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Does physical activity enhance health?
Patient Education and Counseling 33 (1998) S95–S103
Does physical activity enhance health? Ilkka Vuori* The UKK Institute for Health Promotion Research, P.O. Box 30, FIN-33501 Tampere, Finland
Abstract This paper provides the justification of physical activity promotion for health by critically reviewing the recent US Surgeon General’s Report. Evidence is summarized of the effects of physical activity on physiological responses, overall mortality, a number of diseases and disabilities, overall functional capacity, and mental health and quality of life. Cumulating evidence suggests that the effects be applicable to both genders and to a wide age range. The adverse effects of physical activity on health are shown to be small and mostly preventable. It is emphasized that substantial health effects can be gained by moderate daily physical activity which does not require high skill level nor specialized equipment or facilities. It is concluded that the health potential of physical activity is substantial due to the high prevalence of inactive lifestyle in the populations, the great number of health conditions being affected by physical activity, and the feasibility and safety of physical activity as a health measure. 1998 Elsevier Science Ireland Ltd. Keywords: Positive health; Physical activity; Health effects; Prevention
1. Introduction The answer to the question of the title of this paper is critical for the justification of physical activity promotion for health. It is necessary to know what aspects of health might be influenced by physical activity, by what mechanisms, by how much activity, by whom and under what conditions. If physical activity influences prevalent and serious health problems or their risk factors in a substantial and predictable way, its promotion is justified on a population level and its prescription and counselling
*Tel.: 1 358 3 2829111; fax: 1 358 3 2829559; e-mail: [email protected]
in individual cases. This review aims at answering these questions on the basis of current scientific evidence.
2. Definitions Health has been defined in numerous ways. The ‘classic’ definition is found in the WHO constitution of 1948 as: ‘‘a state of complete physical, social and mental well-being and not merely the absence of diseases or infirmity’’. In the WHO Ottawa Charter on Health Promotion [1], health is expressed in more functional terms as a resource which permits people to lead an individually, socially and economically
0738-3991 / 98 / $19.00 1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0738-3991( 98 )00014-7
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productive life: ‘‘Health is a resource for everyday life, not the object of living. It is a positive concept emphasizing social and personal resources as well as physical capabilities’’. In physical activity sciences the definition presented in the 1988 International Consensus Conference [2] is widely cited: ‘‘Health is a human condition with physical, social, and psychological dimensions, each characterized on a continuum with positive and negative poles. Positive health is associated with a capacity to enjoy life and to withstand challenges; it is not merely the absence of disease. Negative health is associated with morbidity and in the extreme with premature mortality. Morbidity can be defined as any departure, subjective or objective, from a state of physical or psychological well-being, short of death. Wellness is a holistic concept describing a state of positive health in the individual and comprising physical, social, and psychological well-being’’. Seedhouse [3] emphasizes health as the foundations for achievement that has degrees and levels. The foundations are not merely those required for biological or physical achievement but those required for a wide range of human achievement, also encompassing emotional, intellectual, spiritual, creative, and recreational potentials. It can also be said that health is the state of the life potential or life energy of an individual at the moment of observation, the potential for survival, performance and achievement in all domains of life. It is characterized by adequate structures and properly balanced and coordinated functions with sufficient potential to tolerate the various stresses in everyday life and in special circumstances. Physical activity is defined as bodily movement produced by the contraction of skeletal muscles that increases energy expenditure above the basal level. Physical activity can be categorized in various ways, including type, intensity or strenuousness and purpose [4]. Exercise is a subcategory of physical activity that is planned, structured, repetitive, and purposive in the sense that improvement or maintenance of one or more components of physical fitness is the objective [5]. These definitions emphasize the physiological aspects of physical activity. A broader scope and more comprehensive understanding of physical activity is presented in the article of Marttila et al. in this issue [6].
3. Effects of physical activity on health Currently the most authoritative review on this topic is the US Surgeon General’s Report on Physical Activity and Health [4]. In the following, the summary statements of that report are presented in abbreviated form and each of them is commented upon in order to give additional information on important new findings, size of the effect, evidence of plausibility of the effect, and characteristics of the activity needed to attain the effect. If no reference is given, more detailed information and references can be found in the Surgeon General’s Report. Also, some health aspects that are not dealt with in the Surgeon General’s Report are reviewed.
3.1. Physiological responses and long-term adaptations to exercise Physical activity has numerous beneficial effects. Most widely appreciated are its effects on the cardiovascular and musculoskeletal systems, but benefits on the functioning of metabolic, endocrine, and immune systems are also considerable. Many of the effects disappear within 2–8 months, if physical activity is not retained. People of all ages, both male and female, undergo beneficial physiological adaptations to physical activity. Comment: Table 1 presents a number of effects of physical activity that are beneficial for health as well as the main characteristics of the activity needed to attain the corresponding effect. The size of the effects depends on many factors, e.g. the initial level of the parameter, age, sex and genetic factors of the individual, and characteristics of the activity. In general, the level of the structural or functional parameter that is deviant from the average or indicates increased health risk is influenced more than the average by physical activity.
3.2. Overall mortality Higher levels of regular physical activity are associated with lower mortality rates for both older and younger adults. Even those who are moderately active on regular basis have lower mortality rates than those who are least active.
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Table 1 The physiological and psychological basis for health benefits [7] Physiological and psychological improvements and benefits to health Prevention / amelioration of disease Functions which can be enhanced by regular physical activity are: (1) Cardiovascular function (i) Cardiac performance / myocardial work (ii) Arterial blood pressure regulation (iii) Cardiovascular and sympathoadrenal response to acute exercise (iv) Electrical stability of heart muscle (2) Skeletal muscle (i) Metabolic capacities nutrient blood supply contractile properties (ii) Strength
(3) Tendons and connective tissues (i) Strength (ii) Supportive function (iii) Increases joint stability (4) The skeleton (i) Maintenance of bone mass (ii) Adjustment of structure to load (5) Joints (i) Lubrication (ii) Range of movement (iii) Maintenance of flexibility (6) Metabolic functions (i) Body weight control regulation of energy balance (ii) Insulin sensitivity and carbohydrate tolerance (iii) Lipid and lipoprotein metabolism (iv) Inhibition of blood clotting processes (7) Psychological function (i) Mood (ii) Self-esteem (iii) Psychomotor development (iv) Memory (v) Stress reduction
Comment: In the studied populations the lower overall mortality of the more active ones is mainly due to lower incidence of fatal cardiovascular events, and the effect of activity is also seen in slightly increased life expectancy. The effect on mortality is largely due to aerobic or endurance activity.
3.3. Cardiovascular diseases Regular physical activity or cardiorespiratory fitness decreases the risk of cardiovascular disease mortality in general, and coronary heart disease mortality in particular. Existing data are not conclu-
Thus regular physical activity:
• Ameliorates the effects of age and chronic disease (including CHD) • Reduces BP in mild hypertension • Reduces risk of cardiac arrhythmias and possibly of sudden death
• Ameliorates the effects of age and chronic disease on reserve capacity for exercise, increasing endurance and reducing fatigue • Reduces risk of injury • Ameliorates the effects of muscle disease • Reduces risk of injury, especially with age, and muscle disease
• ‘Prevents’ osteoporosis and fractures • Avoids limitation of movement • Limits effects of degenerative arthritis • • • •
‘Prevents’ obesity-related disease and excessive weight gain Improves carbohydrate tolerance ameliorates late-onset diabetes ‘Prevents’ coronary heart disease Counters acute precipitants of ‘heart attack’
• • • • •
Reduces mild anxiety and depression Influences mood favourably Contributes to the quality of care for the mentally handicapped Can improve memory in the elderly Can ameliorate stress-related conditions
sive regarding the relationship between physical activity and stroke. The level of decreased risk of coronary heart disease attributable to regular physical activity is similar to that of other lifestyle factors, such as keeping free from cigarette smoking. Regular physical activity prevents or delays the development of high blood pressure in people with hypertension. Comment: The population attributable risk due to physical inactivity, as assessed on the basis of the size of the risk and the prevalence of this risk factor in the population, is e.g., in the Finnish population greater due to physical inactivity than to smoking, high cholesterol level, high blood pressure or over-
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weight [8]. Regular physical activity seems to reduce also the incidence of ischemic heart disease [9,10] as well as the case fatality in myocardial infarction [10]. Generally there is a dose–response relationship between the indices of cardiovascular diseases or their risk factors and the amount or intensity of physical activity. Some of these relationships seem to be non-linear, suggesting that the greatest benefits are attained by being or becoming at least moderately active instead of being sedentary. However, many aspects of the dose–response issues are unsettled [11]. The evidence for the preventive effect of physical activity on stroke was not found to be convincing in the Surgeon General’s report, but this evidence seems to be increasing regarding both men and women [12–16]. Several biologically plausible mechanisms can explain the association between level of physical activity and risk of stroke [17]. The risk of developing hypertension is found to be about 30% higher in the least active men or women as compared with their most active counterparts. Regular exercise training decreases normal systolic and diastolic blood pressure on average by 3 mmHg, slightly elevated pressures by 6 / 7 mmHg, and hypertensive pressures by 10 / 8 mmHg, respectively. The effect of exercise in hypertensive patients is about the same size as that attained by any of the commonly used drugs. Moderately intense, frequent activity seems to be at least as effective as vigorous activity.
physical activity. Plausible biological mechanisms for the risk-reducing effect of physical activity regarding colon cancer [4] and breast cancer [21] have been proposed. Epidemiological evidence, as well as the proposed mechanisms, suggest that the protective effect of activity against these cancers is related mainly to frequent, endurance-type activity.
3.5. Non-insulin-dependent diabetes mellitus ( NIDDM) Regular physical activity lowers the risk of developing non-insulin-dependent diabetes mellitus. Comment: New results from cross-sectional studies on elderly men [22] and male endurance athletes [23], and from prospective studies on middle-aged Japanese-Americans [24,25], British men [26] and American male physicians [27] support the conclusion of the risk-reducing effect of physical activity against NIDDM. The risk-decreasing effect of physical activity is greatest in subjects with high risk of NIDDM. The size of the effect seems to be 20–60%, it seems to be dose dependent, and due to predominantly aerobic, moderate to vigorous activity. However, resistance training has also been shown to cause beneficial effects on disturbed glucose and insulin metabolism [28,29]. Therefore, the combination of endurance and resistance exercise can be recommended as part of treatment of patients with NIDDM.
3.6. Osteoarthritis 3.4. Cancer Regular physical activity is associated with a decreased risk of colon cancer. There is no association between physical activity and rectal cancer. Data are too sparse to draw conclusions regarding a relationship between physical activity and endometrial, ovarian, or testicular cancers. Data are inconsistent regarding an association between physical activity and breast or prostate cancers. Comment: The risk of colon cancer in physically active subjects is found to be 20–50% lower than in sedentary subjects in most studies, but the results are variable. Some recent studies show additional supporting evidence of reduced risk of breast cancer [18,19] and prostate cancer [20] associated with
Regular physical activity is necessary for maintaining normal muscle strength, joint structure, and joint function. In the range recommended for health, physical activity is not associated with joint damage or development of osteoarthritis and may be beneficial for many people with arthritis. Competitive athletics may be associated with the development of osteoarthritis later in life, but sports-related injuries are the likely cause. Comment: It seems that ordinary weight-bearing activities such as walking done on a daily basis are sufficient to maintain normal joint structure. In order to counteract the decrease of muscle mass and increased stiffness the importance of more variable and joint-specific activities, e.g., calisthenics, in-
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creases with age. Several short-term studies have indicated that regular moderate-exercise programs of either aerobic or resistance type, relieve symptoms and improve function among people with both osteoarthritis and rheumatoid arthritis [4].
3.7. Osteoporosis Weight-bearing physical activity is essential for normal skeletal development during childhood and adolescence and for achieving and maintaining peak bone mass in young adults. It is unclear whether resistance- or endurance-type physical activity can reduce the accelerated rate of bone loss in postmenopausal women in the absence of estrogen replacement therapy. Comment: Osteoporosis leads to bone fragility and consequently to increased risk of fractures due to decreased bone mass and deteriorated microarchitecture. The criterion for osteoporosis in women is bone mineral density (BMD) 2.5 standard deviations (25– 35%) or more below the average value of young adult women. This degree of decrease of BMD in the hip increases the risk of fracture at that site by a factor of about six. About one-third of 70–79-yearold and about one-half of 80-year-old or older white American women have lost at least 25% of their femoral bone mass [30]. Physical activity, through its load-bearing effect on the skeleton, is likely the single most important influence on bone density and architecture [31]. At young age, especially during the pubescent years, physical activity can increase BMD substantially [32]. In athletes, BMD of the loaded sites can be more than 30% higher than that of the contralateral non-loaded site. In non-athletic populations, physical activity, which is feasible for large numbers of children, adolescents and young adults, increases BMD by 7–8% on average, as compared with sedentary subjects [33]. If this difference is maintained until old age it is likely to decrease the risk of osteoporotic fractures. In later life, physical activity helps to maintain or even to slightly increase the bone mass [34]. Currently, still inconclusive knowledge suggests that bone formation is stimulated by activity that produces microscopic, transient structural changes or strains in the bone. These strains are induced effec-
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tively by rapid, forceful, versatile movements causing slight shocks or impulses in the bone. These types of movement are characteristic, e.g., in rapid racket games, such as squash, and in certain types of aerobics. When the bones get weaker, the strains can be caused by smaller forces and consequently even fast walking in variable terrain may be effective in counteracting bone weakening in older persons [35]. Physical activity and hormone replacement therapy seem to have additive effects on bone mineral density in older women [36].
3.8. Falling There is promising evidence that strength training and other forms of exercise in older adults preserve the ability to maintain independent living status and reduce the risk of falling. Comment: Recent findings suggest that, at least in independently living older people, the exponential increase in the incidence of hip fractures is explained only to a limited extent by the decrease in bone density associated with age [37]. This observation suggests that other risk factors for hip fractures, such as falling, make a major contribution to the risk. Many of the risk factors for falls such as lower extremity muscle strength, balance, reaction time, coordination, and gait can be influenced positively and to a significant degree by general and specific physical activities [4,34,35,38]. Physical activity may be a particularly promising preventive measure for hip fractures [39]. This finding deserves attention because about one-quarter of hip fractures occurred in independently living old individuals, and men had about the same risk of hip fracture 5 years later than women [37].
3.9. Low back pain The Surgeon General’s Report does not take a position on the role of physical activity in the primary or secondary prevention of mechanical low back pain or neck and shoulder pain. Current evidence on the effect of physical activity in primary prevention of mechanical low back pain suggests that exercises that strengthen the lower body muscles and improve aerobic fitness have a slight preventive effect [35,40]. The data on the
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effects of physical activity in the treatment of acute or subacute low back pain are insufficient for definite conclusions [41,42]. It seems, however, that both strenuous exercises and total lack of activity increase the symptoms and their duration, while early ambulation [43] and gradually increasing exercise that strengthens musculature and improves endurance, mobility, posture, or overall fitness may be beneficial as part of the treatment and rehabilitation of subacute and chronic low back pain [35]. However, there is little consensus regarding the specific goals or content of exercise programs for either primary or secondary prevention of low back pain [44], and part of the exercise-related effects are likely to be nonspecific or indirect [45]. Because mechanical low back pain episodes are very common in the population, there is a great need to find out the real role of physical activity in the prevention and treatment of this condition.
3.10. Neck and shoulder pain The majority of neck and shoulder pain cases is due to cervical muscle tension, but the exact mechanism of the symptoms is unknown [46]. Practical experience supports the idea that increased muscle strength, endurance, or improved muscle relaxation would be helpful in the prevention and treatment of this condition. The results of the few scientifically valid assessments of the effectiveness of exercise programs on the stiff-neck syndrome have been partly promising [46–48], but low-intensity exercise programs have not resulted in improvement [49,50]. Here again, the real role of exercise for prevention and treatment of neck and shoulder pain should be thoroughly evaluated, because the incidence and prevalence of this ailment is high and increasing.
many serious biological diseases, and psychological and social problems [51]. However, the health consequences of overweight (body mass index 29.0– 29.9 (weight in kilograms divided by the square of the height in meters) should not be over-emphasized [52]. It has become clear from hundreds of studies that without regular physical activity, weight control can usually not be achieved [52]. Because all physical activity increases energy expenditure, it is important to choose physically active alternatives in daily life whenever feasible. Maintenance of muscle mass by strength-requiring activity increases in importance with aging.
3.12. Functional capacity Functional capacity is an integrated function of a large number of capabilities, including basic physical and mental tasks, such as walking or reading a standard text. Even simple functional capabilities require input from many organ systems, and they are influenced by various individual and environmental factors. Physical activity influences favorably many elements of functional capabilities (see Table 1). Many of these effects are unique products of physical activity and cannot be compensated by other means. Also, many functional abilities themselves are influenced positively by physical activity [53–56]. These effects are very important in the maintenance of adequate fitness for daily tasks in aging individuals and indicate the great potential of physical activity as a means to contribute to their quality of life.
3.13. Mental health and health-related quality of life
3.11. Obesity Low levels of activity, resulting in fewer kilocalories used than consumed, contribute to the high prevalence of obesity (in the United States). Physical activity may favorably affect body fat distribution. Comment: Obesity is one of the most prevalent health problems in industrialized countries and is increasing. The significance of obesity is accentuated by the fact that it is a potent risk factor or cause of
Physical activity appears to relieve symptoms of depression and anxiety, and to improve mood. Regular physical activity may reduce the risk of developing depression, although further research is needed on this topic. Physical activity appears to improve health-related quality of life by enhancing psychological well-being (e.g., self-concept, self-esteem, mood, and affect) and by improving physical functioning, especially in persons compromised by poor health.
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Comment: The effects of physical activity on mental health and psychological well-being are less thoroughly studied than those related to biological health. They appear to depend strongly on individual and circumstantial factors, and thus they are less predictable than the biological effects. Thus, beneficial activities on individual level are currently to a large extent a matter of personal experimentation. At least in older adults, involvement in physical activity may increase the psychological well-being independently of changes in cardiorespiratory fitness.
3.14. Adverse effects Most musculoskeletal injuries related to physical activity are believed to be preventable by gradually working up to a desired level of activity and by avoiding excessive amounts of activity. Serious cardiovascular events can occur with physical exertion, but the net effect of regular physical activity is a lower risk of mortality from cardiovascular disease. Comment: The risk of injuries related to acute exercise is considerable in sport disciplines that require speed and power and include body contacts, e.g., team ball games. In typical keep-fit activities, such as in walking, jogging, swimming, cross-country skiing and callisthenics, the risk is low, tens of times smaller than in the high-risk sports [57]. In aerobic exercisers, overuse injuries can be frequent, if the total amount or the frequency of the activity is high. The risk of cardiovascular complications, mainly sudden death or myocardial infarction, is low. These events occur practically only in individuals with latent or overt cardiovascular disease [58]. The risk is increased with increasing intensity of the activity, and it is much higher in individuals who are unaccustomed to exercise compared to accustomed persons. Thus, all complications of physical activity can be kept low by exercising sensibly.
3.15. Generalizability of the health benefits of physical activity Most data on the health benefits of physical activity are based on young and middle-aged white middle-class males. An obvious exception is the studies on bone density, most of which have been done on female subjects. Although there are age and sex differences in the responses to physical activity,
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cumulating evidence suggests that most of the effects can be seen in both sexes and within a wide age range. It is especially important that both physiological and protective effects [55] can also be seen in elderly subjects.
3.16. Characteristics of activity necessary for health benefits Aerobic or endurance activities have been traditionally considered as the most beneficial in terms of health. In recent years resistance or strength-requiring activities have been given increasing emphasis. The widest spectrum of health benefits can obviously be gained by a combination of aerobic and resistance activities. However, many aerobic exercise modalities, such as walking and cycling, are not effective in influencing bone density, movement coordination and balance that are important to reduce the risk of fractures. For these purposes different types of exercises are needed. In general it should be emphasized that substantial physiological or preventive effects can be gained by activity that is frequent but moderate, both in total amount and in intensity. Further, effective health-enhancing activities do not require high level of skills nor specialized equipment or sites for practice. These characteristics make health-enhancing physical activities feasible and safe for a large proportion of the population, as the Surgeon General’s Report concludes: ‘‘Significant health benefits can be obtained by including a moderate amount of physical activity (e.g., 30 min of brisk walking or raking leaves, 15 min of running, or 45 min of playing volleyball) on most, if not all, days of the week. Through a modest increase in daily activity, most individuals in industrialized countries can improve their health and quality of life. Additional health benefits can be gained through greater amounts of physical activity. People who can maintain a regular regimen of activity that is of long duration or of vigorous intensity are likely to derive greater benefits’’.
4. Conclusions The health potential of physical activity is substantial on the following grounds: (1) the spectrum of health benefits is large; (2) the size of the effects
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varies from slight to moderate, even to large, and part of the effects cannot be gained by any other means; (3) the number and prevalence of health conditions that are related to sedentariness or amenable to improvement by physical activity is high; (4) the prevalence of inactivity in many populations is high; (5) most physical activities that are effective in enhancing health are feasible, safe and inexpensive for the majority of many populations. On these grounds it is justified, and even the responsibility of the society in industrialized countries, to promote health-enhancing physical activity. One part of physical activity promotion should be the development and use of effective and ethically sound methods for individual and group counselling.
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¨ [43] Malmivaara A, Hakkinen U, Aro T, Heinrichs M-L, Koskenniemi L, Kuosma E, Lappi S, Paloheimo R, Servo C, Vaaranen V, Hernberg S. The treatment of acute low back pain-bed rest, exercises, or ordinary activity?. New Engl J Med 1995;332:351–5. [44] Deyo RA. Exercise in the prevention and treatment of low back pain. In: Goldberg L, Elliot DL, editors. Exercise for prevention and treatment of illness. Philadelphia: Davis, 1991:153–70. [45] Frank A. Low back pain. Br Med J 1993;306:901–9. [46] Berg HE, Berggren G, Tesch PA. Dynamic neck strength training effect on pain and function. Arch Phys Med Rehab 1994;75:661–5. [47] Jordan A, Mehlsen J. Cervicobrachial syndrome: neck muscle function and effects of training. J Musculoskeletal Pain 1993;1:283–8. ¨ [48] Levoska S, Keinanen-Kiukaanniemi S. Active or passive physiotherapy for occupational cervicobrachial disorders? A comparison of two treatment methods with a 1-year followup. Arch Phys Med Rehab 1993;74:425–30. [49] Silverstein BA, Armstron TJ, Longmate A, Woody D. Can in-plant exercise control musculoskeletal symptoms?. J Occup Med 1988;30:922. [50] Takala E-P, Viikari-Juntura E, Tynkkynen E-M. Does group gymnastics at the workplace help in neck pain? A controlled study. Scand J Rehab Med 1994;26:17–20. [51] Lissner L. Psychosocial aspects of obesity: individual and ¨ societal perspectives. Scand J Nutr / Naringsforskning 1997;41:75–9. [52] Byers T. Body weight and mortality. New Engl J Med 1995;333:723–4. [53] Buchner DM, Beresford SAA, Larson EB, Lacroix AZ, Wagner EH. Effects of physical activity on health status in older adults II: Intervention studies. Annu Rev Public Health 1992;13:469–88. [54] Schroll M. The main pathway to musculoskeletal disability. Scand J Med Sci Sports 1994;4:3–12. [55] Shephard RJ. Aging, Physical Activity, and Health. Champaign, IL: Human Kinetics, 1997. [56] Wanger EH, LaCroix AZ. Effects of physical activity on health status in older adults: observational studies. Annu Rev Public Health 1992;13:451–68. [57] Nicholl JP, Coleman P, Williams BT. The epidemiology of sports and exercise related injury in the United Kingdom. Br J Sports Med 1995;29(4):232–8. [58] Vuori I. Sudden death and exercise: effects of age and type of activity. Sport Sci Rev 1995;4:46–84.
Does physical activity enhance health? Ilkka Vuori* The UKK Institute for Health Promotion Research, P.O. Box 30, FIN-33501 Tampere, Finland
Abstract This paper provides the justification of physical activity promotion for health by critically reviewing the recent US Surgeon General’s Report. Evidence is summarized of the effects of physical activity on physiological responses, overall mortality, a number of diseases and disabilities, overall functional capacity, and mental health and quality of life. Cumulating evidence suggests that the effects be applicable to both genders and to a wide age range. The adverse effects of physical activity on health are shown to be small and mostly preventable. It is emphasized that substantial health effects can be gained by moderate daily physical activity which does not require high skill level nor specialized equipment or facilities. It is concluded that the health potential of physical activity is substantial due to the high prevalence of inactive lifestyle in the populations, the great number of health conditions being affected by physical activity, and the feasibility and safety of physical activity as a health measure. 1998 Elsevier Science Ireland Ltd. Keywords: Positive health; Physical activity; Health effects; Prevention
1. Introduction The answer to the question of the title of this paper is critical for the justification of physical activity promotion for health. It is necessary to know what aspects of health might be influenced by physical activity, by what mechanisms, by how much activity, by whom and under what conditions. If physical activity influences prevalent and serious health problems or their risk factors in a substantial and predictable way, its promotion is justified on a population level and its prescription and counselling
*Tel.: 1 358 3 2829111; fax: 1 358 3 2829559; e-mail: [email protected]
in individual cases. This review aims at answering these questions on the basis of current scientific evidence.
2. Definitions Health has been defined in numerous ways. The ‘classic’ definition is found in the WHO constitution of 1948 as: ‘‘a state of complete physical, social and mental well-being and not merely the absence of diseases or infirmity’’. In the WHO Ottawa Charter on Health Promotion [1], health is expressed in more functional terms as a resource which permits people to lead an individually, socially and economically
0738-3991 / 98 / $19.00 1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0738-3991( 98 )00014-7
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productive life: ‘‘Health is a resource for everyday life, not the object of living. It is a positive concept emphasizing social and personal resources as well as physical capabilities’’. In physical activity sciences the definition presented in the 1988 International Consensus Conference [2] is widely cited: ‘‘Health is a human condition with physical, social, and psychological dimensions, each characterized on a continuum with positive and negative poles. Positive health is associated with a capacity to enjoy life and to withstand challenges; it is not merely the absence of disease. Negative health is associated with morbidity and in the extreme with premature mortality. Morbidity can be defined as any departure, subjective or objective, from a state of physical or psychological well-being, short of death. Wellness is a holistic concept describing a state of positive health in the individual and comprising physical, social, and psychological well-being’’. Seedhouse [3] emphasizes health as the foundations for achievement that has degrees and levels. The foundations are not merely those required for biological or physical achievement but those required for a wide range of human achievement, also encompassing emotional, intellectual, spiritual, creative, and recreational potentials. It can also be said that health is the state of the life potential or life energy of an individual at the moment of observation, the potential for survival, performance and achievement in all domains of life. It is characterized by adequate structures and properly balanced and coordinated functions with sufficient potential to tolerate the various stresses in everyday life and in special circumstances. Physical activity is defined as bodily movement produced by the contraction of skeletal muscles that increases energy expenditure above the basal level. Physical activity can be categorized in various ways, including type, intensity or strenuousness and purpose [4]. Exercise is a subcategory of physical activity that is planned, structured, repetitive, and purposive in the sense that improvement or maintenance of one or more components of physical fitness is the objective [5]. These definitions emphasize the physiological aspects of physical activity. A broader scope and more comprehensive understanding of physical activity is presented in the article of Marttila et al. in this issue [6].
3. Effects of physical activity on health Currently the most authoritative review on this topic is the US Surgeon General’s Report on Physical Activity and Health [4]. In the following, the summary statements of that report are presented in abbreviated form and each of them is commented upon in order to give additional information on important new findings, size of the effect, evidence of plausibility of the effect, and characteristics of the activity needed to attain the effect. If no reference is given, more detailed information and references can be found in the Surgeon General’s Report. Also, some health aspects that are not dealt with in the Surgeon General’s Report are reviewed.
3.1. Physiological responses and long-term adaptations to exercise Physical activity has numerous beneficial effects. Most widely appreciated are its effects on the cardiovascular and musculoskeletal systems, but benefits on the functioning of metabolic, endocrine, and immune systems are also considerable. Many of the effects disappear within 2–8 months, if physical activity is not retained. People of all ages, both male and female, undergo beneficial physiological adaptations to physical activity. Comment: Table 1 presents a number of effects of physical activity that are beneficial for health as well as the main characteristics of the activity needed to attain the corresponding effect. The size of the effects depends on many factors, e.g. the initial level of the parameter, age, sex and genetic factors of the individual, and characteristics of the activity. In general, the level of the structural or functional parameter that is deviant from the average or indicates increased health risk is influenced more than the average by physical activity.
3.2. Overall mortality Higher levels of regular physical activity are associated with lower mortality rates for both older and younger adults. Even those who are moderately active on regular basis have lower mortality rates than those who are least active.
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Table 1 The physiological and psychological basis for health benefits [7] Physiological and psychological improvements and benefits to health Prevention / amelioration of disease Functions which can be enhanced by regular physical activity are: (1) Cardiovascular function (i) Cardiac performance / myocardial work (ii) Arterial blood pressure regulation (iii) Cardiovascular and sympathoadrenal response to acute exercise (iv) Electrical stability of heart muscle (2) Skeletal muscle (i) Metabolic capacities nutrient blood supply contractile properties (ii) Strength
(3) Tendons and connective tissues (i) Strength (ii) Supportive function (iii) Increases joint stability (4) The skeleton (i) Maintenance of bone mass (ii) Adjustment of structure to load (5) Joints (i) Lubrication (ii) Range of movement (iii) Maintenance of flexibility (6) Metabolic functions (i) Body weight control regulation of energy balance (ii) Insulin sensitivity and carbohydrate tolerance (iii) Lipid and lipoprotein metabolism (iv) Inhibition of blood clotting processes (7) Psychological function (i) Mood (ii) Self-esteem (iii) Psychomotor development (iv) Memory (v) Stress reduction
Comment: In the studied populations the lower overall mortality of the more active ones is mainly due to lower incidence of fatal cardiovascular events, and the effect of activity is also seen in slightly increased life expectancy. The effect on mortality is largely due to aerobic or endurance activity.
3.3. Cardiovascular diseases Regular physical activity or cardiorespiratory fitness decreases the risk of cardiovascular disease mortality in general, and coronary heart disease mortality in particular. Existing data are not conclu-
Thus regular physical activity:
• Ameliorates the effects of age and chronic disease (including CHD) • Reduces BP in mild hypertension • Reduces risk of cardiac arrhythmias and possibly of sudden death
• Ameliorates the effects of age and chronic disease on reserve capacity for exercise, increasing endurance and reducing fatigue • Reduces risk of injury • Ameliorates the effects of muscle disease • Reduces risk of injury, especially with age, and muscle disease
• ‘Prevents’ osteoporosis and fractures • Avoids limitation of movement • Limits effects of degenerative arthritis • • • •
‘Prevents’ obesity-related disease and excessive weight gain Improves carbohydrate tolerance ameliorates late-onset diabetes ‘Prevents’ coronary heart disease Counters acute precipitants of ‘heart attack’
• • • • •
Reduces mild anxiety and depression Influences mood favourably Contributes to the quality of care for the mentally handicapped Can improve memory in the elderly Can ameliorate stress-related conditions
sive regarding the relationship between physical activity and stroke. The level of decreased risk of coronary heart disease attributable to regular physical activity is similar to that of other lifestyle factors, such as keeping free from cigarette smoking. Regular physical activity prevents or delays the development of high blood pressure in people with hypertension. Comment: The population attributable risk due to physical inactivity, as assessed on the basis of the size of the risk and the prevalence of this risk factor in the population, is e.g., in the Finnish population greater due to physical inactivity than to smoking, high cholesterol level, high blood pressure or over-
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weight [8]. Regular physical activity seems to reduce also the incidence of ischemic heart disease [9,10] as well as the case fatality in myocardial infarction [10]. Generally there is a dose–response relationship between the indices of cardiovascular diseases or their risk factors and the amount or intensity of physical activity. Some of these relationships seem to be non-linear, suggesting that the greatest benefits are attained by being or becoming at least moderately active instead of being sedentary. However, many aspects of the dose–response issues are unsettled [11]. The evidence for the preventive effect of physical activity on stroke was not found to be convincing in the Surgeon General’s report, but this evidence seems to be increasing regarding both men and women [12–16]. Several biologically plausible mechanisms can explain the association between level of physical activity and risk of stroke [17]. The risk of developing hypertension is found to be about 30% higher in the least active men or women as compared with their most active counterparts. Regular exercise training decreases normal systolic and diastolic blood pressure on average by 3 mmHg, slightly elevated pressures by 6 / 7 mmHg, and hypertensive pressures by 10 / 8 mmHg, respectively. The effect of exercise in hypertensive patients is about the same size as that attained by any of the commonly used drugs. Moderately intense, frequent activity seems to be at least as effective as vigorous activity.
physical activity. Plausible biological mechanisms for the risk-reducing effect of physical activity regarding colon cancer [4] and breast cancer [21] have been proposed. Epidemiological evidence, as well as the proposed mechanisms, suggest that the protective effect of activity against these cancers is related mainly to frequent, endurance-type activity.
3.5. Non-insulin-dependent diabetes mellitus ( NIDDM) Regular physical activity lowers the risk of developing non-insulin-dependent diabetes mellitus. Comment: New results from cross-sectional studies on elderly men [22] and male endurance athletes [23], and from prospective studies on middle-aged Japanese-Americans [24,25], British men [26] and American male physicians [27] support the conclusion of the risk-reducing effect of physical activity against NIDDM. The risk-decreasing effect of physical activity is greatest in subjects with high risk of NIDDM. The size of the effect seems to be 20–60%, it seems to be dose dependent, and due to predominantly aerobic, moderate to vigorous activity. However, resistance training has also been shown to cause beneficial effects on disturbed glucose and insulin metabolism [28,29]. Therefore, the combination of endurance and resistance exercise can be recommended as part of treatment of patients with NIDDM.
3.6. Osteoarthritis 3.4. Cancer Regular physical activity is associated with a decreased risk of colon cancer. There is no association between physical activity and rectal cancer. Data are too sparse to draw conclusions regarding a relationship between physical activity and endometrial, ovarian, or testicular cancers. Data are inconsistent regarding an association between physical activity and breast or prostate cancers. Comment: The risk of colon cancer in physically active subjects is found to be 20–50% lower than in sedentary subjects in most studies, but the results are variable. Some recent studies show additional supporting evidence of reduced risk of breast cancer [18,19] and prostate cancer [20] associated with
Regular physical activity is necessary for maintaining normal muscle strength, joint structure, and joint function. In the range recommended for health, physical activity is not associated with joint damage or development of osteoarthritis and may be beneficial for many people with arthritis. Competitive athletics may be associated with the development of osteoarthritis later in life, but sports-related injuries are the likely cause. Comment: It seems that ordinary weight-bearing activities such as walking done on a daily basis are sufficient to maintain normal joint structure. In order to counteract the decrease of muscle mass and increased stiffness the importance of more variable and joint-specific activities, e.g., calisthenics, in-
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creases with age. Several short-term studies have indicated that regular moderate-exercise programs of either aerobic or resistance type, relieve symptoms and improve function among people with both osteoarthritis and rheumatoid arthritis [4].
3.7. Osteoporosis Weight-bearing physical activity is essential for normal skeletal development during childhood and adolescence and for achieving and maintaining peak bone mass in young adults. It is unclear whether resistance- or endurance-type physical activity can reduce the accelerated rate of bone loss in postmenopausal women in the absence of estrogen replacement therapy. Comment: Osteoporosis leads to bone fragility and consequently to increased risk of fractures due to decreased bone mass and deteriorated microarchitecture. The criterion for osteoporosis in women is bone mineral density (BMD) 2.5 standard deviations (25– 35%) or more below the average value of young adult women. This degree of decrease of BMD in the hip increases the risk of fracture at that site by a factor of about six. About one-third of 70–79-yearold and about one-half of 80-year-old or older white American women have lost at least 25% of their femoral bone mass [30]. Physical activity, through its load-bearing effect on the skeleton, is likely the single most important influence on bone density and architecture [31]. At young age, especially during the pubescent years, physical activity can increase BMD substantially [32]. In athletes, BMD of the loaded sites can be more than 30% higher than that of the contralateral non-loaded site. In non-athletic populations, physical activity, which is feasible for large numbers of children, adolescents and young adults, increases BMD by 7–8% on average, as compared with sedentary subjects [33]. If this difference is maintained until old age it is likely to decrease the risk of osteoporotic fractures. In later life, physical activity helps to maintain or even to slightly increase the bone mass [34]. Currently, still inconclusive knowledge suggests that bone formation is stimulated by activity that produces microscopic, transient structural changes or strains in the bone. These strains are induced effec-
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tively by rapid, forceful, versatile movements causing slight shocks or impulses in the bone. These types of movement are characteristic, e.g., in rapid racket games, such as squash, and in certain types of aerobics. When the bones get weaker, the strains can be caused by smaller forces and consequently even fast walking in variable terrain may be effective in counteracting bone weakening in older persons [35]. Physical activity and hormone replacement therapy seem to have additive effects on bone mineral density in older women [36].
3.8. Falling There is promising evidence that strength training and other forms of exercise in older adults preserve the ability to maintain independent living status and reduce the risk of falling. Comment: Recent findings suggest that, at least in independently living older people, the exponential increase in the incidence of hip fractures is explained only to a limited extent by the decrease in bone density associated with age [37]. This observation suggests that other risk factors for hip fractures, such as falling, make a major contribution to the risk. Many of the risk factors for falls such as lower extremity muscle strength, balance, reaction time, coordination, and gait can be influenced positively and to a significant degree by general and specific physical activities [4,34,35,38]. Physical activity may be a particularly promising preventive measure for hip fractures [39]. This finding deserves attention because about one-quarter of hip fractures occurred in independently living old individuals, and men had about the same risk of hip fracture 5 years later than women [37].
3.9. Low back pain The Surgeon General’s Report does not take a position on the role of physical activity in the primary or secondary prevention of mechanical low back pain or neck and shoulder pain. Current evidence on the effect of physical activity in primary prevention of mechanical low back pain suggests that exercises that strengthen the lower body muscles and improve aerobic fitness have a slight preventive effect [35,40]. The data on the
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effects of physical activity in the treatment of acute or subacute low back pain are insufficient for definite conclusions [41,42]. It seems, however, that both strenuous exercises and total lack of activity increase the symptoms and their duration, while early ambulation [43] and gradually increasing exercise that strengthens musculature and improves endurance, mobility, posture, or overall fitness may be beneficial as part of the treatment and rehabilitation of subacute and chronic low back pain [35]. However, there is little consensus regarding the specific goals or content of exercise programs for either primary or secondary prevention of low back pain [44], and part of the exercise-related effects are likely to be nonspecific or indirect [45]. Because mechanical low back pain episodes are very common in the population, there is a great need to find out the real role of physical activity in the prevention and treatment of this condition.
3.10. Neck and shoulder pain The majority of neck and shoulder pain cases is due to cervical muscle tension, but the exact mechanism of the symptoms is unknown [46]. Practical experience supports the idea that increased muscle strength, endurance, or improved muscle relaxation would be helpful in the prevention and treatment of this condition. The results of the few scientifically valid assessments of the effectiveness of exercise programs on the stiff-neck syndrome have been partly promising [46–48], but low-intensity exercise programs have not resulted in improvement [49,50]. Here again, the real role of exercise for prevention and treatment of neck and shoulder pain should be thoroughly evaluated, because the incidence and prevalence of this ailment is high and increasing.
many serious biological diseases, and psychological and social problems [51]. However, the health consequences of overweight (body mass index 29.0– 29.9 (weight in kilograms divided by the square of the height in meters) should not be over-emphasized [52]. It has become clear from hundreds of studies that without regular physical activity, weight control can usually not be achieved [52]. Because all physical activity increases energy expenditure, it is important to choose physically active alternatives in daily life whenever feasible. Maintenance of muscle mass by strength-requiring activity increases in importance with aging.
3.12. Functional capacity Functional capacity is an integrated function of a large number of capabilities, including basic physical and mental tasks, such as walking or reading a standard text. Even simple functional capabilities require input from many organ systems, and they are influenced by various individual and environmental factors. Physical activity influences favorably many elements of functional capabilities (see Table 1). Many of these effects are unique products of physical activity and cannot be compensated by other means. Also, many functional abilities themselves are influenced positively by physical activity [53–56]. These effects are very important in the maintenance of adequate fitness for daily tasks in aging individuals and indicate the great potential of physical activity as a means to contribute to their quality of life.
3.13. Mental health and health-related quality of life
3.11. Obesity Low levels of activity, resulting in fewer kilocalories used than consumed, contribute to the high prevalence of obesity (in the United States). Physical activity may favorably affect body fat distribution. Comment: Obesity is one of the most prevalent health problems in industrialized countries and is increasing. The significance of obesity is accentuated by the fact that it is a potent risk factor or cause of
Physical activity appears to relieve symptoms of depression and anxiety, and to improve mood. Regular physical activity may reduce the risk of developing depression, although further research is needed on this topic. Physical activity appears to improve health-related quality of life by enhancing psychological well-being (e.g., self-concept, self-esteem, mood, and affect) and by improving physical functioning, especially in persons compromised by poor health.
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Comment: The effects of physical activity on mental health and psychological well-being are less thoroughly studied than those related to biological health. They appear to depend strongly on individual and circumstantial factors, and thus they are less predictable than the biological effects. Thus, beneficial activities on individual level are currently to a large extent a matter of personal experimentation. At least in older adults, involvement in physical activity may increase the psychological well-being independently of changes in cardiorespiratory fitness.
3.14. Adverse effects Most musculoskeletal injuries related to physical activity are believed to be preventable by gradually working up to a desired level of activity and by avoiding excessive amounts of activity. Serious cardiovascular events can occur with physical exertion, but the net effect of regular physical activity is a lower risk of mortality from cardiovascular disease. Comment: The risk of injuries related to acute exercise is considerable in sport disciplines that require speed and power and include body contacts, e.g., team ball games. In typical keep-fit activities, such as in walking, jogging, swimming, cross-country skiing and callisthenics, the risk is low, tens of times smaller than in the high-risk sports [57]. In aerobic exercisers, overuse injuries can be frequent, if the total amount or the frequency of the activity is high. The risk of cardiovascular complications, mainly sudden death or myocardial infarction, is low. These events occur practically only in individuals with latent or overt cardiovascular disease [58]. The risk is increased with increasing intensity of the activity, and it is much higher in individuals who are unaccustomed to exercise compared to accustomed persons. Thus, all complications of physical activity can be kept low by exercising sensibly.
3.15. Generalizability of the health benefits of physical activity Most data on the health benefits of physical activity are based on young and middle-aged white middle-class males. An obvious exception is the studies on bone density, most of which have been done on female subjects. Although there are age and sex differences in the responses to physical activity,
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cumulating evidence suggests that most of the effects can be seen in both sexes and within a wide age range. It is especially important that both physiological and protective effects [55] can also be seen in elderly subjects.
3.16. Characteristics of activity necessary for health benefits Aerobic or endurance activities have been traditionally considered as the most beneficial in terms of health. In recent years resistance or strength-requiring activities have been given increasing emphasis. The widest spectrum of health benefits can obviously be gained by a combination of aerobic and resistance activities. However, many aerobic exercise modalities, such as walking and cycling, are not effective in influencing bone density, movement coordination and balance that are important to reduce the risk of fractures. For these purposes different types of exercises are needed. In general it should be emphasized that substantial physiological or preventive effects can be gained by activity that is frequent but moderate, both in total amount and in intensity. Further, effective health-enhancing activities do not require high level of skills nor specialized equipment or sites for practice. These characteristics make health-enhancing physical activities feasible and safe for a large proportion of the population, as the Surgeon General’s Report concludes: ‘‘Significant health benefits can be obtained by including a moderate amount of physical activity (e.g., 30 min of brisk walking or raking leaves, 15 min of running, or 45 min of playing volleyball) on most, if not all, days of the week. Through a modest increase in daily activity, most individuals in industrialized countries can improve their health and quality of life. Additional health benefits can be gained through greater amounts of physical activity. People who can maintain a regular regimen of activity that is of long duration or of vigorous intensity are likely to derive greater benefits’’.
4. Conclusions The health potential of physical activity is substantial on the following grounds: (1) the spectrum of health benefits is large; (2) the size of the effects
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varies from slight to moderate, even to large, and part of the effects cannot be gained by any other means; (3) the number and prevalence of health conditions that are related to sedentariness or amenable to improvement by physical activity is high; (4) the prevalence of inactivity in many populations is high; (5) most physical activities that are effective in enhancing health are feasible, safe and inexpensive for the majority of many populations. On these grounds it is justified, and even the responsibility of the society in industrialized countries, to promote health-enhancing physical activity. One part of physical activity promotion should be the development and use of effective and ethically sound methods for individual and group counselling.
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