2502 NYCC TRANS FINAL2 - New York Chiropractic College

Treating Osteoporosis From an Exercise Perspective
Osteoporosis is a condition in which bone resorption is greater
than bone formation, resulting in a loss of bone density and mass.
Maintaining a high bone density is important in preventing the detrimental
effects of osteoporosis. Between 60 and 80 percent of the
variability in bone mineral density is strongly influenced by genetics.
The remaining 20 to 40 percent variation is largely due to lifestyle
factors that can be modified. Two of the most important of these
factors are diet and exercise.
Without adequate mechanical forces, bone tissue is lost. This
can be seen in situations such as space flight and immobilization,
where as much as two percent of bone calcium is lost each month.
Bone responds to mechanical signals, and the greater the mechanical
signals the more bone will adapt to these signals. Therefore, the
intensity of exercise and resultant mechanical impact on bone is more
important than exercise duration. Activities which generate high
mechanical impact, such as gymnastics, jumping, or weight lifting,
show a much stronger effect on bone mineral density than low-impact
activities such as walking or swimming. (Taaffe, DR, Marcus, R.
Regional and total body bone mineral density in elite collegiate male
swimmers. J. Sports Med. Phys. Fitness (1999), 39:154-159). Obviously,
a person’s poor physical condition or the presence of disease
must be taken into account before recommending high-impact exercise
programs.
Two of the most common forms of exercise recommended for
prevention of osteoporosis are weight-bearing exercises and strength
training. Exercises that are weight bearing include such activities as
running, walking, and aerobics. According to research, women who
walk one mile per day have seven percent greater bone density in
their legs than those who engage in no regular activity. For strength
training, the American College of Sports Medicine (ACSM) currently
recommends performing 8 to10 exercises, two or three times each
week, with at least one day of rest between training. One set of 8
to12 repetitions per exercise is recommended. Remember, the impact
of exercise on bone density is specific to the bones utilized in
the exercise and the response is reversible. Cessation of exercise can
result in loss of any gains obtained.
In order for bone tissue to be maintained or gained through exercise,
proper nutrition should accompany the regimen. Since 70 percent
of bone mass is composed of calcium
phosphate crystals, it is necessary
that people ingest adequate amounts of
calcium. The current recommendation
for calcium intake is approximately 1,000
to 1,500 mg/d. Several studies have
shown that calcium supplements along with exercise programs can
reduce bone loss, specifically in postmenopausal women. (Price, RL,
Smith, M, Dick, IM, et al. Prevention of postmenopausal osteoporosis.
Comparative study of exercise, calcium supplementation, and HRT.
NEJM, (1991), 325:1189-1195). Even with relatively low calcium
supplementation (600 mg/d), a two-year study of resistance training
in postmenopausal women revealed prevention of bone loss in women
by Kimberly Ryder, Ph.D., Assistant Professor
Without adequate mechanical
forces, bone tissue is lost.
Dr. Kimberly Ryder
who strength trained compared to women who did not. (Kere, D.,
Ackland, T., Maslen, B. et al. Resistance training over two years increases
bone mass in calcium-replete postmenopausal women. JBMR,
16, 175-181). A four-year prospective study in women aged 60 to 65
revealed that high calcium intake (> 1200 mg/d) and high levels of
physical fitness were associated with smaller decreases in bone density
than either low levels of physical activity or low levels of calcium
intake. This study also pointed to the importance of exercise
intensity in maintaining bone tissue. (Uusi-Rasi, K., Sievanen, H.,
Pasanen, M. et al. Maintenance of body weight, physical activity and
calcium intake helps preserve bone mass in elderly women. Osteoporosis
Int (2000), 12: 373-379). Finally, a meta-analysis of studies conducted
in postmenopausal women revealed that those studies examining calcium
without exercise or exercise without calcium showed less effect
on bone density than both factors together. (Specker, BL. Evidence
for an interaction between calcium intake and physical activity on
changes in bone mineral density. JBMR (1996), 11:1539-1544). It
appears that exercise stimulates bone formation, and calcium is an
important factor in completing this formation.
In addition to calcium, there are other nutritional requirements
for healthy bone. Trace elements such as magnesium and fluoride
are important matrix factors. Vitamins,
especially vitamin D (known to increase
calcium absorption), are also needed for
optimal bone health. Phytoestrogens, as
found in soy products, have been linked
to maintenance of bone density. Unfortunately,
little available data examines these nutritional factors in
conjunction with exercise. However, a conscious effort to include
all these exercise and dietary items should be considered. Remember,
peak bone density is obtained in the third decade of life, and
most gains in bone density are normally obtained in adolescence.
Therefore, an early awareness of the impact of diet and exercise could
strongly influence one’s later bone health.
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