not advisable. A combination of aerobic exercise, weight-bearing exercise, stretching and training confer the best results – however, any exercise tends to be better than none at all!

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