Transcript Osteoporosis

Chapter 42: Exercise Prescription
for Patients with Osteoporosis
Copyright © 2014 American College of Sports Medicine
Epidemiology
• Osteoporosis is a skeletal disorder characterized by compromised
bone strength that results in an increased susceptibility to fracture.
• 200 million women worldwide currently have osteoporosis.
• Osteoporotic fractures are low-trauma fractures that occur with
forces generated by a fall from a standing height or lower and are
most common at the spine, hip, and wrist.
– Hip fractures are considered to be the most devastating
consequences of osteoporosis.
• Costs $17 billion per year in United States
• Osteoporosis among men and women
– Although women are more susceptible, men also can have
osteoporosis and often go undiagnosed.
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Basic Bone Physiology
• Bone is a biphasic material with crystals of
hydroxyapatite (calcium phosphate) and an organic
collagen matrix.
– Cortical bone
– Trabecular bone
• Modeling and remodeling: affect the quantity, quality,
and structure of the bone; regulated by hormonal and
mechanical environments
– Osteoblasts: bone-forming cells
– Osteoclasts: bone-reabsorbing cells
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FIGURE 42-1. Bone is a dynamic tissue that is vascularized and innervated. Cortical bone is dense and stiff and makes up the shaft of long
bones. Cortical bone also provides a shell of protection around trabecular bone, which is more porous and flexible and is found at the ends of
long bones and in vertebrae.
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FIGURE 42-2. Bone remodeling is the coupled actions of osteoclasts and osteoblasts whereby a portion of older bone is resorbed
by osteoclasts and replaced with newly formed bone by osteoblasts. The new bone begins as osteoid (unmineralized matrix).
Eventually, the osteoid incorporates mineral.
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Osteoporosis Pathophysiology
• Skeletal fragility
– Bone quantity: amount of bone material present
• Rapid accumulation during adolescence
• Peak in second to third decade of life
• Negative bone balance: decline over time with aging
where reabsorption is greater than formation rate
– Bone material quality: ability to withstand stressors
• Amount of bone in human skeleton decreases with
menopause and advancing age.
• Increased mean tissue mineralization and changes in
collagen properties increase fracture risk with age.
• Increased microdamage accumulation
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FIGURE 42-3. Normal pattern of bone mineral accretion and loss throughout the lifespan in men and women.
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Osteoporosis Pathophysiology
• Skeletal fragility
–
Bone structure: distribution of bone material in bone space
• Structural differences in cortical bone geometry may explain some of
the differences in fracture rates between men and women.
• During growth, long bones of boys have greater gains in
periosteal (outer) diameter, resulting in greater overall bone size
in boys that remains throughout life.
• Increased porous bone results in loss of bone strength and increased
fracture risk.
–
Falls
• Falls significantly increase the risk of fracture, especially when
skeletal fragility exists.
• Most hip fractures occur after a sideways fall and landing on the hip.
• Hip fractures are a common occurrence because of falling.
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FIGURE 42-4. Slice of trabecular bone in a normal (A) and an individual with osteoporosis (B) showing loss of trabecular connectivity and
increased microdamage with ageing.
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Diagnosis of Osteoporosis
• Measurement of bone mineral density (BMD) by dualenergy X-ray absorptiometry (DEXA) is the primary
method of diagnosis.
• World Health Organization (WHO) criteria
– Osteopenia (low bone mass): site-specific bone
density between 1.0 and 2.5 standard deviations
below the mean for young white adult women
– Osteoporosis: bone density that is 2.5 standard
deviations or more below the mean for young white
adult women
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Risk Factors for Osteoporotic Fracture
• BMD
• Age
–
Risk of hip fractures increases three to six times from 50 to 80 yr
of age, independent of BMD status.
• Family history of fracture
• Previous fracture
• Physical inactivity
• Medication use
• Hypogonadism
• Menopause
• Hyperthyroidism and bariatric surgery risk for secondary osteoporosis
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Bariatric Surgery: A Risk Factor for
Osteoporosis?
• With rapid and dramatic weight loss, there is an
increasing concern that bariatric surgery may negatively
affect the skeleton by accelerating bone loss and
increasing bone fragility.
• Recent review showed that BMD loss may be as high as
15% at the hip 1 yr following gastric bypass procedures.
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Clinical Management
• Pharmacologic therapy
– Several categories are FDA approved.
• Antiresorptive agents: act by suppressing bone
resorption.
• Bisphosphonates, salmon calcitonin, hormone
replacement therapy (HRT), selective estrogen
receptor modulators (SERMs), and receptor activator
of nuclear factor kappa-B ligand (RANKL) inhibitors
• Anabolic agents: promote bone formation
• Regulation of calcium homeostasis: parathyroid
hormone (PTH)
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Antiresorptive Agents and Increased Risk
of Fracture
• With long-term use, antiresorptive medications may lose
value in preventing fracture and, in some cases, may
lead to fracture.
• Long-term bisphosphonate use remains controversial.
– Fractures appear to occur infrequently
– Lack of strong evidence
– FDA has issued warning regarding possible risk
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Lifestyle Modifications
• Adequate calcium (1,000–1,500 mg · d–1) intake
• Adequate vitamin D (600-800 IU · d–1) intake
• Regular exercise
–
Exercise is the only lifestyle modification that can simultaneously
ameliorate low BMD, augment muscle mass, promote strength
gain, and improve dynamic balance — all of which are
independent risk factors for fracture.
• Smoking cessation
• Avoidance of excessive alcohol intake
• Visual correction to decrease fall risk
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Exercise and Osteoporosis
• Physiologic response of bone to exercise
– Acute physiologic response
• Exercise causes compression, tension, or torsion of
bone tissue and ultimately deformation, which is
the basis for chronic adaptations.
– Chronic physiologic response
• Changes via modeling/remodeling take up to
several months.
• Maintenance of bone tissue quality through
targeted remodeling
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Exercise and Osteoporosis
• Osteogenic activities
– Response is site specific.
– Loading/stress should be designed to affect the
location in which osteoporosis is identified (e.g.,
spine, hip).
– Rest is important for proper bone adaptation or
response.
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Exercise and Osteoporosis
• Exercise during youth: building a strong skeleton
•
–
Exercise in youth is deemed very important for adult bone
health.
–
Period of maximal velocity of height growth may be most
important period of bone mineral accumulation.
–
Studies suggest that the bone response to loading is optimized in
prepuberty and early puberty.
Exercise prescription for optimizing bone development in youth
–
ACSM Position Stand on Physical Activity and Bone Health: 10–
20 min, 3 d · wk–1 of impact activities such as plyometrics,
jumping, moderate-intensity resistance training, and
participation in sports that involve running and jumping (soccer,
basketball)
–
Ten jumps, three times per day has also been shown to
significantly increase bone mineral density in the proximal femur
and intertrochanteric regions.
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Exercise and Osteoporosis
• Exercise during adulthood: maintaining a strong skeleton
– Goal of exercise in adulthood is to gain bone strength and
to offset bone loss observed during this time in life.
– Not as much research in men as women but appears men
can also retard the BMD loss associated with aging.
• Exercise prescription to preserve bone health during adulthood
– ACSM Position Stand on Physical Activity and Bone Health:
30–60 min · d–1 of a combination of moderate-to-high
intensity weight-bearing endurance activities (three to five
times per week), resistance exercise (two to three times
per week), and jumping activities
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Exercise for the Elderly and Individuals with
Osteoporosis
• Exercise testing for those with osteoporosis
– Not contraindicated
– Use of cycle ergometry may be indicated in patients with
severe vertebral osteoporosis if walking is painful.
– Vertebral compression fractures compromise ventilatory
capacity and may affect balance during treadmill walking.
– May have increased false-negative test rate because of
inability to exercise to significant level of stress
– Maximal muscle strength testing may be contraindicated in
those with severe osteoporosis because of risk for
fracture.
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Exercise Prescription for Individuals with
Osteoporosis
• Should consult with patient’s physician first
• Pain may limit exercise program options
• Pain management may be an important part of the
care
• ACSM position statement on physical activity and
bone health: “Exercise programs for elderly men
and women should include not only weight-bearing
endurance and resistance activities aimed at
preserving bone mass but also activities designed to
improve balance and prevent falls.”
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Exercise Prescription for Individuals with
Osteoporosis
• Contraindicated exercise for individuals with osteroporosis
– Contraindicated because they can generate large forces on
relatively weak bone
• Twisting movements (e.g., golf swing)
• Dynamic abdominal exercises (e.g., sit-ups)
• Excessive trunk flexion
• Exercises that involve abrupt or explosive loading
• High-impact loading
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Exercise Prescription for Individuals with
Osteoporosis
• Flexibility training for individuals with osteoporosis
– Increased flexibility can be of benefit (especially with
posture).
– Many commonly prescribed exercises for increasing
flexibility involve spinal flexion and should be
avoided.
– Slow and controlled movements should be the rule.
– Avoid ballistic-type stretching.
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Exercise Prescription for Individuals with
Osteoporosis
• Aerobic training for individuals with osteoporosis
–
Goals
• Increase aerobic fitness
• Decrease cardiovascular disease risk factors
• Help maintain bone strength
• Improve balance
–
Perform 3-5 d · wk–1 at an intensity of 40%–59% of VO2 reserve
or heart rate reserve (HRR)
–
Initial goal of 20–30 min per session with slow increase to 30–60
min once tolerated.
–
When possible, exercise mode should be weight bearing.
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Exercise Prescription for Individuals with
Osteoporosis
• Resistance training for individuals with osteoporosis
– Goals
• Improve bone health
• Improve balance to lower risk of falling
– Perform 2–3 d · wk–1, 8–12 repetitions at a moderate
intensity (60%–80%)
– Those with osteoporosis should avoid any ballistic or
jumping activities.
Copyright © 2014 American College of Sports Medicine