Apart from fitness, physical exercise also has beneficial effects on the brain. A regular routine of aerobic exercise can improve memory, thinking, skills, moods and have protective effects against aging, injuries and neurodegenerative disorders. It is noteworthy that these effects are specific to aerobic exercise, the kind of exercise that accelerates heart and respiratory rate such as running, cycling, swimming, etc. Non aerobic activities such as stretching or muscle building do not have the same effect.
The positive effects of aerobic excercise appear to result from increased blood flow to the brain and subsequent increase in energy metabolism. It is worth noting that a certain degree of intensity in these activities is required to achieve the beneficial outcomes described. Aerobic exercise increases the production of several growth factors of the nervous tissue known as neurotrophins. Among these are BDNF, for brain-derived neurotrophic factor. BDNF exerts a protective effect on existing neurons and stimulates formation of new neurons from neural stem cells in a process called neurogenesis.
BDNF appears to coordinate its action with at least two other growth factors: insulin-like growth factor or IGF and vascular endothelial growth factor or EGF. EGF levels also increase following aerobic exercise, BDNF then interacts with IGF to induce neurogenesis while EGF stimulates growth of new blood vessels, a process known as angiogenesis. Together these processes improve survival of existing neurons produce new brain tissue and constitute the brain’s enhanced plasticity.
These factors underlie the exercise-induced protective effect against degenerative diseases and injuries. Changes in BDNF levels ar eobserved throughout the brain but are most remarkable in the hippocampus, the area that is responsible for memory retention and learning. In fact, regular exercise has been shown to increase the size of the hippocampus and improve cognitive functions, while even a single workout can produce significant changes in BDNF levels and subsequent improvements in learning performance.
A regular exercise program progressively increases BDNF baseline level and makes it respond steadier over time. However, it also appears that some cognitive functions are enhanced immediately after a single workout, while others only improve following a consistent exercise routine. A single aerobic session can promote positive emotions, suppress negative feelings, reduce the body’s response to stress and sometimes, after intense exercise, induce a euphoric state known as runner’s high.
These effects may persist for up to 24 hours and are thought to result from exercise induced up-regulation of several neurotransmitters involved in mood modulation these include dopamine, a neurotransmitter of the brain reward pathways, as well as serotonin, commonly known as the substance of well-being and happiness, whose low levels in the brain have been associated with depressive disorders. Also, the consequent production/release of beta endorphin or endogenous morphine, an endogenous opioid which is related to psychoactive chemicals involved in pain modulation, stress and anxiety reduction may be helpful for those who suffer from accompanying disorders.