Course Authors
Miriam Nelson, Ph.D., and Joel Mason, M.D.
Dr. Miriam Nelson, Ph.D., is Associate Director of the Human Physiology Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. Dr. Nelson reports no commercial conflict of interest. In the last three years, Dr. Mason has received grant/research support from Mead-Johnson Nutritional and also served as a consultant for Mead-Johnson Nutritional.
Estimated course time: 1 hour(s).
Albert Einstein College of Medicine – Montefiore Medical Center designates this enduring material activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
In support of improving patient care, this activity has been planned and implemented by Albert Einstein College of Medicine-Montefiore Medical Center and InterMDnet. Albert Einstein College of Medicine – Montefiore Medical Center is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.
Upon completion of this Cyberounds®, you should be able to:
Discuss the importance of strength training in maintaining adequate muscle mass with aging
Describe how maintaining muscle mass improves the functional status of the elderly
List the benefits of exercise for the frail elderly and those with a burden of chronic disease.
For this Cyberounds® Nutrition, I am delighted to introduce a guest expert who will be providing us with a good deal of information regarding nutrition and exercise. She is Dr. Miriam Nelson, Ph.D., Associate Director of the Human Physiology Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, who has done extensive research on and has much practical experience with the benefits of exercise. Dr. Nelson reports no commercial conflict of interest. In the last three years, Dr. Mason has received grant/research support from Mead-Johnson Nutritional and also served as a consultant for Mead-Johnson Nutritional.
JM
Mim, let me begin our discussion today by asking you a general question. Rob Russell and I have so far in our Cyberounds® largely emphasized preventive aspects of nutrition. Can you elaborate for us on some of the preventive aspects of exercise and how they are connected to nutritional issues?
MN
When investigators first began to scientifically assess the benefits of exercise, the initial observations dealt with heart disease. Soon, we also came to realize that exercise was important in reducing the risk of diabetes. Since then, the list has grown considerably.
We now know that people who are physically active on a regular basis have a reduced risk of hypertension, heart disease, diabetes, osteoporosis, depression, anxiety, sleep problems and frailty -- the latter is not a disease -- but individuals who are frail tend to have bad falls and otherwise poor function. Even the frail do very well with exercise. Exercise reduces the risk of gaining weight and becoming obese, reduces the risk for stroke and, now we have some very good data which indicate certain types of cancer, especially of the breast and colon, may be reduced by exercise.
Exercise is important because it can serve as both a primary prevention for these diseases and as a secondary treatment. For many years, people have worried about taking someone who has a large burden of disease and exercising them. Physicians felt that they could not reverse the heart disease or the diabetes or the obesity, but, in fact, exercise is a great adjunct with other medical practices (such as changes in the diet) for treating many of these disorders.
Why Not Just Prescribe Human Growth Hormone?
JM:
Mim, I strongly agree with you, but let me play devil's advocate for a minute. I have read several studies that have been well-designed and carried out over the past several years(1) which indicate that increases in lean body mass can also be quite readily accomplished by subcutaneous injection of growth hormone(HGH): increases in bone mass and increases in other aspects of non-fat mass have been observed. Certainly, in many respects, the administration of growth hormone requires less discipline than convincing a patient or a population to exercise on a regular basis. Why don't we use growth hormone instead of exercise?
MN
The growth hormone research has been very interesting. When it first hit the medical journals, we were all very excited about it. As you mentioned, the research showed that older individuals did gain lean tissue but the problem with growth hormone is that, while it does increase lean tissue, it does not seem to have a preferential effect on skeletal muscle. When we are thinking about increasing lean tissue, bones are important but so is skeletal muscle. Growth hormone does increase lean tissue but the visceral organs increase as well as the skeletal muscle. Most relevant is the finding that the functional capabilities of the muscle have not been shown to be enhanced, which is one of the major outcomes that was sought.
Growth hormone was originally used because older individuals go through a process which we now call 'sarcopenia,' the loss of skeletal muscle which accompanies aging. Sarcopenia is one of the main reasons that elders become frail. Enhancing the mass of the visceral organs does not allow you to get up out of a chair better, walk faster, or climb stairs any better. Because the muscle in our bodies is really the major depository of glucose -- and the main system that drives our metabolic rate and thus helps us avoid obesity - HGH was promoted.
Also growth hormone is not without its side effects. People taking growth hormone can experience insulin resistance. There can also be problems with the cardiovascular system and with nerve entrapment syndromes. So, in many ways, it is not a particularly desirable means of treating frailty in older individuals.
JM
Parenthetically, Mim, I should also add that one of the side effects of growth hormone therapy is the considerable cost associated with it.
Nutrition and Exercise
JM
Mim, let me now ask you about the interface between nutrition and exercise? More specifically, is it always necessary to supplement your habitual dietary intake when you are exercising? Do the two work synergistically to provide a better outcome than you would get from exercise alone?
MN
Every individual should have a healthy diet regardless of whether they are exercising or not. We really need to strive towards improving our diets (e.g., increasing fruits and vegetables, reducing animal fat and keeping total fat to approximately 30% of total calories) to reduce the likelihood of developing chronic, degenerative diseases and to optimize performance. On the other hand, there is nothing unique about the optimal diet for a person who is in an exercise program. One important aspect about physical activity and its interaction with nutrition is that, when people become physically active, research shows that they will spontaneously eat more.(2) They will be able to maintain energy balance better so that they do not gain weight as they get older. Because of the increased energy demands of physical activity, they need to eat a little bit more in their diet to maintain their body weight. This, in turn, means that they are spontaneously getting more of the other types of nutrients in their diet: protein, vitamins and minerals.
We did a study in the mid-1980s with postmenopausal, sedentary women whose average age was 62 and we compared them to an active group of women. The active group ate, on average, 300 to 400 calories a day more than the sedentary group, yet they had 6 kg less body fat than the sedentary group.(3)
So, you see, the active women are getting more nutrients and they are able to eat more. I think that this is an important aspect of the interaction between physical activity and nutrition. We have also done studies where we have taken sedentary individuals and randomized them into an exercise program alone or an exercise program combined with supplemental protein or micronutrients. In all of those studies, we have seen great benefits of exercise as far as increasing aerobic capacity, muscle strength and function. To date, we have seen little interaction with the nutrition; this is possibly because of the short-term nature of these studies (about 12 weeks). If somebody already has a good diet, then changing it a little bit is not going to make a big difference in someone's performance. Nevertheless, over the long haul, for disease prevention and health promotion, you want to make sure you optimize everybody's diet along with encouraging them to exercise.
Should Patients Take Vitamin Megadoses?
JM
Mim, a related question that has come up in my clinic on several occasions is as follows: several people who enter into regular exercise programs have asked me whether the addition of supplemental protein or whether the addition of 'megadose' vitamins will actually improve or optimize the benefits of their exercise program? I would like to hear from you whether you feel that taking extraordinarily large amounts of protein in the diet, or whether large supplemental doses of vitamins actually improve the outcome of exercise?
MN
There is no evidence whatsoever that increasing protein over and above what people normally take in their diet will optimize the gain in muscle mass with exercise or optimize performance. Most Americans get plenty of protein in their diet. However, there is a subset of older men and women (about 20 to 25% of older men and women) who probably do not get the Recommended Dietary Allowance of protein. For that group (and these are the people who are very frail, may have denture problems and may not have much food intake) you would want to make sure that they are getting adequate protein in their diet when they are starting an exercise program, preferably from food sources, not from supplemental sources. Milk shakes and other dairy-based foods are going to help them the most. For healthy men and women, adding supplements is not going to help at all. There have been many randomized double-blinded controlled trials(4) that have shown that, over and above a normal healthy diet, these protein or vitamin supplements do not make any difference in performance or body composition.
There is one nutrient that we don't often think about that is essential for a successful exercise program -- fluids. I can't emphasize enough the importance of monitoring the hydration level of the physically active patient. Many people are dehydrated subclinically, especially older individuals or people who are exercising in the heat; and, in these situations, hydration needs go up precipitously. We need to encourage people to drink more non-alcoholic, non-caffeinated fluids when they become physically active - amounting to at least 8 glasses of fluid per day.
Calories are another important factor but you do not generally need to worry about them because normal appetite regulation will enable people to adjust their intake, depending on what their energy expenditure dictates. If a person starts an exercise program, their appetite will generally increase to meet the body's extra needs and, in this way, the individual will be able to maintain weight. If a person needs to lose some weight, they probably will, as their appetite will not come all the way back up to compensate for the extra energy that is expended. This is why exercise is particularly helpful when people need to lose weight.
When Exercise Isn't a Good Idea
JM
Thank you. Those are very interesting, practical points you made. Mim, it seems to me that virtually anyone would benefit from a regular exercise program. In this regard, let me ask whether there are any subgroups within the population who you specifically feel would not benefit from an exercise program or for whom an exercise program would not be appropriate?
MN
You are absolutely right. Exercise is really appropriate for almost every type of person. Whether they are frail and elderly; whether they are young; whether they are pregnant; whether they are postpartum or whether they are recovering from a trauma or disease state. However, there are a few situations where exercise would be contraindicated for an individual, particularly with an outpatient-based program. Those with unstable medical conditions: unstable angina, out-of-control diabetes, uncontrolled blood pressure or patients who have experienced other serious medical events within the last six months should not have a regular exercise program until their condition has better stabilized. For instance, if an individual has had major surgery, has a progressive neurological disorder, or any type of progressive disease state that has not been stabilized, further medical intervention needs to occur before an exercise program is instituted. The key here is that once someone is stabilized, they can start to exercise. They need to start out at an easy and durable level and then slowly progress up and start to become more physically active.
Kinds of Exercise
JM
I think our audience would like some insight into some of the particulars about exercise. What are the different types of exercise, which types of exercise provide what type of benefits?
Aerobics
MN
Exercise is much more than just aerobic exercise, the classic exercise that people think about when they think about becoming more physically active. Aerobic exercise is a foundation for physical fitness. Aerobic exercise is an activity in which a person is using a large number of muscle groups in the body and it requires a certain minimum duration of activity. The duration should be at least 20 minutes. The intensity is based on your heart rate or perceived intensity. In aerobic exercise, it is desirable for an individual to be working at a level where their heart is beating faster than at rest. Likewise, their breathing rate should be faster than at rest. An average would be somewhere between 60 and 75 percent of their maximal heart rate. You need to do aerobic activity at least three times a week for 20 minutes at sufficient intensity to obtain the health benefits of aerobic exercise.
Strength Training
MN
Strength training is the other main component of an exercise program. It is a type of exercise activity that investigators had not thought about until very recently. It is probably critically important for older individuals because strength training is the type of activity which will help to preserve bone and muscle mass as we get older. Humans lose about one-third of a pound of muscle every year after age 40. Aerobic activity does not seem to affect that loss. Strength training, an activity in which we lift a heavy object about 8 to 10 times with muscles contracting, seems to attenuate those losses in muscle. For example, if I have a weight in my hand, with my arm at my side, and I contract my biceps muscle to bring my forearm up towards my shoulder, I am causing my biceps muscle to be trained.
The rule of thumb is that if I can lift the weight about 8 to 10 times before I become overly fatigued, that is a good strengthening exercise. However, if I can lift the weight 15 times or 20 times, then such exercise is insufficient to serve as a strengthening exercise and a heavier weight should be used. You need to do strengthening exercises about two to three times a week to get the benefit.
Flexibility and Balance Training
MN
Flexibility exercises should also be part of any good aerobic or any good strength training program. During a warm up or a cool down, you are going to be stretching your muscles. A fourth mode of exercise which I will not talk much about is balance training and working on coordination. With the elderly in particular, specific balance training exercises (in which subjects with a narrow base of support do lateral movements, turning side to side) can actually help individuals develop better coordination and in so doing resist falls. These exercises are particularly interesting for us at the moment. Presently, we have these types of exercise programs going on in the elder community with balance training included.
What type of activity is appropriate for each type of individual is a question that is very important. Aerobic activity is probably the most important exercise for young and middle-aged adults because it is going to help with weight control and cardiovascular health. However, somewhere in our late 40s, probably 50s and especially in the 60s, 70s, 80s and 90s, strengthening exercises become equally important. In the 70s, 80s and 90s, strengthening exercise may be even more important than aerobic activity because you are attempting to reduce frailty, reduce the risks of having falls and maximizing independent living.
JM
Incidentally, for those of you who are interested in some of the detailed particulars of the exercise programs that Miriam Nelson and her laboratory have designed, a widely available book entitled Strong Women Stay Young has recently been published and is available in most bookstores.
Exercise and Osteoporosis
JM
Mim, I thought that we could close our discussion today by going back to something you mentioned early on in our discussion. That topic pertains to both the primary preventive aspects of exercise as well as the secondary therapeutic effects of exercise in particular disease states. I would appreciate if you could elaborate on these two aspects of exercise in a few disease conditions that you have been particularly interested in.
MN
Much of my research has focused on reducing risk factors for osteoporosis. A couple of years ago, we published a study in the Journal of the American Medical Association in which we studied a group of women between the ages of 50 and 70 who were not on estrogen replacement therapy.(5) It was a randomized controlled trial. Half of the women did strength training in our laboratory for two days a week for one year and the other women went along their normal activities. All of the women at baseline were quite sedentary. At the end of the year, the women who had been strength training had become 75 percent stronger. They gained three pounds of skeletal muscle and lost three pounds of body fat. Their balance improved by about 14 percent. Their bone density increased by about 1 percent in the spine and the hip, whereas, the women in the controlled group had the normal age related declines in bone density of about 2 to 2 1/2 percent in the spine and the hip (clinically, this is highly significant when one examines fracture risk).
One of the most exciting aspects of the study was that women who strength trained actually became more physically active in their every day lives, so they took up more activities. They were gardening more, walking more, canoeing and ballroom dancing on the weekend. This is really the heart of what we want to see.
With exercise programs, people become more physically active. When you think of risk factors for osteoporotic fractures, bone density is very important and we were able to reverse the age related losses in bone density. Equally important and many times forgotten, however, is reducing the risk for having a fall. These women were much stronger, they had much better balance and they had more muscle mass. All of those factors are going to reduce their risk of having a fall. If we could keep these women from having a fall, then we could keep them from having a fracture. But if a subject does fall and her bones are stronger, she is still going to be at a reduced risk for having a fracture. Unlike some of the medicines used to enhance bone mass, exercise affects many different determinants of fracture risk.
Exercise and Rheumatoid Arthritis
MN
Historically, most patients with rheumatoid arthritis were told to rest, to take it easy or, if they wanted to exercise, to swim in a pool, limiting their range of motion and not bearing weight. It is true that people with RA have difficulty walking because they are bearing their weight. What we found, however, in our lab is that these individuals can do strengthening exercises very well. The strengthening exercises are particularly important for them because their state of chronic inflammation causes RA patients to lose a lot of muscle mass and lean tissue. In addition, their medications (e.g. corticosteroids) provoke bone and muscle loss. The problem is compounded by the fact that they have a lot of pain in their joints and, because of that, they have a very limited range of motion.
In a recent study done by the Chief of our laboratory,Ronenn Roubenoff, M.D., people with RA undertook programs of strength training and tolerated them very well. They displayed significantly decreased pain, increased range of motion, and the time taken to walk a 50 foot course decreased. The quality of their gait became better and they got much stronger.(2) While, in the short term, we did not see changes in muscle mass, we hope to perform longer term studies to measure the changes in body composition; hopefully, we will be able to reverse the loss of lean tissue and muscle tissue that these individuals experience with their disease. Strength training seems to affect many different factors of their disease state. As was true for the study that I talked about previously, these RA patients actually became more physically active in their overall lives once they developed more muscle strength because their mobility became better.
JM
In closing, I once again would like to thank Dr. Miriam Nelson whose knowledgeable and interesting insights have been both educational and provocative.