Advancing age is associated with a remarkable number of changes in body composition. Reductions in lean body mass have been well characterized. This decreased lean body mass occurs primarily as a result of losses in skeletal muscle mass (9,26). This age-related loss in muscle mass has been termed sarcopenia (4). Loss in muscle mass accounts for the age-associated decreases in basal metabolic rate (BMR), muscle strength, and activity levels, which, in turn are the cause of the decreased energy requirements of the elderly. In sedentary individuals, the main determinant of energy expenditure (EE) is fat-free mass, which declines by about 15% between the 3rd and 8th decade of life. It also appears that declining caloric needs are not matched by a appropriate decline in caloric intake, with the ultimate result an increased body fat content with advancing age. Increased body fatness along with increased abdominal obesity are thought to be directly linked to the greatly increased incidence of Type II diabetes among the elderly.
Age-related reductions in muscle is a direct cause of the age-related decrease in muscle strength. Our laboratory (9) recently examined muscle strength and mass in 200 healthy 45- to 78-yr-old men and women and concluded that muscle mass (not function) is the major determinant of the age and sex-related differences in strength. This relationship is independent of muscle location (upper vs lower extremities) and function (extension vs flexion). Reduced muscle strength in the elderly is a major cause for their increased prevalence of disability. With advancing age and very low activity levels seen in the very old, muscle strength and power are critical components of walking ability (1). The high prevalence of falls among the institutionalized elderly may be a consequence of their lower muscle strength.
The question that we have been attempting to address is: To what extent are these changes inevitable consequences of aging? Our data suggest that changes in body composition and aerobic capacity that are associated with increasing age may not be age-related at all. By examining endurance-trained men, we saw that body fat stores and maximal aerobic capacity were not related to age but rather to the total number of hours these men were exercising per week (19). Even among sedentary individuals, energy spent in daily activities explains more than 75% of the variability in body fatness among young and older men (22). These data and the results of other investigators indicate that levels of physical activity are important in determining EE and ultimately body fat accumulation.
Aerobic exercise has long been an important recommendation for those with many of the chronic diseases typically associated with old age. These include non-insulin dependent diabetes mellitus or NIDDM (and those with impaired glucose tolerance), hypertension, heart disease, and osteoporosis. Regularly performed aerobic exercise increases V˙O2max and insulin action. The responses of initially sedentary young (age 20-30 yr) and older (age 60-70 yr) men and women to 3 months of aerobic conditioning (70% of maximal heart rate (HR), 45 min·d−1, 3 d per week) were examined by Meredith et al. (18). They found that the absolute gains in aerobic capacity were similar between the two age groups. However, the mechanism for adaptation to regular submaximal exercise appears to be different between old and young people. Muscle biopsies taken before and after training showed a more than twofold increase in oxidative capacity of the muscles of the older subjects, whereas that of the young subjects showed smaller improvements. In addition, skeletal muscle glycogen stores in the older subjects, significantly lower than those of the young men and women initially, increased significantly. The degree to which the elderly demonstrate increases in maximal cardiac output in response to endurance training is still largely unanswered. Seals and coworkers (24) found no increases after 1 yr of endurance training whereas, more recently, Spina et al. (25) observed that older men increased maximal cardiac output whereas healthy older women demonstrated no change in response to endurance exercise. If these gender-related differences in cardiovascular response are real, it may explain the lack of response in maximal cardiac output when older men and women are included in the same study population.
The fact that aerobic exercise has significant effects on skeletal muscle may help explain its importance in the treatment of glucose intolerance and NIDDM. Hughes and coworkers (14) demonstrated that regularly performed aerobic exercise without weight loss resulted in improved glucose tolerance, rate of insulin stimulated glucose disposal, and increased skeletal muscle GLUT 4 levels in older glucose intolerance subjects. In this investigation, a moderate intensity aerobic exercise program was compared with a higher intensity program (50 vs 75% of maximal HR reserve, 55 min·d−1, 4 d·wk−1, for 12 wk). No differences were seen between the moderate and higher intensity aerobic exercise on glucose tolerance, insulin sensitivity, or muscle GLUT-4 levels, indicating perhaps that a prescription of moderate aerobic exercise should be recommended for older men or women with NIDDM or a high risk for NIDDM to help to ensure compliance to the program. Although Seals and coworkers (23) found that a high-intensity training program showed greater improvements in the insulin response to an oral glucose load compared with lower intensity aerobic exercise, their subjects began the study with normal glucose tolerance. Kirwan and coworkers (15) found that 9 months of endurance training at 80% of the maximal HR (4 d·wk−1) resulted in reduced glucose stimulated insulin levels; however, no comparison was made to a lower-intensity exercise group.
Endurance training and dietary modifications are generally recommended as the primary treatment in the non-insulin-dependent diabetic. Cross-sectional analysis of dietary intake supports the hypothesis that a low carbohydrate/high fat diet is associated with the onset of NIDDM (17). This evidence, however, is not supported by prospective studies in which dietary habits have not been related to the development of NIDDM (6,16). The effects of a high carbohydrate diet on glucose tolerance have been equivocal (2,11). Hughes et al. (13) compared the effects of a high carbohydrate (60% CHO and 20% fat)/high fiber (25 g dietary fiber/1000 kcal) diet with and without 3 months of high-intensity (75% max HR reserve, 50 min·d−1, 4 d·wk−1) endurance exercise in older, glucose intolerant men and women. Subjects were fed all of their food on a metabolic ward during the 3 months of the study and were not allowed to lose weight. They observed that neither the diet or the diet plus exercise group improved their glucose tolerance or insulin-stimulated glucose uptake. Thus, when combined with exercise, a high carbohydrate diet had a counterregulatory effect.
There appears to be no attenuation of the response of elderly men and women to regularly performed aerobic exercise when compared with those seen in young subjects. Increased fitness levels are associated with reduced mortality and increased life expectancy. It has also been shown (12) to prevent the occurrence of NIDDM in those that are at the greatest risk for developing this disease. Thus, regularly performed aerobic exercise is an important way for older people to improve their glucose tolerance.
Increasing Levels of Physical Activity in the Elderly
Community-based exercise programs for men and women over the age of 50 yr are growing in popularity. For individuals participating in such programs, physician screening for every participant may be either impractical or a barrier to participation.
1. The American College of Sports Medicine recommends a physician-supervised stress test for anyone over the age of 50 yr who wants to begin a vigorous training program. However, if the general recommendation is for an older person to simply walk or participate in a resistance training program, this test is probably not necessary. However, you should use the following questions to determine whether this individual should be carefully examined by a physician. This questionnaire was developed by Maria Fiatarone, M.D., for use in a state-wide, community-based exercise program for men and women over the age of 50 yr. Individuals who answered yes to any of the following questions were strongly encouraged to speak to a physician before participation.
Do I get chest pains while at rest and/or during exertion?
If the answer to question A is "yes," is it true that I have not had a physician diagnose these pains yet?
Have I ever had a heart attack?
If the answer to question C is "yes," was my heart attack within the last year?
Do I have high blood pressure?
If you do not know the answer to question E, answer this: Was my last blood pressure reading more than 150/100?
Am I short of breath after extremely mild exertion and sometimes even at rest or at night in bed?
Do I have any ulcerated wounds or cuts on my feet that do not seem to heal?
Have I lost 10 pounds or more in the past 6 months without trying and to my surprise?
Do I get pain in by buttocks or the back of my legs-my thighs and calves-when I walk?
While at rest, do I frequently experience fast irregular heartbeats or, at the other extreme, very slow beats? (Although a low HR can be a sign of an efficient and well-conditioned heat, a very low rate can also indicate a nearly complete heart block.)
Am I currently being treated for any heart or circulatory condition, such as vascular disease, stroke, angina, hypertension, congestive heart failure, poor circulation in the legs, valvular heart disease, blood clots, or pulmonary disease?
As an adult, have I ever had a fracture of the hip, spine, or wrist?
Did I fall more than twice in the past year (no matter what the reason)?
Do I have diabetes?
In our experience, this sort of questionnaire is effective in identifying individuals who may be at a higher risk than the general population of men and women over the age of 50 yr. Our Massachusetts-wide program (titled "Keep Moving-Fitness after 50") was a community based walking program for men and women over the age of 50 yr. At its peak, between 7500 and 8000 men and women (average age of 67 ± 5 yr old) had registered and participated. Walking "clubs" were located throughout the state in nursing homes, retirement communities, hospitals, and councils on aging (buildings that housed many of the activities provided by the Massachusetts Executive Office of Elder Affairs). The questionnaire was approved by a medical advisory board for this program. During the 8-yr existence of the program, there were no reports of a myocardial infarction, cardiac arrest, or any cardiovascular "event" during the exercise training session.
2. Advancing age results in increased muscle stiffness and reduced elasticity of connective tissue. For this reason, proper warm-up and stretching can have a greater effect in reducing the risk of an orthopedic injury in the elderly than in young men and women. A 5-min warm-up (exercise at a reduced intensity) followed by 5-10 min of slow stretching is highly recommended.
3. Cool down after exercise is important in older individuals. You should never finish a workout by immediately jumping into a hot shower. End your exercise session with a slow walk and more stretching. Your postexercise stretching will be more effective than the stretching you did before the exercise. This is because your muscles have warmed up and, along with tendons and ligaments, are much more elastic.
4. Find a friend to exercise with. The more people you exercise with, the more likely you are to stay with the exercise. This is a perfect opportunity for sons and daughters to spend time with their older parents, to the benefit of both generations.
Although endurance exercise has been the more traditional means of increasing cardiovascular fitness, strength or resistance training is currently recommended by the American College of Sports Medicine as an important component of an overall fitness program. This is particularly important in the elderly, in whom loss of muscle mass and weakness are prominent deficits.
Strength conditioning or progressive resistance training is generally defined as training in which the resistance against which a muscle generates force is progressively increased over time. Progressive resistance training involves few contractions against a heavy load. The metabolic and morphological adaptations resistance and endurance exercise are quite different. Muscle strength has been shown to increase in response to training between 60 and 100% of the one repetition maximum (1 RM); 1 RM is the maximum amount of weight that can be lifted with one contraction. Strength conditioning will result in an increase in muscle size and this increase in size is largely the result of increased contractile proteins. The mechanisms by which the mechanical events stimulate an increase in RNA synthesis and subsequent protein synthesis are not well understood. Lifting weight requires that a muscle shorten as it produces force. This is called a concentric contraction. Lowering the weight, on the other hand, forces the muscle to lengthen as it produces force. This is an eccentric muscle contraction. These lengthening muscle contractions have been shown to produce ultrastructural damage that may stimulate increased muscle protein turnover (5).
Our laboratory examined the effects of high-intensity resistance training of the knee extensors and flexors (80% of 1RM, 3 d·wk−1) in older men (age 60-72 yr). The average increase in knee flexor and extensor strength were 227% and 107%, respectively. CT scans and muscle biopsies were used to determine muscle size. Total muscle area by CT analysis increased by 11.4%, whereas the muscle biopsies showed an increase of 33.5% in Type I fiber area and 27.5% increase in Type II fiber area. In addition, lower body V˙O2max increased significantly whereas upper body V˙O2max did not, indicating that increased muscle mass can increase maximal aerobic power. It appears that the age-related loss in muscle mass may be an important determinant in the reduced maximal aerobic capacity seen in elderly men and women (8). Improving muscle strength can enhance the capacity of many older men and women to perform many activities such as climbing stairs, carrying packages, and even walking.
We have applied this same training program to a group of frail, institutionalized elderly men and women (mean age 90 ± 3 yr, range 87-96). After 8 wk of training, the 10 subjects in this study increased muscle strength by almost 180% and muscle size by 11%. More recently (7), a similar intervention on frail nursing home residents demonstrated not only increases in muscle strength and size, but increased gait speed, stair climbing power, and balance. In addition, spontaneous activity levels increased significantly whereas the activity of a nonexercised control group was unchanged. It should be pointed out that this was a very old, very frail population with diagnoses of multiple chronic diseases. The increase in overall levels of physical activity have been a common observation in our studies (7,10,21). Because muscle weakness is a primary deficit in many older individuals, increased strength may stimulate more aerobic activities like walking and cycling.
In addition to its effect on increasing muscle mass and function, resistance training can also have an important effect on energy balance of elderly men and women (3). Men and women participating in a resistance training program of the upper and lower body muscles required approximately 15% more calories to maintain body weight after 12 wk of training when compared with their pretraining energy requirements. This increase in energy need came about as a result of an increased resting metabolic rate (RMR), the small energy cost of the exercise, and what was presumed to be an increase in the energy cost of increase protein metabolism. Because resistance training can preserve or even increase muscle mass during weight loss, this type of exercise for those older men and women who must loose weight may be of genuine benefit. Although endurance training has been demonstrated to be an important adjunct to weight loss programs in young men an women by increasing their daily energy expenditure, its utility in treating obesity in the elderly may not be great. This is because many sedentary older men and women do not spend many calories when they perform endurance exercise, because of their low fitness levels. Thirty to forty minutes of exercise may increase energy expenditure by only 100-200 kcal with very little residual effect on calorie expenditure. Aerobic exercise training will not preserve lean body mass to any great extent during weight loss. Recently, strength training was demonstrated to cause improved glucose tolerance in elderly subjects (20). By improving bone density, muscle mass, strength, balance, and overall levels of physical activity, resistance training has been recently (21) demonstrated to be an important way to decrease the risk for an osteoporotic bone fracture in postmenopausal women.
Muscle strength training in the elderly. Muscle strength training can be accomplished by virtually anyone. Many health care professionals have directed their patients away from strength training in the mistaken belief that it can cause undesirable elevations in blood pressure. With proper technique, the systolic pressure elevation during aerobic exercise is far greater than that seen during resistance training. Muscle strengthening exercises are rapidly becoming a critical component to cardiac rehabilitation programs as clinicians realize the need for strength as well as endurance for many activities of daily living.
GUIDELINES FOR RESISTANCE EXERCISE PRESCRIPTION IN ELDERLY PEOPLE
Adults of all ages:
* Elderly, hypertensive patients should be carefully evaluated before beginning a strength training program.
* Instead of a treadmill stress test, we use a weight-lifting stress test. Have the patient perform three sets of eight repetitions at approximately 80% of the one repetition maximum. Monitor ECG and blood pressure responses during the exercise.
* Patients with rheumatoid or osteoarthritis may also participate. Patients with a limited range of motion should train within the range of motion that is relatively pain free. Most patients will see a dramatic improvement in the pain-free range of motion as a result of resistance training.
* Resistance training should be directed at the large muscle groups that are important in everyday activities, including the shoulders, arms, spine, hips, and legs.
* Each repetition is performed slowly through a full range of motion, allowing 2-3 s to lift the weight (concentric contraction) and 4-6 s to lower the weight. (eccentric contraction).
* Performing the exercise more quickly will not enhance strength gains and may increase the risk of an injury.
Training Intensity and Duration
* A high-intensity resistance training program has been shown to have the most dramatic effects at all ages. This is a training intensity that will approach or result in muscular fatigue after it has been lifted and lowered with proper form 8-12 times. A weight that you can lift 20 or more times will increase your muscular endurance, but not result in much of a gain in strength or muscle mass.
* The amount of weight that is lifted should increase as strength builds. This should take place about every 2 to 3 wk. In our research studies, we have seen a 10-15% increase in strength per week during the first 8 wk of training.
* We have seen significant gains in muscle strength and mass as well as an improvement in bone density with only 2 d·wk−1 of training.
* Inhale before a lift, exhale during the lift, and inhale as the weight is lowered to the beginning position.
* You should avoid performing the Valsalva maneuver (holding your breath during force production).
* With proper breathing technique, the cardiovascular stress of resistance exercise is minimal.
* HR and blood pressure should rise only slightly above resting values in the elderly who follow these guidelines.
* Any device that provides sufficient resistance to stress muscles beyond levels usually encountered may be used.
* Weight stack or compressed-air resistance machines may be found at many community fitness facilities or purchased for home use.
* Simple weight-lifting devices might include Velcro-strapped wrist and ankle bags filled with sand or lead shot, or heavy household objects, such as plastic milk jugs filled with water or gravel, or food cans of various sizes.
With interest in the establishment of community-based exercise programs for the elderly increasing, the following are recommendations that may be of help:
1. Work with local or state agencies. Often, state agencies for aging have some small amount of resources set aside for health-related activities. The individual working in these agencies have access to the elderly population in your area.
2. Use an already-developed infrastructure. Councils on aging may have a facility specifically for programs to serve the elderly. Contact your local hospital, YMCA, or university.
3. Promote and advertise your program as a "social" exercise program. Often, older women and men will join programs because of increase opportunity for socialization, not necessarily for fitness benefits.
4. More women than men will join. Use strategies to increase your recruitment of men.
5. Plan for a wide variability in functional status. Highly fit and very frail individuals are likely to join. If you establish a walking program, plan for at least two groups, slow and fast.
6. Form a medical advisory group from local physicians.
7. Attempt to incorporate some resistance exercise in any newly established program.
In conclusion, there is no other group in our society that can benefit more from regularly performed exercise, than the elderly. Although both aerobic and strength conditioning are highly recommended, only strength training can stop or reverse sarcopenia. Increased muscle strength and mass in the elderly can be the first step toward a lifetime of increased physical activity and a realistic strategy for maintaining functional status and independence.
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