We started the Bone, Estrogen, Strength Training (BEST) study in the fall of 1995 at the
University of Arizona, Tucson, Arizona. The BEST study is the largest of its kind. It looks
at the effects of hormone replacement therapy and strength training exercise on bone mineral
density. (Bone mineral density affects bone strength and the risk of osteoporosis.) Six
groups of about 300 women each participated in this osteoporosis prevention study. In 1998,
the BEST study received additional funding to examine for another 2 years the long-term
effects of strength training on bone mineral density. By 2001 we will have finished
analyzing the results for all study groups on the 1-year effects of exercise on bone, as
well as additional analyses on the effects of 2, 3, and 4 years of strength training and
weight-bearing exercise on bone.
Osteoporotic fractures associated with low bone mineral density (BMD) are a significant
public health problem for women, resulting in over 1 million fractures per year. The
increasing incidence of fractures will make an already major health problem an even greater
one in the future. Estimates of medical costs for the treatment of osteoporotic fractures
are expected to increase from $14.8 billion in 1995 to $60 billion by 2020. Although the
Women's Health Initiative is investigating dietary and hormonal factors in relation to bone
density, it is not investigating the effects of exercise on reducing bone mineral loss in
This study includes completion of a large, partially randomized clinical trial evaluating
the effect of a 1-year exercise intervention on total body and regional BMD in two
populations (hormone replacement therapy [HRT] versus no HRT) of postmenopausal women with a
previous history of physical inactivity. A major hypothesis is that, compared to the
no-exercise group, the exercise intervention will be an effective alternative to reduce the
risk of osteoporosis and the exercise effects will be larger in the cohort of women on HRT
than those not on HRT.
The exercise program includes progressive resistance exercises using free weights and weight
resistance machines and weight-bearing aerobic exercises. We carefully supervise and monitor
the exercise compliance by keeping records of the amount of exercise completed at each of
three weekly exercise sessions and by measuring strength gains of selected muscle groups. We
will measure biochemical markers of bone formation and resorption and hormonal correlates of
bone mineral density changes including sex steroids at baseline, 6 months, and 1 year.
We have obtained duplicate blood collections, made one week apart, for all cohorts at each
of the three measurement periods. We have also collected duplicate dual energy x-ray
absorptiometry (DXA) scans at each time period to follow changes in axial and appendicular
BMD and total and regional soft tissue body composition as a result of the intervention. We
collected extensive dietary intake records during the first year of intervention; we will
monitor dietary intake in a 2-year followup using food frequency questionnaires. We will
also measure followup BMD, soft tissue, and lean and fat body composition for 2 years in all
women who complete the first-year intervention program.
Two-hundred sixty-six women have completed the first year of the intervention. The study has
a retention rate of 92 percent in the first year for the first four cohorts.
Because of the paucity of information regarding long-term effects of exercise, and because
of the increased emphasis in the scientific community on evaluating the long-term efficacy
of exercise interventions for osteoporosis prevention, this comprehensive 1-year clinical
trial and 2-year followup will make an important contribution to determining the future role
of combining progressive resistance and weight bearing aerobic exercise in the prevention of
osteoporosis in two populations (HRT vs. no HRT) of postmenopausal women.
- Age 40-65 years.
- Post-menopause (3-10.9 years) due to hysterectomy or natural menopause.
- Post-menopausal females, 3-10 years past menopause (natural or surgical menopause);
if subjects are currently taking hormone replacement therapy (HRT), they must be
taking HRT for at least 1 year but no more than 6 years. The subjects must be
relatively sedentary, not currently engaged in strength-training exercises.
- Cancer free for the last 5 years (treatment free for last 5 years) excluding skin
- Resident of Tucson (48 out of 52 weeks of year).
- History of bone fractures or currently have osteoporosis.
- Currently taking medications that control cholesterol or alter bone mineral density.
- Currently taking beta-blockers or steroids in large quantities/frequencies.
- Currently participating in any other research study.
- Amount of physical activity exceeds 120 minutes of moderate exercise per week.
Moderate exercise examples: brisk walking, golfing, gardening, housework, house
painting. Potential subject cannot be weight lifting.