…But first some bad news: By age 70, most people
have at least 20% less muscle tissue that they did at age 30. This slow
process of erosion had recently been recognized as a bona fide medical
condition called sarcopenia, Greek for "vanishing flesh."
Sarcopenia has significant health implications because it impairs balance
and limits strength. Together these two developments increase the likelihood
of falls, which frequently produce bone fractures. Broken bones are
a leading cause if disability and death, especially among the many older
adults who have osteoporosis (weak bones that break easily).
Now the good news: The effects of sarcopenia can be significantly reduced-
even reversed. All that's required is a moderate amount of exercise.
But if your activities are exclusively aerobic (walking, jogging, swimming,
cycling), that's not enough. Although aerobic exercise is essential
for strengthening the heart and bones, thereby preventing heart disease
and osteoporosis, its effect on muscle size and strength is minimal.
Preventing sarcopenia requires adding resistance training to your exercise
routine. Resistance training (also known as strength training, weight
training, or isotonics) is a different type of exercise, which targets
specific muscles.
The problems associated with sarcopenia are so serious, and the benefits
of treatment are so great, that the National Institute on Aging (NIA)
recently held a conference focused exclusively on developing techniques
for studying this condition. In addition, NIA is soliciting research
proposals on the matter and will soon launch an eight-year study involving
3,000 subjects in their 70s.
In the meantime, you can adopt preventative measures to preserve muscle.
This much is abundantly clear: Sarcopenia is not an inevitable consequence
of aging, but everyone is at risk.
Tracking the Decline
Muscle mass generally peaks at age 30 and begins to decline
slowly thereafter, at the rate of about one or two kilograms per decade.
Men and women appear to lose the same percentage of muscle tissue over
time, though men generally start out with a higher muscle-to-fat ratio
than women. Imaging studies show that muscle mass in the thigh can be
as high as 90% in an active young man and as low as 40% in an elderly
man; among women, both figures are about 10% lower.
There are some indications that the rate of decline may be associated
with hormonal changes. In one study reported in the Annals of Internal
Medicine, researchers followed 35 healthy, sedentary women who were
in their mid-to-late 40s when the study began. The researchers monitored
such factors as physical activity, calories burned when resting, and
where the body fat stored.
During a six-year period, half of the women entered menopause. Although
all participants maintained a fairly constant overall body weight, those
who became menopausal lost an average of three kilograms of muscle tissue-
six times the loss seen in those who didn't enter menopause. For unknown
reasons, the menopausal women also became less active than the premenopausal
women, a factor that can itself encourage weight loss.
Preserving Strength
Resistance training can stop and even reverse sarcopenia.
Research shows that older adults who have been lifting weights for 15
to 20 years are at least as strong as inactive 20-year-olds.
And its never too late to reap the benefits of weight-lifting. A recent
study of 100 nursing home residents, reported in the Journal of the
American Medical Association, showed that 10 weeks of weight-lifting
doubled muscle strength in the legs, improved walking ability, and increased
the daily physical activity of subjects by about 35%. At the end of
the study, the mobility of four participants had improved so dramatically
that they abandoned their walkers for canes.
The subjects in the study were among the oldest old: Their mean age
was 87, and 38% were 90 years or older. The majority were also substantially
impaired: 38% met the criteria for depression; most had fallen at least
once; and most needed to use canes or walkers to get around.
Fundamentals of Strength
Resistance training is any type of exercise performed
is one place while standing or sitting, or lying down. It includes leg
lifts, arm curls, and abdominal crunches. Such movements can be performed
using free-weights, weight machines, or by working against gravity.
The goal is to challenge the targeted muscles by performing at least
three sets of 8 to 12 repetitions, and to gradually increase the amount
of weight used. You can learn how to perform such exercises by consulting
the cardiovascular rehabilitation of a local hospital, joining a fitness
program at a senior citizens center, or becoming a member of a local
health club or gym.
In addition to slowing muscle loss, resistance training produces other
important health benefits. Among the most valuable are increased metabolism
(the rate at which the body burns calories to fuel basic body functions
such as breathing); increased bone density; decreased risk of diabetes;
better ratio of "good" HDL cholesterol to "bad"
LDL cholesterol; and pain relief for osteoarthritis and possibly rheumatoid
arthritis.
From the March/April 97 edition of The Johns Hopkins Medical Letter
