The therapeutic properties of exercise is well supported by a substantial amount of research.
Exercise is associated with a reduction in physical illnesses such as cardiovascular disease, colon and breast cancer, obesity and mental illness (including depression and anxiety disorders) across the adult lifespan.
Although some are aware of the benefits of exercise, there are many who are unaware that exercise has considerable benefits for the brain. This is put aptly by John Ratey, author of A User's Guide to the Brain. "Exercise is really for the brain, not the body. It affects mood, vitality, alertness and feelings of well-being."
There is increasing evidence that exercise can improve learning and memory, delay age-related cognitive decline, reduce risk of neurodegeneration and alleviate depression.
Exercise and brain function
Exercise improves brain function in different ways. It enhances learning and plasticity, is neuroprotective, and is therapeutic and protective against depression.
Exercise enhances learning and plasticity, which is the capacity of the brain and nervous system to continuously alter neural pathways and synapses in response to experience or injury.
The effects of exercise have been demonstrated in ageing human populations in which sustained exercise has augmented learning and memory, improved executive functions, impeded age-related and disease-related mental decline, and protected against age-related atrophy in parts of the brain areas that are vital for higher cognitive processes.
Physical activity has a positive effect on cognition, which includes every mental process that may be described as an experience of knowing (including perceiving, recognising, conceiving, and reasoning).
There is a significant relationship between physical activity and improved cognition in normal adults as well as those with early signs of Alzheimer's disease (AD), in which there is mild impairment of memory or cognition.
There is a dose-response relationship between exercise and health-related quality of life, with moderate exercise associated with the best outcomes.
The literature on the effects of exercise on cognition during children's development is less substantial.
However, a meta-analysis by Sibley & Etnier reported a positive correlation between physical activity and cognitive performance in children aged between four and 18 years in eight categories, i.e. perceptual skills, intelligence quotient, achievement, verbal tests, mathematic tests, memory, developmental level/academic readiness and others.
A beneficial relationship was found for all categories, with the exception of memory, which was unrelated to physical activity behaviour, and for all age groups, although it was stronger for children in the ages of four to seven and 11 to 13 years, compared with the ages of eight to 10 and 14 to 18 years.
Recent studies have reported that an increase in the time dedicated to physical health-based activities is not associated with a decline in academic performance.
The literature on the impact of exercise on cognition in young adults is limited, probably because cognition peaks during young adulthood and there is little room for exercise-related improvement at this stage of the lifespan.
Although there is considerable evidence that exercise can facilitate learning in humans and other animals, there are gaps in knowledge regarding the types of learning that are improved with exercise.
Exercise protects the brain (neuroprotective). It reduces the impact of brain injury and delays the onset and decline in several neurodegenerative diseases. For example, therapeutic exercise programmes after a stroke accelerates functional rehabilitation.
Furthermore, physical activity delays the onset and reduces the risk for AD, Huntington's disease and Parkinson's disease, and can even slow functional decline after neurodegeneration has begun.
There is evidence that exercise is therapeutic and protective in depression, which is associated with a decline in cognition.
Depression is considered to be a health burden that is greater than that of ischaemic heart disease, cerebrovascular disease or tuberculosis.
Clinical trials have reported the efficacy of aerobic or resistance training exercise in the treatment of depression in young and older patients, with benefits similar to that of antidepressant medicines. More exercise leads to greater improvements.
Trials have also reported improvement in depressive symptoms in AD compared to those non-exercising individuals whose depressive symptoms worsened.
Bipolar disorders do not appear to respond as well to exercise, but those with anxiety respond even faster.
There is a convergence of the concept that brain health and cognition are influenced by the interplay of various central and peripheral factors.
Brain function is believed to be impaired by peripheral risk factors that lead to cognitive decline, including hypertension, hyperglycemia, insulin insensitivity and dyslipidemia, features that are commonly known as the "metabolic syndrome".
Of these factors, hypertension and glucose intolerance play crucial roles. Exercise not only reduces all these peripheral risk factors but also improves cardiovascular health, lipid-cholesterol balance, energy metabolism, glucose use, insulin sensitivity and inflammation.
As such, exercise improves brain health and function by directly enhancing brain health and cognitive function, and indirectly, by reducing the peripheral risk factors for cognitive decline.
It is believed that exercise initiates an interactive cascade of growth factor signals which lead to the stimulation of plasticity, improvement of cognitive function, reduction of the mechanisms that drive depression, stimulation of neurogenesis and improvement of cerebrovascular perfusion.
Although much is known about the effects of exercise and physical activity on brain and cognition, there are many important questions that are unanswered.
They include questions like the design of exercise interventions which optimise the effects on cognition and brain health; when it is best to begin; what are the best varieties, intensities, frequencies and duration of exercise; is it ever too late to start an exercise programme; and can exercise be used to reduce the effects of neurodegenerative diseases.
Knowing the how
Knowing the how
Exercise affects many sites in the nervous system and stimulates the secretion of chemicals like serotonin and dopamine, which make humans feel calm, happy, and euphoric. You do not have to wait for these feelings to occur - you can initiate them by exercising.
There is no shortage of advice on the various physical exercises that enhances cardiovascular health. Prior to embarking on exercise, a consultation with the doctor would be helpful, especially for senior citizens. This will help in choosing the appropriate exercise for one's individual situation.
In general, what is good for the heart is also good for the brain.
The usual recommended minimum is half an hour of moderate exercise thrice a week. This can be walking, jogging, swimming, playing games, dancing etc.
The public is often reminded about a healthy lifestyle, which is focused on physical health. However, it is also important to exercise mentally and keep the brain healthy.
There are publications and activities available that can help you make a start and continue to improve cognition, memory, creativity and other brain functions.
Anyone at any age can do so, even senior citizens. It is moot to remember the adage: if you don't use it, you lose it.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with. For further information, e-mail email@example.com.
The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader's own medical care.