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Exercise for Osteoporosis Prevention

Slawta, Jennifer N. Ph.D.; Ross, Roberta M.S.

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Learning Objective To discuss the influence of physical activity upon bone and to describe a specific exercise program shown to prevent bone loss in postmenopausal women.

Osteoporosis is predicted to increase by 25% over the next decade. Specific weight-bearing exercises can prevent bone loss and risk of falling in postmenopausal women. This article endorses an exercise program designed to lower such risks.

Jennifer N. Slawta, Ph.D., is an assistant professor in the Health and Physical Education Department at Southern Oregon University. Her research focuses upon exercise science, nutrition, and body composition and their relationship with disease, specifically coronary heart disease, type 2 diabetes, and osteoporosis.

Roberta Ross, M.S., has been teaching the osteoporosis prevention exercise class since 2001. She has worked as a research assistant and is currently employed as health educator at Southern Oregon University.

Osteoporosis is a skeletal disease characterized by low bone mass, increased bone fragility, and increased risk for bone fracture. Women are four times more likely to develop osteoporosis than men (1). Osteoporotic fractures most commonly occur in the hip, spine, and wrist, but also can occur at other sites. Osteoporosis is a silent disease in that a fracture is frequently the first indication of bone loss. The National Osteoporosis Foundation estimates that 50% of women and 25% of men over age 50 will experience an osteoporotic fracture, and that 24% of persons with hip fractures over age 50 die within 1 year of their fracture (1). Osteoporosis is estimated to increase by 25% over the next decade (1).

During childhood and preadolescence, bone formation exceeds bone resorption, and bone mineral density (BMD) increases. In young adulthood, the rate of bone formation and bone resorption is similar so that BMD is maintained. Because of the loss of estrogen's protective influence upon bone at menopause, bone resorption exceeds bone formation and BMD declines. Average bone loss in women during menopause is approximately 2% each year, yet it is possible to lose up to 20% of bone in the 5 to 7 years after menopause (1).

Fracture risk is primarily dependent upon levels of BMD and falling (2). Approximately 90% of hip fractures and 50% of vertebral fractures are associated with a fall (2). The other 50% of vertebral fractures occur spontaneously with simple activities such as lifting or vacuuming. In addition to the reductions in BMD, decrements in muscle strength and power, which also accompany aging, lead to instability and impaired balance, further increasing the risk for fracture resulting from a fall or lifting (3). Osteoporosis and fracture cause pain, less mobility and independence, and fear of falling when participating in daily tasks and activities.

Figure

Figure

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Influence of Physical Activity Upon BMD

The load imposed upon bone through physical activity results in bone deformation. This deformation causes a fluid shift in bone, activating a cellular response that leads to an adjustment of bone mass and architecture to meet the imposed demands of the load (4, 5). Bone responds tohigh-magnitude loads delivered at high rates (4, 5). Low-intensity exercise such as walking is ineffective for stimulating bone (6). Physical activity transmits loads to bone through muscle pull and gravitational force from weight-bearing activity. Because of the increase in gravitational force upon bone in a weight-bearing position, strength-training exercises performed on the feet are considered to be more effective at stimulating bone than machine-based exercises performed in the seated position. In the weight-bearing position, there is an increased load at the hip and greater demand for postural control and balance, which in turn optimizes function in an upright position. Bone increases its response to high-impact, weight-bearing activity and strength training in the presence of adequate calcium consumption (7).

Figure

Figure

The effect of physical activity upon bone varies based upon a person's age (8-10). Weight-bearing activity in children, such as jumping, increases BMD by 5% to 10% (8). Gains in BMD persist several months after completing the jumping activity, suggesting that children who participate in such load-bearing activity will have accumulated more bone as they enter adulthood (11). Jumping activity and strength training in premenopausal women is reported to increase BMD by 1% to 5%, but gains are lost when the weight-training activity ceases (12). Most research in postmenopausal women suggests that jumping and strength-training exercises attenuate the progressive loss of bone in postmenopausal women but do not increase bone mass (5, 10, 13). Some research, however, has reported significant gains in BMD with high-impact loading, including stair climbing and running (14, 15), and strength-training programs involving free weights, machine-based equipment, and rowing activity (15). It is important to add that hormone replace therapy can augment an osteogenic response to physical activity in postmenopausal women (16).

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Osteoporosis Prevention Exercise Program for Postmenopausal Women

In a controlled research setting, the Bone Research Laboratory (BRL) at Oregon State University (OSU) has shown that lower-body exercises with weighted vests and jumping activity prevent age-related hip BMD loss and improve balance, muscle power, muscle mass, and muscle strength in postmenopausal women (13). To determine the applicability and efficacy of the program designed at OSU, the Health and Physical Education Department at Southern Oregon University (SOU) offered the exercise program to the community for 12 months at no cost for participation. Students at SOU were trained by the staff in the BRL at OSU. As a community-targeted program, no one was excluded from participation based upon age, gender, or medication use. There were 24 participants (23 postmenopausal women; 1 man, 83 years old) who completed the 12-month intervention. BMD was determined before and after the 12-month intervention with dual-energy X-ray absorptiometry. Because the majority of fractures result from falls, function-based activities including chair raises and stair stepping were measured before and after the intervention to indirectly assess improvements in balance and postural stability. Body mass index and body fat estimations using skinfold calipers were also measured before and after the intervention. The exercises were performed three times each week for 12 months.

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Exercises Performed

Forward Lunge

  1. Start in a standing position with feet shoulder-width apart.
  2. Take a large step forward with the right leg, keeping the upper body straight (Figure 1).
  3. Figure 1

    Figure 1

  4. To perform the forward lunge, bend the back knee (left) until the back knee almost touches the floor. Knees should be aligned with the feet and not extend beyond (Figure 2).
  5. Figure 2

    Figure 2

  6. During the lunge, the upper body should remain straight in an upright position, not bending forward or backward.
  7. Return to the upright position and repeat lunge for 8 to 15 repetitions.
  8. Return to the initial starting position and repeat the forward lunge with the other leg by taking a large step forward with the left leg, repeating the lunge on that leg for 8 to 15 repetitions.
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Squat

  1. Start in a standing position with legs in a wide stance.
  2. Feet and knees should be angled slightly outward with the knees pointing the same direction as the feet.
  3. Keep the back straight and lean slightly forward at the hip, bending at the hip (not bending at the waist or upper back) (Figure 3).
  4. Figure 3

    Figure 3

  5. To perform the squat, the legs should bend at the knees, keeping the back straight, until a 90° angle is reached.
  6. Rise quickly back to the starting position.
  7. Never bend at the waist or upper back during the squat. Always keep the back straight.
  8. Repeat the squat for 8 to 15 repetitions.
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Sideway Lunge

  1. Start in a standing position with the feet shoulder-width apart.
  2. Take a big step with the right leg to the right, landing with the right knee and foot pointed out at a 45° angle (Figure 4).
  3. Figure 4

    Figure 4

  4. The weight shifts to the right as the foot lunges right.
  5. Use the right leg as a spring to bring the right leg back to the starting position.
  6. Do not turn or twist the upper body.
  7. The knee should track in line with the foot during the sideway lunge.
  8. After 8 to 15 repetitions with the right leg, repeat the sideway lunge with the left leg for 8 to 15 repetitions.
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Chair Raise

  1. Start in a standing position with legs in a wide stance.
  2. Feet and knees should be angled slightly outward with the knees pointing the same direction as the feet.
  3. Keep the back straight and lean slightly forward, bending at the hip (not bending at the waist or upper back).
  4. To perform the chair raise, lower the body towards an armless chair by bending at the knees, keeping the back straight until a 90° angle is reached barely touching the chair (the movement is the same as a squat) (Figure 5).
  5. Figure 5

    Figure 5

  6. Rise quickly, coming back to the starting position.
  7. Never bend at the waist or upper back during the chair raise. Always keep the back straight.
  8. Repeat the chair raise for 8 to 15 repetitions.
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Heel/Toe Raise

  1. Start in a standing position with the feet shoulder-width apart.
  2. Lift both heels off the floor, standing on the toes and balls of the feet. Arms extend upward (Figure 6).
  3. Figure 6

    Figure 6

  4. Hold position for 3 to 4 seconds.
  5. Lower heels to floor slowly and rock back onto to the heels, lifting toes off of the floor. Arms extend forward (Figure 7).
  6. Figure 7

    Figure 7

  7. Hold position for 3 to 4 seconds.
  8. Lower toes to floor slowly, returning to the starting position.
  9. Repeat the heel/toe raise for 8 to 15 repetitions.
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Stepping

  1. Start in a standing position with feet shoulder-width apart.
  2. Step up onto an 8-inch step with the right leg, following with the left leg (Figure 8).
  3. Figure 8

    Figure 8

  4. Step down to floor with right leg, followed by left leg.
  5. After 20 to 25 repetitions of stepping with the right leg leading, repeat the stepping exercise with the left leg leading.
  6. Always maintain good posture with back straight when stepping.
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Alternating Forward, Sideway, and Backward Lunge

  1. Perform a sequence of forward, sideway, and backward lunges, always returning to the center after each lunge.
  2. With the backward lunge, take a step backward and perform the lunge the same as the forward lunge (i.e., bend the back knee until the back knee almost touches the floor).
  3. Perform the sequence for 8 to 15 repetitions with the right leg leading and then with the left leg leading.
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Jumping

Jumping exercises should not be started until 1 to 3 months after beginning the other exercises. Individuals with osteoporosis should not participate in the jumping exercises.

  1. Start in a standing position with feet shoulder-width apart.
  2. Bend the knees, bring the arms back, and lean the body slightly forward (Figure 9).
  3. Figure 9

    Figure 9

  4. Jump as high as possible, swinging arms forward and upward (Figure 10).
  5. Figure 10

    Figure 10

  6. Land on both feet, bending the knees upon impact with the weight distributed toward the heel.
  7. Repeat the jump 8 to 15 times.

The concentric phase of the resistance exercises was performed quickly because fast application of force is more effective for achieving an osteogenic response than slow application of force (5). Warm-up involved 5 to 10 minutes of walking and standing stretches. Cool-down involved 10 minutes of floor stretches on mats and abdominal exercises without abdominal flexion. Weighted vests were used after the first 6 weeks of the exercises so that weight could be gradually added to the musculoskeletal system while performing the lower-body exercises. Because the class is designed for a population that is aging, the weighted vest offers an advantage over holding dumbbells in that the weighted vest enables the arms to remain free, which helps with balance and increases participants' confidence when performing the exercises. In addition, the weighted vest is portable, which allows the exercises to take place in different settings, including home. Although there are no supporting data, it is possible that loading higher up on the axial skeleton with the weighted vest may serve to be a greater stimulus to hip and lumbar spine BMD than holding dumbbells in the appendicular skeleton. The weighted vest also can be used as part of a walking program. The BRL recommends that weight be progressively added to the vests up to 15% of body weight. Although the BRL recommends the weighted vest for jumping exercise for women without osteoporosis, the women participating in our program did not use the weighted vest for jumping or heel/toe raises. The weighted vest and a video demonstrating the exercises can be purchased from Bones and Balance (www.bonesandbalance.com).

The Table describes the progression of exercises in terms of sets, repetitions, and use of the weighted vest.

Table

Table

Table. C

Table. C

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One-Year Results

Based upon paired t tests, no significant losses in hip BMD (femoral neck, trochanter, or total hip) or lumbar spine BMD were observed at 1-year follow-up. Small nonsignificant increases in BMD were observed in the femoral neck (1.0%), total hip (1.3%), and lumbar spine (1.0%) after the intervention. Although not significant, these small increases in BMD are potentially meaningful because postmenopausal women typically lose 1% to 2% of bone each year. BMD decreased nonsignificantly in the trochanter by −0.25%. Results were similar when four participants using bone medications were excluded from the analysis.

The number of chair raises completed in 30 seconds was significantly increased and the number of steps completed in 2 minutes approached significance after the 12-month intervention. Because many falls in older adults occur when rising from a chair, the significant increase in number of chair raises and near-significant improvement in stair stepping suggests an improvement in balance and postural stability, which, in turn, may correspond to a reduction in falls and fear of falling when performing everyday tasks such as rising from a chair and climbing stairs. Significant reductions in body fat were also observed.

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Efficacy of Exercise Program

The findings observed in this small community program are consistent with the majority of findings from controlled studies in postmenopausal women in that weight-bearing exercises can attenuate progressive bone loss but not increase BMD (5, 10, 13). Because the purpose of the intervention was to determine the applicability of the exercise program to a community setting, a control group was not used. The lack of a control group and a controlled research design limit, to some extent, the observations made in this paper. Because most research is controlled, however, many potential participants are excluded based upon age, gender, and medication use. Thus, it is important to examine the applicability and efficacy of such research in a field setting.

The extension of the osteoporosis prevention exercise program to a rural community setting was successful in that no significant losses in bone were observed after the 12-month intervention. Although the program was specifically designed to target hip BMD, our findings suggest that the exercises also may prevent bone loss in the lumbar spine. Because the loss of estrogen's protective influence upon bone can lead to a rapid decline in bone mass at menopause and during the first several years after menopause (16), the small increases in femoral neck, total hip, and lumbar spine BMD after our 12-month intervention is encouraging in this small sample of women, particularly when considering that the positive improvements were maintained when excluding women taking medications known to favorably alter BMD. Because adequate intakes of calcium are beneficial to bone and may augment the osteogenic effect of physical activity upon bone (7), it is important to note that four women increased their intake of calcium and one woman decreased her intake of calcium during the intervention, and this may have influenced the findings observed in this intervention. The program was readily adaptable to the home and community setting. Participants who were unable to attend class did the exercises at home. The program also was easily modified so that participants could progress at their own pace. Although we were concerned that the program would become monotonous over time, the program is currently in its third year, and 20 of the 24 original participants continue to participate.

It is important to include the fact that three women who started the program were unable to continue as a result of preexisting arthritis pain and patellofemoral (knee) pain. Two women developed patellofemoral pain during the intervention. Patellofemoral pain occurs when the patella does not track properly during bending and straightening of the knee. Patellofemoral pain is caused by mechanical imbalances and laxity at the patellofemoral joint. Because patellofemoral pain is often attributed to a lack of quadriceps strength or an imbalance in muscle strength in the quadriceps muscles, it is recommended that participants who are entering the program with preexisting patellofemoral pain spend several weeks strengthening the quadriceps before beginning the weight-bearing exercises described in this article. Strength-training exercises for the quadriceps may include isometric contractions, straight-leg raises from a seated position on the floor with the back supported, and the leg extension machine. It may even be prudent for participants without patellofemoral pain to invest a few weeks strengthening the quadriceps before beginning the bone exercises in order to reduce the risk for patellofemoral pain. Proper form also is required when performing the bone exercises to prevent pain and injury. Although the bone exercises increase strength, balance, and postural stability over time, a lack of these attributes initially and inexperience with the exercises can lead to strain and injury. Bending the knee less when performing squats and lunges may reduce strain on the knee and knee pain. Our experience emphasizes the necessity of working with each participant individually until correct form is achieved, which limits the applicability, to some extent, of offering this type of class to the community with only one or two instructors. We stress the need for supervision with respect to the progression of the number of repetitions, sets, and weight added to the vests to prevent excessive mechanical loading to the musculoskeletal system too soon.

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Conclusion

We recommend the osteoporosis prevention exercise program designed by the BRL at OSU to a community setting. The program was effective in preventing bone loss over the 1-year intervention, and small but nonsignificant improvements were observed in femoral neck, total hip, and lumbar spine BMD. Improvements in balance and postural stability also were indicated. Quadricep strength training before starting the bone exercises, gradual progression of repetitions and sets of the bone exercises, and proper technique when executing the bone exercises must be considered to prevent injury.

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Condensed Version and Bottom Line

Osteoporosis is predicted to increase by 25% over the next decade. Specific weight-bearing exercises can prevent bone loss and risk of falling in postmenopausal women. This may be an effective means for attenuating the development, progression, or consequences of osteoporosis.

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Acknowledgements

The authors thank Ashland Community Hospital and Dr. James Theen for support in conducting BMD scans for the participants in the program. We also thank Nona Neil, Heather Nico, and Jamie Hayden for their contribution to the exercise intervention. Weighted vests, steps, and mats were funded through Northwest Health Foundation.

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References

1. National Osteoporosis Foundation. Disease Statistics "Fast Facts." Available at www.nof.org/osteoporosis/stats.htm/.
2. Melton III, C.J. Hip fractures: a worldwide problem today and tomorrow. Bone 14:S1-S8, 1993.
3. Lord, S.R., J.A. Ward, P. Williams, et al. Physiological factors associated with falls in older community-dwelling women. Journal of the American Geriatrics Society 42:1110-1117, 1994.
4. Khan, K., H. McKay, P. Kannus, et al. Biomechanics. In: Physical Activity and Bone Health. Champaign, IL: Human Kinetics, 2001.
5. Vuori, I.M. Dose-response of physical activity and low back pain, osteoarthritis, and osteoporosis. Medicine & Science in Sports & Exercise® 33 (Suppl.):S551-S586, 2001.
6. Cavanaugh, D.J., and C.E. Cann. Brisk walking does not stop bone loss in postmenopausal women. Bone 9:201-204, 1988.
7. Specker, B.L. Evidence for an interaction between calcium intake and physical activity on changes in bone mineral density. Journal of Bone Mineral Research 11:1539-1544, 1996.
8. Khan, K., H. McKay, P. Kannus, et al. Physical activity and bone in childhood and adolescence. In: Physical Activity and Bone Health. Champaign, IL: Human Kinetics, 2001.
9. Khan, K., H. McKay, P. Kannus, et al. Physical activity, targeted bone loading, and bone mineral in premenopausal women. In: Physical Activity and Bone Health. Champaign, IL: Human Kinetics, 2001.
10. Khan, K., H. McKay, P. Kannus, et al. Physical activity, targeted bone loading, and bone mineral in postmenopausal women. In: Physical Activity and Bone Health. Champaign, IL: Human Kinetics, 2001.
11. Fuchs, R., J. Bauer, and C. Snow. Jumping improves hip and lumbar spine bone mass in prepubescent children: a randomized control trial. Journal of Bone and Mineral Research 16:148-156, 2001.
12. Winters, K.M., and C.M. Snow. Detraining reverses positive effects of exercise on the musculoskeletal system in premenopausal women. Journal of Bone and Mineral Research 15:2495-2503, 2000.
13. Snow, C.M., J.M. Shaw, K.M. Winters, et al. Long-term exercise using weighted vests prevents hip bone loss in postmenopausal women. The Journals of Gerentology, Series A, Biological Sciences and Medical Sciences 55:M489-M491, 2000.
14. Dalsky, G.P., K.S. Stocke, A.A. Ehsani, et al. Weight-bearing exercise training and lumbar spine bone mineral content in postmenopausal women. Annals of Internal Medicine 108:824-828, 1988.
15. Kohrt, W.M., A.A. Ehasani, and S.J. Birge. Effects of exercise involving predominantly either joint-reaction or ground-reaction forces on bone mineral density in older women. Journal of Bone Mineral Research 12:1253-1261, 1997.
16. Lee, K.C.L., and L.E. Lanyon. Mechanical loading influences bone mass through estrogen receptor α. Exercise and Sport Sciences Reviews 32:64-68, 2004.
Keywords:

Osteoporosis Prevention; Bone Gain; Weight-Bearing Exercise; Bone Loss; Bone Mineral Density

© 2004 American College of Sports Medicine