COGNITIVE BENEFITS OF EXERCISE: WORKING THE BRAIN FOR MENTAL LONGEVITY
Medically Reviewed by Dr. Sony Sherpa, (MBBS)
From an evolutionary perspective, the modern human brain formed in response to our ancestor’s constant need for adaptation to environmental challenges. As early man developed the skills needed for survival, they relied heavily on physical activity, which is thought to have been critical to brain development.
Evidence appears to support this notion, as motor and sensory information is stimulated by physical activity and interaction with the environment. The central part of the brain, which connects areas that enable cognition, is activated in this process.
In this article, we will explore how exercise can enhance cognition and keep cognitive decline at bay with aging. In addition, we will also focus on ideal exercises for brain health.
Exercise Supports the Brain through the Cardiovascular System
The overall health effects of exercise are mediated through the cardiovascular system. Working the muscles, including the heart, stimulates blood flow and the transportation of oxygen, nutrients, immune cells while aiding removal of waste products. Lymph drainage is known to be elevated by muscular contractions and thus, exercise may enhance immune cell transport from the site of antigen administration to the drainage of lymph nodes[1]. With this movement, arises a peak in basal metabolism, which encourages new tissue growth, repair, and cell turnover, thereby contributing to all the other known mental benefits of exercise.
Exercise Supports Brain Metabolism. As one of the organs with the largest energy requirements, the brain consumes the most oxygen and other nutrients than any other tissue in the body. Exercise optimizes the movement of these substances into the brain, which indirectly supports its growth, renewal, and development.
Optimal Brain Nourishment Demands Physical Activity. While brain circulation is adequately maintained at all times for our survival, it cannot be optimally sustained without physical activity. This is due to the fact that the brain has a particularly protected blood supply, consisting of two filtration barriers (spine-brain and blood-brain barriers) and specific nutrient transporters. Once in the brain, blood exchanges oxygen and nutrients with waste from the cerebral spinal fluid. The cerebral spinal fluid moves in tandem with the blood supply, circulating in time with the heartbeat and respiration rate. Thus, exercise is vital for regulating brain circulation to ensure that the deeper compartments of the brain can be adequately nourished and oxygenated to meet energy requirements.
Exercise Aids with Deep Brain Waste Disposal. The same applies in reverse with regard to waste products. Aside from exercise, deep sleep is the only other time the brain can rid its deeper compartments of toxins. Toxins are known to build up over the course of the day, and if not properly disposed of, can result in exacerbating neurodegenerative processes that eventually culminate in disease.
4 Anti-Aging Cognitive Benefits of Exercise
Exercise beneficially changes brain structures involved in focus, memory and learning. Through stimulating and regulating brain metabolism, exercise is known to enhance brain function, and protect against age-related cognitive decline in the following four ways:
1. Enhanced mood
Moderate-intensity exercise is known to significantly improve one’s mood after 10-60 mins of activity.
While it is commonly known that this is partly related to the way exercise promotes the release of endorphins (feel-good chemicals), there are several other underlying mechanisms that explain the connection between exercise and mood:
Increase in the level of Neurotransmitters and Regulation. Exercise has been documented to increase levels of vital neurotransmitters, such as dopamine and serotonin. This improves one’s mood and promotes neurotransmitter regulation. Dopamine and serotonin form the precursors to other major neurotransmitters, such as noradrenaline and adrenaline, and regulate their actions. These neurotransmitter gains have been proven to be long-lasting, particularly in regularly physically active individuals.
Enhanced Motivation. As motivation is linked to the regulation of dopamine, and to a lesser extent, serotonin, exercise is capable of improving motivation in the long run. Motivation has been linked to increases in processing and response speed, as well as enhancing cognitive and behavioral control[2]. Loss of motivation toward a specific mental task can detract from one’s ability to perform the task. Exercise can help to preserve motivation by regulating neurotransmitters such as dopamine, however, other factors can still intervene with motivation[3]. Sedentary individuals tend to show symptoms of reduced cognitive ability and less motivation toward any given task.[4] Additionally, activation of the brain’s reward and motivational pathways has been shown to promote memory formation through stimulating dopamine release in the hippocampus.[5]
Daily Physical Activity Promotes a Long-Lasting Positive Mood. Single bouts of exercise (also termed Acute exercise) have been shown to aid in sustaining a positive mood state throughout the day. Studies are mixed regarding the effects of acute exercise on a regular basis in enhancing the mood for longer periods of time, however, several studies suggest this to be the case. [6] Exercise has been proven to reduce the threshold for provoking positive emotions in individuals, which may increase the likelihood of feeling more positive on average through time.
Positivity, Humor, and Memory. It logically follows that a better mood tends to encourage opportunities for humor, and laughter. Studies have linked laughter with substantial improvements in memory recall, learning,[7] and consolidation[8] in participants. This is likely related to the way in which laughter alleviates stress[9], increases factors associated with neuroplasticity and enhances connection in brain regions involved in cognitive processing (areas of the prefrontal cortex). Due to the way in which both laughter and exercise promote endorphins, exercise may also promote laughter by chemical association.
2. Focus
Exercise can improve focus in the following ways:
Enhanced Concentration. Focus and attentional control are associated with brain areas that exercise is known to beneficially affect. According to experts in the field, exercise has been shown to increase one’s ability to concentrate for at least 2 hours afterward. According to studies, 40 mins of aerobic exercise each week improved the cognitive performance of students by up to 8%, with concentration being enhanced by as much as 20%. Children with ADHD exhibited a roughly 30% improvement in performing tasks that were attentionally demanding when exercising prior.[10] In adults, studies have shown that even brief sessions of exercise during work breaks tended to improve productivity, cognition, health, and job satisfaction.[11]
Executive Control and Selective Focus. Studies reveal that exercise beneficially enhances selective focus, allowing the participant to better filter out irrelevant information and distractions. This is attributed to the cardiovascular benefits of exercise, which serve to enhance frontal lobe function.[12]
Mental Alertness and Cognitive Regeneration. Due to the neurotransmitter and cortical stimulating properties of exercise, it is associated with an increase in overall arousal and mental alertness. An acute session of aerobic exercise has been shown to counteract mental fatigue and enhance cognitive regeneration in mentally drained individuals, allowing for sustained focus.[13] These findings do not apply to exhaustive exercise and overexertion, which is capable of increasing both physical and mental fatigue.
3. Memory and Learning
The following points highlight several ways in which exercise contributes towards improving memory, recall and learning capacities of the brain:
Improved Memory Consolidation and Recall. Moderate-intensity exercise has been shown to enhance long-term memory by improving information capture, memory consolidation, and recall at 60 mins and 24 hours post-workout[14]. Animal studies suggest that not all types of exercise can improve recall (e.g. endurance exercise) yet may still enhance learning and consolidation.[15] Quality sleep is also known to enhance memory, consolidation, recall, and overall cognitive performance. Exercise increases sleep quality and was shown to improve memory function prior to taking a nap.[16]
Short-Term Memory Enhancement. Long-term consistent exercise appears to enhance working memory function and helps to retain more information in the short term. Exercise seems to enhance short-term memory more than long-term memory.[17] In age-related cognitive decline, short-term memory often suffers more than long-term memory. This symptom of aging may be partially prevented through regular physical activity, as shown in a one-year study examining the effects of aerobic walking exercise on short-term memory and cognition in a group of elderly participants.[18]
Neurogenesis. Exercise increases the release of neurotrophic factors, which encourages the growth of new neurons and the development of brain structures. Studies observing the long-term effects of exercise reveal that it promotes the growth of the prefrontal cortex, and hippocampus, both of which are involved in forming memories, decision making and learning.
New Blood Vessels and Neurons Develop Together. Increased blood circulation tends to promote the growth of new blood vessels. Nerves and neurons typically form alongside blood vessels, and factors that support their growth also typically support neurogenesis, brain development, and improvements in learning and cognition.
Neuroplasticity. The above association was proven in a small trial conducted on the elderly. Participants enrolled in a one-year aerobic exercise program, showed enhanced neuronal connectivity in the temporal lobes through increasing brain levels of vascular endothelial growth factor (VEGF). This simultaneously promoted neuronal growth factors, neurogenesis, and enhanced brain development.[19]
Enhanced Overall Brain Communication. Gains in white matter volume in the corpus callosum have also been noted in response to aerobic exercise, which can conserve neural communication between the left and right brain hemispheres. As the corpus callosum is a central brain hub for communication between many brain areas, including the sensory-motor cortex, it makes sense that physical activity would promote its growth by stimulating this brain area. [20]
Decreased Processing and Response Time. Just as aerobic exercise has been shown to improve physical responses, it can improve mental responses as well. Studies indicate that lower mental processing and response times are directly linked to the amount of aerobic exercise one does on average. Across studies, this has been linked to greater allocation of brain resources to environmental stimuli, meaning that physically active individuals are able to pay more attention to the information they encounter and also process it faster than sedentary individuals. These findings are particularly pronounced in older adults and aging populations, however, healthy young adults and children also tend to benefit cognitively from aerobic exercise in a similar fashion.
Enhanced Error Detection and Correction. Physically active individuals were shown to have improved behavioral control pertaining to elevated neurologic efficiency and brain function. These improvements correlated with better behavioral error detection and correction. Despite better behavioral control, fewer attentional resources are required to observe behavior in physically fit individuals, allowing more focus to be spent on the environment and processing new information.
These insights highlight how exercise can promote enhanced self-reflexivity, behavioral learning, cognitive control, and emotional stability, all of which contribute towards improved cognition.
Reductions in Stress-Related Brain Activity. While stress is known to be a potent emotional memory imprinter, it ultimately detracts from overall cognition. Excessive stress reduces the brain’s ability for neurogenesis and neuroplasticity by decreasing the production of neurotrophic factors such as BDNF. Chronic stress typically changes brain structures in a way that promotes anxiety, serving to detract from cognition and leading to brain shrinkage. Exercise can stabilize stress hormones and improve resilience towards stress. Furthermore, studies show that physically active individuals experience less activation in brain areas pertaining to stress that are known to be overactive in anxiety-related disorders, including PTSD.
4. Protects Against Age-Related Cognitive Decline
Most of the cognitive effects listed above are known to decline through the aging process. Elderly individuals who are more physically active tend to lead longer, healthier lives and suffer less from age-related cognitive decline[21].
Prolongs Age-Related Brain Shrinkage. Exercise helps to increase the size of the prefrontal cortex and hippocampus. This helps to prolong the onset of neurodegenerative diseases like dementia and age-related cognitive decline, which are both associated with brain shrinkage, specifically in these areas. A few studies highlighted that exercise can prevent or prolong age-related shrinkage in other brain areas too, including the temporal, frontal, and parietal lobes. In an exercise intervention carried out on 120 older adults, aerobic exercise training increased the size of the hippocampus by 2%, estimated to have prolonged its age-related shrinkage by 1-2 years. These findings were also associated with improved memory function.[22]
Conserves White and Grey Matter Integrity. Several studies have highlighted that brain growth in response to exercise serves to conserve both white and grey matter in the brain. In most neurodegenerative diseases, both white and grey matter are degraded over time. The size of both in the frontal cortex increase in response to aerobic workouts, promoting overall cognition.
Promotes Remyelination. Besides conserving white brain matter integrity, preliminary studies highlight that exercise is capable of promoting remyelination as well[23]. This can protect the aging individual from demyelination which is a common aspect of cognitive decline, neurodegenerative disease processes, loss of overall brain connectivity, and flexibility of thought.
Enhances Brain Renewal in Aged Subjects with Cognitive Decline. Exercise in elderly subjects with cognitive decline has been proven to enhance neuronal growth, energy production, mitochondrial function, and the ability of neurons to self-repair. All of these can enhance the renewal of brain tissue and protect aged individuals from cognitive decline.
Reducing Hypoxia Risk in Healthy Individuals. Hypoxia (reduced oxygen supply) in the brain has been shown to contribute towards the onset of cognitive decline and neurodegenerative diseases, including Alzheimer’s Disease. While studies show that hyperbaric oxygenation improved cognitive outcomes in these patient groups, the results of studies gauging the effects of exercise were mixed in this respect. In healthy individuals, exercise has been shown to increase cerebral oxygenation[24], possibly protecting against hypoxia-related cognitive decline and diseases.
Brain Insulin Regulation. Insulin signaling is vital to all cells of the body for optimal metabolic operations to take place. Various neurological diseases, including Alzheimer's disease, have been linked with faulty insulin signaling and cognitive decline. Exercise is known to help regulate insulin levels by promoting better utilization of stored fats and glycogen (stored sugar), as well as lowering hyperglycemia. In the brain, insulin receptors are most densely concentrated in brain regions pertaining to learning, memory, and cognition, including the cerebral cortex and specifically the hippocampus.[25] In animal studies, insulin is known to improve neuroplasticity, memory formation, and learning processes through affecting neurotransmission in the hippocampus[26]. Exercise has been shown to increase insulin levels in the hippocampus, supporting optimal cognition, as well as signaling and function. It has also been shown to restore insulin sensitivity in the brains of overweight individuals[27].
Lifelong Exercise Poses Accumulative NeuroProtection. When studying the effects of physical activity across different age groups, regular exercise has been shown to protect against age-related cognitive decline later in life. This suggests that the more exercise one does throughout the course of one’s life, the less likely one is to suffer from cognitive decline.
Lowered Risk of Neurodegenerative Disease. Regular physical activity has been proven to reduce the risk of acquiring dementia, and other neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease and Huntington’s disease. Additionally, individuals with these conditions have been shown to benefit immensely from exercise, with improvements in learning, memory, and other aspects of cognition highlighted throughout this article. A noteworthy benefit of exercise includes reductions in neuroinflammation, which is known to increase the risk for neurodegeneration, as well as to be an inherent component of related diseases.
Gender Differences in the Brain Health Effects of Exercise
While the overall effects of exercise on preserving cognition are relatively similar between men, and women, there are subtle differences across studies that highlight underlying gender differences.[28]
Female Cognitive Decline Risk Bias. Women are more likely than men to acquire age-related cognitive decline[29], dementia and other similar neurodegenerative disorders. A large study on elderly individuals in the US highlighted that women have greater cognitive ability than men at older ages, but tended to decline cognitively at faster rates.[30]
Females were shown to respond more to exercise in the following cognitive areas:
- Increased Executive Functions, Including Attention. Studies show that older women showed a greater improvement in executive control functions in response to aerobic exercise than older male participants. Long-term studies have linked this to greater left dorsolateral prefrontal cortex volume in women than in men who frequently exercise.
- Enhanced Brain Connectivity. Further evidence reveals that women exhibit higher brain connectivity in brain areas pertaining to the frontoparietal network, implicating a greater general response to physical activity than seen in men. These findings underscore the way in which women tend to be better at social, self-referential, and memory processing than men.
Males were more likely to benefit cognitively from exercise on the following grounds:
- Improved Word Fluency. Studies with more male participants revealed that aerobic exercise improved word fluency more significantly than those with fewer males present.
- Memory and Learning Capacity in the Long-Term. When comparing long-term and short-term interventions, the learning- and memory-enhancing benefits of exercise may be better in men than in women. In a one-year walking trial, the size of the left hippocampus increased more in males than in females. These results may only apply to long-term studies, as the size of the hippocampus showed a greater increase in females during a 7- day trial by comparison to male counterparts.
Despite these differences, older and elderly males typically exercise more on average than their female counterparts, which may explain the lower rates of cognitive decline seen in men.
Exercising for the Brain: Does the Type of Exercise Matter?
All forms of exercise are generally regarded as great for overall health and mental well-being, as they all can stimulate the nervous system, enhance immune function, burn fat and increase blood circulation.
Aerobic Exercise is Best for Brain Health. According to studies, by comparison to other forms of physical activity, there is overwhelming evidence to support that aerobic exercise offers the most cognitive benefits above all other forms. It is now understood that the state of health of one’s brain is largely reflective of cardiovascular fitness levels, including the degree to which the brain grows and develops.
Best Aerobics for Dementia Patients. For elderly patients with dementia, spinning aerobic exercise proved to be more therapeutic than other aerobics exercises.[31]
How other Types of Exercise benefit the Brain. While aerobic exercise may show the most benefit, it should be balanced with other types of exercise for optimal results. Other exercises can enhance our ability to perform aerobic exercise and are able to improve cognition in the following ways:
- Endurance Exercise and Strength/Resistance Training. These types of activities tend to work the muscles repetitively and are associated with muscle-derived elevations in anti-inflammatory substances[32] that benefit overall health and well-being. They have been shown to improve most markers of cognition across studies, except for short-term working memory[33]. Increasing the intensity of such exercises is associated with improved cardiovascular and cognitive benefits, bordering on enhanced aerobic fitness.[34]
- Stretching and Coordination Exercises. Across studies observing the cognitive effects of stretching and exercises that promote physical coordination and balance, the complexity of the exercise dictated the degree of benefit. These types of exercises have been shown to improve selective attention better than endurance exercises in middle-aged individuals[35].
- Cognitively Demanding Exercise. Physical activity that includes a mentally tasking dual component poses greater gains in cognition than exercise alone. In this respect, sports and some forms of dance that require greater use of mental resources are likely to be more beneficial for preserving the brain in the long run.
When Can Exercise Be a Bad Thing?
As with everything else, moderation is the key when it comes to exercise. The below scenarios highlight when too much exercise can be damaging to the body.
Over-Exertion and Physical Exhaustion is Not Recommended. Overly intensive exercise is generally not conducive to physical well-being or brain health. Physical exhaustion can cause increased overall inflammation, mental fatigue, sleep disruptions, and more.
Exercise Can Become Addictive. While not classified as a full-blown addictive disorder, exercise addiction is a rare behavioral addiction that affects a small subset of the global population (with an estimated prevalence of 0.3-3%). Just like other addictions of the same category, those with exercise addiction have a compulsive need to exercise and have difficulty moderating it. These individuals risk chronic overexertion and injuries, which regularly promotes bodily inflammation and often predisposes those inclined towards ongoing respiratory infections.[36] Other symptoms that may occur as a result of overtraining include nausea, hypoglycemia, heart rate irregularities, and respiratory issues.
Infectious Illness or Injury Requires Rest. Exercise induces physiological stress, which under usual circumstances, promotes an optimal metabolism and tissue regeneration, alongside the release of anti-inflammatory compounds. When one has an injury or an infectious illness, exercise should be avoided so as not to overload the system with physiological stress and risk intensifying symptoms. After sufficient processing has occurred for either condition, exercise may be slowly introduced in an effort to assist recovery.
Physical Activity ‘Prescriptions’ for Brain Health and Mental Longevity
Experts recommend a bare minimum of 3-4 exercise sessions per week, consisting of at least 30 mins each. Maximum benefit can be seen in moderate-intensity exercise sessions of 45-60 mins. Physical activity should be varied and needs to include some form of aerobic exercise that increases the heart rate, improving cardiorespiratory fitness.
Metabolic Factors May Increase Exercise Requirements. A new line of research indicates that those with metabolic or energy deficits, such as those with obesity, or who struggle with chronic anxiety, may require 60 min sessions or longer, 5 times a week, to meet their metabolic needs. These individuals are also at an increased risk for developing neurological problems and brain-related diseases, which regular physical activity can help to prevent.
Consistency is the Key. Despite proof that acute doses of exercise can enhance overall health and cognition, the benefit is truly received through consistent effort over time. Regular exercise at a moderate intensity is associated with significant long-term improvement as compared to single bouts of the same.[37]
Less May Be More for the Elderly. In studies comparing exercise types for improving cognition in the elderly, less intensive forms of aerobic exercise appear to show more benefit on an average. These include walking fit programs and spinning aerobics classes. By contrast, more rigorous types of aerobic exercise have been shown to benefit younger to middle-aged individuals.
Conclusion
If done consistently, exercise at a moderate intensity can be a powerful tool for increasing one’s intellectual and cognitive capacity. Research confirms that physical activity is central to brain development at all stages of life, from early childhood right through to the late stages of senescence. It is now known that exercise increases the size of the brain as well as enhances connectivity between brain areas involved in learning and memory. These findings, coupled with the mood- stabilizing effects of exercise, all contribute towards improved concentration and sharper mental response times. While all forms promote cognition, according to research, regular aerobic exercise has been most promising across all ages.
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