In 1985, national survey data revealed that 56% of men and 61% of women in the U.S. either never engaged in physical activity or did so on an irregular basis.¹ Surveillance data from 1991 suggests the prevalence of sedentary lifestyle (58% overall) has not changed.² Coronary heart disease (CHD), the predominant risk associated with a sedentary lifestyle, is the leading cause of mortality in the U.S.³ In the sedentary, an estimated 35% of the excess CHD could be eliminated by becoming more physically active.⁴ The excess CHD risk attributable to sedentary lifestyle, and the societal costs of this excess risk, are higher than those attributed individually to obesity, hypertension, and smoking.^4,5 The total burden of suffering attributable to sedentary lifestyle in the U.S. is unknown but is probably large.

Evidence exists that physical activity and fitness reduce morbidity and mortality for at least six chronic conditions: coronary heart disease, hypertension, obesity, diabetes, osteoporosis, and mental health disorders. Evidence linking sedentary lifestyle with other conditions exists but is not reviewed here.^6-9 Moderate physical activity comprises activities that can be comfortably sustained for at least 60 minutes (e.g., walking, slow biking, raking leaves, cleaning windows, light restaurant work). Vigorous activity describes those of an intensity sufficient to result in fatigue within 20 minutes (e.g., shoveling snow).¹⁰

Coronary Heart Disease

There are no prospective intervention trials of physical activity for the primary prevention of CHD. Evidence from cohort studies, however, has shown a consistent association between physical activity and reduced incidence of CHD.^9,11-15 A relative risk of death from CHD of 1.9 (95% confidence interval, 1.6 to 2.2) for sedentary persons compared with the physically active was calculated in a meta-analysis of studies on primary prevention of CHD.¹¹ A relative risk of 1.9 was also reported in an earlier comprehensive review.¹² In a cohort of men, beginning moderately vigorous sports activity was associated with a 41% lower risk of death from CHD, which was comparable to the risk reduction associated with smoking cessation (44%).¹⁵ In another cohort study, initially unfit men who subsequently became fit had a 52% reduction in cardiovascular disease mortality compared with those who remained unfit.¹⁶ The absolute reduction in the age-adjusted death rate from cardiovascular disease was 34/10,000 man-years. Similar benefits from exercise have been reported in older men.^14,17 Physiologically, the response to physical activity in women appears similar to that in men.¹⁸ Epidemiologic data sufficient to confirm a primary preventive role of physical activity for CHD in women are not yet available, however.^9,19

One reason that those who are physically active may be at decreased risk for CHD is self-selection — persons who choose to exercise may be healthier and have fewer overall risk factors for CHD. Studies controlling for such confounding variables, however, have found that the effects of exercise are independent of other CHD risk factors, and that the cardiovascular benefits may even be augmented in the presence of other risk factors for CHD.^9,15,20 Moreover, the type of individual who adopts athletic behavior is not protected from CHD if regular exercise is discontinued (e.g., college athletes who are sedentary later in adult life).²¹

Although observational data cannot prove causal associations, the strength, consistency, and coherence of the evidence and presence of a biologic gradient, clearly suggest that both physical activity and fitness influence risk for CHD. Inference of a causal relationship between increased physical activity and decreased CHD is supported by demonstrated physiologic effects which suggest plausible biologic mechanisms (e.g., enhanced fibrinolysis, decreased platelet adhesiveness, improved lipoprotein profile, and lessened adrenergic response to stress).^8,22

Hypertension

Cohort studies suggest that physically inactive persons have a 35-52% greater risk of developing hypertension than those who exercise, independent of other risk factors for hypertension.^23,24 A graded inverse relationship between increasing fitness quartile and blood pressure was noted in a large cohort.²⁵ Randomized controlled trials of primary prevention of hypertension to date, however, have been either nonspecific (i.e., exercise grouped together with diet and weight loss)^26,27 or limited in sample size. Inconsistencies in results between studies of secondary prevention^28,29 suggest that certain subsets of individuals (e.g., women and individuals with diastolic elevations) may be more responsive to the blood pressure-lowering effects of physical activity than others.^31,32 A meta-analysis of controlled longitudinal studies found a weighted net drop in systolic over diastolic blood pressure with endurance training of 3/3, 6/7, and 10/8 mm Hg in normotensive, borderline, and hypertensive subjects, respectively.³² A similar effect on blood pressure appears across ages 15-80 years,^33,34 in different social groups, and in both men and women.³⁰ Low- to moderate-intensity endurance training or circuit weight training may be at least as effective in lowering blood pressure as are high-intensity endurance training and resistance training primarily for muscle strength.^22,32,35,36 A sigmoidal relationship between physical activity and blood pressure benefit may exist, and the threshold of activity necessary for significant effect may be lower than that necessary for cardiovascular fitness or improvement in lipid profile.³¹ A possible mechanism is the attenuation of elevated sympathetic nervous system activity from hyperinsulinemia via the effects of exercise.^32,37

Obesity

Data from prospective population studies suggest an increased risk for the development of significant weight gain for persons in lower leisure-time physical activity categories compared to those in higher physical activity categories.^38-40 Experimental data on secondary prevention of obesity confirm such a relationship.^40,41 Physical activity can influence the development of obesity (e.g., assist in long-term maintenance of isocaloric or balanced energy state) and increase the chances of success in initial and long-term weight loss.⁴⁰ This influence stems from increased total energy output, preservation of lean body mass, changes in substrate utilization and fat distribution, and possible reversal of diet-induced suppression of basal metabolic rate, as well as psychologic reinforcement.^9,42-44 An association between low levels of leisure time physical activity and insulin resistance with resultant hyperinsulinemia may link obesity (especially abdominal) with hypertension, hyperlipidemia, and CHD in some individuals.^37,45 Morbidity and mortality in prospective cohort data have been lower in overweight individuals who are physically active even if they remain overweight.^{9,22,40,46,47} Normalization of the metabolic profile (e.g., glucose tolerance, insulin, lipids) is a plausible mechanism for such a decrease in morbidity and mortality.⁴⁸

Non-Insulin-Dependent Diabetes Mellitus

Prospective cohort data reveal an inverse relationship between the level of physical activity and the risk of developing non-insulin-dependent diabetes mellitus (NIDDM).^49-51 This effect is pronounced among overweight men,⁴⁹ but it is also seen in women.⁵⁰ The age-adjusted risk of NIDDM is reduced by 6% for each 500-kcal increment in energy expenditure per week.⁵¹ The protective effect of physical activity is especially pronounced in persons at highest risk for NIDDM (i.e., those with positive family history, obesity, or hypertension).⁵¹ In one cohort study, cardiopulmonary fitness appeared to attenuate mortality at each level of glycemic control.⁵² Possible mechanisms for these primary and secondary preventive effects are reviewed elsewhere,^22,53 but decreased insulin resistance seems to play an important role. Both the onset of positive effects of physical activity on glycemic control and the loss of these effects upon its discontinuation are rapid.^53-55

Osteoporosis

Nonrandomized controlled interventional data,^56-58 confirmed by limited randomized controlled trial data,⁵⁹ support earlier studies suggesting that postmenopausal women can retard bone loss through physical activity.⁶⁰ Cross-sectional studies examining exercise history⁶¹ and fitness level⁶² reveal higher bone mass in the more active and fit, respectively. Some prospective data,^63,64 along with cross-sectional data comparing the bone density of athletic women with that of nonathletic premenopausal women,^60,61 suggest that physical activity can also reduce the rate of bone loss in premenopausal women with a normal hormonal milieu.

Direct evidence that physical activity reduces the incidence of hip fractures includes a recent large case-control study.⁶⁵ This study found a reduction in the risk of hip fracture in women who were active in the past, as well as in those with recent moderate activity.⁶⁵ Prior studies focused on recent activity⁶⁶ or were cross-sectional in study design.⁶⁷ A plausible biologic mechanism is suggested by a large cohort study that substantiated an inverse relationship between bone mineral density and hip fractures.^68,69 Some studies have suggested that skeletal loads generating muscle pull or resistance rather than gravity or weight bearing alone may provide greater benefit to bone mineral density.^63,70 Inconsistencies in the literature exist, however.⁷¹ Important questions remain unanswered, such as the role and relative impact of physical activity with respect to estrogen replacement. Furthermore, the percentage of variance in bone mineral density attribut-able to differences in activity is thought to be modest (20%) compared with the genetic contribution.⁷⁰

Mental Health Disorders

Some consistent findings have emerged from controlled trials assessing problems with affect, such as depression and anxiety, before and after various forms of physical activity. First, improvements are greatest in those who are more depressed and more anxious at the onset of the study.^72,73 Second, improved cardiovascular fitness is not necessary for mood enhancement.⁷⁴ Third, several recent studies have shown diminished gain at high intensity compared to moderate intensity physical activity.^75-77 Prospective cohort data suggest physical activity also has a preventive effect.⁷⁸ Study methodologies to date may lack the sensitivity to detect decreased prevalence in those without preexisting affect disorders, however.^77,79-81 Healthy individuals may derive a preventive effect from physical activity, while those with mild to moderate affect disorders derive a therapeutic benefit.^73,82

General well-being can apparently be enhanced with physical activity.^73,80 Research on self-esteem and physical activity has been criticized as being overly simplistic.⁸³ A more complex model was postulated, giving rise to several new terms that may be considered dimensions of self-esteem, e.g., self-efficacy (capacity to produce a desired effect), self-acceptance, self-concept, physical competence.^82,83 Exercise-induced increases in self-efficacy may have an important role in successful maintenance of physical activity habits.⁸⁴ Study results are mixed as to whether aerobic or anaerobic exercise imparts a greater increase in these components of self-esteem.^85-87 Furthermore, the relative importance of perceived improvements in areas of life not quantified by standard psychometric batteries (e.g., sleep patterns, sex life) remains to be determined.⁸⁸ Cognition does not appear to be improved significantly with physical activity.^82,89 Mechanisms for psychologic benefit remain undefined,^90,91 and the role of beta-endorphins requires further study.^92,93

Quantity and Intensity of Physical Activities

To improve cardiovascular fitness, exercise cannot be performed occasionally or seasonally,⁹⁴ nor can one expect protection from CHD simply by having exercised regularly in the past.²¹ Beginning moderately vigorous physical activity during adulthood, however, may reduce the risk of CHD to the level of those who have been active for many years.¹⁵ Among previously unfit men, achieving fitness, which requires regular physical activity, substantially reduces the risk of both all-cause and cardiovascular disease mortality.¹⁶ In a recent cohort study, participating in increasing levels of vigorous activity was associated with decreasing total mortality in a graded relationship.⁹⁵ Clearly, regular vigorous physical activity sufficient to achieve physical fitness is associated with important health benefits.

While regular vigorous physical activity is likely to be most beneficial, prior recommendations for developing and maintaining cardiorespiratory fitness⁹⁶ may inadequately address the potential benefits of low to moderate levels of physical activity and subsequent risk factor modification, particularly for unfit and sedentary individuals. Moderate physical activities have higher compliance rates than vigorous exercise activities, mesh better with daily lifestyle, and are well maintained over time.^9,97,98 Studies with at least three levels of physical activity exposure uniformly reveal a reduction in CHD risk from the lowest to the next-to-lowest activity level.¹² It is not that more modest amounts of physical activity will provide the maximum reduction in CHD risk, but rather that those at greatest risk (i.e., the sedentary and least fit) may derive substantial benefits from initiating even some activity.^8,99 No clear minimal intensity of physical activity required for benefit has been defined. Intensity can convey an absolute or relative amount (e.g., what might be low intensity to one might be high intensity to another).⁹⁹ A linear dose-response relationship (except for the most vigorous levels or more than 3,000 kcal/week) seems to exist between physical activity and health (both lower incidence of disease and improved functional capability).⁸ Modifications in the physical activity message may be required to accommodate those with differing interests, limitations, or cultural milieu as well as those with disability¹⁰⁰ (especially when mobility is reduced).

A trial of middle-aged men compared the training effect of 30 minutes of moderate physical activity with three 10-minute bouts per day of equivalent activity separated by at least 4 hours. Over an 8-week study period, both groups achieved similar results.¹⁰¹ Also, cohort studies of physical activity exposure have assessed the amounts of activity performed per day and time devoted per week, not duration of specific workouts, and achieved significant results.^15,47 Thus, attention to total energy expenditure per day and per week is warranted.⁸ How the expenditure is accumulated is secondary and dependent more on personal preference, musculoskeletal tolerance, and available facilities.

Potential Adverse Effects of Physical Activity

The benefits of physical activity must be weighed against its potential adverse effects, which include injury, osteoarthritis, myocardial infarction, and, rarely, sudden death. Data remain scarce on the incidence of injury during most noncompetitive physical activity.¹⁰² One exception is running, with an annual risk of injury of 35-65% risk is positively related to the level of exposure to the activity and to prior injury.¹⁰² Aerobic dance participation also carries a relatively high risk, which increases with the frequency of classes.¹⁰² One trial randomly assigned 70-79-year-old men and women to strength training, walk/jog, or control groups. Injury rates were 8.7% for the strength training group during the full 26 weeks, 4.8% for the walk group during weeks 1-13, and 57% for those who jogged during weeks 14-26 and had walked during the first 14 weeks.¹⁰³ In cohort data, physical activity in men and women was also associated with an increased risk of orthopedic problems.¹⁰⁴ Most exercise-induced injuries are preventable. They often occur as a result of excessive levels of physical activity, sudden dramatic increases in activity level (especially in persons with poor baseline fitness), and improper exercise techniques or equipment. Intense exercise training can also result in the interruption of menstrual function, bone loss (partly reversible), and an increased fracture risk.^70,71

Long-term physical activity probably does not accelerate the development of osteoarthritis (OA) in major weight-bearing joints (e.g., hips, knees). Case-control data revealed no significant difference in knee OA among groups with varying leisure-time physical activity OA patients were significantly more likely to have been obese at 20 years of age or had prior knee injury.¹⁰⁵ In a 5-year longitudinal cohort with a mean age of 63, runners were matched with controls and followed radiographically and clinically acceleration of OA in runners was not found.¹⁰⁶ Graduated activity that allows cartilage adaptation is less likely to induce OA than painful or mechanically improper motion that places infrequent but excessive stress on joints.¹⁰⁷ Available data suggest that moderate physical activity performed within the limits of comfort while putting joints through normal motions will not, in the absence of joint abnormality, inevitably lead to joint injury.¹⁰⁸

Adverse cardiovascular events are perhaps the greatest concern about vigorous exercise. Two recent large studies provide estimates of the relative risk of triggering myocardial infarctions within 1 hour of heavy physical activity compared with less strenuous or no exertion. These relative risks are 2.1 (95% confidence interval, 1.6 to 3.1)¹⁰⁹ and 5.9 (4.6-7.7),¹¹⁰ respectively. A protective effect was seen with regular physical activity in both studies, however. As the frequency of exercise per week increased, the relative risk of infarction during vigorous activity dropped.^109,110 The risk of sudden death is known to be increased during vigorous physical activity.¹¹¹ This risk appears greater in sedentary persons who engage in vigorous activity as compared to those who are habitually active.¹¹² In those over 35 years of age, more than 80% of sudden deaths during or shortly after exercise are from CHD.¹¹³ Exercise as a cause of sudden cardiac death was reviewed recently.¹¹⁴ The overall risk of sudden death is lower, however, for those who are habitually active, despite the transient increase in risk during the actual physical activity, when compared with sedentary counterparts.^112,113 

The rationale and evidence for effectiveness of physical activity counseling have been reviewed.⁶⁰ Prior studies that have demonstrated benefits from counseling provide little information about long-term compliance and are of limited generalizability, because the form of counseling, delivery (e.g., inclusion of community health promotion¹¹⁵) type of patients, or clinical setting have not been representative of typical primary care clinician counseling of healthy patients. A recent randomized controlled trial contained similar limitations the frequency of physical activity was not significantly increased and follow-up was limited to 1 month.¹¹⁶ A nonrandomized controlled trial of brief physician counseling plus one brief follow-up phone call demonstrated significant increases in both self-reported and objectively measured (using an electronic monitor) physical activity there were important study limitations, however, including self-selection to the intervention group, use of patient volunteers, and follow-up of only 4-6 weeks.¹¹⁷ A multicenter cohort study using pre- and postintervention surveys to assess changes in several behaviors over 1 year did find an increase in beginning regular physical activity.¹¹⁸ Thus, sufficient published evidence concerning the efficacy of physical activity counseling is lacking. 

The American College of Sports Medicine and the Centers for Disease Control and Prevention recommend that every adult accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week.¹¹⁹ The American Heart Association¹²⁰ and the American Academy of Family Physicians (AAFP)¹²¹ recommend that physicians counsel patients in selecting an exercise program and promote regular exercise. The policy of the AAFP is currently under review. The American College of Obstetricians and Gynecologists has issued guidelines on counseling women about regular exercise.¹²² The Canadian Task Force on the Periodic Health Examination (CTF) recommends that moderate-level physical activity be performed consistently to accumulate 30 minutes or more most days of the week.¹²³ The CTF found insufficient evidence to recommend for or against including physical activity counseling in the periodic health examination.

The American Academy of Pediatrics recommends teaching the importance of regular, moderate to vigorous physical activity as a way to prevent illness in adult life, and encouraging parents to serve as role models by participating in regular physical activity.¹²⁴ The Bright Futures guidelines recommend that children and adolescents participate in regular physical activity, and that parents encourage such activity.¹²⁵ The American Medical Association recommends that all adolescents receive annual guidance about the benefits of exercise and encouragement to engage in safe exercise on a regular basis.¹²⁶ 

Direct evidence is limited that clinician counseling can increase the physical activity of asymptomatic patients, but other considerations warrant devoting time to this intervention. First, given the sizable independent relative risk for impaired health in sedentary individuals together with the large population at risk,⁸ even modest increases in physical activity levels could have great public health impact.¹²⁷ Second, consideration of the total societal cost⁴ associated with the sedentary lifestyle and its disproportionate burden¹²⁸ is also relevant. Third, the success of counseling in other settings and for other behavioral risk factors deserves consideration.⁶⁰ Clinician counseling may reinforce several other important interventions (e.g., school-based emphasis on lifelong activity patterns, reduction of barriers to physical activity at work and in the community) that can change sedentary behavior. 

Counseling to promote regular physical activity is recommended for all children and adults. This recommendation is based on the proven efficacy of regular physical activity in reducing the risk for coronary heart disease, hypertension, obesity, and diabetes ("A" recommendation), although there is currently insufficient evidence that counseling asymptomatic primary care patients to incorporate physical activity into their daily routines will have a positive effect on their behavior ("C" recommendation). Clinicians should determine each patient's activity level, ascertain barriers specific to that individual, and provide information on the role of physical activity in disease prevention. The clinician may then assist the patient in selecting appropriate types of physical activity. Factors that should be considered include medical limitations and activity characteristics that both improve health (e.g., increased caloric expenditure, enhanced cardiovascular fitness, low potential adverse effects) and enhance compliance (e.g., low perceived exertion, minimal cost, and convenience).

An emphasis on regular, moderate-intensity physical activity rather than on vigorous exercise is reasonable in sedentary persons. This emphasis encourages a variety of self-directed, moderate-level physical activities (e.g., walking or cycling to work, taking the stairs, raking leaves, mowing the lawn with a power mower, cycling for pleasure, swimming, racket sports)¹¹⁹ that can be more easily incorporated into an individual's daily routine. An appropriate short-term goal is activity that is a small increase over current levels. Over a period of several months, progression to a level of activity that achieves cardiovascular fitness (e.g., 30 minutes of brisk walking most days of the week) would be ideal. Development and maintenance of muscular strength and joint flexibility is also desirable. Sporadic exercise, especially if extremely vigorous in an otherwise sedentary individual, should be discouraged in favor of moderate-level activities performed consistently.

The draft update of this chapter was prepared for the U.S. Preventive Services Task Force by John Burress, MD, MPH, David Christiani, MD, MPH, and Donald M. Berwick, MD, MPP. 

1. Caspersen CJ, Christenson GM, Pollard RA. Status of 1990 physical fitness and exercise objectives: evidence from NHIS 1985. Public Health Rep. 1986;101:587–592. [PMC free article] [PubMed]
2. Centers for Disease Control and Prevention. Prevalence of sedentary lifestyle—behavioral risk factor surveillance system, United States, 1991. MMWR. 1993;42:576–579. [PubMed]
3. Kochanek KD, Hudson BL. Hyattsville, MD; 1994. Advance report of final mortality statistics, 1992. Monthly vital statistics report; vol. 43 no 6 (suppl).
4. Centers for Disease Control and Prevention. Public health focus: physical activity and the prevention of coronary heart disease. MMWR. 1993;42:669–672. [PubMed]
5. Hahn RA, Teutsch SM, et al. Excess deaths from nine chronic diseases in the U.S., 1986. JAMA. 1990;264:2654–2659. [PubMed]
6. Bouchard C, Shepard RJ, Stephens T, eds. Champaign, IL; 1994. Physical activity, fitness, and health.
7. Lee IM. Physical activity, fitness, and cancer. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
8. Blair SN, Kohl HW, Gordon NF. How much physical activity is good for health? Annu Rev Public Health. 1992;13:99–126. [PubMed]
9. Blair SN, Kohl HW, Paffenbarger RS Jr, et al. Physical fitness and all-cause mortality: a prospective study of healthy men and women. JAMA. 1989;262:2395–2401. [PubMed]
10. American College of Sports Medicine. Guidelines for exercise testing and prescription. Philadelphia: Lea & Febiger, 1991.
11. Berlin JA, Colditz GA.A meta-analysis of physical activity in the prevention of coronary heart disease. Am J Epidemiol. 1990;132:612–628. [PubMed]
12. Powell KE, Thompson PD, Caspersen CJ, et al. Physical activity and the incidence of coronary heart disease. Annu Rev Public Health. 1987;8:253–287. [PubMed]
13. Leon AS, Connett J. Physical activity and 10.5 year mortality in the Multiple Risk Factor Intervention Trial (MRFIT). Int J Epidemiol. 1991;20:690–695. [PubMed]
14. Donahue RP, Abbott RD, Reed DM, et al. Physical activity and coronary heart disease in middle-aged and elderly men: the Honolulu Heart Program. Am J Public Health. 1988;78:683–685. [PMC free article] [PubMed]
15. Paffenbarger RS Jr, Hyde RT, Wing AL, et al. The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. N Engl J Med. 1993;328:538–545. [PubMed]
16. Blair SN, Kohl HW III, Barlow CE, et al. Changes in physical fitness and all-cause mortality: a prospective study of healthy and unhealthy men. JAMA. 1995;273:1093–1098. [PubMed]
17. Morris JN, Pollard R, Everitt MG, et al. Vigorous exercise in leisure-time: protection against coronary events. Lancet. 1980;2:1207–1210. [PubMed]
18. Mitchell JH, Tate C, Raven P, et al. Acute response and chronic adaptation to exercise in women. Med Sci Sports Exerc. 1992;24:S258–S265. [PubMed]
19. Douglas PS, Clarkson TB, et al. Exercise and atherosclerotic heart disease in women. Med Sci Sports Exerc. 1992;24:S266–S275. [PubMed]
20. Siscovick DS, Weiss NS, Fletcher RH, et al. Habitual exercise and primary cardiac arrest: effect of other risk factors on the relationship. J Chronic Dis. 1984;37:625–631. [PubMed]
21. Paffenbarger RS Jr, Hyde RT, Wing AL. A natural history of athleticism and cardiovascular health. JAMA. 1984;252:491–495. [PubMed]]
22. Haskell WL, Leon AS, Caspersen CJ, et al. Cardiovascular benefits and assessment of physical activity and physical fitness in adults. Med Sci Sports Exerc. 1992;24:S201–S220. [PubMed]
23. Paffenbarger RS Jr, Thorne MC, et al. Physical activity and incidence of hypertension in college alumni. Am J Epidemiol. 1983;117:245–257. [PubMed]
24. Blair SN, Goodyear NN, et al. Physical fitness and incidence of hypertension in healthy normotensive men and women. JAMA. 1984;252:487–490. [PubMed]
25. Ekelund LG, Haskell WA, et al. Physical fitness as a predictor of cardiovascular mortality in asymptomatic North American men. The Lipid Research Clinics mortality follow-up study. N Engl J Med. 1988;319:1379–1384. [PubMed]
26. Hypertension Prevention Collaborative Research Group. The effects of nonpharmacologic interventions on blood pressure of persons with high normal levels. JAMA. 1992;267:1213–1220. [PubMed]
27. Stamler R, Stamler J, Gosch CF, et al. Primary prevention of hypertension by nutritional-hygienic means: final report of a randomized clinical trial. JAMA. 1989;262:1801–1807. [PubMed]
28. Gordon NF, Scott CB, et al. Exercise and mild essential hypertension: recommendations for adults. Sports Med. 1990;10:390–404. [PubMed]
29. Blumenthal JA, Siegel WC, Appelbaum M. Failure of exercise to reduce blood pressure in patients with mild hypertension: results of a randomized controlled trial. JAMA. 1991;266:2098–2104. [PubMed]
30. Deleted in proof.
31. Jennings GL, Deakin G, et al. What is the dose-response relationship between exercise training and blood pressure? Ann Med. 1991;23:313–318. [PubMed]
32. Fagard RH, Tipton CM. Physical activity, fitness, and hypertension. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
33. Cononie CC, Graves JE, Pollock ML, et al. Effect of exercise training on blood pressure in 70- to 79-yr-old men and women. Med Sci Sports Exerc. 1991;23:505–511. [PubMed]
34. Hagberg JM, Montain SJ, Martin WH, et al. Effect of exercise training on 60-69 year-old persons with essential hypertension. Am J Cardiol. 1989;64:348–353. [PubMed]
35. American College of Sports Medicine. Position stand: physical activity, physical fitness, and hypertension. Med Sci Sports Exerc. 1993;25:i–x. [[PubMed]
36. National High Blood Pressure Education Program Working Group. Report on primary prevention of hypertension. Arch Intern Med. 1993;153:186–208. [PubMed]
37. Johnson D, Prud'homme D, et al. Relation of abdominal obesity to hyperinsulinemia and high blood pressure in men. Int J Obesity. 1992;16:881–890. [PubMed]
38. Rissanen AM, Heliovaara M, et al. Determinants of weight gain and overweight in adult Finns. Eur J Clin Nutr. 1991;45:419–430. [PubMed]
39. Williamson DF, Madans J, et al. Recreational physical activity and ten-year weight change in a U.S. national cohort. Int J Obesity. 1993;17:279–286. [PubMed]
40. Blair SN. Evidence for success of exercise in weight loss and control. Ann Intern Med. 1993;119:702–706. [PubMed]
41. Bouchard C, Tremblay A, Nadeau A, et al. Long-term exercise training with constant energy intake. 1. Effect on body composition and selected metabolic variables. Int J Obesity. 1990;14:57–73. [PubMed]
42. Stefanick ML. Exercise and weight control. In: Holloszy JO, ed. Exercise and sports medicine reviews. Baltimore: Williams & Wilkins, 1993;(2)1363–396. [PubMed]
43. Despres JP, Pouliot MC, et al. Loss of abdominal fat and metabolic response to exercise training obese women. Am J Physiol. 1991;261:E159–E167. [PubMed]
44. King AC, Frey-Hewitt, Dreon DM, et al. Diet vs. exercise in weight maintenance: the effects of minimal intervention strategies on long-term outcomes in men. Arch Intern Med. 1989;149:2741–2746. [PubMed]
45. Defronzo RA, Ferrannini E. Insulin resistance. A multifaceted syndrome responsible for NIDDM, obesity, hypertension, dyslipidemia, and atherosclerotic cardiovascular disease. Diabetes Care. 1991;14:173–191. [PubMed]
46. Morris JN, Clayton DG, et al. Exercise in leisure time: coronary attack and death rate. Br Heart J. 1990;63:325–334. [PMC free article] [PubMed]
47. Paffenbarger RS Jr, Hyde RT, et al. Physical activity, all-cause mortality, and longevity of college alumni. N Engl J Med. 1986;314:605–613. [PubMed]
48. Tremblay A, Despres JP, et al. Normalization of the metabolic profile in obese women by exercise and a low fat diet. Med Sci Sports Exerc. 1991;23:1326–1331. [PubMed]
49. Manson JE, Nathan DM, et al. A prospective study of exercise and incidence of diabetes among US male physicians. JAMA. 1992;268:63–67. [PubMed]
50. Manson JE, Rimm EB, et al. Physical activity and incidence of non-insulin dependent diabetes mellitus in women. Lancet. 1991;338:774–778. [PubMed]
51. Helmrich SP, Ragland DR, Leung RW, et al. Physical activity and reduced occurrence of non-insulin dependent diabetes mellitus. N Engl J Med. 1991;325:147–152. [PubMed]
52. Kohl HW, Gordon NF, et al. Cardiorespiratory fitness, glycemic status, and mortality risk in men. Diabetes Care. 1992;15:184–192. [PubMed]
53. Wallberg-Henriksson H. Exercise and diabetes mellitusIn: Holloszy JO, ed. Exercise and sport sciences review. 1992;(20)339–368.
54. Rogers MA, Yamamoto C, et al. Improvement in glucose tolerance after 1 week of exercise in patients with mild NIDDM. Diabetes Care. 1988;11:613–618. [PubMed]
55. King DS, Dalsky GP, et al. Effects of lack of exercise on insulin secretion and action in trained subjects. Am J Physiol. 1988;254:E537–E542. [PubMed]
56. Smith EL, Gilligan C, et al. Deterring bone loss by exercise intervention in premenopausal and postmenopausal women. Calcif Tissue Int. 1989;44:312–321. [PubMed]
57. Dalsky GP, Stocke KS, et al. Weight-bearing exercise training and lumbar bone mineral content in postmenopausal women. Ann Intern Med. 1988;108:824–828. [PubMed]
58. Bloomfield SA, Williams NI, et al. Non-weightbearing exercise may increase lumbar spine bone mineral density in healthy postmenopausal women. Am J Phys Med Rehab. 1993;72:204–209. [PubMed]
59. Chow R, Harrison JE, Notarius C. Effect of two randomized exercise programs randomised exercise programmes on bone mass of healthy postmenopausal women. BMJ. 1987;295:1441–1444. [PMC free article] [PubMed]
60. Harris SS, Caspersen CJ, et al. Physical activity counseling for healthy adults as a primary preventive intervention in the clinical setting. JAMA. 1989;261:3590–3598. [PubMed]
61. Jacobson PC, Beaver W, Grubb SA. Bone density in women: college athletes and older athletic women. J Orthop Res. 1984;2:8–32. [PubMed]
62. Chow RK, Harrison JE, et al. Physical fitness effect on bone mass in postmenopausal women. Arch Phys Med Rehab. 1986;67:231–234. [PubMed]
63. Marcus R, Drinkwater B, et al. Osteoporosis and exercise in women. Med Sci Sports Exerc. 1992;24:S301–S307. [PubMed]
64. Snow-Harter C, Bouxsein ML, Lewis BT, et al. Effects of resistance and endurance exercise on bone mineral status of young women: a randomized exercise intervention trial. J Bone Min Res. 1992;7:761–769. [PubMed]
65. Jaglal SB, Kreiger N, Darlington G. Past and recent physical activity and the risk of hip fracture. Am J Epidemiol. 1993;138:107–118. [PubMed]
66. Paganini-Hill A, Ross RK, Henderson BE, et al. Menopausal estrogen therapy and hip fractures. Ann Intern Med. 1981:95:28–31. [PubMed]
67. Chalmers J, Ho KC. Geographic Geographical variations in senile osteoporosis: the association of physical activity. J Bone Joint Surg. 1970;52:371–378. [PubMed]
68. Cummings SR, Black DM, et al. Appendicular bone density and age predict hip fracture in women. The Study of Osteoporotic Fractures Research Group. JAMA. 1990;263:665–668. [PubMed]
69. Seeley DG, Browner WS, et al. Which fractures are associated with low appendicular bone mass in elderly women? The Study of Osteoporotic Fractures Research Group. Ann Intern Med. 1991;115:837–842. [PubMed]
70. Snow-Harter C, Marcus R. Exercise, bone mineral density, and osteoporosis. Exerc Sport Sci Rev. 1991;19:351–388. [PubMed]
71. Drinkwater B. Physical activity, fitness and osteoporosis. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
72. Landers DM, Petruzzello SJ. Physical activity, fitness, and anxiety. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
73. Morgan WP. Physical activity, fitness, and depression. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
74. LaFontaine TP, DiLorenzo TM, et al. Aerobic exercise and mood: a brief review, 1985-1990. Sports Med. 1992;13:160–170. [PubMed]
75. Thirlaway K, Benton D. Participation in physical activity and cardiovascular fitness have different effects on mental health and mood. J Psychosom Res. 1992;36:657–666. [PubMed]
76. Moses J, Steptoe A, et al. The effects of exercise training on mental well-being in the normal population: a controlled trail. J Psychosom Res. 1989;33:47–61. [PubMed]
77. Steptoe A, Edwards S, et al. The effects of exercise training on the mood and perceived coping ability in anxious adults from the general population. J Psychosom Res. 1989;33:537–547. [PubMed]
78. Farmer ME, Locke BZ, et al. Physical activity and depressive symptomatology symptoms: the NHANES I epidemiologic follow-up study. Am J Epidemiol. 1988;128:1340–1351. [PubMed]
79. King AC, Taylor CB, et al. Influence of regular aerobic exercise on psychological health: a randomized, controlled trial of healthy middle-aged adults. Health Psychol. 1989;8:305–324. [PubMed]
80. Cramer SR, Nieman DC, Lee JW. The effects of moderate exercise training on psychological well-being and mood state in women. J Psychosom Res. 1991;35:437–449. [PubMed]
81. Blumenthal JA, Emery CF, et al. Long-term effects of exercise on psychological functioning in older men and women. J Gerontol. 1991;46:352–361. [PubMed]
82. Raglin JS. Exercise and mental health: beneficial and detrimental effects. Sports Med. 1990;9:323–329. [PubMed]
83. Sonstroem RJ, Morgan WP. Exercise and self-esteem: rationale and model. Med Sci Sports Exerc. 1989;21:329–337. [PubMed]
84. McAuley E. Self-efficacy and the maintenance of exercise participation in older adults. J Behav Med. 1993;16:103–113. [PubMed]
85. Caruso CM, Gill DL. Strengthening physical self-perceptions through exercise. J Sports Med Phys Fitness. 1992;32:416–427. [PubMed]
86. Stein PN, Motta RW. Effects of aerobic and nonaerobic exercise on depression and self-concept. Percept Mot Skills. 1992;74:79–89. [PubMed]
87. Ossip-Klein DJ, Doyne EJ, et al. Effects of running or weight training lifting on self-concept in clinically depressed women. J Consult Clin Psychol. 1989;57:158–161. [PubMed]
88. Emery CF, Blumenthal JA. Perceived change among participants in an exercise program for older adults. Gerontologist. 1990;30:516–521. [PubMed]
89. Hill RD, Storandt M, Malley M. The impact of long-term exercise training on psychological function in older adults. J Gerontol. 1993;48:P12–P17. [PubMed]
90. Dunn AL, Dishman RK. Exercise and the neurobiology of depression. Exerc Sport Sci Rev. 1991;19:41–98. [PubMed]
91. Berger BG, Owen DR. Mood alteration with yoga and swimming: aerobic exercise may not be necessary. Percept Mot Skills. 1992;75:1331–1343. [PubMed]
92. Schwarz L, Kindermann W. Changes in beta -endorphin levels in response to aerobic and anaerobic exercise. Sports Med. 1992;13:25–36. [PubMed]
93. Daniel M, Martin AD, Carter J. Opiate receptor blockade by naltrexone and mood state after acute physical activity. Br J Sports Med. 1992;26:111–115. [PMC free article] [PubMed]
94. Magnus K, Matroos A, Strackee J. Walking, cycling, gardening with or without seasonal interruption in relation to acute coronary events. Am J Epidemiol. 1979;110:724–733. [PubMed]
95. Lee IM, Hsieh CC, Paffenbarger RS Jr. Exercise intensity and longevity in men: the Harvard Alumni Health Study. JAMA. 1995;273:1179–1184. [PubMed]
96. American College of Sports Medicine. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness in healthy adults. Med Sci Sports Exerc. 1990;22:256–274. [PubMed]
97. King AC, Haskell WL, Taylor CB, et al. Group- vs home-based exercise training in healthy older men and women: a community-based clinical trial. JAMA. 1991;266:1535–1542. [PubMed]
98. Duncan JJ, Gordon NF, Scott CB. Women walking for health and fitness: how much is enough? JAMA. 1991;266:3295–3299. [PubMed]
99. Blair SN, Powell KE, Bazzarre TL, et al. Physical inactivity: workshop V. Circulation. 1993;88:1402–1405. [PubMed]
100. Fletcher BJ, Dunbar SB, Felner JM, et al. Exercise testing and training in physically disabled men with clinical evidence of coronary artery disease. Am J Cardiol. 1994;73:170–174. [PubMed]
101. Debusk RF, Stenestrand U, Sheehan M, et al. Training effects of long versus short bouts of exercise in healthy subjects. Am J Cardiol. 1990;65:1010–1013. [PubMed]
102. Pate RR, Macera CA. Risks of exercising: musculoskeletal injuries. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
103. Pollock ML, Carroll JF, et al. Injuries and adherence to walk/jog and resistance training programs in the elderly. Med Sci Sports Exerc. 1991;23:1194–1200. [PubMed]
104. Macera CA, Jackson KL, Hagenmaier GW, et al. Age, physical activity, physical fitness, body composition, and incidence of orthopedic problems. Res Q Exerc Sport. 1989;60:225–233. [PubMed]
105. Kohatsu ND, Schurman DJ. Risk factors for the development of osteoarthrosis of the knee. Clin Orthop. 1990;246:242–246. [PubMed]
106. Lane NE, Michel B, Bjorkengren A, et al. The risk of osteoarthritis with running and aging: a 5-year longitudinal study. J Rheumatol. 1993;20:461–468. [PubMed]
107. Swann AC, Seedhom BB. The stiffness of normal articular cartilage and the predominant acting stress levels: implications for the aetiology of osteoarthrosis. Br J Rheumatol. 1993;32:16–25. [PubMed]
108. Panush RS. Physical activity, fitness, and osteoarthritis. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
109. Willich SN, Lewis M, et al. Physical exertion as a trigger of acute myocardial infarction. N Engl J Med. 1993;329:1684–1690. [PubMed]
110. Mittleman MA, Maclure M, et al. Triggering of acute myocardial infarction by heavy physical exertion-protection against triggering by regular exertion. N Engl J Med. 1993;329:1677–1683. [PubMed]
111. Thompson PD, Fink Funk EJ, et al. Incidence of death through jogging in Rhode Island from 1975-1980. JAMA. 1982;247: 2535–2538. [PubMed]
112. Siscovick DS, Weiss NS, et al. The incidence of primary cardiac arrest during vigorous exercise. N Engl J Med. 1984;311:874–877. [PubMed]
113. Kohl HW, Powell KE, et al. Physical activity, physical fitness, and sudden cardiac death. Epidemiol Rev. 1992;14:37–58. [PubMed]
114. Thompson PD, Fahrenbach MC. Risks of exercising: cardiovascular, including sudden cardiac death. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.
115. Campbell MJ, Browne D, Waters WE. Can general practitioners influence exercise habits? Controlled trial. BMJ. 1985;290:1044–1046. [PMC free article] [PubMed]
116. Lewis B, Lynch W. The effect of physician advice on exercise behavior. Prev Med. 1993;22:110–121. [PubMed]
117. Calfas KJ, Long BJ, Sallis JF, et al. A controlled trial of physician counseling to promote the adoption of physical activity. Prev Med. 1996;25(3):225-33. [PubMed]
118. Logsdon DN, Lazaro CM, Meier RV. The feasibility of behavioral risk reduction in primary medical care. Am J Prev Med. 1989;5:249–256. [PubMed]
119. Pate RR, Pratt M, Blair SN, et al. Physical activity and health: a recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA. 1995;273:402–407. [PubMed]
120. American Heart Association. Fletcher GF, Blair SN, Blumenthal J, et al. Statement on exercise: benefits and recommendations for physical activity programs for all Americans. [A statement for health professionals by the Committee on Exercise and Cardiac Rehabilitation of the Council on Clinical Cardiology, American Heart Association.] Circulation. 1992;86:340–343. [PubMed]
121. American Academy of Family Physicians. Age charts for periodic health examination. Kansas City, MO: American Academy of Family Physicians. 1994. (Reprint no. 510.)
122. American College of Obstetricians and Gynecologists. Women and exercise. Technical Bulletin no. 173. Washington, DC: American College of Obstetricians and Gynecologists. 1992
123. Canadian Task Force on the Periodic Health Examination. Canadian guide to clinical preventive care. Ottawa: Canada Communication Group. 1994:560–569.
124. American Academy of Pediatrics Assessing physical activity and fitness in the office setting. [Committee on Sports Medicine and Fitness] Pediatrics. 1994:93: 686–689. [PubMed]
125. Green M, ed. Bright Futures: guidelines for health supervision of infants, children, and adolescents. Arlington, VA: National Center for Education in Maternal and Child Health, 1994.
126. American Medical Association. Guidelines for adolescent preventive services (GAPS): recommendations and rationale. Chicago: American Medical Association, 1994.
127. Centers for Disease Control and Prevention. Geiss LS, Herman WH, Goldschmid MG, et al. Surveillance for diabetes mellitus—United States, 1980-89. MMWR. 1993;42(SS-2):1–20. [PubMed]
128. Dishman RK, Sallis JF. Determinants and interventions for physical activity and exercise. In: Bouchard C, Shepard RJ, Stephens T, eds. Physical activity, fitness, and health. Champaign, IL: Human Kinetics, 1994.