Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons including strengthening muscles and the cardiovascular system, honing athletic skills, weight loss or maintenance, as well as for the purpose of enjoyment. Frequent and regular physical exercise boosts the immune system, and helps prevent the "diseases of affluence" such as heart disease, cardiovascular disease, Type 2 diabetes and obesity. It also improves mental health, helps prevent depression, helps to promote or maintain positive self-esteem, and can even augment an individual's sex appeal or body image, which is also 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. Health care providers often call exercise the "miracle" or "wonder" drug—alluding to the wide variety of proven benefits that it provides.
Types of exercise
Physical exercises are generally grouped into three types, depending on the overall effect they have on the human body:
- Flexibility exercises, such as stretching, improve the range of motion of muscles and joints.
- Aerobic exercises, such as cycling, swimming, walking, skipping rope, rowing, running, hiking or playing tennis, focus on increasing cardiovascular endurance.
- Anaerobic exercises, such as weight training, functional training, eccentric training or sprinting and high-intensity interval training, increase short-term muscle strength.
Categories of physical exercise
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).
Physical exercise is used to improve physical skills. Physical skills fall into the following general categories: Cardiovascular/respiratory endurance, Stamina, Strength, Flexibility, Power, Speed, Coordination, Agility, Balance, and Accuracy.
Physical exercise is important for maintaining physical fitness and can contribute positively to maintaining a healthy weight, building and maintaining healthy bone density, muscle strength, and joint mobility, promoting physiological well-being, reducing surgical risks, and strengthening the immune system.
Frequent and regular aerobic exercise has been shown to help prevent or treat serious and life-threatening chronic conditions such as high blood pressure, obesity, heart disease, Type 2 diabetes, insomnia, and depression.[dead link] Endurance exercise before meals lowers blood glucose more than the same exercise after meals. According to the World Health Organization, lack of physical activity contributes to approximately 17% of heart disease and diabetes, 12% of falls in the elderly, and 10% of breast cancer and colon cancer.
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.
Some studies have shown that vigorous exercise executed by healthy individuals can increase opioid peptides (a.k.a. endorphins, naturally occurring opioids that in conjunction with other neurotransmitters are responsible for exercise-induced euphoria and have been shown to be addictive), increase testosterone and growth hormone, effects that are not as fully realized with moderate exercise. More recent research indicates that anandamide may play a greater role than endorphins in "runner's high". However, training at this[which?] intensity for long periods of time, or without proper warmup beforehand and cooldown afterwards, can lead to an increased risk of injury and overtraining.
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). Such changes are generally beneficial and healthy if they occur in response to exercise.
Not everyone benefits equally from exercise. There is tremendous variation in individual response to training; where most people will see a moderate increase in endurance from aerobic exercise, some individuals will as much as double their oxygen uptake, while others can never augment endurance. However, muscle hypertrophy 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 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.
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. 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. The depression in the immune system following acute bouts of exercise may be one of the mechanisms for this anti-inflammatory effect.
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".
In mice, exercise improves cognitive functioning via improvement of hippocampus-dependent spatial learning, and enhancement of synaptic plasticity and neurogenesis. In addition, physical activity has been shown to be neuroprotective in many neurodegenerative and neuromuscular diseases. For instance, it reduces the risk of developing dementia. Furthermore, anecdotal evidence suggests that frequent exercise may reverse alcohol-induced brain damage.
There are several possibilities for why exercise is beneficial for the brain. Examples are as follows:
- increasing the blood and oxygen flow to the brain
- increasing growth factors that help create new nerve cells and promote synaptic plasticity
- increasing chemicals in the brain that help cognition, such as dopamine, glutamate, norepinephrine, and serotonin
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.
A number of factors may contribute to depression including being overweight, low self-esteem, stress, and anxiety. Endorphins act as a natural pain reliever and antidepressant in the body. 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. However, recent research 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. 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. Exercise alone is a potential prevention method and/or treatment for mild forms of depression. Research has also shown that when exercise is done in the presence of other people (familiar or not), it can be more effective in reducing stress than simply exercising alone.
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.
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.
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.
Stopping excessive exercise suddenly can also create a change in mood. Feelings of depression and agitation can occur when withdrawal from the natural endorphins produced by exercise occurs. 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.
Public health measures
As of 2011 the effects of community wide interventions to increase exercise levels at the population level is unknown. 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.
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 less active recreational pursuits. Personal lifestyle changes however can correct the lack of physical exercise.
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 whilst providing ample micronutrients, in order to aid the body with the recovery process following strenuous exercise.
The benefits of exercise have been known since antiquity. Marcus Cicero, around 65 BC, stated: "It is exercise alone that supports the spirits, and keeps the mind in vigor." 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.
In 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".
- Active living
- Behavioural change theories
- Central governor
- Exercise hypertension
- Exercise induced nausea
- Exercise intensity
- Exercise intolerance
- Exercise-induced anaphylaxis
- Exercise-induced asthma
- Girls on the Run
- Green exercise
- Health club
- Metabolic equivalent
- Outdoor gym
- Stampfer, M. J.; Hu, F. B.; Manson, J. E.; Rimm, E. B.; Willett, W. C. (2000). "Primary Prevention of Coronary Heart Disease in Women through Diet and Lifestyle". New England Journal of Medicine 343 (1): 16–22. doi:10.1056/NEJM200007063430103. PMID 10882764.
- Hu , Manson J., Stampfer M., Graham C. et al. (2001). "Diet, lifestyle, and the risk of type 2 diabetes mellitus in women". The New England Journal of Medicine 345 (11): 790–797.
- "Exercise". medical-dictionary.thefreedictionary.com. In turn citing: Gale Encyclopedia of Medicine. Copyright 2008. Citation: "Strengthening exercise increases muscle strength and mass, bone strength, and the body's metabolism. It can help attain and maintain proper weight and improve body image and self-esteem"
- "WHO: Obesity and overweight". who.int.
- American Association of Kidney Patients, "Physical Activity and Exercise: The Wonder Drug"
- National Center for Biotechnology Information, "The miracle drug"
- "Your Guide to Physical Activity" (NHLBI produced publications: Color). The National Heart, Lung, and Blood Institute (NHLBI). 2007. Retrieved March 2011.
- O'Connor D., Crowe M., Spinks W. (2005). "Effects of static stretching on leg capacity during cycling". Turin 46 (1): 52–56.
- Wilmore J., Knuttgen H. (2003). "Aerobic Exercise and Endurance Improving Fitness for Health Benefits". The Physician and Sportsmedicine 31 (5): 45.
- De Vos N., Singh N., Ross D., Stavrinos T. et al. (2005). "Optimal Load for Increasing Muscle Power During Explosive Resistance Training in Older Adults". The Journals of Gerontology 60A (5): 638–647.
- "What Is Fitness?". The CrossFit Journal. October 2002. p. 4. Retrieved 2010-09-12.
- A. Cornil, A. De Coster, G. Copinschi, J. R. M. Franckson (1965). "Effect of muscular exercise on the plasma level of cortisol in man". European Journal of Endocrinology.
- Cohen S., Williamson G. M. (1991). "Stress and infectious disease in humans". Psychological Bulletin 109: 5–24. doi:10.1037/0033-2909.109.1.5. PMID 2006229.
- Jason Menoutis, Ed.D. (2008). "Physical Activity and Health" (Abstract). Nasm Pro. Retrieved 2008-08-25.
- Borer, KT; Wuorineen EC, Lukos JR, Denver JW, Porges SW, Burant F (August 2009). "Two bouts of exercise before meals but not after meals, lower fasting blood glucose". Medicine in Science and Sports and Exercise 41 (8): 1606–14. doi:10.1249/MSS.0b013e31819dfe14. PMID 19568199.
- Silberner, Joanne (June 7, 2010). "100 Years Ago, Exercise Was Blended Into Daily Life". npr.org. Retrieved 23 November 2010.
- Wislett, Ulrik; Ellingsen O, Kemi O. (July 2009). "High=Intensity Interval Training to Maximize Cardiac Benefit of Exercise Taining?". Exercise and Sports Sciences Reviews 37 (3): 139–146. doi:10.1097/JES.0b013e3181aa65fc. PMID 19550205.
- Hanc, J. 1987. Your Health Behind the Runner\'s Euphoria. \'\'Newsday, April 21, 1987,\'\' 11. Retrieved October 5, 2006, from ProQuest database
- Sparling PB, Giuffrida A, Piomelli D, Rosskopf L, Dietrich A (December 2003). "Exercise activates the endocannabinoid system". NeuroReport 14 (17): 2209–11. doi:10.1097/01.wnr.0000097048.56589.47. PMID 14625449.
- Burfoot, Amby (June 2004). "Runner's High". Runner's World. Retrieved 2009-10-10.
- Bouchard, Claude; Ping An, Treva Rice, James S. Skinner, Jack H. Wilmore, Jacques Gagnon, Louis Perusse, Arthus S. Leon, D. C. Rao (September 1, 1999). "Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study". Journal of Applied Physiology 87 (3): 1003–1008. PMID 10484570. Retrieved 2007-07-17.
- Kolata, Gina (February 12, 2002). "Why Some People Won't Be Fit Despite Exercise". The New York Times. Retrieved 2007-07-17.
- Hubal, MJ; Gordish-Dressman H, Thompson PD, Price TB, Hoffman EP, Angelopoulos TJ, Gordon PM, Moyna NM, Pescatello LS, Visich PS, Zoeller RF, Seip RL, Clarkson PM (June 2005). "Variability in muscle size and strength gain after unilateral resistance training". Medicine and Science in Sports and Exercise 37 (6): 964–972. PMID 15947721.
- Brutsaert, Tom D.; Esteban J. Parra (2006). "What makes a champion? Explaining variation in human athletic performance" (PDF). Respiratory Physiology & Neurobiology 151 (2–3): 109–123. doi:10.1016/j.resp.2005.12.013. PMID 16448865. Archived from the original on 2007-08-10. Retrieved 2007-07-17.
- Geddes, Linda (2007-07-28). "Superhuman". New Scientist. pp. 35–41.
- "Being active combats risk of functional problems".
- AHA: Physical activity recommendations
- Gleeson M (August 2007). "Immune function in sport and exercise". J. Appl. Physiol. 103 (2): 693–9. doi:10.1152/japplphysiol.00008.2007. PMID 17303714.
- Hertzog C, Kramer AF, Wilson S, Lindenberger U. (2008). "Enrichment Effects on Adult Cognitive Development: Can the Functional Capacity of Older Adults Be" (PDF). Psychological Science in the Public Interest 9 (1): 1–65. doi:10.1111/j.1539-6053.2009.01034.x. Retrieved 2009-07-07.
- van Praag H, Kempermann G, Gage FH., H; Kempermann, G; Gage, FH (1999). "Ontogeny Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus". Nature Neuroscience. (Abstractdoi:10.1038/6368. PMID 10195220.) 2 (3): 266–70.
- Clément Grondard, C et al. (2005). "Regular Exercise Prolongs Survival in a Type 2 Spinal Muscular Atrophy Model Mouse". The Journal of Neuroscience. (Abstractdoi:10.1523/JNEUROSCI.1245-05.2005. PMID 16107648.) 25 (33): 7615–7622.
- West Virginia Department of Health and Human Resources
- Could Exercise Regenerate Alcohol-Damaged Neurons? - Levin 41 (23): 20 - Psychiatr News
- van Praag H, Kempermann G, Gage FH (March 1999). "Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus". Nat. Neurosci. 2 (3): 266–70. doi:10.1038/6368. PMID 10195220.
- Hunsberger JG, Newton SS, Bennett AH, Duman CH, Russell DS, Salton SR, Duman RS (2007). "Antidepressant actions of the exercise-regulated gene VGF". Nat. Med. 13 (12): 1476–82. doi:10.1038/nm1669. PMID 18059283.
- Parker-Pope, T. (2001). For a Healthy Brain You Really Need to Use Your Head -- Physical and Mental Exercise Can Stave Off Mental Decline. The Wall Street Journal Europe, November 26, 2001, 8. Retrieved October 5, 2006, from ProQuest database.
- Edward McAuley,* Arthur F. Kramer, and Stanley J. Colcombe, E; Kramer, Arthur F; Colcombe, Stanley J (2004). "Cardiovascular fitness and neurocognitive function in older Adults: a brief review" (PDF). BRAIN, BEHAVIOR, and IMMUNITY. 18 (2004): 214–220. doi:10.1016/j.bbi.2003.12.007. Archived from the original on 2007-06-16. Retrieved 2007-03-28.
- Keith W. Johnsgard (2004). Conquering Depression and Anxiety Through Exercise. Amherst, N.Y.: Prometheus Books. ISBN 978-1-59102-192-6.
- Thase, Michael (2007). "Endorphin Power: Fight Depression With Exercise". everydayhealth.com.
- The influence of physical activity on mental well-being. Dr. Kenneth R. Fox, Department of Exercise and Health Sciences, University of Bristol, Priory House, Woodlands Rd., Bristol, UK
- Byrd, Andrea. "Biology 202, Serotonin and Its Uses. 1999 First Web Reports On Serendip". Retrieved 23 November 2010.
- Public Health Nutrition (1999), 2:411–418 Cambridge University Press doi:10.1017/S1368980099000567 Research Article
- Plante, Thomas G.; Coscarelli, Laura; Ford, Marie (2001). "Does Exercising with Another Enhance the Stress-Reducing Benefits of Exercise". International Journal of Stress Management 8 (3): 201–213. Retrieved 13 November 2011.
- Buman, M.P. and King, A.C.: "Exercise as a Treatment to Enhance Sleep", American Journal of Lifestyle Medicine, Nov-Dec 2010.
- Youngstedt, S.D. (April 2005). "Effects of exercise on sleep". Clin Sports Med. 24(2): 355–65, xi. Retrieved 9 April 2012.
- Alexander, C. 1998. Cutting weight, losing life. News & Observer, February 8, 1998, A.1. Retrieved October 5, 2006, from ProQuest database.
- Möhlenkamp S, Lehmann N, Breuckmann F et al. (2008). "Running: the risk of coronary events". European Heart Journal 29 (15): 1903–1910. doi:10.1093/eurheartj/ehn163.
- Benito B, Gay-Jordi G, Serrano-Mollar A et al. (2011). "Cardiac arrhythmogenic remodeling in a rat model of long-term intensive exercise training". Circulation 123: 13–22. doi:10.1161/CIRCULATIONAHA.110.938282.
- Wilson MG, O'Hanlon R, Prasad S, Deighan A, Macmillan P, Oxborough D, Godfrey RJ, Smith G, Maceira A, Sharma S, George KP, Whyte G (2011). "Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes". J Appl Physiol 110 (6): 1622–6. doi:10.1152/japplphysiol.01280.2010. PMC 3119133. PMID 21330616.
- Joris Aertsens, Bas de Geus, Grégory Vandenbulcke, Bart Degraeuwe, Steven Broekx, Leo De Nocker, Inge Liekens, Inge Mayeres, Romain Meeusen, Isabelle Thomas, Rudi Torfs, Hanny Willems, Luc Int Panis (2010). "Commuting by bike in Belgium, the costs of minor accidents". Accident Analysis and Prevention 42 (6): 2149–2157. doi:10.1016/j.aap.2010.07.008. PMID 20728675.
- Int Panis, L; De Geus, Bas; Vandenbulcke, GréGory; Willems, Hanny; Degraeuwe, Bart; Bleux, Nico; Mishra, Vinit; Thomas, Isabelle et al. (2010). "Exposure to particulate matter in traffic: A comparison of cyclists and car passengers". Atmospheric Environment 44 (19): 2263–2270. doi:10.1016/j.atmosenv.2010.04.028.
- Jacobs, L; Nawrot, Tim S; De Geus, Bas; Meeusen, Romain; Degraeuwe, Bart; Bernard, Alfred; Sughis, Muhammad; Nemery, Benoit et al. (Oct 2010). "Subclinical responses in healthy cyclists briefly exposed to traffic-related air pollution". Environmental Health 9 (64): 64. doi:10.1186/1476-069X-9-64.
- Jimenez C., Pacheco E., Moreno A., Carpenter A. (1996). "A Soldier's Neck and Shoulder Pain". The Physician and Sportsmedicine 24 (6): 81–82.
- The Physician and Sportsmedicine on Overtraining[dead link]
- Julia Berry; Anne Bradley; Hillery Magness. "Amenorrhea". The Female Athlete Triad. University of Oregon, Department of Human Physiology. Retrieved 2007-08-14.[dead link]
- Baker, PR; Francis, DP, Soares, J, Weightman, AL, Foster, C (2011 Apr 13). "Community wide interventions for increasing physical activity". In Baker, Philip RA. Cochrane database of systematic reviews (Online) (4): CD008366. doi:10.1002/14651858.CD008366.pub2. PMID 21491409.
- Kahn, E. B., Ramsey, L. T., Brownson, R. C. et al. (May 2002). "The effectiveness of interventions to increase physical activity. A systematic review". Am J Prev Med 22 (4 Suppl): 73–107. doi:10.1016/S0749-3797(02)00434-8. PMID 11985936.
- Durán, Víctor Hugo. "Stopping the rising tide of chronic diseases Everyone's Epidemic". Pan American Health Organization. paho.org. Retrieved January 10, 2009.
- "WHO: Obesity and overweight". World Health Organization. Archived from the original on December 18, 2008. Retrieved January 10, 2009.
- Kimber N., Heigenhauser G., Spriet L., Dyck D. (2003). "Skeletal muscle fat and carbohydrate metabolism during recovery from glycogen-depleting exercise in humans". The Journal of Phsyiology 548 (3): 919–927.
- "Quotes About Exercise Top 10 List".
- Kuper, Simon (11 September 2009). "The man who invented exercise". Financial Times. Retrieved 12 September 2009.
- Morris JN, Heady JA, Raffle PA, Roberts CG, Parks JW (1953). "Coronary heart-disease and physical activity of work". Lancet 265 (6795): 1053–7. doi:10.1016/S0140-6736(53)90665-5. PMID 13110049.
- Owerkowicz T, Baudinette RV (2008). "Exercise training enhances aerobic capacity in juvenile estuarine crocodiles (Crocodylus porosus)". Comparative Biochemistry and Physiology, Part A 150: 211–216.
- Gleeson T (1987). "Effects of endurance training and captivity on activity metabolism of lizards". Journal of Comparative Physiology 252: R459–R456.
- Garland T, Jr., Else PL, Hulbert AJ, Tap P (1979). "The effects of training and captivity on activity metabolism of lizards". American Journal of Physiology 129: 123–128.
- Garland T, Jr., Schutz H, Chappell MA, Keeney BK, Meek TH, Copes LE, Acosta W, Drenowatz C, Maciel RC, van Dijk G, Kotz CM, Eisenmann JC (2011). "The biological control of voluntary exercise, spontaneous physical activity and daily energy expenditure in relation to obesity: human and rodent perspectives". Journal of Experimental Biology 214: 206–229.
- Kelly SA, Pomp D (2013). "Genetic determinants of voluntary exercise". Trends in Genetics. In press.
- 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 Jr, Montoye HJ, Sallis JF, Paffenbarger RS Jr (1993). "Compendium of physical activities: Classification of energy costs of human physical activities". Medicine and Science in Sports and Exercise 25: 71–80.
- Ainsworth BE, Haskell WL, Whitt MC, Irwin ML, Swartz AM, Strath SJ, O'Brien WL, Bassett DR Jr, Schmitz KH, Emplaincourt PO, Jacobs DR Jr, Leon AS. "Compendium of Physical Activities: An update of activity codes and MET intensities. Medicine and Science in Sports and Exercise, 2000; 32 (Suppl):S498-S516.
- Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett Jr DR, Tudor-Locke C, Greer JL, Vezina J, Whitt-Glover MC, Leon AS. 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine and Science in Sports and Exercise. (in press).
- 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/
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- 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".