Mild Aerobic Exercise No Protection From Osteoporosis

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Mild Aerobic Exercise No Protection From Osteoporosis 

­ Muscle strength, abdominal fat linked to bone mineral density

While day-to-day physical activities such as walking, housework and shopping

may be good for your heart, they don't do much for your bones, according to

a s Hopkins study.

The new report, published in the November issue of the Journal of Internal

Medicine, found that neither light-intensity activities nor aerobic fitness

level contributed to bone health, contrasting previous studies suggesting

that aerobics could play a role. Having a few extra pounds, however, was a

help. Among a group of older adults studied, those with greater muscle

strength and higher body fat, especially in the abdomen, had higher bone

mineral densities.

" Carrying extra body weight increases the forces on bone, strengthening it,

though the largest forces come from more vigorous exercise rather than

routine low-intensity physical activity, " says lead author Kerry J. ,

Ed.D., director of clinical exercise physiology at Hopkins. " In our study of

typical older people, who unfortunately do not participate in regular

vigorous exercise, daily activities and low-intensity exercise like walking

appeared to be relatively ineffective for preventing aging-related bone

loss. "

does not advocate gaining weight to fight osteoporosis.

" Paradoxically, a high percentage of abdominal fat seems to increase bone

mineral density, " he says, " but it also increases the risk of heart disease,

high blood pressure and diabetes, and worsens the symptoms of chronic

conditions such as knee arthritis. Further research is needed to define

methods that will reduce obesity while preserving or enhancing bone health. "

and colleagues studied 84 adults (38 men and 46 women) ages 55 to 75

with higher than normal blood pressure but who were otherwise healthy. They

were not exercising regularly, defined as moderate- or high-intensity

exercise for 30 minutes a day, three or more times per week.

Researchers used X-rays to measure the participants' bone mineral density in

the total skeleton, lower spine and hip, and magnetic resonance imaging to

calculate abdominal fat. They weighed each participant and had each do a

treadmill exercise test and a series of weight-training exercises to measure

aerobic fitness and muscle strength. In addition, the individuals completed

a physical activity questionnaire.

Researchers found that aerobic exercise was not associated with bone mineral

density but abdominal fat was. Muscle strength was associated with bone

mineral density at some but not all sites.

Thirty percent of the women were taking estrogen and progesterone

supplements. While such hormone replacement therapy has been known to

positively benefit bone, in this study it contributed only modestly to bone

mineral density and only at the lower spine.

The study was supported by the National Institutes of Health and the s

Hopkins Bayview General Clinical Research Center. Co-authors were J.R.

DeRegis; K.L. , A.C. Bacher, J. Sung, P.S. Hees, M. Tayback and P.

Ouyang.

, Kerry J., et al, " Fitness, fatness and activity as predictors of

bone mineral density in older persons, " Journal of Internal Medicine, Nov.

2002, Vol. 252, No. 5, pp. 1-8.

http://www.hopkinsmedicine.org/press/2002/October/021030.htm