Exercise

"Workout" and "Exercise" redirect here. For other uses, see Workout (disambiguation) and Exercise (disambiguation).

Running in water

Weight training

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 merely enjoyment. Frequent and regular physical exercise boosts the immune system and helps prevent "diseases of affluence" such as cardiovascular 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, which has been found to be linked with higher levels of self-esteem. 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.

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, the CDC/ACSM consensus statement and the Surgeon General's report states that every adult should participate in moderate exercise, such as walking, swimming, and household tasks, for a minimum of 30 minutes daily.

Classification

Exercise in space: Astronaut Daniel Tani, Expedition 16 flight engineer, works out at the Unity node of the International Space Station using the short bar of the Interim Resistive Exercise Device (IRED) to perform pull-ups to increase his upper body strength while in a microgravity environment

Physical exercises are generally grouped into three types, depending on the overall effect they have on the human body:

• Aerobic exercise is any physical activity that uses large muscle groups and causes the body to use more oxygen than it would while resting. The goal of aerobic exercise is to increase cardiovascular endurance. Examples of aerobic exercise include cycling, swimming, brisk walking, skipping rope, rowing, hiking, playing tennis, continuous training, and long slow distance training.
• Anaerobic exercise, which includes strength and resistance training, can firm, strengthen, and tone muscles, as well as improve bone strength, balance, and coordination. Examples of strength moves are push-ups, pull-ups, lunges, and bicep curls using dumbbells. Anaerobic exercise also include weight training, functional training, eccentric training, Interval training, sprinting, and high-intensity interval training increase short-term muscle strength.
• Flexibility exercises stretch and lengthen muscles. Activities such as stretching help to improve joint flexibility and keep muscles limber. The goal is to improve the range of motion which can reduce the chance of injury.

Physical exercise can also include training that focuses on accuracy, agility, power, and speed.

Sometimes the terms 'dynamic' and 'static' are used. 'Dynamic' exercises such as steady running, tend to produce a lowering of the diastolic blood pressure during exercise, due to the improved blood flow. Conversely, static exercise (such as weight-lifting) can cause the systolic pressure to rise significantly (during the exercise).

Health effects

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. Some studies indicate that exercise may increase life expectancy and quality of life. People who participate in moderate to high levels of physical exercise have a lower mortality rate compared to individuals who are not physically active. Moderate levels of exercise have been correlated with preventing aging and improving quality of life by reducing inflammatory potential. The majority of the benefits from exercise are achieved with around 3500 metabolic equivalent (MET) minutes per week. For example, 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.

Fitness

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.

Cardiovascular system

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.

Children who participate in physical exercise experience 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 exercise. 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. Studies have shown that since heart disease is the leading cause of death in women, regular exercise 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% 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. According to the American Heart Association, exercise reduces blood pressure, LDL and total cholesterol, and body weight. It increases HDL cholesterol, insulin sensitivity, and exercise tolerance.

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; 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 infection occurrence. However, 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. 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 slightly elevated natural killer cell count and cytolytic action, but these are unlikely to be clinically significant.

Vitamin C supplementation has been associated with lower incidence of 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. In individuals with heart disease, exercise 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 exercise may be one of the mechanisms for this anti-inflammatory effect.

Cancer

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".

Epigenetic effects

Physical exercise was correlated with a lower methylation frequency of two tumor suppressor genes, CACNA2D3 and L3MBTL. Hypermethylation of CACNA2D3 is associated with gastric cancer, while hypermethylation of L3MBTL is associated with breast cancer, brain tumors and hematological malignancies. A recent study indicates that exercise results in reduced DNA methylation at CpG sites on genes associated with breast cancer.

Cancer cachexia

Physical exercise is becoming a widely accepted non-pharmacological intervention for the prevention and attenuation of cancer cachexia. "Cachexia is a multiorganic syndrome associated with cancer, characterized by inflammation, body weight loss (at least 5%) and muscle and adipose tissue wasting". Exercise triggers the activation of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), which suppresses FoxO- and NF-κB-dependent gene transcription during muscle atrophy that is induced by fasting or denervation; thus, PGC-1α may be a key intermediate responsible for the beneficial antiatrophic effects of physical exercise on cancer cachexia. The exercise-induced isoform PGC-1α4, which can repress myostatin and induce IGF1 and hypertrophy, is a potential drug target for treatment of cancer cachexia. Other factors, such as JUNB and SIRT1, that maintain skeletal muscle mass and promote hypertrophy are also induced with regular physical exercise.

Neurobiological

Main article: Neurobiological effects of physical exercise

Neurobiological effects of physical exercise
Exercise therapy – medical intervention
A woman engaging in aerobic exercise (jogging)
ICD-9-CM	93.19
MeSH	D005081
LOINC	73986-2
eMedicine	324583

The neurobiological effects of physical exercise involve possible interrelated effects on brain structure, brain function, and cognition. Research in humans has demonstrated that consistent aerobic exercise (e.g., 30 minutes every day) may induce improvements in certain cognitive functions, neuroplasticity and behavioral plasticity; some of these long-term effects may include increased neuron growth, increased neurological activity (e.g., c-Fos and BDNF signaling), improved stress coping, enhanced cognitive control of behavior, improved declarative, spatial, and working memory, and structural and functional improvements in brain structures and pathways associated with cognitive control and memory. The effects of exercise on cognition may affect academic performance in children and college students, improve adult productivity, preserve cognitive function in old age, preventing or treating certain neurological disorders, and improving overall quality of life.

In healthy adults, aerobic exercise has been shown to induce transient effects on cognition after a single exercise session and persistent effects on cognition following consistent exercise over the course of several months. People who regularly perform an aerobic exercise (e.g., running, jogging, brisk walking, swimming, and cycling) have greater scores on neuropsychological function and performance tests that measure certain cognitive functions, such as attentional control, inhibitory control, cognitive flexibility, working memory updating and capacity, declarative memory, spatial memory, and information processing speed.

Aerobic exercise has both short and long term effects on mood and emotional states by promoting positive affect, inhibiting negative affect, and decreasing the biological response to acute psychological stress. Aerobic exercise may affect both self-esteem and overall well-being (including sleep patterns) with consistent, long term participation. Regular aerobic exercise may improve symptoms associated with central nervous system disorders and may be used as adjunct therapy for these disorders. There is some evidence of exercise treatment efficacy for major depressive disorder and attention deficit hyperactivity disorder. The American Academy of Neurology's clinical practice guideline for mild cognitive impairment indicates that clinicians should recommend regular exercise (two times per week) to individuals who have been diagnosed with this condition.

Some preclinical evidence and emerging clinical evidence supports the use of exercise as an adjunct therapy for the treatment and prevention of drug addictions.

Reviews of clinical evidence also support the use of exercise as an adjunct therapy for certain neurodegenerative disorders, particularly Alzheimer's disease and Parkinson's disease. Regular exercise may be associated with a lower risk of developing neurodegenerative disorders.

Long-term effects

Neuroplasticity

Neuroplasticity is the process by which neurons adapt to a disturbance over time, and most often occurs in response to repeated exposure to stimuli. Aerobic exercise increases the production of neurotrophic factors (e.g., BDNF, IGF-1, VEGF) which mediate improvements in cognitive functions and various forms of memory by promoting blood vessel formation in the brain, adult neurogenesis, and other forms of neuroplasticity. Consistent aerobic exercise over a period of several months induces clinically significant improvements in executive functions and increased gray matter volume in nearly all regions of the brain, with the most marked increases occurring in brain regions that give rise to executive functions. The brain structures that show the greatest improvements in gray matter volume in response to aerobic exercise are the prefrontal cortex, caudate nucleus, and hippocampus; less significant increases in gray matter volume occur in the anterior cingulate cortex, parietal cortex, cerebellum, and nucleus accumbens. The prefrontal cortex, caudate nucleus, and anterior cingulate cortex are among the most significant brain structures in the dopamine and norepinephrine systems that give rise to cognitive control. Exercise-induced neurogenesis (i.e., the increases in gray matter volume) in the hippocampus is associated with measurable improvements in spatial memory. Higher physical fitness scores, as measured by VO₂ max, are associated with better executive function, faster information processing speed, and greater gray matter volume of the hippocampus, caudate nucleus, and nucleus accumbens.

Structural growth

Reviews of neuroimaging studies indicate that consistent aerobic exercise increases gray matter volume in nearly all regions of the brain, with more pronounced increases occurring in brain regions associated with memory processing, cognitive control, motor function, and reward; the most prominent gains in gray matter volume are seen in the prefrontal cortex, caudate nucleus, and hippocampus, which support cognitive control and memory processing, among other cognitive functions. Moreover, the left and right halves of the prefrontal cortex, the hippocampus, and the cingulate cortex appear to become more functionally interconnected in response to consistent aerobic exercise. Three reviews indicate that marked improvements in prefrontal and hippocampal gray matter volume occur in healthy adults that regularly engage in medium intensity exercise for several months. Other regions of the brain that demonstrate moderate or less significant gains in gray matter volume during neuroimaging include the anterior cingulate cortex, parietal cortex, cerebellum, and nucleus accumbens.

Regular exercise has been shown to counter the shrinking of the hippocampus and memory impairment that naturally occurs in late adulthood. Sedentary adults over age 55 show a 1–2% decline in hippocampal volume annually. A neuroimaging study with a sample of 120 adults revealed that participating in regular aerobic exercise increased the volume of the left hippocampus by 2.12% and the right hippocampus by 1.97% over a one-year period. Subjects in the low intensity stretching group who had higher fitness levels at baseline showed less hippocampal volume loss, providing evidence for exercise being protective against age-related cognitive decline. In general, individuals that exercise more over a given period have greater hippocampal volumes and better memory function. Aerobic exercise has also been shown to induce growth in the white matter tracts in the anterior corpus callosum, which normally shrink with age.

The various functions of the brain structures that show exercise-induced increases in gray matter volume include:

• Caudate nucleus – responsible for stimulus-response learning and inhibitory control; implicated in Parkinson's disease and ADHD
• Cerebellum – responsible for motor coordination and motor learning
• Hippocampus – responsible for storage and consolidation of declarative memory and spatial memory
• Nucleus accumbens – responsible for incentive salience ("wanting" or desire, the form of motivation associated with reward) and positive reinforcement; implicated in addiction
• Parietal cortex – responsible for sensory perception, working memory, and attention
• Prefrontal and anterior cingulate cortices – required for the cognitive control of behavior, particularly: working memory, attentional control, decision-making, cognitive flexibility, social cognition, and inhibitory control of behavior; implicated in attention deficit hyperactivity disorder (ADHD) and addiction

Persistent effects on cognition

See also: Executive functions

Concordant with the functional roles of the brain structures that exhibit increased gray matter volumes, regular exercise over a period of several months has been shown to persistently improve numerous executive functions and several forms of memory. In particular, consistent aerobic exercise has been shown to improve attentional control, information processing speed, cognitive flexibility (e.g., task switching), inhibitory control, working memory updating and capacity, declarative memory, and spatial memory. In healthy young and middle-aged adults, the effect sizes of improvements in cognitive function are largest for indices of executive functions and small to moderate for aspects of memory and information processing speed. It may be that in older adults, individuals benefit cognitively by taking part in both aerobic and resistance type exercise of at least moderate intensity. Individuals who have a sedentary lifestyle tend to have impaired executive functions relative to other more physically active non-exercisers. A reciprocal relationship between exercise and executive functions has also been noted: improvements in executive control processes, such as attentional control and inhibitory control, increase an individual's tendency to exercise.

Mechanism of effects

Further information: Myokine

BDNF signaling

Further information: Brain-derived neurotrophic factor

One of the most significant effects of exercise on the brain is increased synthesis and expression of BDNF, a neuropeptide and hormone, resulting in increased signaling through its receptor tyrosine kinase, tropomyosin receptor kinase B (TrkB). Since BDNF is capable of crossing the blood–brain barrier, higher peripheral BDNF synthesis also increases BDNF signaling in the brain. Exercise-induced increases in BDNF signaling are associated with improved cognitive function, improved mood, and improved memory. Furthermore, research has provided a great deal of support for the role of BDNF in hippocampal neurogenesis, synaptic plasticity, and neural repair. Engaging in moderate-high intensity aerobic exercise such as running, swimming, and cycling increases BDNF biosynthesis through myokine signaling, resulting in up to a threefold increase in blood plasma and BDNF levels; exercise intensity is positively correlated with the magnitude of increased BDNF biosynthesis and expression. A meta-analysis of studies involving the effect of exercise on BDNF levels found that consistent exercise modestly increases resting BDNF levels as well. This has important implications for exercise as a mechanism to reduce stress since stress is closely linked with decreased levels of BDNF in the hippocampus. In fact, studies suggest that BDNF contributes to the anxiety-reducing effects of antidepressants. The increase in BDNF levels caused by exercise helps reverse the stress-induced decrease in BDNF which mediates stress in the short term and buffers against stress-related diseases in the long term.

IGF-1 signaling

Further information: Insulin-like growth factor 1

IGF-1 is a peptide and neurotrophic factor that mediates some of the effects of growth hormone; IGF-1 elicits its physiological effects by binding to a specific receptor tyrosine kinase, the IGF-1 receptor, to control tissue growth and remodeling. In the brain, IGF-1 functions as a neurotrophic factor that, like BDNF, plays a significant role in cognition, neurogenesis, and neuronal survival. Physical activity is associated with increased levels of IGF-1 in blood serum, which is known to contribute to neuroplasticity in the brain due to its capacity to cross the blood–brain barrier and blood–cerebrospinal fluid barrier; consequently, one review noted that IGF-1 is a key mediator of exercise-induced adult neurogenesis, while a second review characterized it as a factor which links "body fitness" with "brain fitness". The amount of IGF-1 released into blood plasma during exercise is positively correlated with exercise intensity and duration.

VEGF signaling

Further information: Vascular endothelial growth factor

VEGF is a neurotrophic and angiogenic (i.e., blood vessel growth-promoting) signaling protein that binds to two receptor tyrosine kinases, VEGFR1 and VEGFR2, which are expressed in neurons and glial cells in the brain. Hypoxia, or inadequate cellular oxygen supply, strongly upregulates VEGF expression and VEGF exerts a neuroprotective effect in hypoxic neurons. Like BDNF and IGF-1, aerobic exercise has been shown to increase VEGF biosynthesis in peripheral tissue which subsequently crosses the blood–brain barrier and promotes neurogenesis and blood vessel formation in the central nervous system. Exercise-induced increases in VEGF signaling have been shown to improve cerebral blood volume and contribute to exercise-induced neurogenesis in the hippocampus.

Irisin

Further information: FNDC5

A study using FNDC5 knock-out mice as well as artificial elevation of circulating irisin levels showed that irisin confers beneficial cognitive effects of physical exercise and that it can serve an exercise mimetic in mice in which it could "improve both the cognitive deficit and neuropathology in Alzheimer's disease mouse models". The mediator and its regulatory system is therefore being investigated for potential interventions to improve – or further improve – cognitive function or alleviate Alzheimer's disease in humans. Experiments indicate irisin may be linked to regulation of BDNF and neurogenesis in mice.

Short-term effects

Transient effects on cognition

See also: Executive functions

In addition to the persistent effects on cognition that result from several months of daily exercise, acute exercise (i.e., a single bout of exercise) has been shown to transiently improve a number of cognitive functions. Reviews and meta-analyses of research on the effects of acute exercise on cognition in healthy young and middle-aged adults have concluded that information processing speed and a number of executive functions – including attention, working memory, problem solving, cognitive flexibility, verbal fluency, decision making, and inhibitory control – all improve for a period of up to 2 hours post-exercise. A systematic review of studies conducted on children also suggested that some of the exercise-induced improvements in executive function are apparent after single bouts of exercise, while other aspects (e.g., attentional control) only improve following consistent exercise on a regular basis. Other research has suggested immediate performative enhancements during exercise, such as exercise-concurrent improvements in processing speed and accuracy during both visual attention and working memory tasks.

Exercise-induced euphoria

Main article: Runner's high

Continuous exercise can produce a transient state of euphoria – an emotional state involving the experience of pleasure and feelings of profound contentment, elation, and well-being – which is colloquially known as a "runner's high" in distance running or a "rower's high" in rowing.

Effects on neurochemistry

β-Phenylethylamine

Biosynthetic pathways for catecholamines and trace amines in the human brain

L-Phenylalanine

L-Tyrosine

L-DOPA

Epinephrine

Phenethylamine

p-Tyramine

Dopamine

Norepinephrine

N-Methylphenethylamine

N-Methyltyramine

p-Octopamine

Synephrine

3-Methoxytyramine

AADC

AADC

AADC

primary
pathway

PNMT

PNMT

PNMT

PNMT

AAAH

AAAH

brain
CYP2D6

minor
pathway

COMT

DBH

DBH

In humans, catecholamines and phenethylaminergic trace amines are derived from the amino acid L-phenylalanine.

β-Phenylethylamine, commonly referred to as phenethylamine, is a human trace amine and potent catecholaminergic and glutamatergic neuromodulator that has similar psychostimulant and euphoriant effects and a similar chemical structure to amphetamine. Thirty minutes of moderate to high intensity physical exercise has been shown to induce an enormous increase in urinary β-phenylacetic acid, the primary metabolite of phenethylamine. Two reviews noted a study where the average 24 hour urinary β-phenylacetic acid concentration among participants following just 30 minutes of intense exercise increased by 77% relative to baseline concentrations in resting control subjects; the reviews suggest that phenethylamine synthesis sharply increases while an individual is exercising, during which time it is rapidly metabolized due to its short half-life of roughly 30 seconds. In a resting state, phenethylamine is synthesized in catecholamine neurons from L-phenylalanine by aromatic amino acid decarboxylase (AADC) at approximately the same rate at which dopamine is produced.

In light of this observation, the original paper and both reviews suggest that phenethylamine plays a prominent role in mediating the mood-enhancing euphoric effects of a runner's high, as both phenethylamine and amphetamine are potent euphoriants.

β-Endorphin

β-Endorphin (contracted from "endogenous morphine") is an endogenous opioid neuropeptide that binds to μ-opioid receptors, in turn producing euphoria and pain relief. A meta-analytic review found that exercise significantly increases the secretion of β-endorphin and that this secretion is correlated with improved mood states. Moderate intensity exercise produces the greatest increase in β-endorphin synthesis, while higher and lower intensity forms of exercise are associated with smaller increases in β-endorphin synthesis. A review on β-endorphin and exercise noted that an individual's mood improves for the remainder of the day following physical exercise and that one's mood is positively correlated with overall daily physical activity level.

However, humans studies showed that pharmacological blockade of endogenous endorphins does not inhibit a runner's high, while blockade of endocannabinoids may have such an effect.

Anandamide

Anandamide is an endogenous cannabinoid and retrograde neurotransmitter that binds to cannabinoid receptors (primarily CB₁), in turn producing euphoria. It has been shown that aerobic exercise causes an increase in plasma anandamide levels, where the magnitude of this increase is highest at moderate exercise intensity (i.e., exercising at ~⁠70⁠–⁠80⁠% maximum heart rate). Increases in plasma anandamide levels are associated with psychoactive effects because anandamide is able to cross the blood–brain barrier and act within the central nervous system. Thus, because anandamide is a euphoriant and aerobic exercise is associated with euphoric effects, it has been proposed that anandamide partly mediates the short-term mood-lifting effects of exercise (e.g., the euphoria of a runner's high) via exercise-induced increases in its synthesis.

Cortisol and the psychological stress response

Diagram of the hypothalamic–pituitary–adrenal axis

See also: Effects of stress on memory

The "stress hormone", cortisol, is a glucocorticoid that binds to glucocorticoid receptors. Psychological stress induces the release of cortisol from the adrenal gland by activating the hypothalamic–pituitary–adrenal axis (HPA axis). Short-term increases in cortisol levels are associated with adaptive cognitive improvements, such as enhanced inhibitory control; however, excessively high exposure or prolonged exposure to high levels of cortisol causes impairments in cognitive control and has neurotoxic effects in the human brain. For example, chronic psychological stress decreases BDNF expression, which has detrimental effects on hippocampal volume and can lead to depression.

As a physical stressor, aerobic exercise stimulates cortisol secretion in an intensity-dependent manner; however, it does not result in long-term increases in cortisol production since this exercise-induced effect on cortisol is a response to transient negative energy balance. Aerobic exercise increases physical fitness and lowers neuroendocrine (i.e., HPA axis) reactivity and therefore reduces the biological response to psychological stress in humans (e.g., reduced cortisol release and attenuated heart rate response). Exercise also reverses stress-induced decreases in BDNF expression and signaling in the brain, thereby acting as a buffer against stress-related diseases like depression.

Glutamate and GABA

Glutamate, one of the most common neurochemicals in the brain, is an excitatory neurotransmitter involved in many aspects of brain function, including learning and memory. Based upon animal models, exercise appears to normalize the excessive levels of glutamate neurotransmission into the nucleus accumbens that occurs in drug addiction. A review of the effects of exercise on neurocardiac function in preclinical models noted that exercise-induced neuroplasticity of the rostral ventrolateral medulla (RVLM) has an inhibitory effect on glutamatergic neurotransmission in this region, in turn reducing sympathetic activity; the review hypothesized that this neuroplasticity in the RVLM is a mechanism by which regular exercise prevents inactivity-related cardiovascular disease.

Exerkines and other circulating compounds

Exerkines are putative "signalling moieties released in response to acute and/or chronic exercise, which exert their effects through endocrine, paracrine and/or autocrine pathways".

Effects in children

Engaging in active physical pursuits has demonstrated positive effects on the mental health of children and adolescents, enhances their academic performance, boosts cognitive function, and diminishes the likelihood of obesity and cardiovascular diseases among this demographic. Establishing consistent exercise routines with regular frequency and duration is pivotal. Cultivating beneficial exercise habits and sustaining adequate physical activity may support the overall physical and mental well-being of young individuals. Therefore, identifying factors that either impede or encourage exercise behaviors could be a significant strategy in promoting the development of healthy exercise habits among children and adolescents.

A 2003 meta-analysis found a positive effect of exercise in children on perceptual skills, intelligence quotient, achievement, verbal tests, mathematic tests, and academic readiness. The correlation was strongest for the age ranges of 4–7 and 11–13 years.

A 2010 meta-analysis of the effect of activity on children's executive function found that aerobic exercise may briefly aid children's executive function and also influence more lasting improvements to executive function. Other studies suggested that exercise is unrelated to academic performance, perhaps due to the parameters used to determine exactly what academic achievement is. This area of study has been a focus for education boards that make decisions on whether physical education should be implemented in the school curriculum, how much time should be dedicated to physical education, and its impact on other academic subjects.

Another study found that sixth-graders who participated in vigorous physical activity at least three times a week had the highest scores compared to those who participated in moderate or no physical activity at all. Children who participated in vigorous physical activity scored three points higher, on average, on their academic test, which consisted of math, science, English, and world studies.

Neuroimaging studies indicate that exercise may influence changes in brain structure and function. Some investigations have linked low levels of aerobic fitness in children with impaired executive function when older as adults, but lack of selective attention, response inhibition, and interference control may also explain this outcome.

Effects on central nervous system disorders

See also: Central nervous system disorders

Exercise as prevention and treatment of drug addictions

Clinical and preclinical evidence indicate that consistent aerobic exercise, especially endurance exercise (e.g., marathon running), actually prevents the development of certain drug addictions and is an effective adjunct treatment for drug addiction, and psychostimulant addiction in particular. Consistent aerobic exercise magnitude-dependently (i.e., by duration and intensity) may reduce drug addiction risk, which appears to occur through the reversal of drug-induced, addiction-related neuroplasticity. Moreover, aerobic exercise decreases psychostimulant self-administration, reduces the reinstatement (i.e., relapse) of drug-seeking, and induces opposite effects on striatal dopamine receptor D₂ (DRD2) signaling (increased DRD2 density) to those induced by pathological stimulant use (decreased DRD2 density). Consequently, consistent aerobic exercise may lead to better treatment outcomes when used as an adjunct treatment for drug addiction. As of 2016, more clinical research is still needed to understand the mechanisms and confirm the efficacy of exercise in drug addiction treatment and prevention.

Summary of addiction-related plasticity

Form of neuroplasticity or behavioral plasticity	Type of reinforcer						Sources
	Opiates	Psychostimulants	High fat or sugar food	Sexual intercourse	Physical exercise (aerobic)	Environmental enrichment
ΔFosB expression in nucleus accumbens D1-type MSNsTooltip medium spiny neurons	↑	↑	↑	↑	↑	↑
Behavioral plasticity
Escalation of intake	Yes	Yes	Yes
Psychostimulant cross-sensitization	Yes	Not applicable	Yes	Yes	Attenuated	Attenuated
Psychostimulant self-administration	↑	↑	↓		↓	↓
Psychostimulant conditioned place preference	↑	↑	↓	↑	↓	↑
Reinstatement of drug-seeking behavior	↑	↑			↓	↓
Neurochemical plasticity
CREBTooltip cAMP response element-binding protein phosphorylation in the nucleus accumbens	↓	↓	↓		↓	↓
Sensitized dopamine response in the nucleus accumbens	No	Yes	No	Yes
Altered striatal dopamine signaling	↓DRD2, ↑DRD3	↑DRD1, ↓DRD2, ↑DRD3	↑DRD1, ↓DRD2, ↑DRD3		↑DRD2	↑DRD2
Altered striatal opioid signaling	No change or ↑μ-opioid receptors	↑μ-opioid receptors ↑κ-opioid receptors	↑μ-opioid receptors	↑μ-opioid receptors	No change	No change
Changes in striatal opioid peptides	↑dynorphin No change: enkephalin	↑dynorphin	↓enkephalin		↑dynorphin	↑dynorphin
Mesocorticolimbic synaptic plasticity
Number of dendrites in the nucleus accumbens	↓	↑		↑
Dendritic spine density in the nucleus accumbens	↓	↑		↑

Attention deficit hyperactivity disorder

Regular physical exercise, particularly aerobic exercise, is an effective add-on treatment for ADHD in children and adults, particularly when combined with stimulant medication (i.e., amphetamine or methylphenidate), although the best intensity and type of aerobic exercise for improving symptoms are not currently known. In particular, the long-term effects of regular aerobic exercise in ADHD individuals include better behavior and motor abilities, improved executive functions (including attention, inhibitory control, and planning, among other cognitive domains), faster information processing speed, and better memory. Parent-teacher ratings of behavioral and socio-emotional outcomes in response to regular aerobic exercise include: better overall function, reduced ADHD symptoms, better self-esteem, reduced levels of anxiety and depression, fewer somatic complaints, better academic and classroom behavior, and improved social behavior. Exercising while on stimulant medication augments the effect of stimulant medication on executive function. It is believed that these short-term effects of exercise are mediated by an increased abundance of synaptic dopamine and norepinephrine in the brain.

Major depressive disorder

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. Several systematic reviews have analyzed the potential for physical exercise in the treatment of depressive disorders. The 2013 Cochrane Collaboration review on physical exercise for depression noted that, based upon limited evidence, it is more effective than a control intervention and comparable to psychological or antidepressant drug therapies. Three subsequent 2014 systematic reviews that included the Cochrane review in their analysis concluded with similar findings: one indicated that physical exercise is effective as an adjunct treatment (i.e., treatments that are used together) with antidepressant medication; the other two indicated that physical exercise has marked antidepressant effects and recommended the inclusion of physical activity as an adjunct treatment for mild–moderate depression and mental illness in general. One systematic review noted that yoga may be effective in alleviating symptoms of prenatal depression. Another review asserted that evidence from clinical trials supports the efficacy of physical exercise as a treatment for depression over a 2–4 month period. These benefits have also been noted in old age, with a review conducted in 2019 finding that exercise is an effective treatment for clinically diagnosed depression in older adults.

A meta-analysis from July 2016 concluded that physical exercise improves overall quality of life in individuals with depression relative to controls.

Cerebrovascular disease

Physical exercise plays a significant role in the prevention and management of stroke. It is well established that physical activity decrease the risk of ischemic stroke and intracerebral haemorrhage. Engaging in physical activity before experiencing a stroke has been found to have a positive impact on the severity and outcomes of stroke. Exercise has the potential to increase the expression of VEGF, caveolin, and angiopoietin in the brain. These changes may promote angiogenesis and neovascularization that contribute to improved blood supply to the stroke affected areas of the brain. Exercise may affect the activation of endothelial nitric oxide synthase (eNOS) and subsequent production of nitric oxide (NO). The increase in NO production may lead to improved post-stroke cerebral blood flow, ensuring a sufficient oxygen and nutrient supply to the brain. Physical activity has been associated with increased expression and activation of hypoxia-inducible factor 1 alpha (HIF-1α), heat shock proteins, and brain-derived neurotrophic factor (BDNF). These factors play crucial roles in promoting cellular survival, neuroprotection, and repair processes in the brain following a stroke. Exercise also inhibit glutamate and caspase activities, which are involved in neuronal death pathways. Additionally, it may promote neurogenesis in the brain. These effects collectively contribute to the reduction of brain infarction and edema, leading to potential improvements in neurological and functional outcomes. The neuroprotective properties of physical activity in relation to haemorrhagic strokes are less studied. Pre-stroke physical activity has been associated with improved outcomes after intracerebral haemorrhages. Furthermore, physical activity may reduce the volume of intracerebral haemorrhages. Being physically active after stroke also enhance the functional recovery.

Mild cognitive impairment

The American Academy of Neurology's January 2018 update of their clinical practice guideline for mild cognitive impairment states that clinicians should recommend regular exercise (two times per week) to individuals who have been diagnosed with this condition. This guidance is based upon a moderate amount of high-quality evidence which supports the efficacy of regular physical exercise (twice weekly over a 6-month period) for improving cognitive symptoms in individuals with mild cognitive impairment.

Neurodegenerative disorders

Alzheimer's disease

Alzheimer's disease is a cortical neurodegenerative disorder and the most prevalent form of dementia, representing approximately 65% of all cases of dementia; it is characterized by impaired cognitive function, behavioral abnormalities, and a reduced capacity to perform basic activities of daily life. Two reviews found evidence for possible positive effects of physical exercise on cognitive function, the rate of cognitive decline, and the ability to perform activities of daily living in individuals with Alzheimer's disease. A subsequent review found higher levels of physical activity may be associated with reduced risk of dementia and cognitive decline.

Parkinson's disease

Parkinson's disease symptoms reflect various functional impairments and limitations, such as postural instability, gait disturbance, immobility, and frequent falls. Some evidence suggests that physical exercise may lower the risk of Parkinson's disease. A 2017 study found that strength and endurance training in people with Parkinson's disease had positive effects lasting for several weeks. A 2023 Cochrane review on the effects of physical exercise in people with Parkinson's disease indicated that aquatic exercise might reduce severity of motor symptoms and improve quality of life. Furthermore, endurance training, functional training, and multi-domain training (i.e., engaging in several types of exercise) may provide improvements.

See also

• Brain fitness
• Exercise is Medicine
• Exercise prescription
• Exercise therapy
• Memory improvement
• Neuroinflammation#Exercise
• Nootropic

References

Depression

Further information: Neurobiological effects of physical exercise § Major depressive disorder

Physical exercise has established efficacy as an antidepressant in individuals with depression and current medical evidence supports the use of exercise as both a preventive measure against and an adjunct therapy with antidepressant medication for depressive disorders. A July 2016 meta-analysis concluded that physical exercise improves overall quality of life in individuals with depression relative to controls. One systematic review noted that yoga may be effective in alleviating symptoms of prenatal depression. The biomolecular basis for exercise-induced antidepressant effects is believed to be a result of increased neurotrophic factor signaling, particularly brain-derived neurotrophic factor.

Continuous aerobic exercise 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).

A systematic review noted that, although limited, some evidence suggests that the duration of engagement in a sedentary lifestyle is positively correlated with a risk of developing an anxiety disorder or experiencing anxiety symptoms. It noted that additional research is needed in order to confirm these findings.

Sleep

A 2010 review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the possible exception of heavy exercise taken shortly before bedtime, which may disturb sleep. There is, in any case, insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep.

According to a 2005 study, exercise is the most recommended alternative to sleeping pills for resolving insomnia. Sleeping pills are more costly than to make time for a daily routine of staying fit, and may have dangerous side effects in the long run. Exercise can be a healthy, safe and inexpensive way to achieve more and better sleep.

Excessive exercise

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. Specifically, high cardiac output has been shown to cause enlargement of the left and right ventricle volumes, increased ventricle wall thickness, and greater cardiac mass. These changes further result in myocardial cell damage in the lining of the heart, leading to scar tissue and thickened walls. During these processes, the protein troponin increases in the bloodstream, indicating cardiac muscle cell death and increased stress on the heart itself.

Inappropriate exercise can do more harm than good, with the definition of “inappropriate” varying according to the individual. For many activities, especially running and cycling, there are significant injuries that occur with poorly regimented exercise schedules. Injuries from accidents also remain a major concern, whereas the effects of increased exposure to air pollution seem only a minor concern.

In extreme instances, over-exercising induces serious performance loss. Unaccustomed overexertion of muscles leads to rhabdomyolysis (damage to muscle) most often seen in new army recruits. Another danger is overtraining, in which the intensity or volume of training exceeds the body's capacity to recover between bouts. One sign of Overtraining Syndrome (OTS) is suppressed immune function, with an increased incidence of upper respiratory tract infection (URTI). An increased incidence of URTIs is also associated with high volume/intensity training, as well as with excessive exercise (EE), such as in a marathon.

Stopping excessive exercise suddenly may create a change in mood. Exercise should be controlled by each body's inherent limitations. While one set of joints and muscles may have the tolerance to withstand multiple marathons, another body may be damaged by 20 minutes of light jogging. This must be determined for each individual.

Too much exercise may cause a woman to miss her periods, a symptom known as amenorrhea. This is a very serious condition which indicates a woman is pushing her body beyond its natural boundaries.

Mechanism of effects

Skeletal muscle

Resistance training and subsequent consumption of a protein-rich meal promotes muscle hypertrophy and gains in muscle strength by stimulating myofibrillar muscle protein synthesis (MPS) and inhibiting muscle protein breakdown (MPB). The stimulation of muscle protein synthesis by resistance training occurs via phosphorylation of the mechanistic target of rapamycin (mTOR) and subsequent activation of mTORC1, which leads to protein biosynthesis in the ribosome via phosphorylation of mTORC1's immediate targets (the p70S6 kinase and the translation repressor protein 4EBP1). The suppression of muscle protein breakdown following food consumption occurs primarily via increases in plasma insulin; however, a suppression of MPB of comparable magnitude has also been shown to occur in humans from a sufficient elevation of plasma β-hydroxy β-methylbutyric acid.

Aerobic exercise induces mitochondrial biogenesis and an increased capacity for oxidative phosphorylation in the mitochondria of skeletal muscle, which is one mechanism by which aerobic exercise enhances submaximal endurance performance. These effects occur via an exercise-induced increase in the intracellular AMP:ATP ratio, thereby triggering the activation of AMP-activated protein kinase (AMPK) which subsequently phosphorylates peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), the master regulator of mitochondrial biogenesis.

Diagram of the molecular signaling cascades that are involved in myofibrillar muscle protein synthesis and mitochondrial biogenesis in response to physical exercise and specific amino acids or their derivatives (primarily L-leucine and HMB). Many amino acids derived from food protein promote the activation of mTORC1 and increase protein synthesis by signaling through Rag GTPases.

Abbreviations and representations:

 • PLD: phospholipase D
 • PA: phosphatidic acid
 • mTOR: mechanistic target of rapamycin
 • AMP: adenosine monophosphate
 • ATP: adenosine triphosphate
 • AMPK: AMP-activated protein kinase
 • PGC‐1α: peroxisome proliferator-activated receptor gamma coactivator-1α
 • S6K1: p70S6 kinase
 • 4EBP1: eukaryotic translation initiation factor 4E-binding protein 1
 • eIF4E: eukaryotic translation initiation factor 4E
 • RPS6: ribosomal protein S6
 • eEF2: eukaryotic elongation factor 2
 • RE: resistance exercise; EE: endurance exercise
 • Myo: myofibrillar; Mito: mitochondrial
 • AA: amino acids
 • HMB: β-hydroxy β-methylbutyric acid
 • ↑ represents activation
 • Τ represents inhibition

Resistance training stimulates muscle protein synthesis (MPS) for a period of up to 48 hours following exercise (shown by dotted line). Ingestion of a protein-rich meal at any point during this period will augment the exercise-induced increase in muscle protein synthesis (shown by solid lines).

Other peripheral organs

Summary of long-term adaptations to regular aerobic and anaerobic exercise. Aerobic exercise can cause several central cardiovascular adaptations, including an increase in stroke volume (SV) and maximal aerobic capacity (VO₂ max), as well as a decrease in resting heart rate (RHR). Long-term adaptations to resistance training, the most common form of anaerobic exercise, include muscular hypertrophy, an increase in the physiological cross-sectional area (PCSA) of muscle(s), and an increase in neural drive, both of which lead to increased muscular strength. Neural adaptations begin more quickly and plateau prior to the hypertrophic response.

Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ. That is, contracting muscles release multiple substances known as myokines which promote the growth of new tissue, tissue repair, and multiple anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases. Exercise reduces levels of cortisol, which causes many health problems, both physical and mental. Endurance exercise before meals lowers blood glucose more than the same exercise after meals. There is evidence that vigorous exercise (90–95% of VO₂ max) induces a greater degree of physiological cardiac hypertrophy than moderate exercise (40 to 70% of VO₂ max), but it is unknown whether this has any effects on overall morbidity and/or mortality. Both aerobic and anaerobic exercise work to increase the mechanical efficiency of the heart by increasing cardiac volume (aerobic exercise), or myocardial thickness (strength training). Ventricular hypertrophy, the thickening of the ventricular walls, is generally beneficial and healthy if it occurs in response to exercise.

Central nervous system

The persistent long-term neurobiological effects of regular physical exercise are believed to be mediated by transient exercise-induced increases in the concentration of neurotrophic factors (e.g., BDNF, IGF-1, VEGF, and GDNF) and other biomolecules in peripheral blood plasma, which subsequently cross the blood–brain barrier and blood–cerebrospinal fluid barrier and bind to their associated receptors in the brain. Upon binding to their receptors in cerebral vasculature and brain cells (i.e., neurons and glial cells), these biomolecules trigger intracellular signaling cascades that lead to neuroplastic biological responses – such as neurogenesis, synaptogenesis, oligodendrogenesis, and angiogenesis, among others – which ultimately mediate the exercise-induced improvements in cognitive function.

Public health measures

Multiple component community-wide campaigns are frequently used in an attempt to increase a population's level of physical activity. A 2015 Cochrane review, however, did not find evidence supporting a benefit. The quality of the underlying evidence was also poor. However, there is some evidence that school-based interventions can increase activity levels and fitness in children. Another Cochrane review found some evidence that certain types of exercise programmes, such as those involving gait, balance, co-ordination and functional tasks, can improve balance in older adults. Following progressive resistance training, older adults also respond with improved physical function. Survey of brief interventions promoting physical activity found that they are cost-effective, although there are variations between studies.

Environmental approaches appear promising: signs that encourage the use of stairs, as well as community campaigns, may increase exercise levels. The city of Bogotá, Colombia, for example, blocks off 113 kilometers (70 mi) of roads on Sundays and holidays to make it easier for its citizens to get exercise. These pedestrian zones are part of an effort to combat chronic diseases, including obesity.

To identify which public health strategies are effective, a Cochrane overview of reviews is in preparation.

Physical exercise was said to decrease healthcare costs, increase the rate of job attendance, as well as increase the amount of effort women put into their jobs.

Children will mimic the behavior of their parents in relation to physical exercise. Parents can thus promote physical activity and limit the amount of time children spend in front of screens which may decrease the risk of childhood obesity.

Overweight children who participate in physical exercise experience greater loss of body fat and increased cardiovascular fitness. According to the Centers for Disease Control and Prevention in the United States, both children and adults should do 60 minutes or more of physical activity each day. Implementing physical exercise in the school system and ensuring an environment in which children can reduce barriers to maintain a healthy lifestyle is essential.

Exercise trends

File:Jumping Fitness (26364647332).jpg

Jumping fitness exercise

Main article: Exercise trends

Worldwide there has been a large shift towards less physically demanding work. This has been accompanied by increasing use of mechanized transportation, a greater prevalence of labor saving technology in the home, and fewer active recreational pursuits. Personal lifestyle changes however can correct the lack of physical exercise.

Research in 2015 indicates integrating mindfulness to physical exercise interventions increases exercise adherence, self-efficacy and also has positive effects both psychologically and physiologically.

Nutrition and recovery

Proper nutrition is as important to health as exercise. When exercising, it becomes even more important to have a good diet to ensure that the body has the correct ratio of macronutrients while providing ample micronutrients, in order to aid the body with the recovery process following strenuous exercise.

Active recovery is recommended after participating in physical exercise because it removes lactate from the blood more quickly than inactive recovery. Removing lactate from circulation allows for an easy decline in body temperature, which can also benefit the immune system, as an individual may be vulnerable to minor illnesses if the body temperature drops too abruptly after physical exercise.

History

The benefits of exercise have been known since antiquity. Marcus Cicero, around 65 BCE, stated: "It is exercise alone that supports the spirits, and keeps the mind in vigor."

Several mass exercise movements were started in the early twentieth century to realise the benefits of exercise. The first and most significant of these in the UK was the Women's League of Health and Beauty founded in 1930 by Mary Bagot Stack that had 166,000 members in 1937.

However, the link between physical health and exercise (or lack of it) was only discovered in 1949 and reported in 1953 by a team led by Jerry Morris. Dr. Morris noted that men of similar social class and occupation (bus conductors versus bus drivers) had markedly different rates of heart attacks, depending on the level of exercise they got: bus drivers had a sedentary occupation and a higher incidence of heart disease, while bus conductors were forced to move continually and had a lower incidence of heart disease. This link had not previously been noted and was later confirmed by other researchers.

Other animals

Physical exercise has been shown to benefit a wide range of other mammals, as well as salmon, juvenile crocodiles, and at least one species of bird.

However, several studies have shown that lizards display no benefit from exercise, leading them to be termed "metabolically inflexible". Indeed, damage from overtraining may occur following weeks of forced treadmill exercise in lizards.

A number of studies of both rodents and humans have demonstrated that individual differences in both ability and propensity for exercise (i.e., voluntary exercise) have some genetic basis.

Several studies of rodents have demonstrated that maternal or juvenile access to wheels that allow voluntary exercise can increase the propensity to run as adults. These studies further suggest that physical activity may be more "programmable" (for discusison, see Thrifty phenotype) than food intake.

See also

Main article: Outline of exercise

• Active living
• Behavioural change theories
• Exercise hypertension
• Exercise-induced nausea
• Exercise intensity
• Exercise intolerance
• Exercise-induced anaphylaxis
• Exercise-induced asthma
• Kinesiology
• Metabolic equivalent
• Supercompensation
• Physical fitness

Further reading

• Donatelle, Rebecca J. (2005). Health, The Basics (6th ed.). San Francisco: Pearson Education. ISBN 0-8053-2852-1.
• Hardman A, Stensel D (2009). Physical Activity and Health: The Evidence Explained. London: Routledge. ISBN 978-0-415-42198-0.
• Ainsworth BE, Haskell WL, Leon AS, Jacobs DR, Montoye HJ, Sallis JF, Paffenbarger RS; Haskell; Leon; Jacobs Jr; Montoye; Sallis; Paffenbarger Jr (1993). "Compendium of physical activities: Classification of energy costs of human physical activities". Medicine and Science in Sports and Exercise. 25 (1): 71–80. doi:10.1249/00005768-199301000-00011. PMID 8292105.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Ainsworth BE, Haskell WL, Whitt MC, Irwin ML, Swartz AM, Strath SJ, O'Brien WL, Bassett DR, Schmitz KH, Emplaincourt PO, Jacobs DR, Leon AS; Haskell; Whitt; Irwin; Swartz; Strath; O'Brien; Bassett Jr; Schmitz; Emplaincourt; Jacobs Jr; Leon (2000). "Compendium of physical activities: an update of activity codes and MET intensities". Med Sci Sports Exerc. 32 (9 Suppl): S498–504. doi:10.1097/00005768-200009001-00009. PMID 10993420.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett DR, Tudor-Locke C, Greer JL, Vezina J, Whitt-Glover MC, Leon AS; Haskell; Herrmann; Meckes; Bassett Jr; Tudor-Locke; Greer; Vezina; Whitt-Glover; Leon (2011). "2011 Compendium of Physical Activities: a second update of codes and MET values". Med Sci Sports Exerc. 43 (8): 1575–81. doi:10.1249/MSS.0b013e31821ece12. PMID 21681120.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett Jr DR, Tudor-Locke C, Greer JL, Vezina J, Whitt-Glover MC, Leon AS. The Compendium of Physical Activities Tracking Guide. Healthy Lifestyles Research Center, College of Nursing & Health Innovation, Arizona State University. Retrieved [date] from the World Wide Web. https://sites.google.com/site/compendiumofphysicalactivities/

External links

• Media related to Fitness training at Wikimedia Commons
• MedLinePlus's Topic on Exercise and Physical Fitness
• Science Daily's reference on Physical Exercise
• Guidance on the promotion and creation of physical environments that support increased levels of physical activity."Physical activity and the environment".