Exercise Training for Coronary Artery Disease in the Elderly

CORONARY ARTERY DISEASE IN THE ELDERLY

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EXERCISE TRAINING FOR CORONARY ARTERY DISEASE IN THE ELDERLY William F. Brechue, PhD, and Michael L. Pollock, PhD

VOLUME 12. NUMBER I FEBRUARY 1996

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BRECHUE & POLLOCK

physiologic decline associated with aging and the effects of exercise training and describe how exercise training is prescribed and used in the primary and secondary prevention of the clinical problems associated with aging and CAD.

PHYSIOLOGIC DECLINE WITH AGE AND CARDIAC DISEASE

The decline in organ function that accompanies aging is a consequence of agerelated decrements in cardiovascular, ~ulmonarv,and musculoskeletal structure. Ultimately, these result in impaired 'dhysical f&ction in the elderly. The major changes in these organ structure-function relationships as they pertain to loss of function in the elderly and aged patient with cardiac disease are discussed.

Cardiovascular Structure-Function

Perhaps the most important age-related structural change in the cardiovascular system is the reduction in vascular smooth muscle compliance caused by Age-related reductions in infiltration of connective tissue and cal~ification.~~ Windkessel vessel (aorta and arteries) compliance and function lead to increased systolic and end-systolic pressures. Thus, at a given stroke volume and peripheral resistance, a higher afterload is placed on the heart. The aged myocardium contracts slower, prolonging systole, and at high systolic loads, at the expense of diastole. Reduced diastole impairs coronary perfusion and oxygen delivery when myocardial oxygen demand is high because of high afterload. Additionally, vascular wall stiffening occurs and results in a 2- to 3-fold increase in pulse-wave velocity.65Thus the third pulse-wave, which is normally reflected back to the heart after systole has ended (in young individuals), arrives at the heart earlier and become superimposed on end-systolic pressure, increasing the afterload of the left ventricle. This additional afterload exacerbates the impingement on diastolic time and myocardial oxygen demand. Cardiac structural compensation resulting from systolic hypertension includes increased cardiac mass reflective of left ventricular wall and septa1 wall h y p e r t r ~ p h y Additionally, .~~ the hypertrophic responses are compensatory for declining myocardial contractile function and speed of contraction. Myocardial enlargement appears to be limited to changes in wall thickness50in individuals less than 70 years of age, with additional left ventricular wall thickening and chamber volume hypertrophy occurring after 70 years of age.50Resting systolic function, stroke volume and cardiac output, do not appear to change with age despite a decrease in ejection fraction. Diastolic function is affected by age. Diastolic filling of the heart is delayed by reduced early filling and prolonged time-to-peak filling. This aspect of reduced diastolic function is related to slower relaxation of ventricular tension (delayed -..-...,.. I .-.C l ~ - . ! , - ~ . - . - . ! ! ~ ?.--I l ? ; --:-----\ L' 1--------1 ?I:--c-1:, ,,,1 ,:,,,-, fn 1 r ; l r L v v u l v~ ~;i;lLiii:j, iI:;=CL:=L; '-l;l=L.-';l' ' 1 ; : ' ."-. . .. -cnmn,d,7nr - --. ...-.. J -ventricular hypertrophy,'j5and stiffening and slowing of cardiac v a l v e ~Diastolic .~~ filling is compensated by a larger atrial systole and evidence exists for atrial h y p e r t r ~ p h yUltimately, .~~ end-diastolic volume is elevated, which leads to the reduced ejection fraction. Important neurohumoral changes are associated with the aging cardiovascular system. A decline in the responsiveness to beta receptor agonists leads to reduced sympathetic control of the heart. Changes in sympathetic drive apparently do not occur in the elderly. Plasma norepinephrine is elevated about 10%to 15% IILLILILCIIUIUI

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EXERCISE TRAINING FOR CORONARY ARTERY DISEASE IN THE ELDERLY

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per decadez7in the elderly and is probably related to reduced clearance. Release of epinephrine from the adrenal medulla appears to be reduced in the elderly. Resting heart rate is predominantly controlled by the parasympathetic nervous system. There is a tendency for a decrease in vagal tone with age and thus a slight increase occurs in resting heart rate. Pulmonary Structure-Function

The proliferation of connective tissue in the chest wall results in decreased chest wall compliance and elastic recoil of the lungs. Lung tissue compliance is increased with age. Each of these factors results in a decline in vital capacity (4% to 5% per decade) and forced expiratory capacity as residual volume increases. Tidal volume increases (as much as 20% over that of younger individuals) but no change occurs in respiratory rate. Changes in the chest wall and lung compliance result in an increased work of breathing with decreased respiratory muscle strength and endurance. Musculoskeletal Structure-Function

Bone is a living tissue that functions as the supporting framework of the body and provides the mechanical levers for movement. It also plays a role in organ protection and mineral balance and produces the formed elements of blood. On the other hand, skeletal muscle attaches to bone and is primarily responsible for the conversion of chemical energy to mechanical energy and, ultimately, motion. Thus, the musculoskeletal system plays a central role in movement and physical function. Age-related decline in physical function is correlated with agerelated declines in bone and muscle. From about age 25, bone mass begins to decline.80This loss of bone mass may result in frail bones and can lead to the development of osteoporosis. In women, who are 6 times more likely to develop the disease than are men, osteoporosis is associated with increased bone loss after menopause. The loss in men is more gradual; about 3% per decade u p to age 90.e0This weakening of bone increases the likelihood of fracture with or without trauma or stress. Bone mineral density (BMD)is positively correlated with strength,4land women with osteoporosis have less muscular strength than do age- and weight-matched controls.83 From about age 30, muscle mass (cell size and number) and motor unit number begin to decrea~e.~' The reductions in muscle mass appear to result from selective loss of Type 11, fast-twitch fiberse2because Type I, slow-twitch fiber crosssectional area does not appear to change. Motor neurons to limb muscle decrease in older individuals resulting in a decrease in active motor units.58Type I motor unit size increases (number of fibers per nerve) while Type I1 motor unit size decreases. Decline in Function with AgelDisease

The cardiovascular and pulmonary systems provide the basic metabolites for energy transduction (oxygen, nutrients, etc.). The musculoskeletal system defines our physical structure and ambulatory function. Cardiovascular and musculoskeletal health has great impact on all facets of physical function and is the basis for independence. However, one of the major decrements associated with aging is

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the degeneration of the cardiovascular and musculoskeletal systems, which significantly increases frailty and disability, and results in a negative impact on Reduced cardiovascular fitness, function, independence, and quality of life.'0,30,31 decreased maximum oxygen uptake (hZmax) is a primary clinical predictor of impaired physical function and clinical survival.59 Several studies show that fractures and the associated pain and skeletal deformity lead to individual perceptions of impairment, dysfunction, and disabilBone loss has a negative impact on health and psychosocial well-being. Leg extension strength is closely related to speed of walking, stair-climbing power, or standing from a chair.'' Lack of strength with aging is highly correlated with reduced physical function, risk of falling, and fracture.64

Decline in Fitness

Fitness is defined in many ways. For present purposes fitness will be defined as "the set of attributes that people have or achieve that relates to the ability to perform moderate to vigorous levels of physical activity without undue fatigue and the capability of maintaining such ability throughout life."9' In the present case physical activity refers to one's ability to function independently in society. This may include activities of occupation or activities of daily life or leisure time. The operational definition includes a "multifactorial construct" encompassing several components that relate to one's capacity or ability for movement. The four components of fitness are cardiorespiratory endurance, body composition, muscular strength and endurance, and flexibility. Cardiorespiratory endurance is defined as the ability to perform dynamic, moderate-to-high intensity work using a large muscle mass for relatively long periods of time. The accepted measure of cardiorespiratory endurance is 0 0 ~ ~ ~ ~ VoZm,,is a marker of fitness and clinical status because it requires functional involvement from the cardiovascular, pulmonary, and skeletal muscle systems. \iToZmax declines at a rate of about 10%per decade after 25 years of age.47A significant fraction of decline in Vo2with age can be explained by age-related loss of muscle mass and increase in body fat. Included in skeletal muscle are decreases in aerobic enzyme activities (average 25%)36, 79 and muscle capillary density.17,18 Glycolytic activity and phosphagen stores do not appear affected by increased age.'7,62 Decrements in 0oZmax related to the cardiovascular system include a significantreduction in maximal cardiac output (heart rate and stroke volume), which reduces maximal limb blood flow. In patients with impaired chronotropic responses to exercise or beta-blocker therapy, the lack of heart rate response greatly affects cardiac output. The systolic hypertension and impaired diastolic function that accompany aging contribute to reduced stroke volume and increased myocardial oxygen demand, further limiting cardiovascular function. Pulmonary changes outlined above result in a reduced maximal ventilation as compared to that in young individuals. ??.-..-?;; -.,- , *,.r--;;ln.-.cS+lnr; s c - 1 ~ C n e . A :n the t-:.t.r- - ~----c . - n c r t m n f--.- -0A.nl j c. p-f -i ~.- - ~ 3 + . n q . -- -.- -.-.. r fat-free mass (FFM) and fat mass. Fat-free mass constitutes bone, skeletal muscle, and organs. Body weight increases up to the age of 50 to 60 years and then decreases with age. The predominate reason for this decrease after age 50 is the loss of FFM (that is, loss of bone and muscle mass). In addition, deposition of fat is increased, particularly centrally stored fat. An increase in body fat is associated with a poorer blood lipid profile. Serum total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides are increased and high-density lipoprotein (HDL) cholesterol is decreased with age. A&r--A.A-A.

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Muscular strength and endurance decreases with age. Many have observed a decline in muscular strength (30% to 50% decreases in maximal force) with aging.8,20 This loss in strength correlates with a decrease in muscle mass and a concomitant change in the skeletal muscle's intrinsic ability to produce force.85Frail elderly men and women are reported to be profoundly lacking in ~ t r e n g t h . ~ Flexibility ~ , ~ ' , ~ ~ also decreases with age; the reductions are exacerbated when patients rely on assistance with daily a ~ t i v i t i e s . ~ ~ Decline in Health with Age, Coronary Artery Disease

All-cause morbidity and mortality increases with age. Coronary artery disease is the major form of heart disease and is the most responsible for morbidity and mortality in the elderly. Two primary risk factors for CAD are hypertension and blood lipid abnormalities. Both are consequences of aging, thus age is a risk factor for CAD. As described above, reduced compliance in the aorta/arteries leads to significant rises in systolic blood pressure and afterload, hence hypertension. Increased loading of the heart with declining contractile function leads to cardiac morbidity. Also, the lipid abnormalities lead to atherosclerotic lesions in coronary and peripheral vessels. Almost all CAD is the result of atherosclerosis.The narrowing of coronary vessels leads to limited myocardial blood flow and an unmatching of oxygen supply and demand again leading to cardiac morbidity. Peripheral plaque formation also results in reduced aortic/arterial vessel compliance and hypertension. Age-related structural changes and atherosclerosis can affect vessel compliance independently, but are additive when both are present. Secondary factors imparting risk of CAD include the independent and interactive effects of obseity and diabetes. Again, both are consequences of aging and lifestyle and thus place the elderly individual at risk of CAD. Increased body fat was described above. The high prevalence of non-insulin-dependent diabetes associated with aging is the result of age-related insulin resistance and secondary glucose intolerance. Insulin resistance is also a consequence of obesity-in particular, centrally stored fat. Physical inactivity is also recognized as a risk factor for development of CAD. Physical inactivity exacerbates the decline in health and fitness with age through specific effects on body composition (muscle mass, body fat, and bone density), Vo2max, muscular strength and endurance, BMD, blood pressure, and insulin sensitivity. In addition, physical inactivity that follows with the progression of disease leads to further declines in health, fitness, and physical function. Thus, the remainder of this chapter focuses on the use of exercise training (physical activity) and its prescription specific to the rehabilitation of the elderly patient with cardiac disease. OUTCOME OF EXERCISE TRAINING IN THE ELDERLY Cardiovascular Changes with Exercise Training

Regular endurance exercise training in healthy, asymptomatic elderly people (>60 years of age) results in significant improvement in Vo2max.2634n,72 Improvements in VO~,,~range from 10% to 40% depending on the initial level of f i t n e s ~ . ~ ~ , ~ ~ Improvement in cardiac output by way of increased stroke volume and peripheral oxygen extraction are associated with these findings.39The improvement in VO~,,~correlates with increases in muscle aerobic enzyme activities, mitochondrial density, and capillary density.I7Aerobic training does not appear to af-

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fect glycolytic enzyme activities or phosphagen stores in the young or elderly.17,'8 Reductions in lactate dehydrogenase activity, as seen following endurance training, were similar in young and elderly participant^.^ At standardized levels of work, submaximalheart rate, systolicand diastolicblood pressure, and blood lactatelevels are reduced after endurance trainingz6The magnitude of the endurance training responses in the elderly is similar to that of younger individ~als.~'

Musculoskeletal Changes with Exercise Training

Exercise training significantly improves muscle mass, BMD, strength, aerobic capacity,3O,31- 35, 40, 51, 79 and physical function30, 31 in both elderly men and women. Resistance and aerobic training exercises are an effective means of minimizing or After 5 years of follow-up, women who reversing age-related bone loss.16,21,41,57,61,81 were endurance trained had significantly greater BMD than did their untrained counterpart^.^^ Though both strength and aerobic training, individually or in combination, appear to improve bone mass eq~ivalently,'~, one study shows that strength training may be superiorz1and may lead to more specific, regional changes.60Further, when exercise is stopped, detraining is associated with losses of BMD back to pretraining levels.19Several studies show that lumbar exercise can reduce back pain and disability while increasing BMD in elderly patients Bone loss and/or osteoporosis can be treated with hormone with osteopor~sis.~~ replacement or supplementation with calcium, calcitonin, or bisphosphoExercise in combination with hormone replacement or nutrient supplenates.45,56,87 mentation potentiates the improvements in BMD.'6,45 Progressive resistance exercise training programs result in increases in strength of up to 150% for the elderly and frail elderly.5,15, 30, 31, 35*36, 63, 79 After 8 weeks of strength training in frail elderly men and women (>80 years of age), increases in strength (174%)and muscle hypertrophy (15%)were reported with significant improvements in tandem gait speed?0,31,35 These high-intensity training protocols were both safe and effective. These increases in strength were partially explained by increases in skeletal muscle hypertrophy (10% to 20% increase in cross-sectional area) and increases in both Type I and I1 fiber^?^ Increased motor unit recruitment also accompanies increases in strength in the elderly.63Both elderly men and women showed equivalent changes in skeletal muscle hypertrophy. Importantly, the increased muscle mass resulted in improved 002,,, in the elderly?5,36 The magnitude of the change in strength after resistance exercise training of the elderly reflects their initial low levels of strength. The expected magnitude of change for both aerobic and strength training depends on the system's potential for improvement.

Regular aerobic exercise leads to significant improvements in FFM and fat mass and better body weight control. Programs involving exercise alone, without dieting, are associated with moderate reductions in body weight (1 to 3 kg) and percent fat (1%to 3%).71 Reductions in resting systolic and diastolicblood pressure, increased insulin sensitivity, and improved blood lipid profiles (decreased plasma triglycerides and LDL cholesterol and increased HDL cholesterol) are seen. Resistance exercise can positively impact upon insulin sensitivity/glucose tolerance

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but does not appear to have any effect (positive or negative) on blood pres~ure.4~ Though resistance exercise does not appear to have any specific effects on lipid profile or body fat, relative body fat (%) will decrease with the increases in body weight and FFM associated with this type of training.

GOAL OF EXERCISE TRAINING AND CARDIAC REHABILITATION IN THE ELDERLY

Many of the structural and functional decrements described above are in part related to level of physical activity. Training studies in the "healthy" elderly show that the cardiovascular and musculoskeletal systems are plastic and respond to an exercise stimulus as would those of younger individuals. Thus, activity/exercise can be used in primary prevention to improve or maintain fitness and/or health. Further, activity/exercise can be used as an intervention for rehabilitation from a cardiovascular event and secondary prevention of disease progression. The personal impact of maintained or recovered function in the elderly or aged patient would be improvements in quality of life and restoration of independence. The social impact would be a decreased need for medication or institutionalization and a decrease in health-care costs. The focuses of an exercise program for the elderly patient with cardiac disease should be restoring physical function and health, decreasing risk of cardiovascular morbidity, and reducing all-cause mortality. Cardiac rehabilitation is most effective when a multi-interventional approach is used. This approach should include patient education, lifestyle change, diet and lipid management, and smoking cessation in conjunction with an exercise program. The exercise program should include a well-rounded approach of both endurance- and resistive-type exercise that will affect three major areas specific to rehabilitating elderly patients with cardiac disease. 1. Reduction of CAD risk factors-One of the major goals in cardiac rehabilitation in general is reduction and control of hypertension. Regular endurance exercise will prove beneficial in this regard. Additionally, endurance exercise results in decreased body fat and aids in body weight control. Both endurance and resistance exercise will improve insulin sensitivity and glucose tolerance. 2. Restoration of BMD and muscle mass-Given the loss of muscle and BMD and profound muscular weakness of elderly individuals, we believe that the logical beginning to rehabilitation of function in the elderly patient with cardiac disease is generalized improvement in musculoskeletal integrity: increased BMD, muscle mass, and ultimately muscular strength. Increases in strength would improve ability to complete an appropriate endurance program and may reduce susceptibility to injury. In this respect, inclusion of a resistance exercise program is paramount because this is the only apparent way to specifically counteract age-related decreases in muscle mass and strength. 3. Restoration of fitness-A well-rounded exercise program will lead to significant improvements in aerobic capacity interaction of endurance and resistance exercise), muscular strength and endurance, and flexibility.

The following is a discussion of the guidelines for prescribing exercise and the components of a well-rounded exercise program that can accomplish these goals.

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GUIDELINES FOR EXERCISE PRESCRIPTION FOR ELDERLY PATIENTS WITH CARDIAC DISEASE Exercise Guidelines for Healthy Young and Middle-Aged Persons

The American College of Sports Medicine (ACSM)7and the American Heart Association (AHA)33have drafted guidelines/standards for exercise training that promote cardiovascular and muscular fitness in healthy adults. These standards are outline in Table 1. The difference between the two exercise statements is that the American Heart Association's statement lists only the minimum recommended exercise (3 d/wk, for 20 to 30 minutes at 50% to 60% of 002,,,),whereas the ACSM statement lists a range of training parameters. Intensity, Frequency, and Duration of Exercise

Improvement in aerobic capacity is related to an individual's initial level of ~ ~ -total ~ ~ amount fitness and the frequency and amount of work a c ~ o r n p l i s h e d .The of work performed is related to the duration and intensity of training, which are inversely related. Activities performed at lower intensity but for a longer duration provide the same benefit as activities carried out at higher intensities and shorter duration as long as the energy requirements are similar. Similar conclusions can be drawn for mode of activity. Training adaptations are independent of training modality when energy requirements are For example, similar imand body composition were found with walking, running, provements in Vozmax and stationary cycling exercise when frequency, duration, and intensity of training were Thus, when walking (a generally low-to-moderate intensity form

Table 1. SUMMARY OF EXERCISE TRAINING GUIDELINES

Frequency Intensity

Duration Mode

ACSM

AHA

3-5 dlwk 55%-90% HR, or 401 50%-85% \'02max Or HR, reserve 15-60 min, continuous Aerobic activities

3 dlwk, minjmum 50%-60% VO ,, or HR, reserve

Resistance 1 set, 8-12 Training repetitions, 8-1 0

Frequency

CDCIACSM Daily Moderate

AACVPR 3-5 d!wk 50% V02max, minimum

30 min, minimum Accumulate 30 30-45 min minld Health promotion Health promotion Health promotion activities activities activities 1 set, 10-15 Addressed, but 1-3 sets, repetitions, amount not 10112-15 8-10 specified repetitions,

~XBICIS~S,

bxbiti~sbs,

major muscle groups 2 dlwk, minimum

major muscle groups 2-3 dlwk

BABKISBS 17Ui

specified most days, preferably all

2-3 dlwk

ACSM = American College of Sports Medicine Guidelines7;AHA = 1995 American Heart Association Exercise standard^^^; CDCIACSM = 1995 Center for Disease Control and American College of Sports Medicine Public Health Statementw; AACVPR = 1995 American Association for Cardiovascular and Pulmonary Rehabilitation exercise standards6

Table 2. COMPONENTS AND GUIDELINES FOR EXERCISE PRESCRIPTION FOR HEALTHY YOUNG, MIDDLE-AGED, AND ELDERLY PATIENTS WITH CARDIAC DISEASE Patients with Cardiac Disease Component Warm-up Stretching, low-level calisthenics, walking Muscular conditioning Resistance exercise all major muscle groups Aerobics Frequency Duration Intensity Cool-down Low-level aerobic exercise, stretching

Healthy Adults

Elderly

5-1 0 min

10-15 min

20-30 min 2-3 dlwk

20-30 min 2-3 dlwk

3-5 dlwk 20-60 min

3-5 dlwk 30-60 min

4 0 4 5 % HRR, 30-75% HRR, 4 0 4 5 % V O ~ , , , ~ ~ 30-75% V O RPE: 12-16 RPE: 12-14 5-10 min

10-15 min

Phase i 15-20 min ROM daily

2-3 x/day MI: 5-20 min CABG: 10-20 min RHR: +20 blm ~ RPE: ~ ~ 11-12 ~ 15 min

Phase ll

Phase Ill-IV

10-15 min

10-15 min

10-20 min 3 dlwk

15-30 min 2-3 dlwk

1-2 x/day MI: 20-60 min CABG: 20-60 min RHR: +20 blm* RPE: 12-13

3-5 dlwk 30-60 min 5 0 4 5 % HRR, RPE: 12-15

15 min

15 min

*After 3-6 weeks, intensity is set at 50% HHR, based on a symptom-limited graded exercise test. Phase I = inpatient period; Phase I1 = immediate outpatient; Phase Ill-IV = intermediate outpatienthnaintenance according toAACVPR6; MI = myocardial infarction; CABG = coronary artery bypass graft; ROM = range of motion exercise; b/m = beats = maximal heart rate reserve; V O , , ~ ~= maximal oxygen uptake; RPE = ratings of perceived exertion per minute; HRR,

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of exercise) is prescribed for training, the duration or frequency of exercise should be increased. Aerobic training can be accomplished with a variety of activities such as running, walking, cycling, swimming, stair climbing/stepping, skating, dancing, or cross-country skiing. The specific activities prescribed should relate to an individual's needs, goals, and personal preference. Recommendations for aerobic exercise (Tables 1 and 2) include a wide range for duration (20 to 60 minutes) and intensity (60% to 90% maximum heart rate [HR,,,]). As described above, duration and intensity are inversely related; when intensity is lower (50% to 70%HR,,,), duration should be longer (40 to 60 minutes). The key factor, however, is that the intensityjduration of exercise should result in a total energy expenditure of 250 to 300 kcal per session or approximately 1000 to 1500 k ~ a l / w k . ~ , ~ l Intensity of exercise can also be judged by ratings of perceived exertion (RPE). The RPE scale was first described by BorgI3as an adjunct to heart rate for monitoring intensity of training. The 15-grade Borg scale is presented in Table 3. A linear relationship exists between heart rate and and RPE also correlates highly with pulmonary ventilation and blood lactate levels. Thus, RPE provides a subjective index of a patient's fatigue or response to exercise. Healthy adults should exercise at an RPE range of 12 to 16 (moderate to hard, see Table 2). When exercising according to the standards described in Tables 1 and 2, the expected average improvement is a 15% to 30% increase in and a 1 to 2 kg loss in body weight (1% to 3% decrease in body fat).4"74, 75, 89 Training fewer than 3 d/wk results i n less than a 15% improvement in 002,,,38.75, 77, 89 and no change in body weight or fat.74 The ACSM and AHA guidelines for exercise training focus on the development of fitness, that is, improved aerobic capacity and muscular fitness. However, a distinction is now made between exercise training for health versus fitness. The exercise stimulus necessary to elicit health benefits is less than that required for improvement of fitness. This usually relates to a lower intensity of exercise. Recently, the Centers for Disease Control and Prevention (CDC) and ACSM67published a new exercise statement based on the notion of physical activity for health. Table 3. BORG SCALES FOR RATING PERCEIVED EXERTION* 10-Grade Scale Nothing Very, very weak (just noticeable) Very weak Weak (light) Moderate Somewhat strong Strong (heavy) Very strong Very, very strong (almost maximum)

15-Grade Scale 6 7 8 9 10 11 12 13 14 15 16 17

Very, very light Very light Fairly light Somewhat hard iard

Very hard

18

Maximum

19 20

Very, very hard

* Scales for rating perceived exertion. The original scale (6-20 is given on the right, the recent 10point scale is given on the left. The 10-point scale has ratio properties. For further explanation see reference 13.

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This new public health approach to exercise states that "every American should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week (see Table 1). This new concept of the CDC/ ACSM stresses the "accumulation of exercise." Here the health benefits of exercise are independent of duration, intensity, or mode of exercise as long as the accumulated energy expenditure for each day is greater than 200 kcal. Thus, individuals can perform multiple short-duration and/or moderate-intensity bouts of activity Activities with an accumulative energy expenditure of 200 kcal/d or more.24*25 for this type of physical activity program can include the traditional exercise modes such as walking, cross-country skiing, or cycling but can also include lifestyle activities such as golfing, bowling, home care, carpentry, gardening and lawn care, climbing stairs rather than using the elevator, or walking part of the way to work. The focus is accumulative physical activity and is centered on a lifestyle approach: including physical activity that leads to a change in lifestyle. Given the many health benefits, health-related exercise programs do not consiscardiac output) and peripheral (aerobic tently induce the traditional central (VoZmax, enzymes, capillary density) adaptations generally associated with a higher intensity, fitness-related exercise program. The CDC/ACSM statement acknowledges that more studies concerning this approach to exercise prescription are needed, but concludes that any lifestyle change that includes an increase in physical activity is a beneficial alternative to physical inactivity. This conclusion is based on reports of improved all-cause and cardiovascular mortalitv in individuals who became or r e k i n e d physically active throughout life.", ?he additional importance of this tvve of avvroach is that it minimizes the need for "exercise clothine" " and gymnasium-based or long-duration/high intensity type exercise programs and should increase general physical activity levels and improve exercise adherence. _I

I

I I

Progression of Training Stimulus

As an individual accommodates or adapts to exercise training, the level of the exercise stimulus should be increased to continually overload and stimulate the system. The rate of progression of stimulus should be divided into three stages: (1) starting, (2) slow-to-moderate progression, and (3) maintenance (see Fig. 1, p 14). The starting phase should include low-level exercise to introduce individuals to their training regimen. This allows ample time for adaptation and minimizes undue soreness and injury. Depending on the individual's tolerance, this stage should last 2 to 6 weeks. Longer stages may be required for people with disease depending on the severity of the disease, length of hospital stay, and prior exercise history. The second stage, slow-to-moderate progression, involves a gradual and systematic increase in the duration and intensity of exercise. Whereas this stage generally continues for up to 6 months in younger persons, individuals with a low fitness level or the elderly may require up to 1 year. The maintenance stage is determined by the achievement of the desired level of fitness or health goals. The focus of this stage is long-term continued training. For this stage the training stimulus remains generally constant, with emphasis on maintenance and incorporation strategies to facilitate compliance. Muscular fitness is related to muscular strength and endurance. The development of muscular strength and endurance is accomplished by a functional overloading of the musculoskeletal system. Overload is administered by moving through a muscle's or group of muscles' full range of motion (ROM) with an external load. This external load or resistance can be provided by calisthenics or free weights or through specific resistance exercise machines. Strengthening exercises should be performed with all of the major muscle groups of the body

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(shoulder, trunk, arms, lower back, abdomen, hips, and legs) because the training effect is specific to the area being exercised. For muscular fitness, ACSM recommends one set of resistance exercises performed with a minimum frequency of 2 d/wk (see Tables 1 and 2). Performing three sets of resistance exercises, 3 days per week may produce slightly greater strength gains, but this benefit (increased strength) is outweighed by increased training time and reduced exercise compliance. The interaction of intensity and duration (repetitions) is slighly different for resistance exercise than for aerobic exercise and results in different outcomes with respect to muscular fitness. In general, maximum improvement in strength is accomplished by lifting heavy loads (high intensity) for a few repetitions (low duration), whereas endurance is improved by lifting light loads (low intensity) for many repetitions (high duration). The recommended 8 to 12 repetitions results in significant improvements in both muscular strength and endurance and ultimately muscular fitness. Components of a Training Session

The components of a typical training session to meet the ACSM exercise guidelines are listed in Table 2.71A 10-minute warm-up period is an essential and often neglected part of a workout. The warm-up should include activities such as low-level calisthenics, dynamic and static stretching, and dynamic exercise such as walking, slow jogging, or cycling. The purpose of the warm-up is to increase blood flow, muscle temperature, and metabolic rate to prepare for more intense activity. Muscular conditioning (15 to 30 minutes) and aerobic exercise (20 to 60 minutes) is performed next. The order of these two components is left to personal preference and should be based on specific needs. These components are administered as described above. All training sessions should conclude with a 5- to 10-minute cool-down period. This usually entails stretching and light aerobic activity (such as walking). Like the warm-up period, the cool-down is very important and often neglected. The continued activity enhances venous return as peripheral vasodilation continues briefly post-exercise. In addition, stretching may minimize soreness and stiffness and enhances flexibility because muscles are more effectively stretched after being warmed up. Exercise Guidelines for the Healthy, Asymptomatic Elderly

Guidelines for exercise training of the healthy, asymptomatic elderly (prescription and the components for the exercise session) are essentially the same as those described for the healthy young and middle-aged adult (see Table 2):' however, the application of the principles is varied. The elderly generally have different needs and goals . .to be met by an exercisetoprogram. - - lne eideriy reyulre * ioiigei wai-ii-,--Gp ayiow fGT lGnger ;d;Asirncnk to exercise (onset of steady-state heart rate, blood pressure and ventilatory responses). The exercise prescription should call for more moderate-intensity (30% to exercise for a longer duration. Prescribing intensity based on HR,, 75% of 0oZmax) reserve (30% to 75%) accounts for the 5% to 10% underestimation of intensity by this technique regarding the elderly.88Also, the RPE scale can be used to estimate intensity because the relationship between RPE and percent of HR,,, and 0 0 is the same in younger and elderly individuals. With the decline in HR,,, with ,,,s

~

~

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Table 4. INCIDENCE OF INJURY BY AGE AND ACTIVITY Age (Y)

20-35 49-65 40-65 70-79 40-56 60-79

Activity Walkingljogging Walkingljogging Walkingljogging Walkingljogging Walking Walking

Injury (#)

n

Injury (%)

9 9

50

20

50

8 2 7

14

18 41 40 57 12 14

22

19 50

Data fromcarroll J. Pollock M, Graves J, et al: Incidence of injury during moderate- and high-intensity walking training in the elderly. J Gerontol 47:M61, 1992; Pollock ML, Carroll J, Graves JE, et al: Injuries and adherence to walkljog and resistance training programs in the elderly. Med Sci Sports Exerc 23:1194, 1991; and Pollock ML, Wilrnore JH: Exercise in Health and Disease: Evaluation and Prescription for Prevention and Rehabilitation, ed 2. Philadelphia, WB Saunders, 1990

age, the RPE and heart rate of the elderly does not match that of middle-aged adults; however, the linear nature of the relationship is independent of age. Thus, the RPE scale can be used for the elderly to establish intensity. For example, an RPE of 12 to 13 corresponds to 50% to 75% V O ~ ~ ~ ~ . ~ ~ As above, the training response is independent of modality used if all other criteria are met. However, in the training of the elderly, musculoskeletal injuries are more common than in younger participants and are related to high-impact activities such as running or high-impact aerobic dance. Additionally, the injury rate is 4 to 5 times greater in women than in men and is probably related to lack 71 The injuries include of muscle mass, reduced BMD, and greater Q angle.'4,69, bruises, strains, sprains, and rare incidences of stress fracture, as well as pain/ discomfort secondary to common ailments like arthritis and back pain. Studies show that the frequency of exercise impact-related injuries is associated with the age of the participant and the characteristics of the impact forces (data summarized in Table 4). Therefore, low-impact exercises should be prescribed for individuals older than 50 to 60 years. The object is to minimize shock to the musculoskeletaljoint structure. Low-impact exercise causes little stress on bones and joints, whereas high-impact exercise causes repeated impact on hips, knees, ankles, and feet. Various forms of low- and high-impact exercises are summarized in Table 5. Generally, these activities provide well-tolerated low-impact exercise with excellent training outcomes. If high-impact exercise is used, then beginning with low Table 5. ACTIVITYIEXERCISE MODALITY CATEGORIZED BY MUSCULOSKELETAL IMPACT High-impact Jogginglrunning Basketball Jumping Rope skipping Aerobic dance* Downhill skiing

Walkinglhiking Cycling, stationary or free Swimming, water walking Rowing Cross-country skiing Skating (roller, ice, or in-line) Stair climbinglstepping

* Newly designed low-impact aerobic dance programs exist that would be appropriate for exercise training Adapted from Pollock ML, Wilmore JH: Exercise in Health and Disease: Evaluation and Prescription for Prevention and Rehabilitation, ed 2. Philadelphia, WB Saunders, 1990, p 393.

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levels of such activities and progressing slowly is important. Equally important is allowing sufficient time between exercise sessions (approximately 1 day) to permit adequate recovey and gradual adaptation. As shown in Figure 1, the progression of training for the elderly is slower and more gradual than that for young, healthy adults, to allow for adaptation. A suggested rule of thumb is a 40% increase in the time allowed for adaptation from training for each decade after 30 years of age.71 Resistance exercise is an important part of an exercise program for the elderly because it is the only apparent way to specifically counteract age-related bone density, muscle mass, and strength losses. The use of resistance exercise does not pose any significant cardiovascular risk. Recent studies of the elderly or of lowrisk patients with stable cardiac disease have documented the cardiovascular safety of resistance exercise with training loads between 30% and 80% of the one 44,71 Lower heart rates and rate pressure products were repetition rnaxim~m.2~recorded during resistance exercise circuit weight training (resistance < 80% of the one repetition maximum) than were recorded during graded exercise testing Subjects showed none of the heart rate or blood pressure on a treadmi11.22,23*84 abnormalities or indications of myocardial ischemia (increased signs of STsegment depression or angina pectoris) found in maximal treadmill tests.", 49 Despite increases in systolic blood pressure and afterload, average pulse pressure remains relatively constant suggesting that stroke volume and left ventricular function are not impaired. Increases in diastolic blood pressure may actually be an advantage for myocardial perfu~ion.~~ Resistance exercise machines are designed in such a manner that they are suitable and safe for use by the elderly. Some important safety features include: (1) weight loads can be applied at low levels with small increments for more gradual progression; (2) exercise is usually performed in a seated position with the individual strapped into the machine thus limiting balance problems and

Stage I

Stage I1

Stage I11

Healthy young or middle-age adult

Cardiac Patient m m a

3

6 8 10 12 15

20

Early MI

9

12

18

t

Weeks

24 b

Months

Figure 1. Comparison of relative progression of training intensity among populations of

healthy young and middle-aged adults, cardiac patients, and the elderly.

EXERCISE TRAINING FOR CORONARY ARTERY DISEASE IN THE ELDERLY

221

providing back support, which may limit injuries; (3) weight stacks can be "doubled-pinned" either for safety when the individual has a limited ROM or to allow work through the "pain free" part of the ROM; (4) use of machines limits the need for the individual to balance and support the weight, thus limiting the possibility of falling, losing balance, or dropping the weight on himself or herself; and (5) machines provide variable resistance. After the work-out, a greater emphasis should be placed on the cool-down, during which in addition to flexibility work, surveillance is necessary for safety reasons. Elderly individuals are likely to experience problems with orthostatic hypotension and impaired heat dissipation. Exercise Guidelines for Cardiac Rehabilitation

Rehabilitation of cardiac patients includes patient education, risk factor modification, and exercise. Patient education and risk factor modification are important because they lay the groundwork for the task of functional rehabilitation and direct individuals through the proper lifestyle changes necessary for successful cardiac rehabilitation. The physical activity/exercise part of cardiac rehabilitation is usually divided into four phase^.^ Phase I, the inpatient program, begins as soon after the cardiac event or surgery as possible, as soon as the patient is considered stable. For example, Phase I could begin 1 to 2 days after surgery or 2 to 4 days after an uncomplicated myocardial infarction. This phase continues for the duration of the hospital visit. Phase 11, the immediate outpatient program, begins with patient discharge from the hospital. This 4- to 12-week phase of rehabilitation can be based in the hospital or community or private clinic as well as the home. More contemporary programs use risk stratification as a means of determining the likelihood of having a future event (low, <2%; medium 5% to 10%;or high, >15% mortality in the first year). Patients are then triaged with the lower-risk patients being progressed to Phase I11 or home programs (or combinations thereof) as early as after their sixth visit.33Phase 111, the intermediate outpatient phase, is a community-based program in which less monitoring of the patient is needed. The patient is still experiencing improvements in response to the exercise training program. Phase IV, the maintenance phase, is generally a community-based or home program. The basic components of a rehabilitation exercise program for the patient with cardiac disease are similar to those for healthy adults, but the timing of each component varies with the patient's medical and physical status.78These differences are outlined in Table 2. Further, the progression of exerciseintensity is slower and more gradual compared to the progression of healthy adults (see Fig. 1). Phase I

Patients with cardiac disease generally need longer warm-up periods during Phase I because of the detrimental effects of myocardial infarction, surgery, and bed rest. This necessitates stretching (ROM) exercises to prepare the muscles and joints for exercise. This is especially true during the postsurgical period because of damage to the chest wall and chest and shoulder musculature. The specific focus on ROM exercises, for both upper and lower body, is important as it may avert adhesion development and aid in maintaining muscle flexibility and strength early in rehabilitation. The upper body ROM is especially important because patients tend to limit upper extremity work, facilitating future postural, ROM, and strength problems. In Phase I, musculoskeletal conditioning begins as ROM

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exercise (as described). Aerobic conditioning in Phase I begins with self-care and short ambulation activities performed several times per day. The necessity for multiple, short-duration bouts of activity is related to the patients' inability to perform long-duration exercise. Patients progress to longer, more continuous bouts of exercise in later phases of rehabilitation. Phase I1

A longer warm-up period is required in Phase I1 as described for Phase I. In Phase 11, musculoskeletal conditioning focuses on dynamic, strengthening exercises and requires the use of calisthenics, free weights, or resistance exercise machines. Usually light dumbells (1 to 5 lbs.) are used during the first 3 to 6 week^.^',^^ Initially, aerobic exercise bouts are extended for longer periods of time and are carried out once or twice per day. Once the patient improves his or her condition and/or returns to work, exercising one time per day, 3 to 5 days per week becomes more realistic. Phase 111 and IV

Warm-up for the cardiac patient is similar to that described for a low-fit but healthy adult or elderly individual. The period of time allotted for musculoskeletal conditioning is increased to allow for a total body workout (all major muscle groups). Aerobic conditioning is carried out with a single longer-duration bout of exercise or by using a continuous aerobic circuit. A longer cool-down period is generally recommended in all phases for patients with cardiac disease. This longer cool-down is important in aiding the recovery process and in surveillance. Though cardiac events are rare in rehabilitation programs, approximately 40% of recurrent cardiac events take place during the recovery period.43Thus, a minimum of 15 minutes for cool-down and surveillance is recommended. During rehabilitation, patient differences occur in the type and duration of supervision and frequency of electrocardiographicmonitoring. These differences are related to the risk of future cardiac involvement. The level of risk (low, medium, or high) is estimated from the patient's medical history and clinical progression. Risk can be stratified according to a patient's functional capacity or ventricular function or the presence of ischemia, significant dysrhythmia including previous occurrence of sudden death, ST segment depression at rest or during exercise, or adverse heart rate or blood pressure responses to exercise. Guidelines for risk stratification have been p~blished.~, Exercise Guidelines for Elderly Cardiac Rehabilitation

Elderly patients with cardiac disease can benefit from a cardiac rehabilitation

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tance exercise program due to its specific effects on muscle mass, BMD, and strength which are of similar importance as described with the asymptomatic elderly. Further, resistance exercise serves to improve functional capacity and aerobic capacity (mainly through increased muscle mass). The health-related impact of resistance exercise (increased insulin sensitivity, improved glucose tolerance, improved body composition) is described above and applies to this population. More so than in other populations, rehabilitation of the elderly patient with cardiac disease requires specific exercise prescription according to the age, fitness

EXERCISE TRAINING FOR CORONARY ARTERY DISEASE IN THE ELDERLY

223

level, and health status of the individual. The components and guidelines for exercise training of the elderly patient with cardiac disease are outlined in Table 6 and are essentially the same as for the asymptomatic elderly individual or the patient with cardiac disease, with a few adjustments in application. All phases require a longer warm-up and cool-down period as described for asymptomatic elderly and younger patients with cardiac disease. These periods should emphasize improvements and maintenance of ROM. Phase I-inpatient rehabilitation should include any and all activities used with younger patients with cardiac disease. Muscular conditioning is attained using ROM exercises as part of the warm-up. Aerobic conditioning (ambulation) should be performed 3 to 4 times per day. The increased frequency is related to lower functional capacity of the older patient. Exercise will progress more slowly and gradually than described for younger cardiac patients (see Fig. 1).Greater emphasis should be placed on patient education as well. Lifestyle modification is an important component of any intervention for elderly populations. Phase I1 exercise programs should expand the muscular conditioning period to include ROM exercises while beginning to incorporate a free weight resistance exercise program. Aerobic conditioning should continue to progress. The greater frequency and longer minimum duration of training are again related to lower intensity of work engaged by the elderly patient. Phase I11 and IV should include a total body muscular conditioning program involving all major muscle groups. These exercises should be performed 2 to 3 times per week. One set of each exercise should be performed for 10 to 15 repetitions approximating 30% to 50% of the one repetition maximum. Usually patients are encouraged to stop when the exercise reaches the level of moderate fatigue. The aerobic conditioning period can now be expanded to a single bout of exercise performed for a minimum of 30 minutes. As with the asymptomatic elderly, the elderly patient with cardiac disease will work at slightly lower intensity for a longer duration. This type of prescription emphasizes the health-related aspects of exercise training and thus is highly specific for the elderly patient. In addition, moderate intensity low-impact exercise is indicated for the elderly patient to minimize the risk of injury. Low-impact activities such as cycling, walking, swimming, stair-climbing, or cross-country skiing should be prescribed. As discussed above, for the elderly patient, avoiding high-intensity and high-impact activities will significantly reduce risk of injury or precipitation of a cardiac event and will improve exercise compliance. Safety and efficacy for resistance exercise training were discussed and apply to the elderly patient with cardiac disease as well. In all phases of cardiac rehabilitation, progression of training should be slow and gradual to optimize the training response and to allow adequate time for adaptation. Outcomes of Exercise Training for the Elderly Patient with Cardiac Disease

As is evident from the above discussion, the cardiovascular and musculoskeletal systems retain plasticity well into the ninth decade. Further, physical activity/ exercise training can have a positive impact on health and fitness in the asymptomatic elderly. Ultimately, a beneficial negative relationship exists between fitness Elderly patients with cardiac and cardiac morbidity55and all-cause m~rtality.",~~ disease can benefit from exercise training in a manner similar to asymptomatic elderly and/or younger patients with cardiac disease. Physiologic adaptations to 12 weeks of aerobic-type exercise training performed in elderly patients with cardiac disease are summarized in Table 7. In general, these studies show that

Table 6. COMPONENTS AND GUIDELINES FOR EXERCISE PRESCRIPTION AND REHABILITATION OF ELDERLY PATIENTS WITH CARDIAC DISEASE

Cornponent Warm-up Stretching, low-level calisthenics, walking Muscular Conditioning Resistance exercise all major muscle groups Aerobics Frequency Duration Intensity Activities Cool-down Low-level aerobic exercise, stretching

Phase l Inpatient 15-20 min

Phase II Immediate Outpatient

Phase Ill Intermediate Outpatient

Phase IQ Maintenance

10-1 5 min

10-15 min

10-15 min

ROM 10-20 min 3 dlwk

20-30 min 2-3 dlwk

20-30 min 2-3 dlwk

2-3 dday MI: 5-15 min CABG: 5-15 min RHR: +20 blm RPE: 11

1-2 dday MI: 15-45 min CABG: 15-45 min RHR: +20 blm* RPE: 11-13

3-5 dlwk 30-60 min

3-5 dlwk 30-60 min

15 min

15 min

15 min

30-75% HRR, 30-75% HRR, 30-75% \jo2,, 30-75% Vo2RPE: 12-13 RPE: 12-14 Activities should focus on low impact exercise at all levels of the exercise prescription: walking, swimming, cycling, stair climbing, cross-country skiing, etc. 15 min

*After 3-6 weeks, i~l~tensity is set at 40% HHR, based on a symptom-limited graded exercise test. MI = myocardial infarction, CABG = coronary artery bypass graft; = maximal heart rate; V O ~ = , ~maximal ~ oxygen uptake ROM = range of motion exercise; b/m = beats per minute; HR,.

EXERCISE TRAINING FOR CORONARY ARTERY DISEASE IN THE ELDERLY

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Table 7. PHYSIOLOGIC RESPONSES TO PHASE-II (12 WEEKS) CARDIAC REHABILITATION EXERCISE PROGRAM IN ELDERLY PATIENTS WITH CARDIAC DISEASE Percent Change Absolute Change Body Composition Body weight Body fat Lipid Profile Total cholesterol LDL cholesterol HDL cholesterol Triglycerides Pulmonary function Vital capacity FEV, Cardiovascular, resting Heart rate Systolic pressure Diastolic pressure Maximal exercise Work capacity Exercise duration VO, peak Heart rate Systolic pressure Rate x Pressure x 10-, Submaximal exercise Exercise duration Heart rate Systolic pressure Minute ventilation RPE

w)

Decrease Decrease

0-2 kg

0-3 0-3

No change Decrease Increase Decrease

3 mg1dL 3 mg1dL 11 mg1dL

2 3-6

No change Increase Decrease No change No change

8

5.5% of vital capacity 0-9 blmin

12

Increase Increase Increase Increase Increase Increase

3-5 METS 3-6 min 2-4 mUkg . min 10-15 blmin 10-20 mmHg 15-30

40-60 40-60 10-20 9-25 6-1 2 10-22

Increase Decrease Decrease Decrease Decrease

11 min 10-11 blmin 3-5 mmHg 7.1 Umin 1.2-2.3

37 10 2-5 15 12-16

* Refer to text for an explanation of apparent training effects on maximal heart rate, blood pressure, and rate-pressure product. FEV = forced expiratory capacity; Vo, = oxygen uptake; RPE = ratings of perceived exertion; blmin = beats per minute; METS = metabolic equivalent of a Vo, of 3.5 mUkg . min. Data from references numbers 1, 2, 4, 52, and 90.

elderly patients with cardiac disease can decrease body weight and body fat after ~ , ~ ~includes ,~~ a modest change 12 weeks (Phase 11) of cardiac r e h a b i l i t a t i ~ n . This in lipid profile; though total cholesterol did not change, a small decrease (-2%) occurred in LDL cholesterol, a small increase occurred in HDL cholesterol (-6%), and an 8%decrease occurred in trigly~erides.~' These programs did not emphasize strong dietary intervention, but were attempting to quantify the specific effect of exercise training. Decreases in resting heart rate have been reported1z90without changes in resting systolic and diastolic blood pressure. However, 12- to 15-mmHg decreases in resting systolic and diastolic pressure have been reported in longer duration studies (> 12 month^).^ One study showed a favorable change in pulmonary function as forced expired capacity (FEVJ increased without a change in vital capacity.90 Elderly patients with cardiac disease significantly increase maximal and submaximal exercise tolerance1,2,4,90 and 0 0 during ~ ~ Phase~I1 cardiac ~ rehabilitation (12 weeks). This included significant increases in maximal heart rate (HR,,,),

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systolic blood pressure, and rate-pressure product. Care should be taken in the interpretation of these data because maximal heart rate and blood pressure generally do not increase after exercise training. The elderly cardiac patients in these studies were treated conservatively during the initial exercise tests and were pushed harder after 1 2 weeks of training. That would account for the higherthan-average improvement in 002max compared to other studies in which maximal heart rate did not change. Consistent reports exist of dramatic decreases in exercise heart rate, systolic blood pressure, rate-pressure product, ventilation, and perception of effort (RPE) with a concomitant significant increase in exercise tolerance at a given submaximal exercise intensity.', 4, 90 Though the women in this population are generally less fit and less likely to be referred to a rehabilitation program, several studies have shown that their response to exercise rehabilitation is similar to that of men.3Though the data are limited, the response to and beneficial effects of a cardiac rehabilitation exercise training program appear independent of age.90 No specific studies have evaluated the effectsof resistance exercise for elderly patients with cardiac disease. The specific needs, benefits and importance, and rationale for incorporating resistance exercise into the exercise rehabilitation program of the elderly patient with cardiac disease were addressed above and are the same as for the asymptomatic elderly.

References 1. Ades PA, Hanson JS, Gunther JGS, et al: Exercise conditioning in the elderly coronary patient. J Am Geriatr Soc 35:121, 1987 2. Ades PA, Grunvald MH: Cardiopulmonary exercisetesting before and after conditioning in older cardiac patients. Am Heart J 120:585, 1990 3. Ades PA, Waldmann M, Polk D, et al: Referral patterns and exercise response in the rehabilitation of coronary patients 2 62 years. Am J Cardiol 69:1442, 1992 4. Ades PA, Waldmann ML, Poehlman, ET, et al: Exercise conditioning in older coronary patients: Submaximal lactate response and endurance capacity. Circulation 88:572,1993 5. Agre JC, Pierce, LE, Raab DA, et al: Light resistance and stretching exercise in elderly women: Effect upon strength. Arch Phys Med Rehabil 69:273, 1988 6. American Association for Cardiovascular and Pulmonary Rehabilitation: Guidelines for cardiac rehabilitation programs, 2 ed. Champaign, IL, Human Kinetics, 1995 7. 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 22:265,1990 8. Aniansson A, Hedberg M, Henning GB, et al: Muscle morphology, enzymatic activity, and muscle strength in elderly men: A followup study. Muscle Nerve 9:585, 1986 9. Apple FS, Rogers MA: Skeletal muscle lactate dehydrogenase isozyme alterations in men and women marathon runners. J Appl Physiol61:477, 1986 10. Bassey EJ, Bendall MJ, Pearson M: Muscle strength in the triceps surae and objectively measured customary walking activity in men and women over 65 years of age. Clin C , ~ ",?-"C: : 1G"" UL. r r.ur, A/""

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67. Pate RR, Pratt M, Blair SM, et al: Physical activity and public health: A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 273:402, 1995 68. Pollock ML, Gettman LR, Milesis CA, et al: Effects of frequency and duration of training on attrition and incidence of injury. Med Sci Sports 9:31-36, 1977 69. Pollock ML, Carroll J, Graves JE, et al: Injuries and adherence to walk/jog and resistance training programs in the elderly. Med Sci Sports Exerc 23:1194, 1991 70. Pollock ML, Graves JE, Swart DL, et al: Exercise training and prescription for the elderly. South Med J 82S88, 1994

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