Physical<unk>  is important for maintaining physical fitness and can contribute to maintaining a healthy weight, regulating the digestive system, building and maintaining healthy bone density, muscle strength, and joint mobility, promoting physiological well-being, reducing surgical risks, and strengthening the immune system. Some studies indicate that<unk>  may increase life<unk> pectancy and the overall quality of life. People who participate in moderate to high levels of physical<unk>  have a lower mortality rate compared to individuals who by comparison are not physically active. Moderate levels of<unk>  have been correlated with preventing aging by reducing inflammatory potential. The majority of the benefits from<unk>  are achieved with around 3500 metabolic equivalent (MET) minutes per week, with diminishing returns at higher levels of activity. For<unk> ample, climbing stairs 10 minutes, vacuuming 15 minutes, gardening 20 minutes, running 20 minutes, and walking or bicycling for transportation 25 minutes on a daily basis would together achieve about 3000 MET minutes a week. A lack of physical activity causes approximately 6% of the burden of disease from coronary heart disease, 7% of type 2 diabetes, 10% of breast cancer and 10% of colon cancer worldwide. Overall, physical inactivity causes 9% of premature mortality worldwide. + Metabolic and musculoskeletal adaptations from endurance and strength training Type of adaptation Endurancetraining effects Strengthtraining effects Sources Skeletal muscle morphology and<unk>  performance adaptations Muscle hypertrophy ↔ ↑ ↑ ↑ Muscle strength and power ↔ ↓ ↑ ↑ ↑ Muscle fiber size ↔ ↑ ↑ ↑ ↑ Myofibrillar protein synthesis ↔ ↑ ↑ ↑ ↑ Neuromuscular adaptations ↔ ↑ ↑ ↑ ↑ Anaerobic capacity ↑ ↑ ↑ Lactate tolerance ↑ ↑ ↔ ↑ Endurance capacity ↑ ↑ ↑ ↔ ↑ Capillary growth (angiogenesis) ↑ ↑ ↔ Mitochondrial biogenesis ↑ ↑ ↔ ↑ Mitochondrial density and oxidative function ↑ ↑ ↑ ↔ ↑ Whole-body and metabolic adaptations Bone mineral density ↑ ↑ ↑ ↑ Inflammatory markers ↓ ↓ ↓ Flexibility ↑ ↑ Posture ↔ ↑ Ability in activities of daily living ↔ ↑ ↑ ↑ Basal metabolic rate ↑ ↑ ↑ Body composition Percent body fat ↓ ↓ ↓ Lean body mass ↔ ↑ ↑ Glucose metabolism Resting insulin levels ↓ ↓ Insulin sensitivity ↑ ↑ ↑ ↑ Insulin response to glucose challenge ↓ ↓ ↓ ↓ Cardiovascular adaptations Resting heart rate ↓ ↓ ↔ Stroke volume (resting and maximal) ↑ ↑ ↔ Systolic blood pressure (resting) ↔ ↓ ↔ Diastolic blood pressure (resting) ↔ ↓ ↔ ↓ Cardiovascular risk profile ↓ ↓ ↓ ↓ Fitness Most people can increase fitness by increasing physical activity levels. Increases in muscle size from resistance training are 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. There is evidence that<unk> ng in middle age may lead to better physical ability later in life. Early motor skills and development is also related to physical activity and performance later in life. Children who are more proficient with motor skills early on are more inclined to be physically active, and thus tend to perform well in sports and have better fitness levels. Early motor proficiency has a positive correlation to childhood physical activity and fitness levels, while less proficiency in motor skills results in a more sedentary lifestyle. The type and intensity of physical activity performed may have an effect on a person's fitness level. There is some weak evidence that high-intensity interval training may improve a person's VO2 max slightly more than lower intensity endurance training. Cardiovascular system The beneficial effect of<unk>  on the cardiovascular system is well documented. There is a direct correlation between physical inactivity and cardiovascular disease, and physical inactivity is an independent risk factor for the development of coronary artery disease. Low levels of physical<unk>  increase the risk of cardiovascular diseases mortality. Children who participate in physical<unk> <unk> perience greater loss of body fat and increased cardiovascular fitness. Studies have shown that academic stress in youth increases the risk of cardiovascular disease in later years; however, these risks can be greatly decreased with regular physical<unk> . There is a dose-response relationship between the amount of<unk>  performed from approximately kcal of energy<unk> penditure per week and all-cause mortality and cardiovascular disease mortality in middle-aged and elderly men. The greatest potential for reduced mortality is seen in sedentary individuals who become moderately active. Studies have shown that since heart disease is the leading cause of death in women, regular<unk>  in aging women leads to healthier cardiovascular profiles. Most beneficial effects of physical activity on cardiovascular disease mortality can be attained through moderate-intensity activity (40–60% of maximal oxygen uptake, depending on age). Persons who modify their behavior after myocardial infarction to include regular<unk>  have improved rates of survival. Persons who remain sedentary have the highest risk for all-cause and cardiovascular disease mortality. According to the American Heart Association,<unk>  reduces the risk of cardiovascular diseases, including heart attack and stroke. Immune system Although there have been hundreds of studies on physical<unk>  and the immune system, there is little direct evidence on its connection to illness. Epidemiological evidence suggests that moderate<unk>  has a beneficial effect on the human immune system; an effect which is modeled in a J curve. Moderate<unk>  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<unk>  was associated with an increased risk of infection occurrence. However, another study did not find the effect. Immune cell functions are impaired following acute sessions of prolonged, high-intensity<unk> , and some studies have found that athletes are at a higher risk for infections. Studies have shown that strenuous stress for long durations, such as training for a marathon, can suppress the immune system by decreasing the concentration of lymphocytes. The immune systems of athletes and nonathletes are generally similar. Athletes may have a slightly elevated natural killer cell count and cytolytic action, but these are unlikely to be clinically significant. Vitamin C supplementation has been associated with a lower incidence of upper respiratory tract infections 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<unk>  may be due to its anti-inflammatory effects. In individuals with heart disease,<unk>  interventions lower blood levels of fibrinogen and C-reactive protein, an important cardiovascular risk marker. The depression in the immune system following acute bouts of<unk>  may be one of the mechanisms for this anti-inflammatory effect. Cancer A systematic review evaluated 45 studies that<unk> amined the relationship between physical activity and cancer survival rates. According to the review, "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. There is currently insufficient evidence regarding the association between physical activity and mortality for survivors of other cancers." Evidence suggests that<unk>  may positively affect the quality of life in cancer survivors, including factors such as anxiety, self-esteem and emotional well-being. For people with cancer undergoing active treatment,<unk>  may also have positive effects on health-related quality of life, such as fatigue and physical functioning. This is likely to be more pronounced with higher intensity<unk> .<unk>  may contribute to a reduction of cancer-related fatigue in survivors of breast cancer. Although there is only limited scientific evidence on the subject, people with cancer cachexia are encouraged to engage in physical<unk> . Due to various factors, some individuals with cancer cachexia have a limited capacity for physical<unk> . Compliance with prescribed<unk>  is low in individuals with cachexia and clinical trials of<unk>  in this population often suffer from high drop-out rates. Many go as far as to argue that supervised high-intensity resistance training should be made a critical part of rehabilitation for breast cancer survivors as it increases overall quality of life. There is low-quality evidence for an effect of aerobic physical<unk> s on anxiety and serious adverse events in adults with hematological malignancies. Aerobic physical<unk>  may result in little to no difference in the mortality, quality of life, or physical functioning. These<unk> s may result in a slight reduction in depression and reduction in fatigue. Neurobiological Depression Continuous aerobic<unk>  can induce a transient state of euphoria, colloquially known as a "runner's high" in distance running or a "rower's high" in crew, through the increased biosynthesis of at least three euphoriant neurochemicals: anandamide (an endocannabinoid), β-endorphin (an endogenous opioid), and phenethylamine (a trace amine and amphetamine analog). Sleep Preliminary evidence from a 2012 review indicated that physical training for up to four months may increase sleep quality in adults over 40 years of age. A 2010 review suggested that<unk>  generally improved sleep for most people, and may help with insomnia, but there is insufficient evidence to draw detailed conclusions about the relationship between<unk>  and sleep. A 2018 systematic review and meta-analysis suggested
Exercise
Diet 
Obesity
Allostatic load
Ageing
Vegetation 
Medication
Hypertension