“ Geriatricians have known for a while that you can’t make treatment decisions based on age alone,” said Dr. Thomas T. Perls, director of the New England Centenarian Study at the Boston University School of Medicine. “I think the medical literature is just catching up with the social observations that 80 is the new 50.” http://www.msnbc.msn.com/id/28282424/ (Elia, 1991) http://www.unm.edu/~lkravitz/Article%20folder/age.html
( Journal of the American Medical Association JAMA: 2000, Vol. 283. No. 22, pp. 2961-2967) http://www.news.harvard.edu/gazette/1999/10.21/diabetes.html http://www.reuters.com/article/healthNews/idUSTRE53E71N20090415?feedType=RSS&feedName=healthNews http://www.nature.com/bjc/index.html http://www.ncbi.nlm.nih.gov/pubmed/18599492?ordinalpos=18&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
---http://www.cdc.gov/nccdphp/dnpa/physical/health_professionals/index.htm over half of US adults do not engage in physical activity at levels consistent with public health --http://books.nap.edu/openbook.php?record_id=1627&page=118 IOM: Greater then 1/2 of all US children do not get enough exercise to develop a healthy heart and lungs --http://www.cdc.gov/nccdphp/sgr/intro.htm Daily enrollment in physical education classes has declined among high school students from 42 percent in 1991 to 25 percent in 1995. --Only 19 percent of all high school students are physically active for 20 minutes or more, five days a week, in physical education classes. high school students are physically active for 20 minutes or more, five days a week, in physical education classes.
Goals• Define basic concepts• Explore national trends• Review recommendations for exercise• Discuss common benefits of exercise• Discuss Basic Physiology of Aging• Clinical Pearls and Experiential Piece
Define Elderly• State of mind or a number• Biology or chronology
Western World• Elderly > 65• Very Old > 80• Very, very old >100
Exercisemovement of the body resulting in theenhancement of health and improvement of function
Categories of exercise• Leisure time Exercise: organized sports, running, gym activities, rehabilitation etc.• Lifestyle Exercise: activity incorporated into our daily pattern of life – eg: parking in the distant portion of the parking lot rather then the first bumper, taking the stairs instead of the elevator etc.
Types of exercise• Cardiovascular• Strength/Resistance Training• Core Stability/Balance• Flexibility/Coordination
US Gov. Reccomendations 30 minutes/day 4-5 days a week 150 min/wk
Benefits of Exercise• Reduces risk of – Heart Disease ≈ 40% – Obesity: ≈ 30-100% – Stroke ≈ 50% – Type 2 Diabetes ≈ 50% – Hypertension ≈ 50% – Disability delayed ≈15 years – Colon Cancer ≈ 25-40% – Breast Cancer ≈ 20%-44% – Osteoporosis ≈ 20+%• As many as 250,000 deaths per year in the United States are attributable to a lack of regular physical activity
Exercise Trends• > 60% of adults are not regularly active• 25% are not active at all• By age 75 1:3 men and 1:2 women engage in NO physical exercise
“Many people have arthritis and rheumatism; they get bum knees, a bum back. A lot of guysget a little pain in the toe or knee and then theywont exercise. Well gee, you have 640 musclesin your body. There may be a few exercises you cant do, but there are hundreds you can do!” Jack Lallane
Summary• More citizens > 65 than ever before• Exercise is a powerful preventive and vitalizing modality• Few achieve the recommended goals of exercise
The Physiology of Aging• Cardiovascular: – 20-30% in CO by 65 – Max. 02 uptake by 9-5% per decade, for sedentary men and women – Vascular elasticity = 10-40 mm Hg SBP/DBP – Maximum HR app.10 bpm/decade
Physiology of Aging• Respiratory: – FVC of 40 to 50% by age 70 – in chest wall compliance – Maximum Ventilation – in Alveolar size and conc.
Physiology of Aging• Muscles –40% in muscle mass by 70 – muscle fiber size & # –30% in strength by 70
Physiology of Aging• Skeletal health: – 1% in bone mass/yr after 35 – Post-menopause 2-3% per year for 5-10 yrs – rates of OA, sponylo-arthropathy, general joint dysfunction and degeneration
Physiology of Aging• Connective Tissue: – elasticity – shortened muscle fibers – synovial fluid volume – Up to 15% reduction in nerve cond. – Hgb, Hct, RCM
Disuse• Bedrest: – BMD, increased bone resorption – muscle mass and strength – muscle fiber size – fatty infiltration of muscle – Impaired O2 exchange – Cardiac function, efficiency
• “A review of biologic changes commonly attributed to the process of aging demonstrates the close similarity of most of these to changes subsequent toDisuse and Aging a period of enforced physical inactivity. The coincidence of these changes from the subcellular to the whole-body level of organization, and across a wide range of body systems, prompts the suggestion that at least a portion of the changes that are commonly attributed to aging is in reality caused by disuse and, as such, is Walter Bortz MD subject to correction. There is no drug in current or prospective use that holds as much promise for sustained health as a lifetime program of physical exercise.”(JAMA 1982;248:1203-1208)
“There may be no single feature of age-related decline that could more dramatically affect ambulation, mobility, calorie intake, and overall nutrient intake and status, independence, breathing, etc. than the decline in lean body mass.” Aging, Atrophy and Apoptosis:Failing “A’s” for Frailty National Conference on Aging
J Am Geriatr Soc. 2002 May;50(5):889-96. Low relative skeletal muscle mass (sarcopenia) in older persons is associated with functional impairment and physical disability.• NHANES III Data• 4,504 adults aged 60 and older.• Evaluated Skeletal muscle mass as estimated from bioimpedance analysis measurements• Class I sarcopenia when SMI = 1-2 SD of young adult values• Class II sarcopenia when SMI ≤ 2 SD of young adult values
“The likelihood of functional impairment and disability was approximately two times greater in the older men and three times greater in the older women with class II sarcopenia than in the older men and womenwith a normal SMI These observations provide strong support for the prevailing view that sarcopenia may be an important and potentially reversible cause of morbidity and mortality in older persons.”
Wien Klin Wochenschr. 2009;121(23-24):757-64.Efficacy of systematic endurance and resistance training on muscle strength and endurance performance in elderly adults--a randomized controlled trial.• Older Individuals randomized to either endurance training (ET) and resistance training (RT)• Evaluated changes in lean muscle, strength, endurance, O2• RT leads to a genuine increase in lean body mass and muscle strength in healthy elderly adults
Sports Med. 2000 Oct;30(4):249-68. Strength training in the elderly: effects on risk factors for age-related diseases.• (i) produces substantial increases in the strength, mass, power and quality of skeletal muscle• (ii) can increase endurance performance• (iii) normalizes blood pressure in those with high normal values• (iv) reduces insulin resistance• (v) decreases both total and intra-abdominal fat• (vi) increases resting metabolic rate in older men• (vii) prevents the loss of BMD with age• (viii) reduces risk factors for falls• (ix) may reduce pain and improve function in those with osteoarthritis in the knee region
Arch Phys Med Rehabil. 1996 Apr;77(4):399-405.Health-related fitness test battery for adults: aspects of reliability.• Balance: – standing on one leg with eyes open for balance• Flexibility – side-bending of the trunk for spinal flexibility• Upper Body Strength – modified push-ups for upper body muscular function• Lower Body Strength – jump and reach and one leg squat
American College of Sports Medicine Position Stand. Exercise and physical activity for older adults.• Participation in a regular exercise program is an effective intervention/ modality to reduce/prevent a number of functional declines associated with aging. Further, the trainability of older individuals (including octo- and nonagenarians) is evidenced by their ability to adapt and respond to both endurance and strength training. Endurance training can help maintain and improve various aspects of cardiovascular function (as measured by maximal VO2, cardiac output, and arteriovenous O2 difference), as well as enhance submaximal performance. Importantly, reductions in risk factors associated with disease states (heart disease, diabetes, etc.) improve health status and contribute to an increase in life expectancy. Strength training helps offset the loss in muscle mass and strength typically associated with normal aging. Additional benefits from regular exercise include improved bone health and, thus, reduction in risk for osteoporosis; improved postural stability, thereby reducing the risk of falling and associated injuries and fractures; and increased flexibility and range of motion. While not as abundant, the evidence also suggests that involvement in regular exercise can also provide a number of psychological benefits related to preserved cognitive function, alleviation of depression symptoms and behavior, and an improved concept of personal control and self-efficacy. It is important to note that while participation in physical activity may not always elicit increases in the traditional markers of physiological performance and fitness (e.g., VO2max, mitochondrial oxidative capacity, body composition) in older adults, it does improve health (reduction in disease risk factors) and functional capacity. Thus, the benefits associated with regular exercise and physical activity contribute to a more healthy, independent lifestyle, greatly improving the functional capacity and quality of life in this population.
Summary• Much atrophy, weakness, frailty and disease risk are associated with disuse and de- conditioning• These can be modified by adopting a habit of regular exercise
Clinical Pearls• The Sharpened Rombergs test: – In the tandem stance, the patient places one foot in front of the other, heel touching toe, with his or her eyes closed. A patient who is not able to maintain this position for more than 10 seconds is at increased risk for falls.
Clinical Pearls• The Unipedal Balance Test – is used to detect subtle balance impairments. The patient is asked to stand on one foot with the other foot raised 2 inches off the floor and not touching the other ankle or foot. Increased fall risk is associated with an inability to remain in that position for at least 5 seconds.
Clinical Pearls• The timed 360-degree turn test – assesses dynamic balance. The patient is asked to turn in a circle while taking steps. An inability to complete the maneuver in less than 4 seconds indicates an increased risk of falling.
Clinical Pearls• 180-degree turn test – where the number of steps the patient needs to turn halfway around is counted. Staggering during the turn, an inability to pivot during the turn, using five or more steps to complete the turn, or taking 3 seconds or longer to accomplish the turn are indicative of problems in turning while walking.
Clinical Pearls• The five times sit to stand test – is used to assess lower extremity strength. The patient is asked to rise from a standard chair, with arms folded across the chest, five times consecutively. The ability to rise from a chair requires vision, proprioception, balance, and sensorimotor skills. An inability to complete the maneuver, standing and sitting back down in less than 14 seconds, indicates an increased level of disability.
J Am Geriatr Soc. 2001 May;49(5):664-72. Guideline for the prevention of falls in older persons. American Geriatrics Society,British Geriatrics Society, and American Academy of Orthopaedic Surgeons Panel on Falls Prevention.• The AGS/BGS guidelines – Timed Up and Go Test (TUGT) as a screening tool for identifying older people at increased risk of falls. Indicator of ‘basic mobility’ – 3 retrospective studies have examined the relationship between TUGT performance and falls in community-dwelling people. – a TUGT cut-point of 14 seconds significantly discriminated between the faller and non-faller groups. Using this criterion, 13/15 subjects from both groups were correctly classified, providing a sensitivity and specificity for identifying falls outcome of 87%. Rose et al.  used a similar classification of faller status (no falls versus two plus falls in the past year) in their study of 134 subjects. A considerably lower cut-point (10 seconds) was identified as optimal for discriminating between non-fallers and recurrent fallers. With this criterion the overall prediction rate was 80%: specificity 86% and sensitivity 71%. The third study comprised 157 subjects classified as either fallers (one plus fall in the past year) or non-fallers . In this sample, the TUGT had very high sensitivity with 98% of the 109 fallers being correctly classified, but considerably lower sensitivity, with only 15% of the 48 non- fallers being correctly classified.
Clinical Pearls• Get up and Go Test: – Pt seated on 46-cm-high chair – Stand up – Walk 3 m at their usual walking pace – Turn 180° – Walk back to the chair – Sit down• >10 seconds = risk of falls
• Sensitivity of a modified version of the timed get up and go test to predict fall risk in the elderly: a pilot study.• Giné-Garriga M, Guerra M, Marí-DellOlmo M, Martin C, Unnithan VB.• FPCEE Blanquerna, Universitat Ramon Llull, Department of Physical Activity and Sport Sciences, Císter 34, 08022 Barcelona, Spain.• Abstract• The purpose of this study was to assess the sensitivity of a modified version of the Timed Get Up and Go (TGUG) test in predicting fall risk in elderly individuals, using both a quantitative and qualitative approach in individuals older than 65 years. Ten subjects (83.4+/-4.5 years) undertook the test twice. To assess inter-rater reliability, three investigators timed the two trials using a stopwatch (quantitative). The reproducibility of a qualitative evaluation of the trials was accomplished by the completion of an assessment questionnaire (AQ) at each trial by three investigators. To assess the agreement between the three investigators, the coefficients of reliability (CR), intra-class correlation coefficients (ICC) and limits of agreement were determined for the total time to do the test (TT). The weighted Kappa K of Cohen and ICC was calculated for the AQ. Inter- group comparison: 60 subjects (74.2+/-4.9 years) were divided equally into four groups: (1) sedentary with previous history of falls, (2) sedentary without history of falls, (3) active with history of falls, and (4) active without history of falls. All of them undertook the modified TGUG test once. One investigator undertook the timing and completed the AQ. CR values for the TT were above 98% and with ICC of TT=0.999. The differences in TT between the three investigators measures ranged from 0.19-0.55 s S.D. of the mean difference. Weighted Kappa K of Cohen ranged 0.835-0.976, with ICC of AQ=0.954. Inter-group comparison study. Significant differences (p<0.05) were noted between the mean score of TT of Group 4 and the rest of the groups, and between Groups 2 and 1. Significant differences (p<0.05) were noted between the mean score of points obtained in the AQ of Group 1 and the rest of the groups. The modified version of the TGUG test demonstrated good sensitivity for detecting fall risk in elderly individuals, and good inter-tester reliability from both a quantitative and qualitative perspective.
• Age Ageing. 2008 Jul;37(4):442-8. Epub 2008 May 30.• Prognostic validity of the Timed Up-and-Go test, a modified Get-Up-and-Go test, staffs global judgement and fall history in evaluating fall risk in residential care facilities.• Nordin E, Lindelöf N, Rosendahl E, Jensen J, Lundin-Olsson L.• Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, SE-901 87 Umeå, Sweden. firstname.lastname@example.org• Abstract• OBJECTIVES: to evaluate and compare the prognostic validity relative to falls of the Timed Up-and-Go test (TUG), a modified Get-Up-and-Go test (GUG-m), staffs judgement of global rating of fall risk (GLORF) and fall history among frail older people. DESIGN: cohort study, 6-month prospective follow-up for falls. Participants: 183 frail persons living in residential care facilities in Sweden, mean age 84 years, 73% women. METHODS: the occurrence of falls during the follow-up period were compared to the following assessments at baseline: the TUG at normal speed; the GUG-m, a rating of fall risk scored from 1 (no risk) to 5 (very high risk); the GLORF, staffs rating of fall risk as high or low; a history of falls in the previous 6 months. These assessment tools were evaluated using sensitivity, specificity and positive and negative likelihood ratios (LR(+) to rule in and LR(-) to rule out a high fall risk). RESULTS: 53% of the participants fell at least once. Various cut-off values of the TUG (12, 15, 20, 25, 30, 35, 40 s) and the GUG-m showed LR(+) between 0.9 and 2.6 and LR(-) between 0.1 and 1.0. The GLORF showed an LR(+) of 2.8 and an LR(-) of 0.6 and fall history showed an LR(+) of 2.4 and an LR(-) of 0.6. CONCLUSIONS: in this population of frail older people, staff judgement of their residents fall risk as well as previous falls both appear superior to the performance-based measures TUG and GUG-m in ruling in a high fall risk. A TUG score of less than 15 s gives guidance in ruling out a high fall risk but insufficient information in ruling in such a risk. The grading of fall risk by GUG-m appears of very limited value.• PMID: 18515291 [PubMed - indexed for MEDLINE]Free Article
• Age Ageing. 2007 Jan;36(1):78-83. Epub 2006 Dec 15.• A comparison of different balance tests in the prediction of falls in older women with vertebral fractures: a cohort study.• Morris R, Harwood RH, Baker R, Sahota O, Armstrong S, Masud T.• Nottingham City Hospital, UK. email@example.com• Abstract• BACKGROUND: people with vertebral fractures are at high risk of developing hip fractures. Falls risk is important in the pathogenesis of hip fractures. AIM: to investigate if balance tests, in conjunction with a falls history, can predict falls in older women with vertebral fractures. METHODS: a cohort study of community-dwelling women aged over 60 years, with vertebral fractures. Balance tests investigated were: 5 m-timed-up-and-go-test (5 m-TUG), timed 10 m walk, TURN180 test (number of steps to turn 180 degrees ), tandem walk, ability to stand from chair with arms folded. Leg extensor power was also measured. OUTCOME MEASURE: fallers (at least one fall in a 12 month follow-up period) versus non-fallers. RESULTS: one hundred and four women aged 63-91 years [mean=78 +/- 7], were recruited. Eighty-six (83%) completed the study. Four variables were significantly associated with fallers: previous recurrent faller (2+ falls) [OR=6.52; 95% CI=1.69-25.22], 5 m- TUG test [OR=1.03; 1.00-1.06], timed 10 m walk [OR=1.07; 1.01-1.13] and the TURN180 test [OR=1.22; 1.00-1.49] [P <0.05]. Multi-variable analysis showed that only two variables, previous recurrent faller [OR=5.60; 1.40-22.45] and the 5 m-TUG test [OR=1.04; 1.00-1.08], were independently significantly associated with fallers. The optimal cut-off time for performing the 5 m-TUG test in predicting fallers was 30 s (area under ROC=60%). Combining previous recurrent faller with the 5 m-TUG improved prediction of fallers [OR=16.79, specificity=100%, sensitivity=13%]. CONCLUSIONS: a previous history of recurrent falls and the inability to perform the 5 m-TUG test within 30 s predicted falls in older women with vertebral fractures. Combining these two measures can predict fallers with a high degree of specificity (although a low sensitivity), allowing the identification of a group of patients suitable for fall and fracture prevention measures
• Aging Clin Exp Res. 2005 Jun;17(3):181-5.• Concurrent and predictive validity of "getting up from lying on the floor".• Bergland A, Laake K.• Faculty of Health Sciences, Oslo University College, Oslo, Norway. Astrid.Bergland@hf.hio.no• Abstract• BACKGROUND AND AIMS: Older age, higher morbidity and lower functional capacity are associated with fall injuries. Inability to get up from the floor is associated with older age, higher morbidity and lower functional capacity. The purpose of this study was to assess the concurrent and predictive validity of the ability of elderly women to get up from lying on the floor. METHODS: In a random sample of 307 women aged 75 years and over (mean 80.8 years, response rate 74.5%) living in the community, baseline registrations of ability to get up from lying on the floor, health and function were recorded. Serious fall injuries during the subsequent year served as the outcome. RESULTS: 240 (78.2%) managed to get up independently. The highest independent association was with items primarily related to mobility, e.g., ability to climb steps and performance on the Timed Up & Go test (TUG). However, arthrosis of the hip and difficulty with walking indoors were among the variables independently associated with the ability to get up from lying on the floor. During the follow-up year, 50.5% experienced falls, of which one in four resulted in serious injury and one in eight in a fracture. The ability to get up from lying on the floor was a significant predictor of serious fall-related injury (OR 2.1). Among those who experienced a fall, the risk of injury was markedly higher for those unable to rise (OR 3.7). The positive predictive value of being unable to rise for serious injury was 0.30, indicating that nearly one out of three of the elderly women with such problems are predicted to experience a serious fall-related injury during the following 12 months. CONCLUSIONS: The test "get up from lying on the floor" is a marker of failing health and function in the elderly and a significant predictor of serious fall injuries.
• Arch Phys Med Rehabil. 2004 Feb;85(2):284-9.• Get up and go test in patients with knee osteoarthritis.• Piva SR, Fitzgerald GK, Irrgang JJ, Bouzubar F, Starz TW.• Department of Physical Therapy, SHRS, University of Pittsburgh, Pittsburgh, PA 15260, USA. firstname.lastname@example.org• Abstract• OBJECTIVE: To determine the reliability, minimum detectable change (MDC), and validity of the Get Up and Go (GUG) test. DESIGN: Repeated-measures test-retest for reliability. Correlational study for validity. SETTING: Institutional practice. PARTICIPANTS: Convenience sample of 130 people, 105 with knee osteoarthritis (OA) (80 women; mean age, 62+/-9 y) and 25 healthy controls (21 women; mean age, 57+/-8 y). INTERVENTIONS: Not applicable. Main outcome measures Western Ontario and McMaster Universities Osteoarthritis Index, the Activity of Daily Living Scale of the Knee Outcome Survey, and the 8 scales of the Medical Outcomes Study 36-Item Short-Form Health Survey. RESULTS: Intratester and intertester reliability was.95 (95% confidence interval [CI],.72-.98) and.98 (95% CI,.94-.99), respectively. The MDC, based on measurements by a single tester and between testers, was 1.5 and 1.2 seconds, respectively. Time to perform the GUG test was longer for persons with knee OA than it was for the controls (mean difference, 3.3s; 95% CI, 1.8-4.9). Correlations between the GUG test and measures of physical function did not differ significantly from correlations between the GUG test and measures that do not specifically evaluate physical function. CONCLUSIONS: The GUG test is reliable and has an MDC that is adequate for clinical use. Validity of the GUG test as a single measure of physical function was not supported. Further research should include testing a battery of performance-based measures of physical function.
Where it all started!• Arch Phys Med Rehabil. 1986 Jun;67(6):387-9.• Balance in elderly patients: the "get-up and go" test.• Mathias S, Nayak US, Isaacs B.• Abstract• The "get-up and go test" requires patients to stand up from a chair, walk a short distance, turn around, return, and sit down again. This test was conducted in 40 elderly patients with a range of balance function. Tests were recorded on video tapes, which were viewed by groups of observers from different medical backgrounds. Balance function was scored on a five-point scale. The same patients underwent laboratory tests of gait and balance. There was agreement among observers on the subjective scoring of the clinical test, and good correlation with laboratory tests. The get-up and go test proved to be a satisfactory clinical measure of balance in elderly people.
Clinical Pearls• Simple in clinic or hospital evals can provide a general sense of pt fall risk and foundational fitness
Summary• Aging is a natural part of living• Atrophy, Sarcopenia and disability can be slowed or prevented• Simple, daily choices can alter our own and our patient’s course• Simple clinical evaluations can be of value• We can have great influence in our patient’s health
“Physical fitness can neither beachieved by wishful thinking nor outrightpurchase.” Joseph Pilates
“First say to yourself what you would be; and then do what you have to do” Epictectus Greek Stoic Philosopher AD 55–AD 135
• BIBLIOGRAPHY• BROWN, M.; SINACORE, D. R.; EHSANI, A. A.; BINDER, E. F.; HOLLOSZY, J. O.; and KOHRT, W. M. "Low-Intensity Exercise As a Modifier of Physical Frailty in Older Adults." Archives of Physical Medicine and Rehabilitation 81 (2000): 960–965.• BUCHNER, D. M., and WAGNER, E. H. "Preventing Frail Health." Clinics in Geriatric Medicine 8 (1992): 1–17.• FIATARONE, M. A.; ONEILL, E. F.; RYAN, N. D.; et al. "Exercise Training and Nutritional Supplementation for Physical Frailty in Very Elderly People." New England Journal of Medicine 330 (1994): 1769–1774.• HUNTER, G. R.; TREUTH, M. S.; WEINSIER, R. L.; et al. "The Effects of Strength Conditioning on Older Womens Ability to Perform Daily Tasks." Journal of the American Geriatrics Society 43 (1995): 756–760.• JACKSON, A. S.; BEARD, E. F.; and WIER, L. T. "Changes in Aerobic Power of Men Ages 25–70." Medical Science of Sports and Exercise 27 (1995): 113–120.• KENNIE, D. C.; DINAN, S.; and YOUNG, A. "Health Promotion and Physical Exertion." In Brocklehursts Textbook of Geriatric Medicine and Gerontology, 5th ed. Edited by R. Tallis, H. Fillit, and J. C. Brocklehurst. Edinburgh: Churchill Livingstone, 1998. Pages 1461–1472.• PROVINCE, M. A.; HADLEY, E. C.; HORNBROOK, M. C.; et al. "The Effects of Exercise on Falls in Elderly Patients: A Preplanned Meta-Analysis." Journal of the American Medical Association 273 (1995): 1341–1344.• SHEPHARD, R. J. "Physical Fitness and Exercise." In Principles and Practice of Geriatric Medicine. Edited by M. S. J. Pathy. Chichester, U.K.: John Wiley & Sons, 1998. Pages 137–151.• WOLFSON, L.; WHIPPLE, R.; DERBY, C.; et al. "Balance and Strength Training in Older Adults: Intervention Gains and Tai-Chi Maintenance." Journal of the American Geriatrics Society 44 (1996): 498–506.
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