Physical exercise has many diverse and linked impacts on brain anatomy, brain function, and cognition. These effects are known as the neurobiological effects of physical exercise.[2][3][4][5] Human research has shown that regular aerobic exercise, such as 30 minutes a day, produces beneficial forms of neuroplasticity and behavioral plasticity as well as long-lasting improvements in specific cognitive functions.
These long-term effects include increased neuron growth, increased neurological activity (such as c-Fos and BDNF signaling), improved stress coping, enhanced cognitive control of behavior, improved declarative, spatial, and working memory, and structural and functional improvements in brain structures and pathways related to memory and cognitive control.[6][7][8][9]
Exercise’s beneficial effects on cognition have a wide range of applications, including enhancing adult productivity, preventing or treating certain neurological illnesses, preserving cognitive function in old age, and enhancing overall quality of life.[2][10][11][12]
It has been demonstrated that aerobic exercise in healthy adults produces both temporary benefits on cognition following a single workout and long-lasting impacts on cognition after consistent exercise over several months.[2][9][13]
Regular aerobic exercisers score higher on neuropsychological function and performance tests measuring various cognitive functions, including declarative memory, spatial memory, attentional control, inhibitory control, cognitive flexibility, and information processing speed. Examples of these activities include running, jogging, brisk walking, cycling, and swimming.
Improvements in the majority of executive functions (e.g., working memory, attention, cognitive flexibility, inhibitory control, problem solving, and decision making) and information processing speed are among the short-term cognitive benefits of exercise. These effects can last for up to two hours following physical activity.[13]
By fostering positive affect, stifling negative affect, and lowering the body’s reaction to acute psychological stress, aerobic exercise affects mood and emotional states in both the short and long term.[13] Aerobic exercise has euphoric and antidepressant effects in the short term[16].[17]While regular physical exercise leads to overall mood and self-esteem gains [18][19].[20][21]
Frequent aerobic exercise can be used as adjuvant therapy for a number of illnesses affecting the central nervous system and helps to improve their symptoms. There is some evidence that major depressive disorder and attention deficit hyperactivity disorder can be effectively treated with exercise.[10][18][22][23] Clinicians should advise patients with mild cognitive impairment to engage in regular exercise, preferably twice a week, according to the American Academy of Neurology’s clinical practice guideline.[24]
The use of exercise as an adjuvant therapy for some neurodegenerative conditions, including Alzheimer’s and Parkinson’s disease, is also supported by reviews of clinical evidence.[25][26] Engaging in regular exercise has also been linked to a decreased risk of neurodegenerative diseases.[27] Exercise is beneficial, and there is a wealth of preclinical and increasing clinical evidence for this.
Long-term effects of Physical exercise
Neuroplasticity
The process by which neurons gradually adjust to a disruption is known as neuroplasticity, and it typically happens in response to repeated exposure to stimuli.[34] Aerobic physical exercise stimulates the synthesis of neurotrophic factors (BDNF, IGF-1, VEGF, etc.) that promote adult neurogenesis, blood vessel creation in the brain, and other forms of neuroplasticity.
These factors influence improvements in cognitive functions and various forms of memory.[3][6][20][36] Over several months, regular aerobic exercise increases gray matter volume and improves executive functions in almost every region of the brain in a clinically relevant way [37], with the most notable changes shown in the brain regions responsible for executive processes.
The prefrontal cortex, caudate nucleus, and hippocampus are the brain regions that exhibit the largest increases in gray matter volume in response to aerobic exercise;[2]Less noticeable increases in gray matter volume can be found in the nucleus accumbens, anterior cingulate cortex, parietal cortex, and cerebellum [6].Among the most important brain regions in the dopamine and norepinephrine systems that give birth to cognitive control are the prefrontal cortex, anterior cingulate cortex, and caudate nucleus.38 Measurable gains in spatial memory have been linked to exercise-induced neurogenesis in the hippocampal regions, or increases in gray matter volume.[21][39]
Greater gray matter volumes in the hippocampus, caudate nucleus, and nucleus accumbens are linked to improved executive function, quicker information processing, and higher physical fitness scores as determined by VO2 max.[2]
Structural growth of physical exercise
Reviews of neuroimaging research show that regular aerobic exercise enhances gray matter volume in almost every area of the brain, with more noticeable increases in areas linked to reward, memory processing, cognitive control, and motor function;[37][6]The prefrontal cortex, caudate nucleus, and hippocampus—which assist cognitive control and memory processing among other cognitive functions—show the most notable increases in gray matter volume [37].[2][8] Furthermore, sustained aerobic activity appears to increase the functional connectivity between the hippocampus, cingulate cortex, and left and right portions of the prefrontal cortex.[2][7]
According to three reviews, individuals in good health who consistently participate in moderate-intense physical activity for several months experience notable increases in their prefrontal and hippocampal gray matter volumes.[2][40] Additional brain regions that show moderate to less significant increases in gray matter volume during neuroimaging are the nucleus accumbens, anterior cingulate cortex, parietal cortex, and cerebellum.[6][41]
Frequent exercise has been demonstrated to counteract the natural decline in memory and hippocampal shrinkage that happens in late adulthood.[6] Over 55-year-old sedentary persons have a yearly 1-2 percent decrease in hippocampus volume.
Over a one-year period, engaging in regular aerobic exercise increased the volume of the left hippocampal by 2.12% and the right hippocampal by 1.97%, according to a neuroimaging study involving 120 people.[42] Higher fitness levels at baseline were associated with decreased hippocampus volume loss in the low intensity stretching group, suggesting that exercise protects against age-related cognitive decline.[42]
People who exercise more consistently over time tend to have larger hippocampus sizes and improved memory.[6] Additionally, it has been demonstrated that aerobic exercise causes the anterior corpus callosum’s white matter tracts—which typically shrink with aging—to expand.[6][40]
Persistent effects on cognition
Consistent improvement of several executive skills and multiple kinds of memory over several months of regular physical exercise is demonstrated, which is consistent with the functional responsibilities of brain areas that exhibit higher gray matter volumes.[6,7,8][49,50,51]
Particularly, regular aerobic exercise has been demonstrated to enhance inhibitory control, working memory update and capacity, declarative memory, spatial memory, information processing speed, attentional control, and cognitive flexibility (e.g., task switching).[6][7][8][9][49][50] The effect sizes of gains in cognitive performance in young and middle-aged persons in good health are greatest for indices of executive functions and small to moderate for characteristics of memory and information processing speed.[2][9]
It’s possible that engaging in both aerobic and weight training at a minimum moderate level improves cognitive function in older adults.[53] Sedentary people typically do worse on executive functions as compared to other non-exercisers who have more physically active lives.[8][49] Exercise and executive functions have also been found to be correlated: gains in executive control mechanisms including attentional control and inhibitory control make people more likely to exercise.[8]
BDNF signaling
enhanced synthesis and expression of the neuropeptide and hormone BDNF, which results in enhanced signaling through its receptor tyrosine kinase, tropomyosin receptor kinase B (TrkB), is one of the most important impacts of exercise on the brain.[5][56][57] Higher peripheral BDNF production raises BDNF signaling in the brain because BDNF can cross the blood–brain barrier.[36]
Increases in BDNF signaling brought on by exercise are linked to better mood, memory, and cognitive performance.[20][56] Moreover, a substantial body of evidence supports the function of BDNF in synaptic plasticity, brain repair, and hippocampus neurogenesis.
Running, swimming, and cycling are examples of moderate-to-high intensity aerobic exercise that increases BDNF biosynthesis through myokine signaling. This can lead to a threefold increase in blood plasma and BDNF levels. Exercise intensity has a positive correlation with the amount of increased BDNF expression and biosynthesis.[5][56][57] Consistent exercise also slightly raises resting BDNF levels, according to a meta-analysis of studies on the impact of exercise on BDNF levels.[20]
This has significant ramifications for the use of exercise as a stress-reduction strategy because stress is directly associated with lower hippocampal levels of BDNF. Actually, research indicates that BDNF plays a role in the antidepressant drugs’ ability to lessen anxiety. Exercise raises BDNF levels, which counteracts the drop in BDNF brought on by stress.
IGF-1 signaling
Growth hormone’s activities are partially mediated by a peptide called IGF-1, which also functions as a neurotrophic factor. According to research, IGF-1 binds to a particular receptor tyrosine kinase, the IGF-1 receptor, to control tissue growth and remodeling.[59] Like BDNF, IGF-1 is a neurotrophic factor in the brain that is important for neurogenesis, neurogenesis, and neuronal survival.[56][60][61]
Increased blood serum levels of IGF-1, which may cross the blood–brain and blood–cerebrospinal fluid barriers and is known to support neuroplasticity in the brain, are linked to physical activity;[6][56][59][60] As a result, IGF-1 has been identified in two reviews as a critical mediator of exercise-induced adult neurogenesis and as a factor that connects “body fitness” with “brain fitness.”[59][60]
VEGF signaling
VEGF is a neurotrophic and angiogenic (blood vessel growth-promoting) signaling protein that attaches to VEGFR1 and VEGFR2, two receptor tyrosine kinases that are present in the brain’s glial and neuronal cells.[61] Insufficient cellular oxygen supply, or hypoxia, causes VEGF expression to be significantly upregulated. In hypoxic neurons, VEGF has a neuroprotective effect.[61] Similar to BDNF and IGF-1, aerobic exercise has been demonstrated to raise peripheral tissue VEGF production.
This VEGF then crosses the blood–brain barrier and stimulates the development of new blood vessels and neurogenesis in the central nervous system.[36][63] It has been demonstrated that increases in VEGF signaling brought on by exercise enhance cerebral blood volume and support exercise-induced hippocampal regeneration.[6][63]
Irisin
Irisin confers the beneficial cognitive effects of physical exercise and can act as an exercise mimetic in mice, where it could “improve both the cognitive deficit and neuropathology in Alzheimer’s disease mouse models,” according to a study using FNDC5 knock-out mice and artificially elevated circulating irisin levels.
Therefore, research is being done on the mediator and its regulatory system in hopes of developing therapies that could enhance cognitive function or lessen the effects of Alzheimer’s disease in people.[64][65][66] Research suggests that irisin could be connected to the control of BDNF and neurogenesis in mice.[67]