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[EXERCISE IS MEDICINE]

Decreased Mobility in the Elderly: The Exercise Antidote

Joseph A. Buckwalter, MD

Series Editor: Nicholas A. DiNubile, MD

THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 9 - SEPTEMBER 97


In Brief: There is no age limit to the benefits of exercise. Regular activity, in fact, can often slow or reverse the decreased mobility that contributes to disease and disability in old age. Teasing out the relative contributions of disuse and genetically programmed decline can be difficult. However, clinical research demonstrates that for most elderly patients, including many who are frail or have concurrent illnesses, a program of aerobic, strength training, and flexibility exercise helps maintain mobility, improve quality of life, and prolong independence.

The capacity for free, comfortable movement is a foundation of well-being that healthy people take for granted. But increasing age brings unwelcome changes. Musculoskeletal weakness, stiffness, and pain—among the most frequent complaints physicians hear from middle-aged and older patients—often lead to a general decline in physical activity.

The consequences of decreased mobility ripple through the older individual's life. Financial status and quality of life decline along with the ability to work and participate in leisure activities. Self-image suffers, sleep quality deteriorates, and mood may be lowered. In time, reduced capacity for exercise can compromise the health of diverse organ systems, increasing the risk of heart disease, stroke, diabetes, and colon cancer (1).

If it progresses unchecked, decreased mobility undermines the capacity for activities of daily living: the ability to feed and clothe oneself, attend to personal hygiene, and perform such routine tasks as shopping for groceries. Besides promoting mental deterioration and cardiovascular disease, the loss of mobility is a significant cause of loss of independence among the elderly (2).

The Course of Decline

There are multiple causes for the soft-tissue changes responsible for restricted movement, including physiologic and anatomic processes that appear to be genetically programmed, as well as specific diseases and lifestyle factors such as disuse and poor nutrition. While little can be done about the first, the second group of factors suggests the possibility of interventions to slow, prevent, or even reverse the course of decreased mobility associated with age. Chief among them: the exercise prescription.

Broadly speaking, the overall reduction in physical activity with age parallels musculoskeletal changes on the level of cell, tissue, and organ system. When various parameters (eg, alterations in cell synthetic activity and responsiveness to growth factors, soft-tissue tensile strength, and overall musculoskeletal strength and flexibility) are compared between age- groups, their course is progressively, inexorably downward. But age-related declines in cellular, tissue, and musculoskeletal system function are far from uniform between individuals, nor do they always lead to impairment. Indeed, the rate of decline varies widely, and differences in absolute values can be striking: One person at 68 may function at a higher level than another at 18 (3).

On the whole, age-related changes in soft-tissue function can be related to reductions in a number of factors: for example, a decrease in the number of muscle cells, an alteration in the synthetic and proliferative capacity of bone and cartilage cells, and a decline in the ability of these cells to perform their specialized functions. Altered tissue environment—the result of systemic changes (notably in circulation and hormone secretion)—also plays a role.

Muscle loss. Changes in muscle are striking. Between the ages of 30 and 80, mean strength of back, arm, and leg muscles drops as much as 60%, largely reflecting a progressive loss of muscle mass at an average rate of 4% per decade from 25 to 50, and 10% per decade thereafter (4). Along with neuromuscular changes and decreased hormone levels, reduced exercise (particularly contractions against high loads) appears to be responsible (2).

Muscle endurance falls as well, leading to more rapid fatigue. Animal studies (5) have found the ability of muscles to provide sustained power during contraction to diminish by 50% with age. This seems due to a decline in enzyme-linked oxidative capacity, related to the loss of mitochrondria.

Aging muscles are more easily injured by their own contractions, and take longer to recover (6). The consequences of this vulnerability can be profound. Protracted healing extends the period of immobility due to the pain of injury; if this period is long enough, normal strength may never return, and newly weakened muscle will be more vulnerable to further injury. Once set in motion, this vicious cycle is very difficult to interrupt.

Joint stiffness. Age-related changes in joint structures—articular cartilage, ligaments, and synovium—can lead to stiffness, limited range of motion, and increased vulnerability to injury. In cartilage, chondrocyte synthetic function and responsiveness to stimuli such as cytokines change in ways that reduce the cells' ability to repair the matrix (2). Tensile stiffness, fatigue resistance, and cartilage strength decline (7). It has been observed that regular joint loading and motion are necessary to maintain articular cartilage function and synovial joint range of motion, and that reduced activity decreases synthetic processes in chondrocytes, adversely altering the mechanical properties of cartilage (2).

Ligament failure. The tensile strength of ligament-bone complexes has been shown to decline with age—by as much as half from age 21 to 79 (8). In individuals aged 60 to 97, ligament complexes fail at less than one-third the load required in young adults (ages 22 to 35) (9).

Injury propensity. Older people's muscles, joints, and ligaments are all more prone to injury than those of the young. Although bone fractures are the most dramatic musculoskeletal mishaps associated with age, they cause less impairment, in the population as a whole, than changes in soft tissues responsible for restricted movement (10). (Muscle weakness, for that matter, increases the risk of falls, and therefore of fractures.)

The vulnerability to musculoskeletal soft-tissue injury is probably responsible for much of the soreness that older people commonly have after exercise, as well as the risk of more serious events that can lead to lasting impairment via the cycle described above.

Reversing the Trend

It is difficult to sort out the relative contributions of disuse and genetically programmed processes to the overall progress of musculoskeletal deterioration. But it seems clear that while aging is not synonymous with disuse, disuse exacerbates the changes that occur with aging. Research confirms that regular exercise can significantly slow or reverse many changes associated with the age-related loss of strength, endurance, and flexibility.

Aerobic exercise benefits. A decline in aerobic fitness clearly contributes to decreased mobility: As the activities of daily living represent an increasing percentage of his or her maximum capacity, an elderly person becomes disinclined to perform them (11). But this process can be redressed, to a great extent, with endurance exercise. One study (12) of healthy patients aged 60 to 70 years found that VO2 max increased by 30%, on average, with 6 months of aerobic exercise. In another (13) a 9- to 12-month program of walking or running for 45 minutes 4 days per week produced a mean increase of 24% in aerobic capacity.

These effects appear to reflect peripheral adaptations that increase oxidative capacity of muscle by reversing age-linked declines in capillary density and enzymatic activity. Potentially, rigorous training can achieve levels comparable to those of younger individuals. In one study (14), mitochondrial concentration was 24% to 31% higher in the gastrocnemius muscles of master athletes (mean age, 63 years), than in 27-year-old runners who finished a race with similar times.

Strength training gains. The most dramatic exercise benefits, however, have been achieved with strength training. Indeed, it appears that resistance exercise may forestall declines in strength and muscle mass for decades. When investigators (15) compared 68-year-old men who had engaged in 12 to 17 years of strength training with 28-year-old men who were active in aerobic sports, isometric strength and cross-sectional areas of the quadriceps femoris and elbow flexor muscles were similar in the two groups.

Perhaps more important clinically, there is growing evidence that training of sufficient intensity can increase strength as effectively in older individuals as in younger ones (11). One study (16) showed that a rigorous 12-week resistance training regimen doubled knee extensor strength and tripled flexor strength in older men. Incremental changes in strength, roughly 5% per session, were similar to those seen in younger men.

Most heartening of all is research documenting substantial benefits of strength training even into the tenth decade of life. A classic study (17) enrolled 10 frail nursing home residents, (aged 86-96) in 8 weeks of high-intensity resistance exercise. For the 9 who completed the study, quadriceps strength increased progressively during the program, to a mean of 74% above baseline at its conclusion. Midthigh muscle area increased an average of 9% in the individuals who were measured. Most important of all, significant functional improvements accompanied the strength and muscle mass gains. In the 5 subjects who were assessed, gait speed increased by nearly 50%. Two subjects no longer needed canes to walk.

A larger study (18) involving 100 frail nursing home residents of similar age found smaller, but still robust, strength increases (mean: 13% above baseline), and a broader array of functional improvements: Stair climbing, gait velocity, and spontaneous physical activity increased.

Other research points to the need for interventions to prevent functional decline. One study (19) of 1,122 individuals, 71 years or older, linked measures of lower-extremity function to disability 4 years later. Those with lowest scores in tests of walking speed, balance, and ability to rise from a chair were nearly five times more likely to be disabled 4 years later, compared with those who scored highest. Another study (20) found runners aged 50 to 72 significantly less likely than controls to be disabled 8 years later.

The Exercise Prescription

Put simply, it is never too early and rarely too late to implement a regular exercise program to prevent or reverse age-related decreases in mobility. Aerobic exercise has substantial benefits in reducing the risk of illness and improving general fitness, and a long-term goal of 30 minutes per day of walking or other aerobic exercise is ideal (see "Exercise Your Independence."). It is strength training and a program to enhance flexibility, however, that constitute the specific prescription for maintaining function.

A thorough physical examination should precede any exercise program for previously sedentary individuals. It is also essential to assess the patient's muscle strength and range of motion to design a regimen that carries a low risk of injury.

Strengthening program. Generally, I recommend that patients begin resistance exercise with very light loads, counsel them to progress slowly, and educate them in realistic expectations: It is reasonable to allow 6 weeks before changes become noticeable. If patients expect swift, dramatic improvements, they will become discouraged and discontinue.

The ideal, for patients who are willing and able to invest the money and time in equipment or club memberships, is a regimen using exercise machines like Cybex (Ronkonkoma, New York), Nautilus (Independence, Virginia), or LifeCycle (Franklin Park, Illinois) that control resistance and take the joint through a full range of motion.

Such devices are not necessary, however. A complete program can be designed with a modest investment in simpler equipment such as plastic-coated dumbbells, ankle weights, and elastic bands. For some patients, standard aerobic exercise with a stationary cross-country ski machine or stationary exercise bicycle will provide adequate resistance as well as endurance training. Walking in knee-high or waist-high water in a swimming pool can also provide effective resistance.

Whatever devices or strategies are used, the exercise prescription should include work for shoulder, arm, and trunk muscles, the abdominals, and the lower extremities.

Flexibility component. It is important to supplement resistance training with stretching exercises that move the joint through a full range of motion to ensure flexibility and prevent or ameliorate stiffening.

Individualized plans. Musculoskeletal limitations must be kept in mind in tailoring an exercise program to the patient. Swimming might be more appropriate than walking for a woman with a valgus deformity of the knee, for example, and a man with a rotator cuff tear must modify his upper-body weight lifting program to protect his shoulder.

With appropriate adjustments, exercise should be possible for most patients with concurrent medical conditions, even heart disease or osteoarthritis. To make the program safe and effective, however, such conditions should be managed optimally, monitored carefully, and corrected to the extent possible for each patient.

Maintaining motivation. Compliance can be a problem for any patient, but particularly for older people who have been sedentary for decades. I urge patients to exercise with like-minded companions, or to integrate their workouts with regular daily activities: to do their strengthening and stretching routine while watching the 6 pm news, for example. Many patients find that exercising to music is enjoyable. Educating patients in realistic expectations, as described above, is also important.

Other Interventions

For the vast majority of healthy individuals, exercise is the most important and effective intervention for correcting the decreased mobility related to the musculoskeletal changes of aging. Although human growth hormone and androgen supplementation can increase muscle mass, they remain experimental. These supplements do not address other aspects of the age-related decline in musculoskeletal function, such as diminished flexibility, and their adverse effects (on glucose metabolism, blood pressure, etc) make them unacceptable for general use.

Poor nutrition may play a role in muscle depletion, and a marginal diet must be improved for exercise to be effective. But for patients with adequate calorie and protein intake, I have not found any change in diet necessary for initiating an exercise program.

Rewarding Results

It wasn't long ago that most people—including physicians—felt that past a certain age, exercise did little good and could do significant harm. Now, however, it has become clear that most older patients benefit substantially from exercise, and the vision of Ernst L. Wynder, head of the American Health Foundation in Valhalla, New York—that it be "...the function of medicine to have people die young as late as possible"—may be closer to fruition. In many cases, physician counseling, instruction, and encouragement can make the difference between progressive immobility and deterioration, and an active, rewarding old age.

References

  1. US Department of Health and Human Services: Physical Activity and Health: A Report of the Surgeon General. Atlanta, DHSS, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, 1996
  2. Buckwalter JA, Woo SL, Goldberg VM, et al: Current concepts review: soft-tissue aging and musculoskeletal function. J Bone Joint Surg (Am) 1993;75(10):1533-1548
  3. Buckwalter JA: Maintaining and restoring mobility in middle and old age: the importance of soft tissues. Instructional Course Lectures, Vol 46. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 459-469
  4. Faulkner JA, Brooks SV: Age-related immobility: the roles of weakness, fatigue, injury and repair, in Buckwalter JA, Goldberg VM, Woo SL (eds): Musculoskeletal Soft-Tissue Aging: Impact on Mobility. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1993, pp 187-194
  5. Brooks SV, Faulkner JA: Maximum and sustained power of extensor digitorum longus muscles from young, adult, and old mice. J Gerontol 1991;46(1):B28-B33
  6. Faulkner JA, Brooks SV, Zerba E: Skeletal muscle weakness and fatigue in old age: underlying mechanisms. Annu Rev Gerontol Geriatr 1990;10:147-166
  7. Kempson GE: The mechanical properties of articular cartilage, in Sokoloff L (ed): The Mechanical Properties of Articular Cartilage. New York City, Academic Press, 120210, pp 177-238
  8. Neumann P, Ekstrom LA, Keller TS, et al: Aging, vertebral density, and disc degeneration alter the tensile stress-strain characteristics of the human anterior longitudinal ligament. J Orthop Res 1994;12(1):103-112
  9. Noyes FR, Grood ES: The strength of the anterior cruciate ligament in humans and Rhesus monkeys. J Bone Joint Surg (Am) 1976;58(8):1074-1082
  10. Praemer A, Furner S, Rice DP: Musculoskeletal Conditions in the United States. Park Ridge, IL, American Academy of Orthopaedic Surgeons, 1992
  11. Evans WJ: Exercise, nutrition, and aging. Clin Geriatr Med 1995;11(4):725-734
  12. Seals DR, Hagberg JM, Hurley BF, et al: Endurance training in older men and women. I: cardiovascular responses to exercise. J Appl Physiol 120214;57(4):1024-1029
  13. Coggan AR, Spina RJ, King DS, et al: Skeletal muscle adaptations to endurance training in 60- to 70-year-old men and women. J Appl Physiol 1992;72(5):1780-1786
  14. Coggan AR, Spina RJ, Rogers MA, et al: Histochemical and enzymatic characteristics of skeletal muscle in master athletes. J Appl Physiol 1990;68(5):1896-1901
  15. Klitgaard H, Zhou M, Schiaffino S, et al: Ageing alters the myosin heavy chain composition of single fibres from human skeletal muscle. Acta Physiol Scand 1990;140(1):55-62
  16. Frontera WR, Meredith CN, O'Reilly KP, et al: Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J Appl Physiol 120218;64(3):1038-1044
  17. Fiatarone MA, Marks EC, Ryan ND, et al: High-intensity training in nonagenarians: effects on skeletal muscle. JAMA 1990;263(22):3029-3034
  18. Fiatarone MA, O'Neill EF, Ryan ND, et al: Exercise training and nutritional supplementation for physical frailty in very elderly people. N Engl J Med 1994;330(25):1769-1775
  19. Guralnik JM, Ferrucci L, Simonsick EM, et al: Lower-extremity function in persons over the age of 70 years as a predictor of subsequent disability. N Engl J Med 1995;332(9):556-561
  20. Fries JF, Singh G, Morfeld D, et al: Running and the development of disability with age. Ann Intern Med 1994;121(7):502-509

This article was prepared by contributing editor Carl Sherman.

Dr Buckwalter is a professor in the department of orthopedic surgery at The University of Iowa Hospitals and Clinics in Iowa City, Iowa. He is chair of the American Academy of Orthopaedic Surgeon's Council on Research and Scientific Affairs and team physician for the University of Iowa football program. Dr DiNubile is an orthopedic surgeon in private practice in Havertown, Pennsylvania, specializing in sports medicine and arthroscopy. He is the director of Sports Medicine and Wellness at the Crozer-Keystone Healthplex in Springfield, Pennsylvania; a clinical assistant professor in the department of orthopedic surgery at the University of Pennsylvania in Philadelphia; and a member of the editorial board of The Physician and Sportsmedicine. Address correspondence to Joseph A. Buckwalter, MD, The University of Iowa Hospitals and Clinics, Dept of Orthopaedic Surgery, Division of Oncology, 200 Hawkins Dr 01013JPP, Iowa City, IA 52242-1088; send e-mail to [email protected].


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