9.
`
`10.
`
`11.
`
`12.
`
`Blair, S. N., Jacobs, D. R., and Powell, K. E.: Relation-
`ships between exercise or physical activity and other health
`behaviors. Public Health Rep 100: 172-180, March-April
`1985.
`Siscovick, D. S., LaPorte, R. E., and Newman, J. M.: The
`disease-specific benefits and risks of physical activity and
`exercise. Public Health Rep 100: 180-188, March-April
`1985.
`Koplan, J. P., Siscovick, D. S., and Goldbaum, G. M.: The
`risks of exercise: A public health view of injuries and
`hazards. Public Health Rep 100: 189-195, March-April
`1985.
`Taylor, C. B., Sallis, J. F., and Needle, R.: The relationship
`between physical activity and exercise and mental health.
`Public Health Rep 100: 195-202, March-April 1985.
`
`13.
`
`14.
`
`15.
`
`Iverson, D. C., Fielding, J. E., Crow, R. S., and Christen-
`son, G. M.: The promotion of physical activity in the U.S.
`population: the status of programs in medical, worksite,
`community, and school settings. Public Health Rep 100:
`212-224, March-April 1985.
`Paffenbarger, R. J., Wing, A. L., and Hyde, R. T.: Physical
`activity as an index of heart attack risk in college alumni.
`Am J Epidemiol 108: 161-175, September 1978.
`Paffenbarger, R. S.: Countercurrents of physical activity
`and heart attack trends. In Proceedings of the Conference
`on the Decline in Coronary Heart Mortality, edited by R. J.
`Havlik and M. Feinleib. NIH Publication No. 79-1610.
`U.S. Government Printing Office, Washington, DC, May
`1979.
`
`Physical Activity, Exercise,
`and Physical Fitness:
`Definitions and Distinctions
`for Health-Related Research
`
`CARL J. CASPERSEN, PhD, MPH
`KENNETH E. POWELL, MD, MPH
`GREGORY M. CHRISTENSON, PhD
`
`Dr. Caspersen and Dr. Powell are epidemiologists and Dr.
`Christenson is an evaluation researcher in the Behavioral Epi-
`demiology and Evaluation Branch, Division of Health Educa-
`tion, Center for Health Promotion and Education, Centers for
`Disease Control, Atlanta, GA 30333.
`Tearsheet requests to Dr. Caspersen.
`
`Synopsis .....................................
`
`"Physical activity," "exercise," and "physical
`fitness" are terms that describe different concepts.
`
`However, they are often confused with one another,
`and the terms are sometimes used interchangeably.
`This paper proposes definitions to distinguish them.
`
`Physical activity is defined as any bodily move-
`ment produced by skeletal muscles that results in
`energy expenditure. The energy expenditure can be
`measured in kilocalories. Physical activity in daily
`life can be categorized into occupational, sports,
`conditioning, household, or other activities. Exer-
`cise is a subset ofphysical activity that is planned,
`structured, and repetitive and has as a final or an
`intermediate objective the improvement or mainte-
`nance ofphysicalfitness. Physicalfitness is a set of
`attributes that are either health- or skill-related.
`The degree to which people have these attributes
`can be measured with specific tests.
`These definitions are offered as an interpreta-
`tional framework for comparing studies that relate
`physical activity, exercise, and physical fitness to
`health.
`
`T HE EPIDEMIOLOGIC STUDY of any concept or
`event requires that the item under investigation be
`defined and measured. The common and profes-
`sional uses of the terms "physical activity," "exer-
`cise," and "physical fitness" reveal a need for clar-
`ification. This paper, therefore, defines physical ac-
`tivity, exercise, and physical fitness, with the hope
`that each definition will provide a framework in
`which studies can be interpreted and compared.
`Ideally, standardized terminology will promote
`greater understanding of the relation between phys-
`ical activity, exercise, physical fitness, and health.
`
`Physical Activity
`
`Several elements of physical activity have been
`identified (see box page 127). Physical activity is
`defined as any bodily movement produced by
`skeletal muscles that results in energy expenditure.
`The amount of energy required to accomplish an
`activity can be measured in kilojoules (kJ) or
`kilocalories (kcal); 4.184 kJ is essentially equivalent
`to 1 kcal (1). Technically, the kJ is preferred be-
`cause it is a measure of energy expenditure; how-
`ever, historically the kcal, a measure of heat, has
`
`126 Public Health Reports
`
`Exhibit 2009 - Page 1 of 6
`
`

`

`been employed more often. We have chosen to fol-
`low historical precedent.
`Expressed as a rate (kcal per unit time), the
`amount of energy expended by each person is a
`continuous variable, ranging from low to high. The
`total amount of caloric expenditure associated with
`physical activity is determined by the amount of
`muscle mass producing bodily movements and the
`intensity, duration, and frequency of muscular con-
`tractions (2).
`Everyone performs physical activity in order to
`sustain life; however, the amount is largely subject
`to personal choice and may vary considerably from
`person to person as well as for a given person over
`time. The most common units of time used to refer
`to kcals spent in physical activity are the week (3)
`and the day (2). Physical activity during monthly,
`seasonal, or yearly periods may also be examined to
`establish the stability of physical activity for longer
`time periods.
`
`Categories of physical activity. Physical activity can
`be categorized in a variety of ways. A commonly
`used approach is to segment physical activity on the
`basis of the identifiable portions of daily life during
`which the activity occurs. The simplest categoriza-
`tion identifies the physical activity that occurs while
`sleeping, at work, and at leisure (4). A simple for-
`mula can be used to express the caloric contribution
`of each category to the total energy expenditure due
`to physical activity:
`
`kcalsieep+ kcaloccupation+ kcalleisure = kcaltotai daily physical activity
`The caloric contribution of each category to the
`total energy expenditure due to physical activity is
`above basal metabolic rate and does not include the
`effect of diet-induced thermogenesis (which is the
`energy expenditure above the metabolic rate in the
`resting state) (5). The energy expenditure due to
`physical activity during sleep would, of course, be
`small.
`Leisure-time physical activity can be further sub-
`divided into categories such as sports, conditioning
`exercises, household tasks (for example, yardwork,
`cleaning, and home repair) (6), and other activities.
`Substituting in the formula these subcategories for
`the leisure category previously used, the formula
`becomes:
`
`kcalde+ kcaloccupation + kCaIconditionlin + kcahousehold+ kC ,other
`= kcaltotal daily physical activity
`Physical activity is complex behavior, however,
`and may be meaningfully partitioned into other cat-
`egories mutually exclusive of each other but not
`
`necessarily of those mentioned previously. Exam-
`ples might be to divide all physical activities into
`those that are of light, moderate, or heavy intensity;
`those that are willful or compulsory; or those that
`are weekday or weekend activities. All of these are
`acceptable ways of subdividing physical activity.
`The only requirement is that the subdivisions be
`mutually exclusive and that they sum to the total
`caloric expenditure due to physical activity.
`There are undoubtedly many methods of catego-
`rizing daily physical activity. Each system would
`allow measurement not only of total calories ex-
`pended but also of the calories expended in a vari-
`ety of subcategories, any one of which may relate to
`a specific aspect of health. Distinction between an
`evenly accumulated total caloric expenditure (that
`is, equivalent contribution from several categories)
`and an unevenly accumulated total expenditure
`(that is, major contribution from one category) is
`possible. In this manner, individuals and groups can
`be described by the absolute energy expenditure for
`a specific category, by the relative contribution of
`that category to total energy expenditure, or both.
`To the extent that each of the categories has differ-
`ent determinants (7) and different health effects,
`these categorical distinctions have both epidemi-
`ologic utility and public health implications in
`terms of promotion and intervention strategies
`(8).
`Few studies of physical activity allow estimates
`for each of the categories or for the total. Discus-
`
`March-April 1985, Vol. 100, No. 2 127
`
`Exhibit 2009 - Page 2 of 6
`
`

`

`Figure 1. Probability that physical activity performed during
`selected categories is exercise
`
`Figure 2. Components of physical fitness
`
`sion and comparison of studies of physical activity
`will be facilitated if the data in the studies are dis-
`cussed in terms of specific identifiable categories.
`
`Exercise
`
`The term "exercise" has been used interchange-
`ably with "physical activity" (9), and, in fact, both
`have a number of common elements (see box p.
`127). For example, both physical activity and exer-
`cise involve any bodily movement produced by
`skeletal muscles that expends energy, are measured
`by kilocalories ranging continuously from low to
`high, and are positively correlated with physical
`fitness as the intensity, duration, and frequency of
`movements increase. Exercise, however, is not
`synonymous with physical activity: it is a subcate-
`gory of physical activity. Exercise is physical activ-
`ity that is planned, structured, repetitive, and pur-
`posive in the sense that improvement or mainte-
`nance of one or more components of physical
`fitness is an objective. The formula relating physical
`activity and exercise is:
`
`kCalexerclse+ kCalnonexerctse` kcaltotal daily Physical activity
`
`Exercise, then, is a subset of physical activity and
`may constitute all or part of each category of daily
`
`128 Public Health Reports
`
`activity except sleep. However, it is more likely to
`be an important part of some categories of physical
`activity than of others (fig. 1). For example, vir-
`tually all conditioning and many sports activities are
`performed to improve or maintain components of
`physical fitness. In such instances they are planned,
`structured, and, more often than not, repetitive.
`Activities such as occupational, household, and
`many daily tasks are typically performed in the
`most efficient manner possible. These physical ac-
`tivities are done with little regard to physical fitness
`and are often structured with conservation of
`energy expenditure as a goal. However, a worker
`may plan and structure the performance of some
`work tasks in a less efficient manner to develop
`muscular strength or to "burn up" calories. Simi-
`larly, a person may plan and structure the perfor-
`mance of household or other tasks in a labor-
`producing rather than a labor-saving manner. Tasks
`regularly performed in this manner are considered
`exercise.
`
`Physical Fitness
`
`In contrast with physical activity, which is related
`to the movements that people perform, physical
`fitness is a set of attributes that people have or
`achieve. Being physically fit has been defined as
`"the ability to carry out daily tasks with vigor and
`alertness, without undue fatigue and with ample
`energy to enjoy leisure-time pursuits and to meet
`unforeseen emergencies" (10). Although the defini-
`tion may be conceptually sound, things such as
`vigor, alertness, fatigue, and enjoyment are not eas-
`ily measured. On the other hand, a number of
`measurable components do contribute to physical
`fitness (fig. 2). The most frequently cited compo-
`nents fall into two groups: one related to health and
`the other related to skills that pertain more to ath-
`letic ability (11).
`The health-related components of physical fitness
`are (a) cardiorespiratory endurance, (b) muscular
`endurance, (c) muscular strength, (d) body compo-
`sition, and (e) flexibility. These components are
`defined in the glossary (p. 129). Just as the amount
`of physical activity ranges from low to high, so does
`the level of physical fitness. Moreover, the levels of
`the five health-related components need not vary in
`concert; for example, a person may be strong but
`lack flexibility. The five health-related components
`of physical fitness are more important to public
`health than are the components related to athletic
`ability; therefore, we limit our discussion to these.
`
`Exhibit 2009 - Page 3 of 6
`
`

`

`Operational definitions and methods of measuring
`components of physical fitness vary with the inter-
`ests and needs of investigators and evaluators (12-
`14). The table below lists procedures commonly
`employed to evaluate health-related physical fitness
`components for laboratory, epidemiologic, and
`self-assessment techniques. Although the compara-
`bility of these measures has not been addressed
`formally, the cost, precision, and accuracy of the
`measures are generally assumed to decline as one
`
`moves from laboratory measures to self-assess-
`ment. Within these three levels of evaluation, one
`may choose to employ a different measure of
`greater or lesser precision or accuracy, depending
`on the specific objectives of the investigation and
`cost constraints.
`Discussion
`The definitions of physical activity and physical
`fitness we have proposed contain useful parallels.
`
`Health-related physical fitness measures
`
`Fitness component
`
`Laboratory
`
`Cardiorespiratory ..........
`
`Body composition .........
`
`Muscular strength .........
`
`Maximum oxygen uptake on
`treadmill (16) or cycle
`ergometer (15).
`Underwater weighing,
`potassium-40 (20).
`Cable tensiometer (23).
`
`Muscular endurance .......
`
`Isokinetic tests (24).
`
`Flexibility ..................
`
`Leighton flexometer (27).
`
`Evaluation procedures
`
`Epidemiologic
`
`Self-assessment
`
`Canadian Home Fitness Test
`(17), cycle ergometer (18).
`
`Canadian Home Fitness Test
`(17), 12-minute run (19).
`
`Skinfold (209, body mass
`index (21).
`Handgrip dynamometer
`(24,25).
`
`...
`
`Sit-and-reach flexometer
`(26).
`
`Skinfold pinch test (22).
`
`Upper-lower trunk lift,
`hanging leg lift (26).
`Pull-ups, flexed arm hang,
`situps (26).
`Sit-and-reach test (13).
`
`March-April 1985, Vol. 100, No. 2
`
`129
`
`Exhibit 2009 - Page 4 of 6
`
`

`

`Both physical activity and physical fitness vary
`among members of the population from low to high.
`No member has no activity just as no person has no
`fitness-all are active or fit to greater or lesser de-
`grees. When it is necessary to categorize members
`of the population into those who achieve certain
`levels and those who do not, operational definitions
`can be used.
`In contrast, the definition of exercise we have
`proposed is considerably more restrictive and fo-
`cused than those in common use. A crucial element
`of this definition is that exercise be intended to
`improve or maintain components of physical fitness
`rather than to achieve or maintain an established
`level. Therefore, it is not necessary to determine the
`specific achievements necessary to become "physi-
`cally fit," which will vary, at least, by age and sex.
`The proposed definition of exercise is not encum-
`bered by questions concerning whether all of the
`five components of fitness are achieved, nor does it
`require the determination of whether the desired
`level of fitness has, or even could be, achieved by
`the activity under consideration. In contrast, the
`definition of exercise we propose requires only that
`the activity be intended to improve or maintain
`some component of fitness. The improvement or
`maintenance of fitness may be an intermediate ob-
`jective, and the participant does not need to be
`continuously aware of it. The proposed definition
`applies at all levels of physical fitness and does not
`require predetermined levels of achievement. Ac-
`tivities to improve or maintain the flexibility of a
`person with arthritis may require and achieve less
`joint flexion than activities of the gymnast, yet still
`satisfy this definition of exercise.
`We have not addressed the underlying motivation
`to perform; to do so would compound the concept
`being defined with the reason for doing. One
`hoped-for advantage of carefully defining exercise
`as we propose is that investigators will be encour-
`aged to describe the activity under study with more
`care. More careful descriptions and considerations
`of the components of daily living will facilitate
`cross-study comparisons. Discussion of activities
`that are not "exercise" may require more descrip-
`tive words but should produce a clearer understand-
`ing of how the categories of physical activity relate
`to physical or mental health.
`Physical activity is a complex behavior. The
`major purpose of this paper has been to encourage
`more careful descriptions of the categories of physi-
`cal activity that are being studied and discussed.
`This would facilitate comparison of reports in the
`scientific literature and hasten progress in this im-
`
`130 Public Health Reports
`
`portant area of study. In addition, we think it is
`likely that the different subcategories of physical
`activity have different determinants, may relate to
`very specific aspects of physical fitness and health,
`and may require different intervention and promo-
`tion strategies.
`
`References ..................................
`
`1.
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`2.
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`3.
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`4.
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`5.
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`6.
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`11.
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`12.
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`13.
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`14.
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`15.
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`16.
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`17.
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`18.
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`Davidson, S., Passmore, R., Brook, J. F., and Truswell,
`A. S.: Human nutrition and dietetics. Ed. 7. Churchill
`Livingstone, New York, 1979.
`Taylor, H. L., et al.: A questionnaire for the assessment of
`leisure time physical activity. J Chronic Dis 31: 741-755
`(1978).
`Paffenbarger, R. S., Wing, A. L., and Hyde, R. T.: Physical
`activity as an index of heart attack in college alumni. Am J
`Epidemiol 108: 161-175 (1978).
`Montoye, H. J.: Physical activity and health: an epi-
`demiologic study of an entire community. Prentice-Hall,
`Inc., Englewood Cliffs, NJ, 1975.
`Jecquier, E.: Thermogenic responses induced by nutrients
`in man: their importance in energy balance regulation. Ex-
`perientia [Suppl] 44: 26-44 (1983).
`Folsom, A. R., et al.: Distribution of leisure time physical
`activity and its relationship to coronary risk factors in a
`metropolitan area: the Minnesota Heart Survey. Am J
`Epidemiol. In press.
`Dishman, R. K., Sallis, J. F., and Orenstein, D. R.: The
`determinants of physical activity and exercise. Public
`Health Rep 100: 158-171, March-April 1985.
`Iverson, D. C., Fielding, J. E., Crow, R. S., and Christen-
`son, G. M.: The promotion of physical activity in the U.S.
`population: the status of programs in medical, worksite,
`community, and school settings. Public Health Rep 100:
`212-224, March-April 1985.
`Taylor, H. L.: Physical activity: is it still a risk factor? Prev
`Med 12: 20-24 (1983).
`President's Council on Physical Fitness and Sports: Physi-
`cal Fitness Research Digest. Series 1, No. 1. Washington,
`DC, 1971.
`Pate, R. R.: A new definition of youth fitness. Physician
`Sports Med 11: 77-83 (1983).
`de Vries, H. A.: Physiology and exercise for physical edu-
`cation and athletics. W. C. Brown & Company, Publishers,
`Dubuque, IA, 1974.
`Corbin, C. B., Dowell, L. J., Lindsay, R., and Tolson, H.:
`Concepts of physical education with laboratories and exper-
`iments. Ed. 3. W. C. Brown & Company, Publishers,
`Dubuque, IA, 1978.
`Sharkey, B. J.: Physiological fitness and weight control.
`Mountain Press Publishing Company, Missoula, MT, 1974.
`Astrand, P. O., and Rodahl, K.: Textbook of work physiol-
`ogy: physiological bases of exercise. Ed. 2. McGraw-Hill
`Book Company, New York, 1977.
`Taylor, H. L., Buskirk, E. R., and Henschel, A.: Maximal
`oxygen uptake as an objective measure of cardiorespiratory
`performance. J Appl Physiol 8: 73-80 (1955).
`Jette, M.: The standardized test of fitness in occupational
`health: a pilot study. Can J Public Health 69: 431-438
`(1978).
`Siconolfi, S. F., Cullinane, E. M., Carleton, R. A., and
`Thompson, P. D.: Assessing VO2ma,, in epidemiologic stud-
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`Exhibit 2009 - Page 5 of 6
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`

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`19.
`
`20.
`
`21.
`
`22.
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`23.
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`ies: modification of the Astrand-Rhyming test. Med Sci
`Sports Exer 14: 335-338 (1982).
`Cooper, K. H.: The aerobics way. M. Evans and Company,
`Inc., New York, 1978.
`Behnke, A. R., and Wilmore, J. H.: Evaluation and regula-
`tion of body build and composition. Prentice-Hall, Inc.,
`Englewood Cliffs, NJ, 1972.
`Keys, A., et al.: Indices of relative weight and obesity. J
`Chronic Dis 25: 329-343 (1974).
`Farquhar, J. W.: The American way of life need not be
`hazardous to your health. W. W. Norton and Company,
`New York, 1978.
`Clarke, H. H.: Improvements of objective strength tests of
`muscle groups by cable tension methods. Res Q 21: 399
`(1950).
`
`24.
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`25.
`
`26.
`
`27.
`
`McArdle, W. D., Katch, F. I., and Katch, V. L.: Exercise
`physiology: energy, nutrition and human performance. Lea
`and Febiger, Philadelphia, 1981.
`Larson, L. A., editor: Fitness, health, and work capacity:
`international standards for assessment. MacMillan Publish-
`ing Co., Inc., New York, 1974.
`Blair, S. N., Falls, H. B., and Pate, R. R.: A new physical
`fitness test. Physician Sports Med 11: 87-95 (1983).
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`range of joint motion. Arch Phys Med Rehabil 38: 24-28
`(1955).
`
`Assessment of Physical
`Activity in Epidemiologic
`Research: Problems
`and Prospects
`
`RONALD E. LAPORTE, PhD
`HENRY J. MONTOYE, PhD
`CARL J. CASPERSEN, PhD, MPH
`
`Dr. LaPorte is an Associate Professor in the Department of
`Epidemiology, Graduate School of Public Health, University of
`Pittsburgh, 130 DeSoto St., Pittsburgh, PA 15261. Dr. Montoye
`is a Professor in the Department of Physical Education ind
`Dance, School of Education, University of Wisconsin-Madison,
`Madison, WI 53706. Dr. Caspersen is an Epidemiologist in the
`Behavioral Epidemiology and Evaluation Branch, Division of
`Health Education, Center for Health Promotion and Education,
`Centers for Disease Control, Atlanta, GA 30333. Richard A.
`Washburn, PhD, Research Fellow, Department of Epidemiol-
`ogy, School of Public Health, University of Pittsburgh, made
`helpful suggestions.
`Tearsheet requests to Dr. LaPorte.
`
`Synopsis .....................................
`
`More than 30 different methods have been used
`to assess physical activity. These methods can be
`grouped into seven major categories: calorimetry,
`job classification, survey procedures, physiological
`markers, behavioral observation, mechanical and
`electronic monitors, and dietary measures. No
`single instrument fulfills the criteria of being valid,
`reliable, and practical while not affecting behavior.
`The instruments that are very precise tend to be
`impractical on a population basis. Surveys are the
`most practical approach in large-scale studies, al-
`though little is known about their reliability and
`validity. Studies employing objective monitoring
`through heart rate, movement sensors, and doubly
`labeled water procedures appear promising, but are
`still experimental and costly. Despite the difficulty
`of measurement, relatively strong association has
`been found between physical activity and health,
`suggesting that, with improvements in assessment
`techniques, even stronger associations should be
`seen.
`
`A CRITICAL FACTOR FOR EPIDEMIOLOGIC RE-
`SEARCH is the accurate assessment of the variables
`under study. For the cardiovascular risk factors of
`smoking, serum cholesterol, and blood pressure,
`there are standardized techniques for assessment of
`the factors that provide consistency of measure-
`ment and definition across studies. However, with
`research on physical activity this has not been the
`case.
`This review considers seven major categories of
`physical activity assessment procedures that have
`been used in various settings (table 1) and evaluates
`
`their potential for use in epidemiologic studies with
`respect to four important criteria:
`
`* To be valid, the instrument must measure what it
`is intended to measure.
`* To be reliable, the instrument must consistently
`give the same results under the same circum-
`stances. If the instrument is reliable and valid, it is
`also accurate.
`* To be practical, the instrument must have accept-
`able costs to both the investigator and the partici-
`pant.
`
`March-April 1985, Vol. 100, No. 2
`
`131
`
`Exhibit 2009 - Page 6 of 6
`
`