5. Physical actvity as therapy for osteoporosis

Jerilynn C. Prior, MD, FRCPC; Susan 1. Barr, PhD, RDN; Raphael Chow, MD, FRCPC;Robert A. Faulkner, PhD

Objective: To examine exercise as a therapy for people with osteoporosis.Options: Immobilization, standing low-load and high-load physical activities.Outcomes: Risk of injury, quality of life, risk of falls and fractures, strength and posture and pain

management.Evidence: Relevant epidemiologic studies, clinical trials and reviews were examined, including the

large-scale FICSIT trial in the United States, a prospective 4-year study of women enrolled in anexercise program in Toronto and the large-scale Study of Osteoporotic Fractures.

Values: Minimizing risk of injury and increasing quality of life were given a high value.Benefits, harms and costs: Moderate physical activity in people with osteoporosis can reduce the

risk of falls and fractures, decrease pain and improve fitness and overall quality of life. It may alsostimulate bone gain and decrease bone loss. Its positive effects are an adjunct to other interven-tions, such as hormonal therapy. It may give patients the confidence to resume regular activity andcan provide social interaction and support. During exercise programs, proper nutrition is neces-sary to prevent excessive weight loss and impaired immune function resulting from inadequateprotein, vitamin and mineral intake.

Recommendations: Immobilization should be avoided if possible in anyone with osteoporosis or atincreased risk for osteoporosis. Regular, moderate physical activity is recommended for those withosteoporosis. Elderly people should be assessed for risk of falling to identify those in greatest needof an exercise program. Community group exercise programs are beneficial. Younger people withosteoporosis also need exercise that will preserve or improve bone mass, muscular strength, en-durance and cardiovascular fitness. Weight loss as a result of physical activity should be avoidedand adequate intake of protein, vitamins and minerals assured. Because the benefits of physical ac-tivity are independent of the effects of other therapies, physical activity is an essential adjunct toappropriate nutrition and other therapies.

Validation: These recommendations were developed by the Scientific Advisory Board of the Osteo-porosis Society of Canada at its 1995 Consensus Conference. They are in agreement with the po-sition taken on osteoporosis and exercise by the United States Centers for Disease Control andPrevention and the American College of Sports Medicine.

Sponsors: Sponsors of the 1995 conference included the Dairy Farmers of Canada, Eli Lilly Canada,Inc., Hoffinann-La Roche Canada Ltd., Merck Frosst Canada Inc. and Procter & Gamble Phar-maceuticals Canada Inc.

T he health benefits of physical activity are well doc- independent of other bone therapies, it can provide anumented.',' The purpose of this paper is to examine essential adjunct to other interventions, both hormonal

whether exercise is a useful therapy for people diagnosed and nonhormonal therapies.4with osteoporosis. In general, although exercise mayplay a role in enhancing bone gain or reducing bone Physical activity and biomechanical factorsloss,3 the primary purpose of physical activity in thosewith osteoporosis is to reduce the risk of falls and frac- Although the overall geometric properties ofbone aretures. In addition, as physical activity has positive effects determined genetically, internal architecture, bone min-

Dr. Prior is in the Department ofMedicine, Division of Endocrinology and Dr. Barr is with the School of Family and Nutritional Sciences, University of BritishColumbia, Vancouver, BC; Dr. Chow is at the Department of Medicine, Division of Physiatry, University of Toronto, Toronto, Ont.; and Dr. Faulkner is with theCollege of Physical Education, University of Saskatchewan, Regina, Sask.

This statement was prepared at the 1995 Consensus Conference of the Osteoporosis Society of Canada.

Reprint requests to: Ms. Mary Bowyer, Osteoporosis Society of Canada, 33 Laird Dr., Toronto ON M4G 3S9; 416 696-2663

940 CAN MED ASSOC J * 1er OCT. 1996; 155 (7)

eral density (BMD) and internal and external bone di-ameters respond to environmental forces.5 Mechanicalstrain is the key intermediate variable between mechani-cal loading of the skeleton and bone mass.26 Changes ininternal strain in bone (defined as the fractional changein dimension of a bone in response to a changing load)appear to activate osteocytes, which in turn alter the bal-ance between bone resorption and formation. Increasedload, over time, increases bone mass. (Conversely, de-creased load over time decreases bone mass.) Increasedbone mass results in a relative reduction in internalstrain caused by any external load because the load isspread over a larger amount of bone. Thus, forces ap-plied to bone create a new equilibrium of bone mass.The osteogenic response to mechanical loading ap-

pears to be site specific; that is, the effects of exercise arenot homogeneous, but rather reflect the strains imposedat individual sites.7

In some cases, the relation between strength andBMD is site specific, but in others it is not as strong.8For example, arm activity may be related to increases inlumbar spine BMD.9 Although it is tempting to infersome systemic effect of exercise from these data, a moreplausible explanation is that trunk muscles are stabilizersin all upper body activity; hence arm activities also loadthe muscles of the vertebral column.The characteristics of the strain are important- os-

teogenesis is caused by dynamic, not static, strains. Theoptimal type of osteogenic activity should provide rela-tively high levels of strain.5 Greater loads and fewer rep-etitions of a load result in greater gains in bone massthan lower loads repeated more times.'0 However, pre-scribing high loads for anyone with osteoporosis, espe-cially an older person who may lack good conditioning,must be done with caution. Fortunately, moderate loadsare likely sufficient in these populations.1",2 A beneficialresponse at submaximal loads may occur because habit-ual strain levels are lower in the older skeleton; there-fore, even low to moderate loading activities can beosteogenic. Relatively low-intensity resistance exerciseis possible and can be effective in even frail elderly peo-ple.'3 Therefore, it is imperative that loads are expressedin relative rather than absolute terms when prescribingactivities for older people and those with low bonemass.

Major benefits of physical activity

The aims of individual physical activity or exerciseprograms are to improve physical well-being, generalendurance, strength, posture, flexibility, pain control andto prevent falls and progression of spinal deformity (ifpresent).'4"5 In addition, physical activity will help tomaintain bone density or decrease the rate of bone loss.2These effects have led the US Centers for Disease Con-trol and Prevention and the American College of Sports

Medicine to make the following general recommenda-tion regarding exercise:

Every U.S. adult should accumulate 30 minutes or more ofmoderate intensity physical activity on most, preferably all, daysof the week.'6

Those in group exercise programs can derive addi-tional benefits from the social interactions, support andinformation that is shared when people with a similarhealth problem gather in a therapeutic environment. Pa-tients with osteoporosis, especially but not only thosewho are elderly, are fearfiul of falls and may become inac-tive or housebound. Regular exercise can help them re-gain self-confidence and pursue a more productivelifestyle.

Aspects of physical activity for patientswith osteoporosis

Postural retraining is a key goal for people with os-teoporosis. Those with compression fractures in the tho-racic spine, which tend to collapse anteriorly, developrounding of the back (kyphosis), which leads to loss ofheight and may lead to back and shoulder pain, a protu-berant abdomen and difficulty with sleep. An importantpart of this component of exercise is education onproper posture during standing and sitting. In addition,it is important to teach ways of carrying out daily activi-ties, such as bending and getting up after lying down,that are effective and will not present a threat of furtherfractures. Every effort must be made to avoid slouchingposture or prolonged bending. An erect posture requiresstrong back and abdominal muscles.

Back exercises, including the pelvic tilt, isometric ab-dominal strengthening exercises and gentle back exten-sion exercise, should be performed regularly. Those witha history of vertebral compression fractures should avoidflexion exercises, such as bending from a standing posi-tion and full sit-ups, which have been associated with anincreased number of spinal compression fractures com-pared with extension exercise.'7

Another aim of physical activity in the treatment ofosteoporosis is to strengthen muscles. For example,weakness in hip and thigh muscles may prevent a personfrom using public transport, as buses commonly havehigh steps. Given that muscular contractions exert strainon the bone (which may be osteogenic), musclestrengthening exercises for the upper and lower bodyand axial skeleton are beneficial. The strengthening pro-gram should be submaximal, incorporate the major mus-cle groups and be performed as tolerated for each indi-vidual.

To promote endurance and improve cardiovascularfitness, low-impact forms of aerobic exercise, such aswalking, are suggested. Cardiovascular exercise may in-

CAN MED ASSOC J * OCT. 1, 1996; 155 (7) 941

clude walking, bicycling, swimming, dance routine orlow-impact aerobics. Endurance exercises performed ondry land produce a greater stress load than those carriedout in water, but both are probably effective for car-diorespiratory conditioning.

Patients with osteoporosis should use extreme cautionin performing activities where impact is excessive, suchas jogging on pavement, skipping or high-impact aero-bics, because they may cause stress fracture. Physical ac-tivity should not cause pain or aggravate existing pain.

Exercises to improve balance and, therefore, decreasethe risk of falling are another important component inosteoporosis therapy. Balance exercises are an integra-tion of strength in the trunk and legs, proprioceptionand central vestibular input. Exercises aimed specificallyat balance, such as Tai Chi'8 and Tinetti's progressivebalance exercises,'9 have been shown to prevent falls.20

Nutritional aspects of exercise

Besides the clear need for adequate calcium (see pages93 5-939), two general aspects of nutrition relating to ex-ercise are important for those with osteoporosis. Theseare the preservation of a healthy weight despite the in-creased energy demands of exercise, and the provision ofadequate nutrients during exercise to prevent impairedimmune function.The amount of energy expended in an exercise pro-

gram may be modest, and results are equivocal regardingthe extent to which energy needs in older people are in-creased by an exercise program.21'22 Nevertheless, weightloss may occur if energy intake does not increase tocompensate for the increased expenditure. A recommen-dation to avoid significant weight loss in underweightpeople is based on the following considerations:* Relative weight is a determinant of fracture risk in

both men and women.23-26* Changes in fat mass over 2 years have been directly

associated with changes in bone mineral density in27postmenopausal women.

* Relative risk of hip fracture was shown to increase inmiddle-aged Norwegians who lost weight over a pe-riod of 11 years.28In addition to the value of normal weight, recent

studies have emphasized the importance of protein, vita-min and mineral intake in maintaining immune func-tion. In a double-blind study, Chandra and associates29found that days of infection-related illness were halvedin 96 independently living elderly people receiving a vi-tamin-mineral supplement. Although not reported bythe authors, it is not unreasonable to speculate that thenumber of days confined to bed or with reduced activitylevels may also have been lower in the supplementedgroup. Not only is bed rest associated with bone loss,but an important portion of falls in older people is asso-ciated with acute illnesses.30

Adequate protein intake is also necessary for immunefunction. Castaneda and collaborators3' found that olderwomen given a low intake of protein were in negativenitrogen balance, lost lean tissue, had decrements in im-mune response and experienced decreased muscle fimc-tion. This study is relevant in that some people with os-teoporosis may be attempting to decrease their proteinintake on the basis of research showing that the higherthe protein intake the greater the urinary calcium loss.32Reducing protein intake, however, is undesirable forthose whose initial intakes are relatively low because in-adequate intakes clearly compromise immune function.Recent research suggests that, to maintain nitrogen bal-ance, elderly people require slightly higher protein in-takes than younger adults (about 1.0 g/kg v. 0.8 g/kg).33Resistance training has been found to improve nitrogenbalance in elderly people.34

Exercise and the prevention of falls

In older people, 5% to 10% of falls result in fracturesand a quarter of falls result in other significant injuries.35The American College of Sports Medicine recently pub-lished a position paper linking exercise with the preven-tion of falls:

The optimal program for older women would include activitiesthat improve strength, flexibility and coordination [which] mayindirectly but effectively decrease the incidence of osteoporoticfractures by lessening the likelihood of falling.'6

The best evidence that an exercise program can de-crease falling comes from a planned meta-analysis of theUnited States Frailty and Injuries: Cooperative Studiesof Intervention Techniques (FICSIT) trial.'0 This was a2- to 4-year follow-up of about 2300 women over age65, randomly assigned to some formal exercise or con-trol program. The outcome variable was the docu-mented rate of falling in relation to the exercise andother interventions. The adjusted incidence ratio (IR)for falling in the centres that included general exercisewas 0.9 (95% confidence interval [CI] 0.81 to 0.99).There was an even more important reduction of 17% inthe risk for falls if the exercise included some activitiesaimed at improving balance (such as Tai Chi'8 orTinetti's progressive balance exercises'9) (IR 0.83, CI0.70 to 0.98).2° In a study of 200 women from Atlanta,the 72 women assigned to Tai Chi exercise decreasedtheir risk of falling by almost 40% (IR 0.63, p = 0.01).18

Exercise and the prevention of fractures

In addition to preventing falls, is there evidence thatexercise will decrease the risk of fractures by othermechanisms, such as improved bone density or bonequality? Most of the data are inferential or indirect (withbone density as the end point). Some data from a 4-year

942 CAN MED ASSOC j * 1 er OCT. 1996; 155 (7)

follow-up of an exercise program in Toronto indicate anonsignificant reduction in fracture rates in women whoexperienced the most improvement in cardiovascular fit-ness. The prevalence of fractures decreased over 4 yearsin 78 women (some of whom were also treated with es-trogen or fluoride) to 0.08/woman in those with mostimproved fitness compared with 0.44/woman in the lessimproved group (p = 0.09).'4

These data predict the results of the Study of Osteo-porotic Fractures, in which 9515 female volunteers over65 years of age were followed for over 4 years.37 Fiftypercent of the population reported that they walked forexercise and 90% reported being on their feet for 4 ormore hours a day. The 192 first hip fractures among thisgroup were analyzed for risk factors. Among the manyvariables entering the model, walking for exercise pro-vided a 30% reduction in relative risk (RR) of fracture(RR 0.7, CI 0.5 to 0.9). This risk ratio was not signifi-cantly changed when bone density and non-hip fractureswere added to the equation.37 In addition, not standingfor 4 or more hours a day increased risk of hip fractureby 70% (RR 1.7, CI 1.2 to 2.4), a relationship that wasnot altered by adjustment for bone density and otherfractures.37

Thus, there are now increasing and reasonably con-gruent epidemiologic and experimental data to showthat mild activities, such as standing or walking, or rela-tively nonstrenuous exercises, such as Tai Chi, can pre-vent falling and hip fractures.

Exercise and quality of life

Can exercise decrease pain, increase ability to per-form activities of daily living and improve quality of lifein those with osteoporosis? The prospective 4-yearstudy of women with osteoporosis enrolled in theToronto program showed that pain, assessed yearly, de-creased in the whole group, but decreased more signifi-cantly in those with the greatest improvement in aerobicfitness (p < 0.025).14 An Osteoporosis Functional Disabil-ity Questionnaire developed by Helmes and colleagues38in London, Ont., was used to assess pain and activities ofdaily living. Those with osteoporosis who chose to par-ticipate in the exercise sessions compared with thosewho did not experienced a significant decrease in paininterfering with their daily activities (p = 0.005) and im-provement in activities of daily living over the last 6months compared with greater pain and decreased activ-ity in the controls.38

Identifying people for exercise programs

Young people with osteoporosis can often be inte-grated into existing low-impact aerobic programs, butthe same cannot be said for older people. Given limitedhealth care resources, can we identify a group of older

people who are at increased risk of falling and for whomexercise would be most beneficial? There are a variety ofgenerally available tests of balance and ambulation, suchas the Berg Balance and the timed "up and go" tests.3940It seems reasonable to recommend that family physi-cians screen those over 65 who have osteoporosis or areill or those of any age who are frail for balance and fimc-tional mobility. In addition, a clinical review of medica-tions (with a view to avoiding long-acting sedatives) andan assessment of alertness, vision and hearing are recom-mended.

Summary and conclusions

* Evidence is now available- based on biomechanicaleffects on bone mass, practical physical activity pro-grams, epidemologic studies and clinical trials- toassert that regular, moderate exercise is likely to de-crease the risk of falling, decrease fractures and im-prove the quality of life of those with osteoporosis.

* The primary purposes of physical activity in thosewith osteoporosis are to decrease the risk of falling;improve balance, muscular strength, range of motionand endurance; improve posture; lessen pain; and im-prove overall quality of life.

* Because walking for exercise has been shown to beassociated with a decreased risk of hip fractures andfalling, most elderly people with osteoporosiseven those with coexistent problems such as arthritis,heart disease or frailty- should be encouraged to bephysically active and, wherever possible, to join com-munity group exercise programs, provided that theprogram begins gradually and the activity remainsmoderately intense.

* Younger people with osteoporosis also need exercisethat will preserve or improve bone mass, muscularstrength, endurance and cardiovascular fitness.

* Elderly people should be assessed for risk of fallingto target those in greatest need of an exercise pro-gram. A basic evaluation includes a clinical review ofmedications with a view to avoiding long-actingsedatives, a review of alertness, vision and hearingand one of the generally available tests of balance andambulation.

* In those with osteoporosis who are initially under-weight, weight loss as a result of physical activityshould be avoided. Moreover, because decreased im-mune function related to inadequate diet may lead toillness and, therefore, immobilization and increasedrisk of falling, everyone with osteoporosis who be-gins an exercise program should ensure that he orshe receives adequate intakes of protein, vitamins andminerals.

* Immobilization should be avoided, if possible, inanyone with osteoporosis or at increased risk for os-teoporosis.

CAN MED ASSOC j * OCT. 1, 1996; 155 (7) 943

* Benefits of physical activity are independent of theeffects of other therapies. Therefore, physical activityis an essential adjunct to appropriate nutrition andother therapies.

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