Does Late-Life Physical Activity or Exercise Prevent or Minimize Disablement? A Critical Review of the Scientific Evidence Julie J. Keysor, PhD, PT Abstract:
Physical activity and exercise are widely purported to enhance health and minimize or prevent functional loss and disability. Yet, do the benefits of late-life physical activity or exercise extend beyond disease and impairment-level factors? Does late-life physical activity minimize or prevent functional limitations and disability? To address these questions, a best-evidence framework was used to examine the effects of late-life physical activity on disablement outcomes. This review shows that exercise—particularly walking—increases muscle strength and aerobic capacity and reduces functional limitations. It is less clear, however, whether physical activity or exercise prevents or minimizes physical disability. Furthermore, this review shows a discrepancy between prospective and experimental studies: several well-conducted prospective studies show a beneficial effect of physical activity on minimizing disability, whereas the majority of experimental studies that have examined disability as an outcome do not show improvements in disability. Three research priorities are identified that would advance the science in this field: (1) development of a clear conceptual and theoretical framework of late-life physical activity and assessment; (2) use of a disablement outcomes framework to examine the outcomes of late-life physical activity; and (3) development of a mechanism of action explaining the relationship between physical activity and exercise and disablement outcomes. (Am J Prev Med 2003;25(3Sii):129 –136) © 2003 American Journal of Preventive Medicine
Introduction
P
hysical activity and exercise are widely promoted as effective means to enhance health and physical functioning of elderly persons.1–3 A link between physical activity and premature mortality and prevention of coronary heart disease, hypertension, colon cancer, and diabetes is well established in the scientific literature.4 –14 A substantial amount of scientific evidence shows that older adults who engage in progressive resistance training and aerobic exercise are able to increase muscle strength, aerobic capacity, and bone density.15–19 Furthermore, several randomized controlled trials show a beneficial effect of resistance training on muscle strength among frail elderly persons20 –24 and older adults with knee or hip osteoarthritis.25–30 Yet, do the benefits of late-life physical activity or exercise extend beyond disease and impairment-level factors? Does late-life physical activity or exercise minimize or prevent functional limitations and disability? To From the Sargent College of Health and Rehabilitation Science, Department of Rehabilitation Sciences, Boston University, Boston, Massachusetts Address correspondence and reprint requests to: Julie J. Keysor, PhD, PT, Department of Rehabilitation Science, Sargent College of Health and Rehabilitation Science, 635 Commonwealth Ave. 521, Boston MA 02215. E-mail:
[email protected].
address these questions, Nagi’s31,32 disablement framework is used to examine outcomes of physical activity or exercise programs performed by older adults, defined in this article as persons aged ⱖ60 years. To examine the strength of evidence for these questions, a bestevidence approach is used.33 Meta-analyses and systematic reviews of randomized controlled trials (RCTs) with adequate research synthesis will represent the best evidence. RCTs with adequate internal validity and sample size will represent strong evidence. Communitybased longitudinal observational studies will represent good evidence. Before these questions are addressed, it is imperative to define the terms “physical activity” and “exercise.” In a recent review article, Fiatarone Singh3 argued that some of the discrepancies in the literature on late-life physical activity and exercise are due to inconsistent and incorrect use of the terms “physical activity” and “exercise.” Fiatarone Singh’s argument is certainly valid: clearly defining and distinguishing independent variables (in this case, the type of intervention) is as important as clearly defining and distinguishing dependent variables (in this case, disablement outcomes). Traditionally, physical activity is defined as “any bodily movement produced by contraction of skeletal muscle that substantially increases energy expenditure above the basal level,” and exercise is defined as
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“planned, structured, repetitive bodily movements that are performed, with or without the explicit intent of improving one or more components of physical fitness,”34 and is viewed as a subcategory of physical activity. Although there are important distinctions between these terms, distinguishing between them is challenging because many activities commonly performed by elderly persons, such as walking, could be considered exercise or physical activity. This may, at least in part, explain some of the inconsistencies in this literature. A critical analysis of the type, duration, intensity, and mode of exercise and physical activity interventions in relation to outcomes is needed to guide the classification scheme for physical activity and exercise programs. This is, however, beyond the scope of the current paper. For the purpose of this review, the term “exercise” or the specific type of exercise, such as “progressive resistance training” or “aerobic” training, will be used when describing interventions that consist of planned, structured, and repetitive bodily movements. Most of the RCTs in this review can be classified as exercise interventions. Physical activity, on the other hand, will be used to classify bodily movement as defined previously. Most of the prospective longitudinal studies in this review examine physical activity types of behaviors. Whenever possible, I will specifically state the type of exercise or physical activity, such as strength training (e.g., progressive resistive training) and aerobic activities (e.g., walking, running, biking, dancing, and hiking).
Methods Cochrane, Best Evidence, and Medline databases were searched for: (1) meta-analyses and systematic review articles on the effects of late-life physical activity or exercise on impairments, functional limitations, and disability; (2) RCTs that examined the effects of late-life physical activity or exercise interventions on minimizing or preventing functional loss or disability; and (3) longitudinal observational studies that examined the relationship between physical activity and incident functional limitation or physical disability in late life. The terms “exercise,” “physical activity,” “strength training,” “resistance training,” and “aerobic” were used to capture studies related to physical activity. Articles were included if they were published between 1995 and 2002; addressed an older adult population (aged ⱖ60 years); were written in English; and assessed disablement outcomes— particularly functional limitations and disability as defined by Nagi31,32 and elaborated on by other articles in this special issue.35,36 Review articles were included if they examined the effects of late-life physical activity, aerobic exercise, or resistance training on impairments, functional limitations, or disability. RCTs were included if they contributed critical information above and beyond the meta-analyses or systematic reviews. Longitudinal observational studies were included if they were population based, defined functional limitation and disability outcomes as defined in this article, controlled
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for multiple confounders, and used advanced statistical methods to account for losses to follow-up and longitudinal trajectories. The intent of this review was to examine the effects of physical activity and exercise programs among a general population of older adults. However, studies that examined the effects of late-life exercise among people with arthritis were included. These studies were included because tibiofemoral osteoarthritis is the most prevalent chronic musculoskeletal condition among adults aged ⱖ65 years and the leading cause of self-reported functional limitations,37,38 and it is likely that many of the subjects in the older adult study populations had symptomatic or asymptomatic osteoarthritis. On the other hand, studies that focused on the effects of physical activity or exercise among specific disease or impairment groups were excluded (e.g., Parkinson disease, chronic obstructive pulmonary disease, congestive heart failure, osteoporosis, chronic lower back pain, and balance). Although it is important to examine the outcomes of exercise interventions for these populations, expanding the review to include all disease-related interventions would be a daunting task, and synthesizing these studies would be difficult because there may be certain disease and impairment characteristics that will affect the type of exercise intervention, such as rigidity and bradykinesia in Parkinson disease and the use of metronomes or external timing and sequencing devices for gait and ambulation for this population.39,40 Interventions that focused on balance training were excluded because the prevention of falls was not a focus of the disablement outcome framework used for this article.
Results Effects of Late-Life Physical Activity and Exercise on Functional Limitations Randomized-controlled trials and several critical reviews show strength training and walking programs improve function, particularly walking (see Table 1).19,30,41,42 Latham et al.19 pooled data from 14 studies and found an increase in walking speed of 0.07 meters per second—a small to moderate effect—among elderly people who engaged in progressive resistancetraining interventions. Likewise, a small, significant effect on walking speed was found for older adults with hip or knee osteoarthritis who participated in an exercise program,30 although these findings were primarily based on two trials that had acceptable internal validity and adequate power.43,44 Recent research on the effects of exercise on walking among people with osteoarthritis, however, confirms these findings.25,28 The evidence suggests that other functional activities (e.g., chair-rise transfers and stair-climbing ability) seem to improve among elderly persons who engage in resistance or aerobic exercise programs, although the evidence is inconsistent and the outcomes have not been studied as extensively as walking. Keysor and Jette41 found that ten trials examined chair rise (with or without a short walk), with five of the studies showing improvements in performance with strength or aerobic
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Table 1. Reviews on effects of late-life physical activity or exercise on impairments, functional limitations, and disability Study
Number and types of studies reviewed
Impairments
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Latham et al., 200319
Systematic review of 41 Strength: moderate to RCTs of progressive large effect resistance training among Aerobic capacity: small older adults (aged ⬎60) or no effect
van Baar et al., 199930
Systematic review of 11 RCTs of physical activity or exercise programs for hip or knee osteoarthritis
Pain: small to moderate effect
Keysor and Jette, 200141
Review of 31 RCTs or quasi-experimental trails
PE: Strength PE: aerobic capacity
Chandler and Hadley, 199642
Review of 33 resistance PE: Physiological factors training, aerobic training, all ages and levels of or combined training impairment
PE, physical exercise; RCT, randomized clinical trial.
Functional activities
Disability
Comments
Cochrane review, Walking speed: small effect No effect pooled data, Chair-rise speed: moderate assessment of effect internal validity Balance: small, nonsignifiand power cant effect Timed up and go: small, or no effect Walking: small effect PE: one study with acceptable Findings based internal validity and primarily on two adequate power studies that had acceptable internal validity; thus, findings need to be interpreted with caution Questionable effect on Positive and null PE: Walking physical disability (5 of findings of 31 PE: chair rise with/without 14 studies reported studies were short walk (5 of 10 positive associations) summed to studies reported positive indicate whether associations) effects were PE: stair climbing (3 of 6 present studies reported positive associations) PE: Walking and chair rise, Most studies did not report; particularly among frail unclear whether physical persons disability was improved (2 of 4 studies examining physical disability outcomes reported positive benefits)
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training. Latham et al.19 showed a moderate to large effect of resistance training on chair rise (walking was not included), although only a few studies examined this outcome. The effects of late-life exercise on stair climbing have been examined in a few studies and the findings are inconsistent. Keysor and Jette41 reported that of 31 studies in their review, six studies examined this outcome, with three studies showing improvements in stair-climbing performance. Recent trials of exercise for osteoarthritis, however, show beneficial effects of exercise on self-reported physical function and performance-based measures.25,28 Recent well-conducted prospective studies show a protective effect of physical activity on functional limitations,45–51 although there are some discrepancies.51,52 Using data from the Longitudinal Study on Aging (LSOA) and complex statistical methods including weighted population estimates, trajectory modeling strategies, and methods to account for loss to follow-up, Miller et al.49 showed that persons who were physically active (defined as walking at least a mile a week) had a slower progression of functional limitations over a 6-year follow-up period, after controlling for co-morbidity disease, age, gender, and the previous level of functional limitations. In a related study that used data from the Aerobics Center Longitudinal Study,50 men and women who were classified with moderate or high fitness were less likely to report at least one functional limitation at an average 5.5-year follow-up compared to persons in the lowest tertile of fitness. In this study, there was a trend for similar findings regarding a protective effect of physical activity. An interesting finding in this study was that this relationship between physical fitness, physical activity, and functional limitation was observed in middle-aged and older persons.
Effects of Physical Activity and Exercise on Disability The evidence regarding the beneficial effect of exercise to minimize or prevent disability is limited. Keysor and Jette41 reported that 45% of the randomized controlled studies or quasi-experimental studies in their review examined physical disability as an outcome, whereas Latham et al.19 reported that only 21% of the RCTs of progressive resistance training reported physical disability outcomes. This discrepancy is likely due to Keysor and Jette’s41 approach of limiting the studies included in the review to those that examined a functional or disability outcome—that is, articles examining effects only on impairments were excluded from the review. Latham et al.,19 however, included articles that examined impairment, function, or disability outcomes. Furthermore, of the studies that have examined disability outcomes, the results are inconsistent. 132
Latham et al.19 showed no effect of progressive resistance training on disability outcomes when data from several RCTs on progressive resistance training were pooled. Keysor and Jette41 reported that a beneficial effect was found in 35% of the studies that examined physical disability as an outcome. Of the RCTs that do show a beneficial effect on disability, three studies include populations of elderly persons with osteoarthritis,53–55 and three include populations of elderly persons living in residential nursing care or the community who have functional limitations or disabilities.23,26,56 The strongest evidence for a link between physical activity and disability among persons with osteoarthritis comes from the Fitness Arthritis and Seniors Trial (FAST), a randomized controlled trial of 439 community-dwelling adults aged ⱖ60 years with radiographically diagnosed knee osteoarthritis and pain and difficulty with at least one functional activity.54 The intervention consisted of an aerobic walking program, a resistance-training program, and a health education attention control group. Participants received a 3-month facility-based program followed by a 15-month home-based program. At the end of the 18 months, people in the walking and resistance-training groups reported less activities of daily living (ADL) disability compared to the control group, although the effect size was small. In a related study using data from 250 persons of the FAST trial who did not report ADL disability at baseline, Penninx et al.55 showed that people who participated in strength and aerobic training were less likely to develop incident disability at the end of an 18-month intervention program compared to people in the control group (cumulative ADL incidence: 37% in exercise group vs 53% in the exercise group; incident ADL disability: relative risk [RR]⫽0.57, 95% confidence interval [CI], 0.38 – 0.85). To my knowledge, this is the first randomized controlled study that shows that resistance training or walking prevents disability, at least among persons with knee osteoarthritis. Although there are inconsistencies in the RCT scientific literature regarding the benefits of exercise on disability, there is evidence from prospective studies that physical activity has a protective effect on disability. Several recent well-conducted observational studies show a protective effect of physical activity on incident disability. Using data from the LSOA, Miller et al.49 reported that 5151 persons at baseline who were physically active (walked ⱖ1 mile a week) were less likely to report severe or moderate disability at a 2-year or 4-year follow-up (RR 2-year⫽0.74, 95% CI, 0.62– 0.89; RR 4-year⫽0.64, 95% CI, 0.54 – 0.77) but not at the 6-year follow-up. As described in the previous section, the authors used complex analytical techniques to account for losses to follow-up and attempted to account for pre-existing poor health at baseline by adjusting for 13 co-morbidities.
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Table 2. Definitions of physical activity used in prospective studies Study
Definition of physical activity 49
Miller et al., 2000 Wu et al., 199957 Leveille et al., 199958 Huang et al., 199850
Physically active: walking 1 mile at least once a week at baseline Exercise (folk dancing, hiking, jogging, or walking at least twice a week) Physical activity: frequency of walking, gardening, and doing vigorous exercise (several times per week; once a week or several times per month; once a month or less) Physical fitness (total time on a treadmill). Low fitness: lowest 20%; moderate fitness: next 40%; high fitness: next 40% Physical activity. Sedentary: no leisure time physical activity; moderate: some regular leisuretime activity or walking, running, or jogging ⬍10 miles per week; active: walking, running, or jogging ⱖ10 miles per week
In another community-based study of 1321 elderly people in Taiwan who did not report ADL disability at baseline, survival analysis was used to predict the onset of ADL disability over a 3-year period.57 People who were physically active (engaged in folk dancing, hiking, jogging, or walking at least twice a week) were less likely to develop ADL disability (unable to perform independently for longer than 3 months at least one of the following: eating, bathing, dressing, toileting, transfers, or walking inside the house) than were persons who were sedentary (RR⫽⫺0.52; 95% CI, 0.39 – 0.68), after adjusting for age, gender, education, marital status, number of chronic medical conditions, self-perceived health status, smoking, or heavy/moderate alcohol consumption. In a recently published study from the Established Populations of Epidemiological Studies of the Elderly (EPESE), one of the largest population-based studies of older persons, persons who reported high levels of physical activity at baseline (frequency of walking, gardening, and vigorous exercise) were more likely to die without disability compared to sedentary elders (odds ratio⫽1.86; 95% CI, 1.24 –2.79).58
Summary: A Critique of the Evidence In this synthesis of the scientific literature on exercise and disablement, it is clear that exercise enhances strength, aerobic capacity, and function, particularly walking. It is less clear, however, whether exercise prevents or minimizes physical disability. On the other hand, the evidence from prospective studies suggests an inverse relationship between physical activity and functional limitations and disability. Others have noted these conflicting results.59 A critical review needs to evaluate research findings within the constraints of the type of research. RCTs and observational studies have potential biases that need to be addressed. These findings are based on reviewing literature of RCTs and prospective, observational studies. Both types of scientific literature have biases that need to be addressed when evaluating the strength of their scientific evidence. First, the systematic reviews and general reviews did not examine variations in
interventions, such as intensity or duration of training. It may be that beneficial outcomes, particularly at the level of disability, require a certain intensity or duration. Ettinger et al.,54 for example, showed a positive effect of exercise on decreasing disability with an 18-month intervention. Most RCTs of exercise among elders consist of an 8- to 12-week training period.41 Some of the discrepancies in findings or lack thereof may be due to differences in study or intervention design. Second, the findings from the reviews cannot be used to examine whether exercise prevents functional limitations or disability; the RCTs in the reviews did not examine incident functional loss or disability. On the other hand, the observational studies in this review were well designed and used analytical techniques to account for many of the biases of observational studies, such as loss to follow-up resulting from death, institutionalization, refusal, or the inability to locate the participant, as well as techniques to adjust for poor health status at baseline. Nonetheless, there are some methodologic problems that may potentially bias the results. First, physical inactivity at baseline may be the result of poor health or functional limitations that are not captured on baseline measures. Although this critique is true for many prospective cohort studies, the study by Huang et al.50 used a maximal stress test with a treadmill and excluded persons who were unable to attain at least 85% of their age-predicted maximal heart rate. This type of baseline assessment should eliminate persons with functional limitations or health problems that could limit physical activity. Second, the assessment of physical activity in many longitudinal, observational studies—probably in part due to respondent burden—is estimated by self-report and often categorized into tertiles or quartiles representing low to high physical activity. This assessment approach is crude and may not accurately assess physical activity levels. However, Huang et al.50 addressed this concern by including a measure of physical fitness with assessments of physical activity. Furthermore, assessments of physical activity are varied, with none of the studies in this review using the same conceptual definition of physical activity (Table 2). Am J Prev Med 2003;25(3Sii)
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Key Challenges to Advancing the Scientific Evidence on Physical Activity on Disablement The scientific research on physical activity, exercise, and disablement has grown substantially over the past decade. Yet, in order for the scientific evidence to continue to strengthen in this area, there are several crucial challenges that need to be addressed. First, the concepts “physical activity” and “exercise” need to be clearly defined. What is physical activity? How does physical activity differ from “exercise?” What are the important characteristics of these behaviors that we should evaluate? What aspects of these behaviors are important in terms of disablement outcomes? Do the existing definitions of physical activity and exercise adequately meet the theoretical framework needed to examine the outcomes of late-life physical activity? Are activity programs, such as walking or dancing, classified as physical activity or exercise? Does it matter? Is energy expenditure more important? Or are characteristics of the activity—the nature of the task itself—more important (see Frank and Patla60). Is activity that integrates balance, endurance, trunk rotation, transfers, weightshift transitions, and strengthening more effective at minimizing disablement than conventional physical activity or exercise? Does engaging in these multifactorial activities enhance outcomes? What characteristics of activity are important? While clarifying the input or independent variable (e.g., physical activity) is crucial for progress to occur, it is equally important to clearly define outcomes. Over the past decade, there has been a substantial amount of progress in disablement outcomes assessment. Articles in this supplement by Guralnik and Ferrucci36 and Jette35 address conceptual underpinnings and challenges to assessing functional activity and disability. Although the geriatric research community seems to be developing a consensus on the domains of disablement, most studies do not examine outcomes at multiple levels, and investigators often use measures at one level of analysis to make conclusions about another. For example, as shown in this review and others,19,41 disability is not commonly assessed as an outcome to physical activity interventions. Therefore, we have little scientific evidence upon which to base conclusions regarding the effects of exercise on disability. Moreover, researchers commonly use measures of functional limitations for evidence that there has been a change in disability. A third key challenge to advancing the scientific evidence on physical activity, exercise, and disablement is the development of a better understanding of the mechanism of action. If we improve our understanding of how physical activity or exercise enhances functioning and decreases disability, we may develop more effective interventions or at least identify persons who are likely to experience a wide range of benefits from 134
physical activity. As a means to accomplish this task, we can examine the studies that show beneficial effects on disablement outcomes. In this vein, it is interesting to note the growing research linking exercise to improvements in function and disability among persons with knee and hip osteoarthritis. Rejeski et al.61 suggest that self-efficacy and pain mediate the relationship between exercise and functional limitations (i.e., stair-climbing time). Using data on the first 357 participants enrolled in the FAST trial, the authors found that self-efficacy increased and pain decreased among persons with symptomatic knee osteoarthritis who exercised and that knee pain and self-efficacy mediated the effect of exercise on stair-climbing times. Although this model is specific to exercise and knee osteoarthritis, it is interesting to note the integration of cognitive-behavioral factors with impairments, exercise, and functional outcomes. Cognitive-behavioral approaches are recognized as crucial components of promoting physical activity and exercise among older adults,62,63 yet there is little scientific evidence examining cognitive processes as they relate to physical activity and disablement outcomes.
Summary Understanding the full range of benefits derived from late-life physical activity and exercise has policy, research, and clinical implications. Although there is a growing literature showing the benefits of late-life physical activity and exercise on proximal disablement outcomes, such as impairments and functional limitations, the effects on distal outcomes, such as disability, are not as apparent. The conceptual frameworks presented in this paper and in other articles in this supplement could be used to advance our understanding of late-life physical activity, disablement outcomes, and how these two domains are related. This work was supported by the National Institute on Aging (grant AG11669) and National Institute on Disability and Rehabilitation Research (grant H113B990005). I am grateful to Alan Jette and Nancy Latham for their insightful comments on this article and research topic.
References 1. Carlson JE, Ostir GV, Black SA, Markides KS, Rudkin L, Goodwin JS. Disability in older adults 2: physical activity as prevention. Behav Med 1999;24:157–68. 2. Evans WJ. Exercise as the standard of care for elderly people. J Gerontol Med Sci 2002;57:260 –1. 3. Fiatarone Singh MA. Exercise comes of age: rationale and recommendations for a geriatric exercise prescription. J Gerontol Med Sci 2002;57:262– 82. 4. Berlin JA, Colditz GA. A meta-analysis of physical activity in the prevention of coronary heart disease. Am J Epidemiol 1990;132:612–28. 5. Lindsted KD, Tonstad S, Kuzma JW. Self-report of physical activity and patterns of mortality in Seventh-Day Adventist men. J Clin Epidemiol 1991;44:355–64.
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6. Helmrich SP, Ragland DR, Leung RW, Paffenbarger RS Jr. Physical activity and reduced occurrence of non–insulin-dependent diabetes mellitus. N Engl J Med 1991;325:147–52. 7. Paffenbarger RS Jr, Hyde RT, Wing AL, Lee IM, Jung DL, Kampert JB. The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. N Engl J Med 1993;328:538 –45. 8. Paffenbarger RS Jr, Kampert JB, Lee IM, Hyde RT, Leung RW, Wing AL. Changes in physical activity and other lifeway patterns influencing longevity. Med Sci Sports Exerc 1994;26:857–65. 9. Kaplan GA, Strawbridge WJ, Cohen RD, Hungerford LR. Natural history of leisure-time physical activity and its correlates: associations with mortality from all causes and cardiovascular disease over 28 years. Am J Epidemiol 1996;144:793–7. 10. Burchfiel CM, Sharp DS, Curb JD, et al. Physical activity and incidence of diabetes: the Honolulu Heart Program. Am J Epidemiol 1995;141:360 –8. 11. Giovannucci E, Ascherio A, Rimm EB, Colditz GA, Stampfer MJ, Willett WC. Physical activity, obesity, and risk for colon cancer and adenoma in men. Ann Intern Med 1995;122:327–34. 12. Longnecker MP, Gerhardsson le Verdier M, Frumkin H, Carpenter C. A case– control study of physical activity in relation to risk of cancer of the right colon and rectum in men. Int J Epidemiol 1995;24:42–50. 13. Whaley MH, Blair SN. Epidemiology of physical activity, physical fitness and coronary heart disease. J Cardiovasc Risk 1995;2:289 –95. 14. Boule NG, Haddad E, Kenny GP, Wells GA, Sigal RJ. Effects of exercise on glycemic control and body mass in type 2 diabetes mellitus: a meta-analysis of controlled clinical trials. JAMA 2001;286:1218 –27. 15. Wolff I, van Croonenborg JJ, Kemper HC, Kostense PJ, Twisk JW. The effect of exercise training programs on bone mass: a meta-analysis of published controlled trials in pre- and postmenopausal women. Osteoporos Int 1999;9:1–12. 16. Lemura LM, von Duvillard SP, Mookerjee S. The effects of physical training of functional capacity in adults. Ages 46 to 90: a meta-analysis. J Sports Med Phys Fitness 2000;40:1–10. 17. Kelley GA, Kelley KS, Tran ZV. Resistance training and bone mineral density in women: a meta-analysis of controlled trials. Am J Phys Med Rehabil 2001;80:65–77. 18. Kelley GA, Sharpe Kelley K. Aerobic exercise and resting blood pressure in older adults: a meta-analytic review of randomized controlled trials. J Gerontol Med Sci 2001;56:298 –303. 19. Latham N, Anderson CS, Bennett D, Stretton C. Progressive resistance strength training for physical disability in older people (Cochrane Review), version 2. Oxford: The Cochrane Library, 2003. 20. Chandler JM, Duncan PW, Kochersberger G, Studenski S. Is lower extremity strength gain associated with improvement in physical performance and disability in frail, community-dwelling elders? Arch Phys Med Rehabil 1998;79:24 –30. 21. Lazowski DA, Ecclestone NA, Myers AM, et al. A randomized outcome evaluation of group exercise programs in long-term care institutions. J Gerontol A Biol Sci Med Sci 1999;54:621–8. 22. Fiatarone MA, O’Neill EF, Ryan ND, et al. Exercise training and nutritional supplementation for physical frailty in very elderly people. N Engl J Med 1994;330:1769 –75. 23. Jette AM, Lachman M, Giorgetti MM, et al. Exercise—it’s never too late: the Strong-for-Life program. Am J Public Health 1999;89:66 –72. 24. Judge JO, Whipple RH, Wolfson LI. Effects of resistive and balance exercises on isokinetic strength in older persons. J Am Geriatr Soc 1994;42:937–46. 25. Baker KR, Nelson ME, Felson DT, Layne JE, Sarno R, Roubenoff R. The efficacy of home based progressive strength training in older adults with knee osteoarthritis: a randomized controlled trial. J Rheumatol 2001;28: 1655–65. 26. Morris JN, Fiatarone M, Kiely DK, et al. Nursing rehabilitation and exercise strategies in the nursing home. J Gerontol Med Sci 1999;54:494 –500. 27. Maurer BT, Stern AG, Kinossian B, Cook KD, Schumacher HR Jr. Osteoarthritis of the knee: isokinetic quadriceps exercise versus an educational intervention. Arch Phys Med Rehabil 1999;80:1293–9. 28. Petrella RJ, Bartha C. Home based exercise therapy for older patients with knee osteoarthritis: a randomized clinical trial. J Rheumatol 2000;27:2215– 21. 29. O’Reilly SC, Muir KR, Doherty M. Effectiveness of home exercise on pain and disability from osteoarthritis of the knee: a randomized controlled trial. Ann Rheum Dis 1999;58:15–9. 30. van Baar ME, Assendelft WJ, Dekker J, Oostendorp RA, Bijlsma JW. Effectiveness of exercise therapy in patients with osteoarthritis of the hip or
31. 32.
33.
34.
35. 36. 37.
38.
39.
40.
41. 42. 43.
44.
45.
46.
47. 48.
49.
50.
51. 52. 53.
54.
55.
knee: a systematic review of randomized clinical trials. Arthritis Rheum 1999;42:1361–9. Nagi SZ. A study in the evaluation of disability and rehabilitation potential: concepts, methods, and procedures. Am J Public Health 1964;54:1568 –79. Nagi SZ. Disability concepts revisited: implications for prevention. In: Pope AM, Tarlove AR, eds. Disability in America: toward a national agenda for prevention. Washington DC: National Academy Press, 1991:309 –27. Oxford Centre for Evidence-Based Medicine. Oxford Centre for EvidenceBased Medicine levels of evidence. Available at: http://minerva.minervation.com/cebm/docs/levels.html#levels. Accessed November 25, 2002. Caspersen C, Powell KE, Christenson GM. Physical activity, exercise and physical fitness: definitions and distinctions for health-related research. Public Health Rep 1985;100:126 –30. Jette AM. Assessing disability in studies on physical activity. Am J Prev Med 2003;25(suppl):122– 8. Guralnik JM, Ferrucci L. Assessing the building blocks of function: utilizing measures of functional limitation. Am J Prev Med 2003;25(suppl):112–21. Centers for Disease Control and Prevention. Arthritis prevalence and activity limitations—United States, 1990. MMWR Morb Mortal Wkly Rep 1994;43:433–8. Centers for Disease Control and Prevention. Prevalence of self-reported arthritis or chronic joint symptoms among adults—United States, 2001. MMWR Morb Mortal Wkly Rep 2002;51:948 –50. Freedland RL, Festa C, Sealy M, et al. The effects of pulsed auditory stimulation on various gait measurements in persons with Parkinson disease. Neuro Rehabil 2002;17:81–7. Thaut MH, McIntosh GC, Rice RR, Miller RA, Rathbun J, Brault JM. Rhythmic auditory stimulation in gait training for Parkinson disease patients. Mov Disord 1996;11:193–200. Keysor JJ, Jette AM. Have we oversold the benefit of late-life exercise? J Gerontol A Biol Sci Med Sci 2001;56:412–23. Chandler JM, Hadley EC. Exercise to improve physiologic and functional performance in old age. Clin Geriatr Med 1996;12:761–84. Ettinger WH Jr, Burns R, Messier SP, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis. The Fitness Arthritis and Seniors Trial (FAST). JAMA 1997;277:25–31. van Baar ME, Dekker J, Oostendorp RA, et al. The effectiveness of exercise therapy in patients with osteoarthritis of the hip or knee: a randomized clinical trial. J Rheumatol 1998;25:2432–9. Berkman LF, Seeman TE, Albert M, et al. High, usual and impaired functioning in community-dwelling older men and women: findings from the MacArthur Foundation Research Network on Successful Aging. J Clin Epid 1993;46:1129 –40. LaCroix AZ, Guralnik JM, Berkman LF, Wallace RB, Satterfield S. Maintaining mobility in late life. II. Smoking, alcohol consumption, physical activity, and body mass index. Am J Epidemiol 1993;137:858 –69. Mor V, Murphy J, Masterson-Allen S, et al. Risk of functional decline among well elders. J Clin Epidemiol 1989;42:895–904. Stewart AL, Hays RD, Wells KB, Rogers WH, Spritzer KL, Greenfield S. Long-term functioning and well-being outcomes associated with physical activity and exercise in patients with chronic conditions in the Medical Outcomes Study. J Clin Epidemiol 1994;47:719 –30. Miller ME, Rejeski WJ, Reboussin BA, Ten Have TR, Ettinger WH. Physical activity, functional limitations, and disability in older adults. J Am Geriatr Soc 2000;48:1264 –72. Huang Y, Macera CA, Blair SN, Brill PA, Kohl HW 3rd, Kronenfeld JJ. Physical fitness, physical activity, and functional limitation in adults aged 40 and older. Med Sci Sports Exerc 1998;30:1430 –5. Pinsky JL, Leaverton PE, Stokes J 3rd. Predictors of good function: the Framingham study. J Chronic Dis 1987;40:159 –67, 181–2. Simonsick EM, Lafferty ME, Phillips CL, et al. Risk due to inactivity in physically capable older adults. Am J Public Health 1993;83:1443–50. Kovar PA, Allegrante JP, MacKenzie CR, Peterson MG, Gutin B, Charlson ME. Supervised fitness walking in patients with osteoarthritis of the knee. A randomized, controlled trial. Ann Intern Med 1992;116:529 –34. Ettinger WH, Burns R, Messier SP, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis: the fitness arthritis and seniors trail. JAMA 1997;277:25–31. Penninx BW, Messier SP, Rejeski WJ, et al. Physical exercise and the prevention of disability in activities of daily living in older persons with osteoarthritis. Arch Intern Med 2001;161:2309 –16.
Am J Prev Med 2003;25(3Sii)
135
56. Meuleman JR, Brechue WF, Kubilis PS, Lowenthal DT. Exercise training in the debilitated aged: strength and functional outcomes. Arch Phys Med Rehabil 2000;81:312–8. 57. Wu SC, Leu S, Li C. Incidence of and predictors for chronic disability in activities of daily living among older people in Taiwan. J Am Geriatr Soc 1999;47:1082–6. 58. Leveille SG, Guralnik JM, Ferrucci L, Langlois JA. Aging successfully until death in old age: opportunities for increasing active life expectancy. Am J Epidemiol 1999;149:654 –64. 59. DiPietro L. Physical activity in aging: changes in patterns and their relationship to health and function. J Gerontol Med Sci 2001;56(suppl 2):13–22.
136
60. Frank JS, Patla AE. Balance and mobility challenges in older adults: implications for preserving community mobility. Am J Prev Med 2003; 25(suppl):157– 63. 61. Rejeski WJ, Ettinger WH, Martin K, Morgan T. Treating disability in knee osteoarthritis with exercise therapy: a central role for self-efficacy and pain. Arthritis Care Res 1998;11:94 –101. 62. King AC, Rejeski WJ, Buchner DM. Physical activity interventions targeting older adults. A critical review and recommendations. Am J Prev Med 1998;15:316 –33. 63. Lachman ME, Jette AM, Tennstedt S, Howland J, Harris BA, Peterson E. A cognitive-behavioral model for promoting regular physical activity in older adults. Psychol Health Med 1997;2:251–61.
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