Physical exercise

"Workout" redirects here. For other uses, see Workout (disambiguation).

"Exercise" redirects here. For other uses, see Exercise (disambiguation).

Participant in a triathlon at Catoctin Mountain in 2005

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.^[1][2] 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.^[3] Childhood obesity is a growing global concern^[4] 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.^[5][6]

Contents   [hide]  1 Classification 1.1 Types of exercise 1.2 Categories of physical exercise 1.3 Categories 1.4 Metabolic equivalent of task 2 Health effects 2.1 Cardiovascular system 2.2 Immune system 2.3 Brain function 2.4 Depression 2.5 Sleep 2.6 Excessive exercise 3 Public health measures 4 Metabolic equivalent of task 5 Exercise trends 6 Nutrition and recovery 7 History 8 In other animals 9 See also 10 References 11 Sources 12 External links

Classification

Types of exercise

Physical exercises are generally grouped into three types,^[7] 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.^[8]
• Aerobic exercises, such as cycling, swimming, walking, skipping rope, rowing, running, hiking or playing tennis, focus on increasing cardiovascular endurance.^[9]
• Anaerobic exercises, such as weight training, functional training, eccentric training or sprinting and high-intensity interval training, increase short-term muscle strength.^[10]

Categories of physical exercise

• Strength training
• Agility training
• Eccentric training
• Resistance training
• Interval training
• Continuous training

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).

Categories

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.^[11]

Metabolic equivalent of task

The Compendium of Physical Activities was developed for use in epidemiologic studies to standardize the assignment of metabolic equivalent of task (MET) intensities in physical activity questionnaires. The Compendium is list of physical activities and the associated energy cost of each activity. The original Compendium was published in 1993, the first update in 2000, and the most recent update in 2011.^[12]

MET (Metabolic Equivalent): The ratio of the work metabolic rate to the resting metabolic rate. One MET is defined as 1 kcal/kg/hour and is roughly equivalent to the energy cost of sitting quietly. A MET also is defined as oxygen uptake in ml/kg/min with one MET equal to the oxygen cost of sitting quietly, equivalent to 3.5 ml/kg/min.

Health effects

A common elliptical training machine

US Marines exercising on theUSS Bataan

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.

Exercise reduces levels of cortisol,^[13] which causes many health problems, both physical and mental.^[14]

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.^{[15][dead link]} Endurance exercise before meals lowers blood glucose more than the same exercise after meals.^[16] 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.^[17]

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.^[18]

Exercise in space: Astronaut Daniel Tani, Expedition 16 flight engineer, works out at the Unity node of theInternational 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

Some studies have shown that vigorous exercise executed by healthy individuals can increase opioid peptides (a.k.a. endorphins, naturally occurringopioids that in conjunction with other neurotransmitters are responsible for exercise-induced euphoria and have been shown to be addictive), increase testosterone and growth hormone,^[19] effects that are not as fully realized with moderate exercise. More recent research^[20][21] indicates that anandamidemay 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.^{[citation needed]}

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.^[22][23] However, muscle hypertrophy from resistance training is primarily determined by diet and testosterone.^[24] This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population.^[25][26] Studies have shown that exercising in middle age leads to better physical ability later in life.^[27]

Cardiovascular system

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.^[28]

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. 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.^[29]

Vitamin C supplementation has been associated with lower incidence of URTIs in marathon runners.^[29]

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.^[29]

technology

The use of the term technology has changed significantly over the last 200 years. Before the 20th century, the term was uncommon in English, and usually referred to the description or study of the useful arts.^[2] The term was often connected to technical education, as in the Massachusetts Institute of Technology (chartered in 1861).^[3] "Technology" rose to prominence in the 20th century in connection with the Second Industrial Revolution. The meanings of technology changed in the early 20th century when American social scientists, beginning with Thorstein Veblen, translated ideas from the German concept of Technik into "technology." In German and other European languages, a distinction exists between Technik and Technologie that is absent in English, as both terms are usually translated as "technology." By the 1930s, "technology" referred not to the study of the industrial arts, but to the industrial arts themselves.^[4] In 1937, the American sociologist Read Bain wrote that "technology includes all tools, machines, utensils, weapons, instruments, housing, clothing, communicating and transporting devices and the skills by which we produce and use them."^[5] Bain's definition remains common among scholars today, especially social scientists. But equally prominent is the definition of technology as applied science, especially among scientists and engineers, although most social scientists who study technology reject this definition.^[6] More recently, scholars have borrowed from European philosophers of "technique" to extend the meaning of technology to various forms of instrumental reason, as in Foucault's work on technologies of the self ("techniques de soi").

Dictionaries and scholars have offered a variety of definitions. The Merriam-Webster dictionary offers a definition of the term: "the practical application of knowledge especially in a particular area" and "a capability given by the practical application of knowledge".^[1] Ursula Franklin, in her 1989 "Real World of Technology" lecture, gave another definition of the concept; it is "practice, the way we do things around here".^[7] The term is often used to imply a specific field of technology, or to refer to high technology or just consumer electronics, rather than technology as a whole.^[8] Bernard Stiegler, in Technics and Time, 1, defines technology in two ways: as "the pursuit of life by means other than life", and as "organized inorganic matter."^[9]

Technology can be most broadly defined as the entities, both material and immaterial, created by the application of mental and physical effort in order to achieve some value. In this usage, technology refers to tools and machines that may be used to solve real-world problems. It is a far-reaching term that may include simple tools, such as a crowbar or wooden spoon, or more complex machines, such as a space station or particle accelerator. Tools and machines need not be material; virtual technology, such as computer software and business methods, fall under this definition of technology.^[10]

The word "technology" can also be used to refer to a collection of techniques. In this context, it is the current state of humanity's knowledge of how to combine resources to produce desired products, to solve problems, fulfill needs, or satisfy wants; it includes technical methods, skills, processes, techniques, tools and raw materials. When combined with another term, such as "medical technology" or "space technology", it refers to the state of the respective field's knowledge and tools. "State-of-the-art technology" refers to the high technology available to humanity in any field.

Technology can be viewed as an activity that forms or changes culture.^[11] Additionally, technology is the application of math, science, and the arts for the benefit of life as it is known. A modern example is the rise of communication technology, which has lessened barriers to human interaction and, as a result, has helped spawn new subcultures; the rise of cyberculture has, at its basis, the development of the Internet and the computer.^[12] Not all technology enhances culture in a creative way; technology can also help facilitate political oppression and war via tools such as guns. As a cultural activity, technology predates both science and engineering, each of which formalize some aspects of technological endeavor.

Science, engineering and technology

The distinction between science, engineering and technology is not always clear. Science is the reasoned investigation or study of phenomena, aimed at discovering enduring principles among elements of the phenomenal world by employing formal techniques such as the scientific method.^[13] Technologies are not usually exclusively products of science, because they have to satisfy requirements such as utility, usability and safety.

Engineering is the goal-oriented process of designing and making tools and systems to exploit natural phenomena for practical human means, often (but not always) using results and techniques from science. The development of technology may draw upon many fields of knowledge, including scientific, engineering, mathematical, linguistic, and historical knowledge, to achieve some practical result.

Technology is often a consequence of science and engineering — although technology as a human activity precedes the two fields. For example, science might study the flow of electrons inelectrical conductors, by using already-existing tools and knowledge. This new-found knowledge may then be used by engineers to create new tools and machines, such as semiconductors,computers, and other forms of advanced technology. In this sense, scientists and engineers may both be considered technologists; the three fields are often considered as one for the purposes of research and reference.^[14]

The exact relations between science and technology in particular have been debated by scientists, historians, and policymakers in the late 20th century, in part because the debate can inform the funding of basic and applied science. In the immediate wake of World War II, for example, in the United States it was widely considered that technology was simply "applied science" and that to fund basic science was to reap technological results in due time. An articulation of this philosophy could be found explicitly in Vannevar Bush's treatise on postwar science policy, Science—The Endless Frontier: "New products, new industries, and more jobs require continuous additions to knowledge of the laws of nature... This essential new knowledge can be obtained only through basic scientific research." In the late-1960s, however, this view came under direct attack, leading towards initiatives to fund science for specific tasks (initiatives resisted by the scientific community). The issue remains contentious—though most analysts resist the model that technology simply is a result of scientific research.^[15][16]

History

Main articles: History of technology and Timeline of historic inventions

Paleolithic (2.5 million – 10,000 BC)

A primitive chopper

Further information: Outline of prehistoric technology

The use of tools by early humans was partly a process of discovery, partly of evolution. Early humans evolved from a species of foraging hominids which were already bipedal,^[17] with a brain mass approximately one third that of modern humans.^[18] Tool use remained relatively unchanged for most of early human history, but approximately 50,000 years ago, a complex set of behaviors and tool use emerged, believed by many archaeologists to be connected to the emergence of fully modern language.^[19]

Stone tools

Hand axes from the Acheulianperiod

A Clovis point, made viapressure flaking

Human ancestors have been using stone and other tools since long before the emergence of Homo sapiens approximately 200,000 years ago.^[20] The earliest methods of stone tool making, known as the Oldowan "industry", date back to at least 2.3 million years ago,^[21] with the earliest direct evidence of tool usage found in Ethiopia within the Great Rift Valley, dating back to 2.5 million years ago.^[22] This era of stone tool use is called the Paleolithic, or "Old stone age", and spans all of human history up to the development of agriculture approximately 12,000 years ago.

To make a stone tool, a "core" of hard stone with specific flaking properties (such as flint) was struck with a hammerstone. This flaking produced a sharp edge on the core stone as well as on the flakes, either of which could be used as tools, primarily in the form of choppers or scrapers.^[23] These tools greatly aided the early humans in their hunter-gatherer lifestyle to perform a variety of tasks including butchering carcasses (and breaking bones to get at the marrow); chopping wood; cracking open nuts; skinning an animal for its hide; and even forming other tools out of softer materials such as bone and wood.^[24]

The earliest stone tools were crude, being little more than a fractured rock. In the Acheulian era, beginning approximately 1.65 million years ago, methods of working these stone into specific shapes, such as hand axes emerged. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of theprepared-core technique, where multiple blades could be rapidly formed from a single core stone.^[23] The Upper Paleolithic, beginning approximately 40,000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely.^[25]

Fire

Main article: Control of fire by early humans

The discovery and utilization of fire, a simple energy source with many profound uses, was a turning point in the technological evolution of humankind.^[26] The exact date of its discovery is not known; evidence of burnt animal bones at the Cradle of Humankind suggests that the domestication of fire occurred before 1,000,000 BC;^[27] scholarly consensus indicates that Homo erectus had controlled fire by between 500,000 BC and 400,000 BC.^[28][29] Fire, fueled with woodand charcoal, allowed early humans to cook their food to increase its digestibility, improving its nutrient value and broadening the number of foods that could be eaten.^[30]

Clothing and shelter

Other technological advances made during the Paleolithic era were clothing and shelter; the adoption of both technologies cannot be dated exactly, but they were a key to humanity's progress. As the Paleolithic era progressed, dwellings became more sophisticated and more elaborate; as early as 380,000 BC, humans were constructing temporary wood huts.^[31][32] Clothing, adapted from the fur and hides of hunted animals, helped humanity expand into colder regions; humans began to migrate out of Africa by 200,000 BC and into other continents, such as Eurasia.^[33]

Neolithic through classical antiquity (10,000BC – 300AD)

An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools.

Man's technological ascent began in earnest in what is known as the Neolithic period ("New stone age"). The invention of polished stone axes was a major advance because it allowed forest clearance on a large scale to create farms. The discovery of agriculture allowed for the feeding of larger populations, and the transition to a sedentist lifestyle increased the number of children that could be simultaneously raised, as young children no longer needed to be carried, as was the case with the nomadic lifestyle. Additionally, children could contribute labor to the raising of crops more readily than they could to the hunter-gatherer lifestyle.^[34][35]

With this increase in population and availability of labor came an increase in labor specialization.^[36] What triggered the progression from early Neolithic villages to the first cities, such as Uruk, and the first civilizations, such as Sumer, is not specifically known; however, the emergence of increasinglyhierarchical social structures, the specialization of labor, trade and war amongst adjacent cultures, and the need for collective action to overcome environmental challenges, such as the building of dikes and reservoirs, are all thought to have played a role.^[37]

Metal tools

Continuing improvements led to the furnace and bellows and provided the ability to smelt and forge native metals (naturally occurring in relatively pure form).^[38] Gold, copper, silver, and lead, were such early metals. The advantages of copper tools over stone, bone, and wooden tools were quickly apparent to early humans, and native copper was probably used from near the beginning of Neolithic times (about 8000 BC).^[39] Native copper does not naturally occur in large amounts, but copper ores are quite common and some of them produce metal easily when burned in wood or charcoal fires. Eventually, the working of metals led to the discovery of alloys such as bronze and brass (about 4000 BC). The first uses of iron alloys such as steel dates to around 1400 BC.