Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness.
It is performed for various reasons, including increasing growth and development, preventing aging, strengthening muscles and the cardiovascular system, honing athletic skills, weight loss or maintenance, and also enjoyment. Frequent and regular physical exercise boosts the immune system and helps prevent certain “diseases of affluence” such as coronary heart disease, type 2 diabetes, and obesity. It may also help prevent stress and depression, increase quality of sleep and act as a non-pharmaceutical sleep aid to treat diseases such as insomnia, help promote or maintain positive self-esteem, improve mental health, maintain steady digestion and treat constipation and gas, regulate fertility health, and augment an individual’s sex appeal or body image.
Childhood obesity is a growing global concern, and physical exercise may help decrease some of the effects of childhood and adult obesity. Some care-providers call exercise the “miracle” or “wonder” drug—alluding to the wide variety of benefits that it can provide for many individuals. Aside from the health advantages, these benefits may include different social rewards for staying active while enjoying the environment of one’s culture. Many individuals choose to exercise publicly outdoors where they can congregate in groups, socialize, and appreciate life.
In the United Kingdom two to four hours of light activity are recommended during working hours. This includes walking and standing. In the United States, a 1995 CDC/ACSM consensus statement and a Surgeon General’s 1996 report state that every adult should participate in moderate exercise, such as walking, swimming, and household tasks, for a minimum of 30 minutes daily.
Physical exercise is important for maintaining physical fitness and can contribute to maintaining a healthy weight, regulating digestive health, building and maintaining healthy bone density, muscle strength, and joint mobility, promoting physiological well-being, reducing surgical risks, and strengthening the immune system.
Individuals can increase fitness following increases in physical activity levels. Increases in muscle size from resistance training is primarily determined by diet and testosterone. This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population. Studies have shown that exercising in middle age leads to better physical ability later in life.
The beneficial effect of exercise on the cardiovascular system is well documented. There is a direct correlation between physical inactivity and cardiovascular mortality, and physical inactivity is an independent risk factor for the development of coronary artery disease. Low levels of physical exercise increase the risk of cardiovascular diseases mortality.
Although there have been hundreds of studies on physical 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; an effect which is modeled in a J curve.
A systematic review evaluated 45 studies that examined the relationship between physical activity and cancer survivorship. According to the study results “There was consistent evidence from 27 observational studies that physical activity is associated with reduced all-cause, breast cancer–specific, and colon cancer–specific mortality”.
Physical exercise was correlated with a lower methylation frequency of two tumor suppressor genes.
Physical exercise is becoming a widely accepted non-pharmacological intervention for the prevention and attenuation of cancer cachexia.
The neurobiological effects of physical exercise are numerous and involve a wide range of interrelated effects on brain structure, brain function, and cognition.
A number of medical reviews have indicated that exercise has a marked and persistent antidepressant effect in humans, an effect believed to be mediated through enhanced BDNF signaling in the brain.
A 2010 review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia.
Too much exercise can be harmful. Without proper rest, the chance of stroke or other circulation problems increases, and muscle tissue may develop slowly. Extremely intense, long-term cardiovascular exercise, as can be seen in athletes who train for multiple marathons, has been associated with scarring of the heart and heart rhythm abnormalities.