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Senior Citizen Fitness & Exercise
Estrogen Loss is Culprit in Loss of Muscle Mass for
Older Women
Women lose 10 to 15% of muscle mass between 20 and
50, then the decline accelerates: resistance exercise can help
 July 8, 2006 With the increase in longevity,
women now live about a third of their lives after menopause and in an
estrogen-depleted state. At has been believed that menopause plays a
part in the loss of muscle mass in aging women. And, it is known
inactivity can accelerate loss of muscle mass and strength as women age.
A University of Missouri-Columbia researcher studied the effect of
inactivity combined with the loss of estrogen and was surprised to find
the real culprit is loss of estrogen.
It was not a lifestyle link; it was an estrogen
link, said Marybeth Brown, professor of physical therapy in MUs School
of Health Professions. The role of female sex hormones on skeletal
muscle has been unclear in the past. In fact, some reports have
suggested that the hormones have no effect.
Brown studied the effect of low hormone levels
combined with physical inactivity in rats. The rats ovaries were
removed, and the rats were then put on simulated bed rest for four
weeks. Surprisingly, the loss of muscle mass and strength that occurred
with the simulated bed rest was similar in rats with and without normal
estrogen levels.
What was not the same was the recovery of muscle
mass in rats that lacked estrogen. Brown found that the muscle atrophy
that occurred during the bed rest was not regained in rats that lacked
estrogen. Rats with normal estrogen levels - intact ovaries - had a
robust recovery of muscle mass and strength after the simulated bed rest
was complete.
Women now spend a third of their lives in an
estrogen-depleted state; years ago, women did not even survive long
enough to have a menopause, Brown said.
Consequently, we need to know as much about the
potential consequences of estrogen loss as possible. If
estrogen-deficient women are failing to recover muscle mass from the bed
rest associated with the flu or a hospitalization, the implications for
old age are quite significant. We need all the muscle mass we can get to
make it through old age without losing independence.
Women lose 10 to 15 percent of their muscle mass
between the ages of 20 and 50, and then the decline accelerates.
Loss of muscle mass and strength is a natural
phenomenon, and once muscle is lost, it cannot be regained. According to
Brown, women can increase their muscle mass through resistance exercise,
which will help maintain independence for a longer period of time.
If women are sedentary, they will lose muscle mass
and strength faster than normal. Results from the study suggest that
sedentary living combined with bouts of bed rest may put estrogen
deficient women at a very high risk for losing independence.
Browns study was published in Aviation, Space, and
Environmental Medicine, the monthly journal of the Aerospace Medical
Association.
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