Effect on the cardiovascular system
The effect of exercise on the cardiovascular system is well documented.
There is a direct relation between physical inactivity and cardiovascular mortality, and physical inactivity is an independent risk factor for the development of coronary artery disease. There is a dose-response relation between the amount of exercise performed from approximately 700 to 2000 kcal of energy expenditure per week and all-cause mortality and cardiovascular disease mortality in middle-aged and elderly populations. The greatest potential for reduced mortality is in the sedentary who become moderately active. Most beneficial effects of physical activity on cardiovascular disease mortality can be attained through moderate-intensity activity (40% to 60% of maximal oxygen uptake, depending on age). … persons who modify their behavior after myocardial infarction to include regular exercise have improved rates of survival. … Persons who remain sedentary have the highest risk for all-cause and cardiovascular disease mortality. [1]
Effect on the immune system
Although there have been hundreds of studies on exercise and the immune system, there is little direct evidence on its connection to illness. Epidemiological evidence suggests that moderate exercise has a beneficial effect on the human immune system while extreme exercise impairs it, an effect which is modeled in a J curve. Moderate exercise has been associated with a 29% decreased incidence of upper respiratory tract infections (URTI), but studies of marathon runners found that their prolonged high-intensity exercise was associated with an increased risk of an infection, although another study did not find the effect. Immune cell functions are impaired following acute sessions of prolonged, high-intensity exercise, and some studies have found that athletes are at a higher risk for infections. The immune systems of athletes and nonathletes are generally similar. Athletes may have slightly elevated natural killer cell count and cytolytic action, but these are unlikely to be clinically significant.[22]
Vitamin C supplementation has been associated with lower URTIs in marathon runners.
Biomarkers of inflammation such as C-reactive protein, which are associated with chronic diseases, are reduced in active individuals relative to sedentary individuals, and the positive effects of exercise may be due to its anti-inflammatory effects. The depression in the immune system following acute bouts of exercise may be one of the mechanisms for this anti-inflammatory effect.[22]
Effects on brain function
A 2008 review of cognitive enrichment therapies (strategies to slow or reverse cognitive decline) concluded that “physical activity, and aerobic exercise in particular, enhances older adults’ cognitive function”.[23]
In mice, exercise improves cognitive functioning via improvement of hippocampus-dependent spatial learning, and enhancement of synaptic plasticity and neurogenesis.[24] In addition, physical activity has been shown to be neuroprotective in many neurodegenerative and neuromuscular diseases.[25] For instance, it reduces the risk of developing dementia.[26] Furthermore, anecdotal evidence suggests that frequent exercise may reverse alcohol-induced brain damage.[27]
There are several possibilities for why exercise is good for the brain:
- increasing the blood and oxygen flow to the brain
- increasing growth factors that help create new nerve cells[28] and promote synaptic plasticity[29]
- increasing chemicals in the brain that help cognition, such as dopamine, glutamate, norepinephrine, and serotonin[30]
Physical activity is thought to have other beneficial effects related to cognition as it increases levels of nerve growth factors, which support the survival and growth of a number of neuronal cells.[31]
Effects on depression
A number of factors may contribute to depression including being overweight, low self-esteem, stress and anxiety.[32] Endorphins act as a natural pain reliever and antidepressant in the body.[33] Endorphins have long been regarded as responsible for what is known as “runner’s high”, a euphoric feeling a person receives from intense physical exertion.[34] However, recent research[14][15] indicates that anandamide may possibly play a greater role than endorphins in “runner’s high”. When a person exercises, levels of both circulating serotonin and endorphins are increased.[35] These levels are known to stay elevated even several days after exercise is discontinued, possibly contributing to improvement in mood, increased self-esteem, and weight management.[34] Exercise alone is a potential prevention method and/or treatment for mild forms of depression.[36]
Exercise also affects the sleep that a person will receive at night. When the body is physically exhausted it will slip into Rapid Eye Movement (REM) sleep easier and for a longer period.
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