Health
Light to moderate exercise key to health in post-menopausal women
By BA (British association for the advancement of science)
Sep 5, 2005, 23:43

Exercise is essential for reducing the risk of osteoporosis and heart disease in post-menopausal women. But too much exercise in pre-menopausal women may actually increase the risks. These claims will be made by Dr Karen Birch, senior lecturer in exercise physiology at the University of Leeds, during the BA festival of science in Dublin this week.

From puberty to the menopause, females cyclically produce the reproductive hormones oestrogen and progesterone. Research has now shown how these hormones interact with both health and physical activity.

Oestrogen is important because it protects against the development of both osteoporosis and cardiovascular disease. Light to moderate intensity physical activity enhances the beneficial effects of the reproductive hormones upon bone strength and the cardiovascular system (heart and blood vessels) and is associated with a decreased risk of disease and early death. In recent large scale studies people who are overweight (not obese), but physically active have been seen to have less risk of disease and disease-related death than those people who are normal weight but sedentary.

"It is essential that women exercise moderately before and during the onset of menopause," argues Dr Birch. "Post-menopause, the loss of the hormone oestrogen results in a reversal of the protective effects. Women�s bone mineral density begins to decrease, their arteries begin to become stiffer, their cholesterol levels begin to rise and their risk of becoming diabetic increases. These physiological changes are much slower in women who participated in an active lifestyle prior to the menopause than in those who were inactive."

However, any loss of exposure, for example by a delayed onset of menstruation or periods of time where menstruation ceases, can have a negative impact upon health. Both have been related to participation in high intensity or high volumes of physical activity. Recent research has indicated that this problem is a result of the body switching off menstruation when energy intake (from food) is less than energy expenditure (energy used in everyday activities and in physical activity). The consequence of high amounts of physical activity in these examples is a loss of fertility and a negative effect upon immediate and long term health.

"The key seems to be to exercise in moderation, but to be sure to do some exercise," stressed Dr Birch.

The relationship between physical activity, reproductive hormones and health is further complicated by the impact of other sources of the hormone oestrogen. For example oestrogen compounds can be found in food sources, contraceptive the pill and hormone replacement therapy (HRT). Traditionally, HRT was seen as a hugely positive product for protecting against bone loss in post-menopausal women, but more recently, researchers have indicated the potential of HRT to increase the risk of both cardiovascular disease and breast cancer in women, and as such HRT is no longer used to protect against osteoporosis. In fact, the use of HRT has decreased significantly due to these problems.

"This work is very timely because levels of obesity are rising and HRT use is falling," says Dr Birch. "The effect of these two things for women is catastrophic to their health and well-being. If light-moderate intensity physical activity can reduce health risks by counteracting the effects of weight gain and loss of oestrogen an enormous hurdle can be jumped."

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