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Exercise reduces risk of heart disease in postmenopausal women

March 18, 2008

Aerobic exercise significantly decreased the chemical imbalances that can lead to heart disease and stroke in postmenopausal women according to a study in the spring issue of the Journal of Women and Aging.

Estrogen is known to reduce the chemical imbalances that can lead to cardiovascular diseases such as coronary heart disease and stroke in postmenopausal women. However, recent studies have reported detrimental effects of long-term use of hormone replacement therapy (HRT) or estrogen replacement therapy, including an increased risk of stroke, heart attack and breast cancer. Faced with these potential consequences, more women are turning to exercise as a natural way to combat postmenopausal effects.

The study found that HRT users and non-HRT users benefited equally from the exercise.

"Given the controversy with HRT, postmenopausal women can now use aerobic exercise training to lower chemical stress levels, thus reducing another risk factor for chronic disease," said Michael D. Brown, Ph.D., a co-author and associate professor of kinesiology at Temple University's College of Health Professions.

The chemical imbalance or stress - called oxidative stress - occurs when oxidants, harmful chemicals that damage tissue and cells, outnumber antioxidants in the body. Antioxidants protect cells and tissues against oxidants. Postmenopausal women have higher levels of oxidative stress.

A single bout of intense exercise acutely raises oxidative stress by increasing the production of oxidants. Conversely, regular exercise of moderate intensity appears to reduce oxidative stress through an adaptive process that increases antioxidant activity.

"Regardless of your hormone replacement therapy status, regular physical activity is a good way to not only decrease postmenopausal symptoms, but also to reduce the risk of cardiovascular disease, the leading cause of death of American women," said study co-author Nicola Fenty-Stewart, Ph.D., also with Temple's College of Health Professions.

"The similar response of the two groups suggests that aerobic exercise training is a powerful therapy that can potentially serve as a way for women to observe the beneficial effects of exercise," she said.

The study followed 48 sedentary postmenopausal women (21 on HRT and 27 not on HRT) through an exercise program consisting of three supervised sessions of aerobic exercise per week for 24 weeks. Participants were between 50 and 75 years of age and were postmenopausal for at least two years.

Since changes in habitual dietary intake could influence oxidative stress levels, qualified subjects were stabilized for six weeks on the American Heart Association Step I diet, which is low in saturated and trans fat, and rich in fruits, vegetables, whole grains and fat-free and low-fat dairy products, Brown said.

Weight loss was limited to 5 percent or less of the women's initial body weight in order to determine the independent effects of aerobic exercise training on oxidative stress, not the effect of exercise and weight loss on oxidative stress.

The HRT users and non-users both experienced an 11 to 18 percent drop in plasma thiobarbituric acid reactive substances, an indicator of oxidative stress.

There were also decreases in body mass index and total body fat, and a significant increase in VO2 max (maximal oxygen uptake or aerobic capacity) in both HRT users and non-users after the exercise intervention, Brown said.

"Exercise was able to reduce oxidative stress levels in these women regardless of whether or not they were using estrogen replacement. In addition, the women did not lose large amounts of body weight or fat," Brown said.

"No one is too old to begin an exercise program, but it is imperative to consult your physician before taking part in any exercise program. It is important to start off slow and build your program to your comfort level. Exercising is not difficult. You just have to want to do it," Brown added.

Temple University