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An exercise may be any movement designed to improve a skill, but it generally refers to physical activities that involve large muscle groups. Exercise includes dance, callisthenics, games, and more formal activities such as jogging, swimming, and running. It may be of low-, moderate-, or high-intensity. The precise definitions of these vary, but as a general guide, low-intensity exercise requires 50 per cent aerobic capacity, little increase in respiration and no breathlessness; moderate-intensity exercise (also called vigorous exercise) requires between 60 per cent to 85 per cent aerobic capacity and causes mild breathlessness and some sweating; and high intensity exercise requires between 80 per cent to 120 per cent aerobic capacity. Exercise above 100 per cent aerobic capacity depends on anaerobic respiration and causes considerable breathlessness, sweating, and acute discomfort. Most people, unless they are ill or physically impaired, can perform low-intensity exercise which helps to expend calories (important in weight control) and reduce the risk of some diseases (e.g. diabetes and heart disease). Moderate exercise can cause some discomfort and may be unwise for those who are unfit. People with a body mass index of more than 30 should seek their doctor's advice before starting a vigorous exercise programme. But for healthy individuals this level is usually recommended as optimal for development of cardiorespiratory fitness. High-intensity exercise is suited only to individuals who are medically fit and interested in reaching a high level of physical performance.

Muscle activity

Exercise is muscular activity. When the word is used, there is almost always the additional implication of the activity being extended over time, but for how long is up to the user. More commonly explicit are the adjectives of intensity (mild, moderate, strenuous/high) and body region (leg, upper body/arm). An important distinction, from the point of view of physiological response, is between exercise predominantly involving movement (dynamic exercise) and that in which the muscles brace against each other or an unmoving outside load (static exercise). Static exercise is also known as ‘isometric’ because the muscles stay at (approximately) constant length.

All exercise, then, starts with the activation of voluntary muscle. Whether there is significant movement depends on whether the force the muscle is producing exceeds, matches, or falls short of the load against which it is acting. The first situation produces dynamic exercise of the form we usually think of; technically, the muscles, successfully shortening, are said to be contracting ‘concentrically’. However, the last situation is dynamic too; here the muscles, extending under the greater external force, are active ‘eccentrically’ (often pronounced ‘ee-centrically’). Only in the middle case, where muscle force equals that against which it is acting, will the exercise be static. Finally, it must be made clear that the muscles need not be working flat out in any of these situations. That will depend on their degree of activation by the nervous system; full activation is uncommon in daily life.

The chemical demands of the muscles underlie most of the other phenomena of exercise. In particular, ample supplies of oxygenated blood must be supplied to every active muscle. Both the heart and the circulation, and the respiratory system, respond accordingly. Scientific understanding of these responses, however, depends on our ability to measure both muscular performance and the metabolic energy input upon which it is based.

Measuring muscular performance and metabolic input

It is a fairly simple matter to measure isometric force production. All that is required is a spring balance or, better, an electronic strain gauge, against which the body-part of interest exerts force through a virtually inextensible wire or rigid lever system. Grip strength, bite force, elbow flexion, or knee extension are easily measured by ‘dynamometers’ (force measurers) of this broad type.

In dynamic exercise, measuring force as such is not often sufficient for the physiologist, though transducers placed in bicycle cranks, or in ‘force plates’ let into a rigid laboratory floor, are examples of instruments which can provide this information. The overall demand of dynamic exercise is, however, most completely indicated by the power output achieved by the body, for power embodies both the force and the rate of movement. Power output is assessed by ‘ergometers’ (work measurers), and can be most readily measured for rhythmic movements against external load, such as in cycling or rowing.

The input of energy from metabolism can be estimated with reasonable precision when the exercise lasts long enough at a steady rate for breathing to come into balance with the muscles' demands (‘aerobic’ exercise). Then the effort may be considered to be entirely founded upon the ‘burning’ of fuel molecules in oxygen. As all the body's fuels (carbohydrate, fat, and — normally used to a much lesser extent — protein) release rather similar amounts of energy when reacted with the same volume of oxygen, measurements of the volume of oxygen consumed per minute (V̇o₂) are the basis of the energy- input calculations. Such measurements are made by collecting the air breathed out by an exercising subject, assaying the percentage of oxygen left in that air, and subtracting that from the percentage of oxygen which would have been in the same volume of air when it was breathed in. The result gives the ‘aerobic power’ of the subject performing that exercise. The maximum aerobic power a subject can achieve (V̇o₂max) is a fundamental indicator of exercise potential.

Changes in heart and circulation

Considering the heart first, its rate of beating rises appreciably even as we stand up and walk gently through the house. In the highest intensity exercise, the pulse rises to its maximum. This varies with the age of the individual, but negligibly with gender and, more surprisingly, only a little with fitness. The thumb rule is that maximum heart rate (HR) (in beats per minute) = 220 - (age in years). People who are trained to sustain high intensity dynamic exercise for periods of many minutes at a time (‘aerobic’ athletes) actually have maximum HRs 10-15 beats per minute lower than would be calculated by that formula. This seeming paradox makes more sense when it is considered that the amount of blood pumped by their hearts in every beat (their ‘stroke volume’, SV) is greater in any given state of rest or exercise than that of an untrained person; thus the aerobic athlete's resting pulse will be slower than the average person's by at least as much as the shortfall at maximum HR, and so allows a greater percentage increase from rest to maximum exercise.

During the responses to increasing exercise intensity there is some increase of SV as well as of HR in everybody, so that in an untrained but healthy young adult, of 70 kg body weight (the standard textbook figure), pulse might rise about threefold, from say 70 beats per minute at rest to 200, SV by about 1.7 times, and thus total cardiac output (CO) from 5 to 25 litres/min. Equivalent figures for the internationally elite aerobic athlete might be from 45 to 185 beats per minute (HR) and 5 to 40 litres/min (CO), implying a near doubling of the already large SV. Notice, however, that the resting CO is the same for both, as the metabolic demands of sitting still are much the same for everybody of a given weight.

Nevertheless, even the élite athlete's eight-fold increase in CO is far from sufficient by itself to explain the total blood flow through each of the muscles that is working flat out. Modern indications are that muscle blood flow can increase by the order of 100-fold from the resting level. Great increases of flow through the active muscles are achieved by dilatation of blood vessels running through them, assisted to some extent by constriction of the vessels supplying organs, such as the gut and kidneys, which do jobs that can take second place during the exercise. (How vessels constrict and dilate is discussed under ‘Blood vessels’.) Finally, the active muscles' metabolism is enabled to increase by yet one more factor — enhanced extraction of oxygen and nutrients from each ml of blood flowing through them. In the case of oxygen, this increase is typically about three-fold.

The limit to maximum power output

Pursuing our figures, if muscle blood flow rose 100-fold and oxygen extraction/ml of blood rose threefold, 300 times as much oxygen would have to be extracted from the air each minute for all muscles in the body to be maximally active at once. Actually, this cannot happen: it has been calculated that the heart can only supply 30-40% of the total musculature, fully active, simultaneously. This puts a significant limitation on running and cycling, and an even more substantial one on activities demanding direct propulsive power from all four limbs — such as cross-country skiing and swimming. Tellingly we find that, if any one of the measures of whole-body effort (such as maximum CO, maximum power output, or maximum oxygen consumption — V̇o₂max) is considered, its values over all these exercises are within about 10% of each other — strongly indicating that the chief limitation on them all is a central function upon which each depends. One expression of this central limitation is the ceiling, just noted, on cardiac output.

Changes in breathing

The limit shows itself in respiratory function, too. However, it is not in the obvious feature, ventilation (the volume of air breathed in and out each minute) ; this increases several times more than CO — namely 15-35-fold, according to aerobic fitness. (Typical patterns of the increase of ventilation during the first few minutes of both moderate and strenuous exercise are described under breathing during exercise.) That the maximum ventilatory rate is more than sufficient to meet requirements is indicated by the fact that oxygen extraction from each litre of air goes slightly down, not up, at high exercise intensities. At such intensities the time available for oxygen to diffuse from the air in the lungs into the blood as it races past, begins to become a limiting factor. In normally healthy people near sea level the limitation is barely, if at all, detectable; but in top athletes racing at sea level the arterial blood, fresh from the lungs, falls clearly short of full saturation with oxygen — comparable to its condition in a resting person at the altitude of an Alpine ski resort.

Anaerobic exercise

A distinction which has been avoided until this point must now be confronted. The discussion has focused on exercise continued long enough (say 4 min or more) that it must be performed in balance with oxygen uptake. Any track race longer than 1500 metres is of this kind once the athlete's body has adjusted fully to the pace. Briefer activities (like a 400 metre race) can be more intense, but only on the basis of the extra power, greater than the aerobic maximum, being supplied via anaerobic metabolic pathways. Such very intensive, short-term exercise is termed ‘anaerobic’; but note that, while aerobic exercise, when we have settled into it, is totally aerobic, even the briefest high-intensity exercise is never wholly anaerobic.

Upper body exercise

Before leaving dynamic exercise, we should note that exercise using only the arms provides less power at a given HR than exercise predominantly using the legs. Among the reasons for this is that external (and therefore measurable) work done by the arms usually requires the trunk to be braced by muscular effort which needs energy but does not move the load.

Static versus dynamic

Bracing actions of the trunk muscles are in fact examples of static exercise. Other instances are the guardsman's posture at attention, the weight-lifter's few seconds of triumph with the bar above his head, and the dinghy crew's efforts to hold the body horizontal over the water, balancing the boat. In all these situations HR is raised (in the latter two instances, very considerably), yet compared with dynamic exercise giving the same HR — especially leg exercise — two things are markedly different:

(i) oxygen consumption is much lower;
(ii) blood pressure is higher, especially during diastole.

The first point is explicable chiefly by the fact that isometrically contracting muscles require substantially less oxygen than the same muscles cyclically shortening and lengthening. The second arises because, in dynamic exercise, blood flows through the active muscles during the periods of relaxation which alternate with their contractions; during the contraction phases it is impeded. There being no relaxation periods during a static exercise, blood pressure must be raised if any flow at all is to be forced through the tensed muscles. This rise is brought about by reflex mechanisms originating in the muscles themselves.

Hormonal adjustments

In addition to the cardiovascular and respiratory adjustments which the body makes in the face of exercise, substantial hormonal adjustments also occur. Adrenaline flow is elevated, especially in anticipation of vigorous exercise; and as exercise proceeds, cortisol and (particularly in really protracted efforts, such as marathon races) growth hormone concentrations are both substantially raised, and may not return to basal levels for some hours afterwards. All these promote mobilization of both carbohydrate and lipid fuels, and growth hormone also promotes tissue adaptation and repair when the activity is over. Insulin flow, however, is reduced during exercise. This at first seems a paradox, for the function of insulin is to promote glucose entry into tissues such as muscle, and exercising muscle surely needs its glucose? It is now clear that increased availability of glucose transporter molecules in the membranes of exercising muscle fibres enables them to take in glucose with less insulin than usual. Suitably controlled exercise therefore has special benefits for diabetics.

Fuel sources

In short bursts of intensive exercise, carbohydrates are the main fuels used. At lower intensities, fats contribute more and, as endurance efforts proceed, they become the major energy source. Four-fifths of carbohydrate storage is as ‘glycogen’ (animal starch) within the muscle fibres themselves. The rest is as glycogen in the liver, from which it can be released as glucose (blood sugar) when circulating levels fall. However, the brain, which uses no other fuel, makes priority demands, so blood-borne glucose does not contribute a major fraction of the energy used by the muscles in a long event unless its concentration is kept topped up by glucose drinks or carbohydrate food.

Fat is stored both within some muscle fibres and in fat cells. The balance, however, is the converse of that for carbohydrate: most activities seem to draw more upon the fat cells than the intramuscular stores.

Health benefits

Clearly, all exercise constitutes a degree of training for the muscles which it uses. All exercise also enhances cardiovascular and respiratory health to some extent, though aerobic exercise benefits these systems most. The hormonal and metabolic consequences of any but the most severe exercise are almost always advantageous too. Of these benefits, the cardiovascular ones are normally emphasized. Sustained aerobic exercise trains the heart, lowers blood pressure, tends to reduce body fat, and promotes a switch from ‘bad’ to ‘good’ lipids — from low to high density serum lipoprotein — thereby reducing the risk of atheromatous plaques.

How much exercise is necessary, and of what form, has naturally been much researched. Recent work indicates that the most marked gains, relative to a sedentary lifestyle, are achieved by a mere 30 min of moderate exercise (such as brisk walking), on each of 3 days a week. The more exercise is taken, within a normal lifestyle, the greater the health benefit; yet a law of diminishing returns applies.

As to the form of exercise, it is clearly undesirable for an unfit person to leap straight into short-term, high-intensity activity. Worse still, isometric exercise will always, in the short term, raise the blood pressure. So exercise for health, in those who have been sedentary, should be dynamic and essentially aerobic. Such exercise will not build up much muscle. Effort against high resistance, in the weights room or equivalent, is the way to achieve that; but such ‘resistance exercises’ are best not embarked upon by people who have not already achieved a fairly good aerobic fitness base.

Exercise in different cultures

Finally, it may be salutary to recall how rare, and for the most part recent, in human societies is the disposition to take exercise when it could have been avoided. Exercise has been toil, for the great majority of mankind, at least until an industrial revolution was well advanced in the society concerned. Wealth and status thus meant indolence and often corpulence, whether in medieval Europe or over a similar period in China. Yet in such civilizations as that of Sparta and Rome, and in sectors of Japanese society over many centuries, exercise was cultivated in the expectation of war. Perhaps it is ancient Athens that, in its attitudes to exercise as in so many other ways, most closely anticipated our own outlook: exercise for sport, for health, and to maintain/improve the body image were all recognized by the contemporaries of Plato, as they are once more by us. It is to be hoped, however, that our physiological understanding is at least a little better.

— Neil Spurway

Bibliography

• Bursztyn, P. (1990). Physiology for sportspeople: a serious user's guide to the body. Manchester University Press.
• Noakes, T. (1991). Lore of running. Human Kinetics, Champaign, Illinois.
• Wilmore, J. H. and Costill, D. L. (2000). Physiology of sport and exercise. 2nd ed. Human Kinetics, Champaign, Illinois

See also breathing during exercise; fatigue; fitness; sport.

noun

1. The act of putting into play: application, employment, exertion, implementation, operation, play, usage, use, utilization. See used/unused.
2. Energetic physical action: activity, exertion. See action/inaction.
3. Repetition of an action so as to develop or maintain one's skill: drill, practice, rehearsal, study, training. See work/play.

verb

1. To put into action or use: actuate, apply, employ, exploit, implement, practice, use, utilize. Idioms: avail oneself of, bring into play, bring to bear, make use of, put into practice, put to use. See used/unused.
2. To bring to bear steadily or forcefully: exert, ply², put out, throw, wield. See cause/effect.
3. To subject to or engage in forms of exertion in order to train, strengthen, or condition: drill, practice, train, work out. See work/play.
4. To carry out the functions, requirements, or terms of: discharge, do, execute, fulfill, implement, keep, perform. Idioms: live up to. See do/not do.

n

Definition: accomplishment, use
Antonyms: disuse, misuse

v

Definition: put to use
Antonyms: avoid, ignore, not use

v

Definition: train
Antonyms: be inactive, be sedentary

v

Definition: worry
Antonyms: overlook

Definition

Exercise is physical activity that is planned, structured, and repetitive for the purpose of conditioning the body. Exercise consists of cardiovascular conditioning, strength and resistance training, and flexibility.

Purpose

Exercise is essential for improving overall health, maintaining fitness, and helping to prevent the development of obesity, hypertension, and cardiovascular disease. Surveys conducted by the Centers for Disease Control and Prevention (CDC) indicate that 61.5 percent of children aged nine to 13 years do not participate in any organized physical activity (for example, sports, dance classes) and 22.6 percent are not physically active during their free time. According to the American Obesity Association, approximately 30 percent of children and adolescents aged six to 19 years are overweight and 15 percent are obese.

A sedentary lifestyle and excess caloric consumption are the primary causes of this increase in overweight and obesity; regular exercise is considered an important factor in controlling weight. Overweight and obese children and adolescents are at higher risk of developing several medical conditions, including the following:

• asthma
• diabetes
• hypertension
• orthopedic complications, such as hip and knee pain and limited range of motion
• cardiovascular disease
• high cholesterol
• sleep apnea
• psychosocial disorders, such as depression, negative body image, and eating disorders

Clinical studies have shown that regular exercise has numerous benefits, including the following:

• preventing weight gain and maintaining healthy weight
• reducing blood pressure and cholesterol
• improving coordination
• improving self-esteem and self-confidence
• decreasing the risk of developing diabetes, cardiovascular disease, and certain types of cancer
• increased life expectancy

Description

Exercise consists of cardiovascular conditioning, strength and resistance training, and flexibility to improve and maintain the fitness of the body's heart, lungs, and muscles.

Cardiovascular Conditioning

Cardiovascular conditioning involves moderate to vigorous physical activity that results in an elevated heart rate for a sustained period of time. Regular cardiovascular exercise improves the efficiency of the functioning of the heart, lungs, and circulatory system. For adults, aerobic exercise within a target heart rate range calculated based on a maximum heart rate by age is recommended. For healthy children, cardiovascular exercise that elevates the heart rate to no greater than a maximum heart rate of 200 beats per minute is recommended.

In general, the American Heart Association recommends at least 60 minutes of moderate to vigorous physical activity every day for children and adolescents. Cardiovascular conditioning activities should be appropriate for the age, gender, and emotional status of the child. Examples of exercise that elevates the heart rate are bicycle riding, running, swimming, jumping rope, brisk walking, dancing, soccer, and basketball.

Strength and Resistance Training

Strength and resistance training increases muscle strength and mass, bone strength, and the body's metabolism. Strengthening exercises increase muscle strength by putting more strain on a muscle than it is normally accustomed to receiving. Strength training can be performed with or without special equipment. Strength/resistance training equipment includes handheld dumbbells, resistance machines (Nautilus, Cybex), and elastic bands. Strength training can also be performed without equipment; exercises without equipment include pushups, abdominal crunches, and squats. Children as young as six years can participate in strength training with weights, provided they are supervised by a fitness professional trained in youth strength training. Child-sized resistance machines may be available at some fitness facilities. According to youth strength training guidelines, children and adolescents should perform strength training for approximately 20 minutes two or three times weekly on nonconsecutive days.

Flexibility

Flexibility is important to improve and maintain joint range of motion and reduce the likelihood of muscle strains. Most young children are naturally more flexible than older children and adults and will instinctively perform movements that promote flexibility. As children age, they should be encouraged to continue to stretch. Flexibility is especially important for children and adolescents engaged in vigorous exercise (running, competitive sports). Stretching is best performed following a warm-up and/or at the completion of an exercise session or sport. One activity that promotes flexibility that is increasing in popularity for children is yoga, in the form of children's yoga classes or exercise videos.

Precautions

Before a child begins any exercise program, he or she should be evaluated by a physician in order to rule out any potential health risks. Children and adolescents with physical restrictions or certain medical conditions may require an exercise program supervised by a healthcare professional, such as a physical therapist or exercise physiologist. If dizziness, nausea, excessive shortness of breath, or chest pain occur during any exercise program, the activity should be stopped, and a physician should be consulted before the child resumes the activity. Children and adolescents who use any type of exercise equipment should be supervised by a knowledgeable fitness professional, such as a personal trainer.

Preparation

A physical examination by a physician is important to determine if strenuous exercise is appropriate or detrimental. Prior to beginning exercise, a proper warm-up is necessary to help prevent the possibility of injury resulting from tight muscles, tendons, ligaments, and joints. Appropriate warm-up exercises include walking, light calisthenics, and stretching.

Aftercare

Proper cool-down after exercise is important and should include a gradual decrease in exercise intensity to slowly bring the heart rate back to the normal range, followed by stretches to increase flexibility and reduce the likelihood of muscle soreness. Following vigorous activities that involve sweating, lost fluids should be replaced by drinking water.

Risks

Improper warm-up and inappropriate use of weights can lead to muscle strains. Overexertion without enough time between exercise sessions to recuperate also can lead to muscle strains, resulting in inactivity due to pain. Some children and adolescents may be susceptible to exercise-induced asthma. For children and adolescents who perform high-impact activities, such as running, stress fractures may occur. Dehydration is a risk during longer activities that involve sweating; children and adolescents should be supplied with water during and after activity.

Normal Results

Significant health benefits are obtained by including at least a moderate amount of physical exercise for 30 to 60 minutes daily. Regular physical activity plays a positive role in preventing disease and improving overall health status. For children and adolescents just beginning an exercise program, results (including weight loss, increased muscle strength, and aerobic capacity) will be noticeable in four to six weeks.

Parental Concerns

Given the increasing prevalence of overweight and obesity in children and adolescents, it is important for parents to encourage regular exercise and also serve as role models by exercising themselves. Television, computers, and video games have replaced physical activity for playtime for the majority of children. Parents should make a commitment to replacing sedentary activities with active indoor and outdoor games. For busy families, exercise can be performed in multiple 10- to 15-minute sessions throughout the day.

For children aged two to five years, physical activities should emphasize basic movement skills, imagination, and play. Examples of appropriate activities for this age group include rolling and bouncing a ball, jumping, hopping, skipping, mimicking animal movements, and pedaling a tricycle.

For children aged five to eight years, physical activities should emphasize basic motor skills and more complex movements (eye-hand coordination). Non-competitive group sports or classes are appropriate for this age, and parents should focus on helping their children find an enjoyable physical activity.

For children aged eight to ten years, physical activities should emphasize the benefits of regular exercise. Team sports and group classes are appropriate for this age. Experts have found that physical activity decreases in this age group, so parents should focus on being supportive and encouraging their children to be physically active.

For children aged 11 to 14 years, physical activities should continue to emphasize the benefits of regular exercise. Participation in team sports, as well as individual activities, such as dance or martial arts, is appropriate for this age. Peer influence and hormonal changes can affect participation in group physical activities, so parents should consider encouraging exercise at home for children reluctant to participate with peers.

Community centers, local YMCAs, health clubs, and other organizations offer age-appropriate exercise programs for children and adolescents led by experienced and knowledgeable instructors. In addition, home exercise videos geared toward children are available in stores and from Web sites.

For children and adolescents with medical conditions that may limit exercise or place them at higher risk for exercise-related complications, supervised exercise programs may be available at hospital-based wellness centers.

Resources

Books

Inspire Kids and Teens to Fitness. San Diego, CA: IDEA Health and Fitness Association, 2003.

LeMay, Michelle. Essential Stretch. New York: Berkeley Publishing Group, 2003.

McArdle, William D., Frank I. Katch, and Victor L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance, 5th ed. Philadelphia: Lippincott, 2001.

Periodicals

Anderson, Ross E., and John M. Jakicic. "Physical Activity and Weight Management: Building the Case of Exercise." The Physician and Sports Medicine 31 (November 2003): 39–45.

Centers for Disease Control and Prevention. "Physical Activity >Levels among Children Aged 9–13 Years—United States, 2002." Morbidity and Mortality Weekly Report 52 (2003): 785–88.

Organizations

Aerobics and Fitness Association of America. 15250 Ventura Blvd, Suite 200, Sherman Oaks, CA 91403. Web site: www.afaa.com.

American College of Sports Medicine. 401 W. Michigan Street, Indianapolis, IN 46202–3233. Web site: www.acsm.org/.

American Council on Exercise. 4851 Paramount Drive San Diego, California 92123. Web site: www.acefitness.org.

American Heart Association. National Center. 7272 Greenville Ave., Dallas, TX 75231. Web site: www.americanheart.org.

Web Sites

Ekeland, E., et al. "Exercise to Improve Self-Esteem in Children and Young People." The Cochrane Collaboration, 2004. Available online at www.medscape.com/viewarticle/486742 (accessed November 29, 2004).

IDEA Health and Fitness Association. Fitness for Your Child.2004. www.ideafit.com/articles/fitness_child.asp (accessed November 29, 2004).

"Physical Education for Preschoolers." KID-FIT, 2004. Available online at www.kid-fit.com (accessed November 29, 2004).

[Article by: Jennifer E. Sisk, MA]

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n. 1. (often exercises) a military drill or training maneuver.

2. (exercises) ceremonies: graduation exercises.

See the Introduction, Abbreviations and Pronunciation for further details.

1. Human movements and physical activities involving large muscle groups, rather than highly specific, relatively non-taxing movements of small muscle groups. Exercise includes dance, callisthenics, games, and more formal activities such as jogging, swimming, and running.

2. Any set of movements designed to train or improve a skill

3. The voluntary component of physical activity. Exercise may be spontaneous and playful, but it is usually performed with a specific objective (e.g. to become healthier, or to prepare for a competition).

Components of Physical Fitness Cardiovascular Fitness The ability of the body to perform prolonged, large-muscle, dynamic exercise at moderate to high levels of intensity. This is dependent on the ability of the heart and lungs to deliver oxygen to the working muscles. As fitness levels improve, the body functions more efficiently and the heart can better withstand the strains of everyday stress. Muscular Strength The maximal amount of force a muscle can exert with a single maximal effort. Strong muscles are important for carrying out everyday tasks, such as carrying groceries, doing yard work, and climbing stairs. Muscular strength can help to keep the body in proper alignment, prevent back and leg pain, and provide support for good posture. Muscular Endurance The ability of a muscle or group of muscles to perform repetitive contractions over a period of time. Endurance is a key for everyday life activities and operates with muscular endurance to help maintain good posture and prevent back and leg pain. In addition, endurance can enhance performance during sporting events, as well as help an individual cope with everyday stress. Flexibility This refers to the range of motion in a joint or group of joints, correlated with muscle length. This component becomes more important as people age and their joints stiffen up, preventing them from doing everyday tasks. Additionally, good range of motion will allow the body to assume more nautral positions to help maintain good posture. Stretching is therefore an important habit to start, as well as continue, as one ages. Body Composition The relative proportion of fat-free mass to fat mass in the body. Fat-free mass is composed of muscle, bone, organs, and water, whereas fat is the underlying adipose tissue. Excessive fat is a good predictor of health problems because it is associated with cardiovascular disease, high cholesterol, and high blood pressure. Higher proportions of fat-free mass indicate an increase in muscle, and thus an increased ability to adapt to everyday stress.

More than 28 percent of Americans are completely sedentary (they engage in no physical activity), with an additional 60 percent being inadequately active (engaging in less than 30 minutes of activity per day). For those who strive to achieve and maintain a high quality of health, it must be recognized that physical activity is vital to optimal health. This is reaffirmed by numerous studies that have found an association between physical activity, health, longevity, and an improved quality of life. In addition, the number of deaths related to sedentary living or obesity is approximately a half-million per year. Physical activity may impact quality of life in several ways: it can be used to improve self-image and self-esteem, physical wellness, and health.

Participation in physical activity can be beneficial for anyone and can be started during any stage of life. One goal of Healthy People 2010, a set of national health objectives established by the U.S. Department of Health and Human Services, is to increase the number of people who participate in daily physical activity. This activity can take many forms, ranging from a regimented exercise program to daily life activities such as house or yard work, walking a pet, or walking around town to complete errands.

Definition of Terms
Physical activity is a broad term that encompasses all forms of muscle movements. These movements can range from sports to lifestyle activities. Furthermore, exercise can be defined as physical activity that is a planned, structured movement of the body designed to enhance physical fitness. Regimented or purposeful exercise consists of a program that includes twenty to sixty minutes of activity at least three to five days a week. Some examples of this type of activity include walking, running, cycling, or swimming.

Exercise may be classified in one of two categories, anaerobic and aerobic, depending on where energy is derived from. There is a distinct difference between the two, and specific training techniques are used to enhance both. Anaerobic exercise does not require oxygen for energy. This is due to the intensity and duration of anaerobic events, which typically are high intensity and last only a few seconds to a minute or two. These activities range from a tennis serve to an eight-hundred-meter run.

Aerobic exercise does require oxygen for energy. This is observed during exercise that is less intense but of longer duration. This energy system is primarily used during events lasting longer than several minutes, such as a two-mile run or the Tour de France bicycle race. The potential does exist that one can use both systems, as in soccer, where a match requires ninety minutes of continual activity with short intense bursts of effort.

Benefits of Exercise
The American College of Sports Medicine (ACSM), the Centers for Disease Control and Prevention (CDC), and the Surgeon General have all issued statements that recommend placing an emphasis on adopting physical activity into one's lifestyle. Their intention is to make the public more aware of the health benefits associated with increased physical activity, as well as to highlight the amount and intensity of activity necessary to achieve optimal benefits.

There are numerous benefits associated with regular participation in an aerobic exercise program, including improved cardiovascular and respiratory functioning, reduced coronary artery disease (CAD) risk, and increased quality of life. Beneficial improvements in cardiovascular and respiratory function include an increased ability of exercising muscles to consume oxygen, lowered resting and exercise heart rates, increased stamina, resistance to fatigue, more effective management of diabetes, reduced bone-mineral loss, decreased blood pressure, and increased efficiency of the heart. Although it is recognized that specific exercises can be used for the purpose of increasing strength, muscular endurance, and flexibility, it is important to recognize that cardiovascular exercise has the most dramatic effect on the body. This is because cardiovascular exercise engages large muscle groups in an aerobic manner.

Role of Exercise in Disease Prevention
Studies have shown that exercise can have a direct effect on preventing heart disease, cancer, and other causes of premature death. Furthermore, participation in regular physical activity may reduce the rate of occurrence of these maladies. An inverse relationship exists between disease and exercise, meaning that with increased levels of physical activity there is a decreased prevalence for certain diseases. Currently, there is strong evidence that exercise has powerful effects on mortality, CAD (including blood lipid profiles), and colon cancer. Research has also confirmed that aerobic exercise can reduce high blood pressure, obesity, type II diabetes, and osteoporosis. In addition, stroke and several types of cancer (such as breast, prostate, and lung cancer) can also be reduced with regular physical activity.

Even more important, several of these factors are interrelated. For example, when an individual lowers his or her high blood pressure, the risk for heart disease, stroke, and kidney disease is also reduced. Another example is that exercise favorably alters blood lipid profiles. These profiles include measurements of total cholesterol (TC, complete count of all cholesterol in the blood), high-density lipoprotein cholesterol (HDL-C, the "good" cholesterol), low-density lipoprotein cholesterol (LDL-C, the "bad" cholesterol), and triglycerides (TRG, storage form of energy), which reduce the risk of plaque buildup in the coronary arteries, a sign of CAD.

Exercise Prescription
Adequate physical activity is dependent on having a well-rounded program that encompasses all aspects of improving health and preventing disease. A well-rounded program includes cardiovascular fitness, muscular strength and endurance, flexibility, posture, and maintenance of body composition.

The most effective way to participate in a well-rounded program is by following a simple mnemonic device called FITT (Frequency, Intensity, Time, Type). The FITT principle includes how many times a week one should exercise (frequency), how intense the workout should be (intensity), how long the workout is (time), and what modality to use (type of exercise). Modality is dependent primarily on what an individual prefers. This exercise prescription in based on an individual's fitness level when entering the exercise program, and ultimately upon the goals of the individual. For example, an untrained individual who wants to lose weight and likes to walk would be placed on a program of treadmill or outdoor walking (type), for thirty minutes a day (time), three to five times per week (frequency), and of light to moderate intensity (intensity).

A good example of an exercise program would include three stages. The first stage is a warm-up, where one should complete light calisthenics to activate and warm the muscles, immediately followed by stretching, which helps to maintain flexibility. The second stage is the conditioning stage, which consists of cardiovascular work to enhance the function of the heart and lungs and a resistance-training regimen to strengthen and tone major muscle groups, such as the quadriceps, hamstrings, chest, biceps, triceps, back, and abdominals. The final stage consists of a cool down, or reduction in heart rate to resting levels, as well as stretching again, since the greatest modification in flexibility comes from post-exercise stretching.

Maintenance of physical activity is important to maintain a healthy lifestyle. In addition, it is important to follow an exercise regime that will start slow and gradually increase as fitness level and exercise tolerance increases. The key is to complete at least thirty minutes of activity most days of the week in the form of activities that one enjoys, such as walking, jogging, swimming, aerobic dance, biking, skateboarding, or participating in a sport. This will enable an individual to reach the goals of Healthy People 2010, which include improving the quality of life through fitness with the adoption and maintenance of regular exercise and physical activity programs.

See also Sports nutrition.

Bibliography
American College of Sports Medicine (2000). ACSM's Guidelines for Exercise Testing and Prescription, 6th edition. Philadelphia: Lippincott, Williams & Wilkins.
Corbin, Charles B.; Lindsey, Ruth; and Welk, Greg (2000). Concepts of Physical Fitness and Wellness: A Comprehensive Lifestyle Approach, 3rd edition. Boston: McGraw-Hill.
McArdle, William D.; Katch, Frank I.; and Katch, Victor L. (2001). Essentials of Exercise Physiology. Philadelphia: Lea & Faber.
Robbins, Gwen; Powers, Debbie; and Burgess, Sharon (2002). A Wellness Way of Life, 5th edition. Boston: McGraw-Hill.
United States Department of Health and Human Services (1996). Physical Activity and Health: A Report of the Surgeon General. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention.
Wallace, Janet P. (2001). "Health Benefits of Exercise and Fitness." In Foundations of Exercise Science, ed. Gary Kamen. Philadelphia: Lippincott, Williams & Wilkins.

This entry contains information applicable to United States law only.

To put into action, practice, or force; to make use of something, such as a right or option.

To exercise dominion over land is to openly indicate absolute possession and control.

To exercise discretion is to choose between doing and not doing something, the decision being based on sound judgment.

When a stockholder takes advantage of a privilege offered by a company or other financial institution. This includes warrants, options and other exotic financial instruments.

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A short piece written to improve performance technique.

(DOD) A military maneuver or simulated wartime operation involving planning, preparation, and execution. It is carried out for the purpose of training and evaluation. It may be a multinational, joint, or single-Service exercise, depending on participating organizations. See also command post exercise; field exercise; maneuver.

as in: physical exercise
sign description: Both hands move away from the body in a curling motion.

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Quotes:

"Exercise: you don't have time not to." - Source Unknown

"I have never taken any exercise except sleeping and resting." - Mark Twain

"Jogging is very beneficial. It's good for your legs and your feet. It's also very good for the ground. If makes it feel needed." - Charles M. Schulz

"The physically fit can enjoy their vices." - Lord Percival

"Other exercises develop single powers and muscles, but dancing embellishes, exercises, and equalizes all the muscles at once." - Jean Paul

"Modern bodybuilding is ritual, religion, sport, art, and science, awash in Western chemistry and mathematics. Defying nature, it surpasses it." - Camille Paglia

See more famous quotes about Exercise

Exercise as part of a training program. See exercise conditioning.

n

The performance of any physical activity for the purpose of conditioning the body, improving health, or maintaining fitness or as a means of therapy for correcting a deformity or restoring the organs and bodily function to a state of health.

For a list of words related to exercised, see:

• Healthy, fit, bright, or strong

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See words rhyming with "exercise."

  See crossword solutions for the clue Exercise.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - træning, øvelse, anvendelse, manøvre, stil, disciplin, skoleeksempel, opvisning
v. tr. - anvende, udvise, udøve, træne, optage, bekymre
v. intr. - få motion, afholde manøvre

idioms:

• exercise book    stilebog

Nederlands (Dutch)
oefenen, zich oefenen, uitoefenen, bezighouden, gebruiken, drillen, oefening, gebruik, uitoefening, uitvoering, lichaamsbeweging, godsdienstoefening

Français (French)
n. - exercice (droit, pouvoir), (Relig) pratique, exercice, (École) exercice, (Mil, Naut, gén, etc) exercice, man¯uvre, opération (de relations publiques), (US) cérémonies (npl)
v. tr. - exercer (le corps, l'esprit), faire faire l'exercice à (des troupes), exercer (un cheval, un chien), exercer (une autorité), faire valoir, user de (d'un droit), employer (ses talents), faire preuve de (patience, tact, etc), préoccuper (qn, l'esprit)
v. intr. - se donner de l'exercice, prendre de l'exercice

idioms:

• exercise book    cahier d'exercices, livre d'exercices

Deutsch (German)
n. - Übung, Bewegung, Feierlichkeiten, Ausübung
v. - ausüben, trainieren

idioms:

• exercise book    Heft

Ελληνική (Greek)
n. - άσκηση, εξάσκηση, (μτφ.) γυμναστική, σχολική άσκηση, (στρατ.) άσκηση, γυμνάσια, ενάσκηση (δικαιώματος κ.λπ.)
v. - ασκώ, (εκ)γυμνάζω/-ομαι, εξασκώ, καταβάλλω, χρησιμοποιώ, ασκούμαι

idioms:

• exercise book    (πρόχειρο) τετράδιο (ασκήσεων)

Italiano (Italian)
esercitare, allenare, esercizio

idioms:

• exercise book    quaderno

Português (Portuguese)
n. - exercício (m), uso (m), tarefa (f)
v. - exercer, usar, cumprir

idioms:

• exercise book    livro (m) didático

Русский (Russian)
упражняться, использовать, применять, тренировка, физзарядка, проявление, обряд

idioms:

• exercise book    тетрадь

Español (Spanish)
n. - ejercicio, gimnasia
v. tr. - ejercer, ensayar, practicar, adiestrar, entrenar, estudiar, salir de paseo, ejercitar, instruir
v. intr. - ejercitarse, practicarse

idioms:

• exercise book    cuaderno, cartapacio, cuaderno borrador

Svenska (Swedish)
n. - motion, träning
v. - utöva, träna, motionera

中文（简体）(Chinese (Simplified))
练习, 运动, 作业, 运用, 锻炼

idioms:

• exercise book    练习本

中文（繁體）(Chinese (Traditional))
n. - 練習, 運動, 作業
v. tr. - 練習, 運用, 運動
v. intr. - 練習, 運動, 鍛煉

idioms:

• exercise book    練習本

한국어 (Korean)
n. - 운동, 연습 문제, 운용, 수업 과정, 예배, 의식
v. tr. - 운동시키다, 주의를 끌다, 구사하다, 괴롭히다
v. intr. - 연습하다

日本語 (Japanese)
n. - 運動, 練習, 練習問題, 演習, 働かせること, 行使, 式
v. - 運動する, 運動させる, 行使する, 及ぼす, 心配させる, 訓練する, 発揮する

idioms:

• exercise book    ノート, 練習問題集

العربيه (Arabic)
‏(الاسم) تدريب, تمرين (فعل) يمرن, يتدرب‏

עברית (Hebrew)
n. - ‮תרגיל, תרגול, אימון, התעמלות, שימוש, הפעלה‬
v. tr. - ‮אימן, תירגל, נהג ב-, השתמש ב-, הפעיל‬
v. intr. - ‮התעמל, התאמן, תירגל‬

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Some good "exercise" pages on the web: