What is
Muscle Loss?
Male
muscle loss is
a common symptom of andropause and it manifests itself in the loss of muscle
strength and overall muscle mass. Age related muscle loss, or sarcopenia
(from the Greek meaning
"poverty of flesh") can start as early as 20 or 25 in some cases, and in 40th in
general, develops a steady trend after about age 50. Then the typical rate of muscle loss
really begins to outpace the rate of muscle gain, so that there's an increasing
net deficit, says Robert Wolfe, a professor of geriatrics and director of the
Center for Translational Research in Aging and Longevity at the University of
Arkansas for Medical Sciences. Over time, muscle cells atrophy and
start converting muscle fibers into fat as a result of motor neurons no longer
sending signals to your brain to move the muscles. The decline in muscle mass weakens an already
frail elderly person so much that he or she is more prone to falls and can't
lift a small bag of groceries onto the counter.
Mechanism of Muscle
Loss
Sarcopenia begins with loss of the nervous system, after
which the muscles that cannot move as they did before begin to atrophy, and the
muscle cells are replaced in that spot by fat cells. The motor neurons are
responsible for sending signals from the brain to the muscles to initiate
movement. A motor unit consists of the motor neuron and all of the muscle
fibers that it connects to, or innervates.
The number of fibers that a motor neuron innervates depends
on the function of that specific muscle. For example, a muscle that requires
precise movements, such as muscles of the eye, will have motor units with a
motor neuron innervating a few muscle fibers. Muscles that require less precise
movements, such as the quadriceps muscles, will have motor units with a motor
neuron innervating hundreds and possibly over a thousand muscle fibers.
Muscle fibers also decline with age. Fewer muscle fibers
translate into reduced numbers of components from which to make muscles. The
result: less muscle mass. As muscle and its protein content diminish they
become fatigued more easily. This leads to a sedentary lifestyle. If this
slow–down in activity and hence, muscle metabolism isn't reversed through
changes in diet and exercise, the slide toward sarcopenia begins.
Causes
of Muscle Loss
While the precise causes of sarcopenia aren't fully
understood, lack of exercise, poor nutrition, hormonal changes, and internal
inflammation are all potential causes. Some of those factors can be proactively
addressed, but there may simply be some inherent consequences of aging that
can't be fully remedied.
Testosterone Levels Decline
Scientists
found a strong proportional relationship between declining levels of
testosterone and muscle loss in men. Testosterone is vital to producing
strong muscles, they go hand in hand. The hormone binds to receptors in your
muscle cells, telling your muscles to contract and grow. When your body is
experiencing a loss of testosterone it can cause male muscle loss
because there is not enough of the hormone to bind to your muscle cells.
Exercise
Muscles
will naturally experience atrophy if the body is largely inactive; if you don’t
use the muscles, you will likely lose them. Every year between the ages of 25
and 60, the physically inactive male will lose muscle mass and muscle strength
at a rate of .5% and although this number may seem low, it adds up quickly.
After the age of 60, male muscle loss doubles to about 1% every year.
After 70, muscle mass and muscle strength declines by 2% every year. This
doubling continues every ten years until death.
The tool that everyone agrees works to shore up muscles:
exercise, at every age. Not only
muscle but the entire musculoskeletal system of muscle, neuromuscular
responsiveness, endocrine function, vasocapillary access, tendon, joint,
ligament, and bone, depends on regular and lifelong exercise to maintain
integrity. The slow attenuation, atrophy, or loss of muscle tissue that medical
professionals sometimes describe as sarcopenia is currently thought to be the
result of cumulative loss of musculoskeletal strength and mass associated with
chronic absence of exercise of sufficient intensity or volume. However, even
highly trained athletes experience the effects of sarcopenia. It is interesting
to note that athletic speed and strength records are generally set by individuals
no older than 30 years of age, although some powerlifters and other strength
athletes continue to set records into their 50s.
Ideally, exercise should include both a basic, progressive
strength-training program as well as an aerobic fitness routine (like a brisk
30-minute walk every day). "Healthy muscle is not only about being
stronger and bigger," says Miriam Nelson, director of the John Hancock
Center for Physical Activity and Nutrition at Tufts University. Strength training
that builds muscle helps keep older folks stable and surefooted, and strong
enough to do basic things like get out of a chair. Indeed, some data suggests
that men who lift weights a few times a week in their 50s and 60s can maintain
their muscle mass, not simply slow the rate of decline, in those years, she
says. But to be healthy, muscle tissue needs to effectively store glycogen and
have capillaries that infuse it with blood, both of which are aided by the
aerobic component.
Nutrition
Poor
nutrition is also a key factor in male muscle loss. Muscles need protein to
grow and if your diet is high in sugar and low in protein, your muscles will
not have the fuel they need to regenerate resulting in male muscle loss.
Insufficient protein, especially if it's accompanied by
insufficient calories in general, can contribute to sarcopenia, says Douglas
Paddon-Jones, director of exercise studies for the General Clinical Research
Center at the University of Texas Medical Branch in Galveston. There's a debate
among protein proponents over how much to eat, expressed in grams per kilogram
of body weight, but the simpler rule of thumb is to eat small amounts of
protein distributed throughout the day, he says. Aim for 4 ounces of quality
protein, like fish, chicken, beef, or dairy products, three times a day, to
maximize muscle growth. (Vegetarians can eat soy, a complete protein, or
combine proteins like rice and beans to get the essential amino acids found in
animal protein.) Four ounces isn't much—about the size of a deck of cards—so
there's no need to go overboard.
Natural Supplements
Omega-3 Fish Oil
The new study, from Washington University, suggests that
omega-3 fish oil may help reduce this age-related muscle loss. Researchers
recruited 16 healthy adults (average age 71) and divided them into two groups.
For eight weeks, one group got corn oil (placebo) capsules and the other group
got four grams of fish oil per day providing 1.86 grams of EPA and 1.5 grams of
DHA.
The results were dramatic: The group receiving the omega-3
supplementation had twice as much muscle building activity as the group
receiving the placebo. “A major cause for the loss of muscle mass with advanced
age is the inability of aging muscle to adequately increase the rate of muscle
protein synthesis in response to nutritional stimuli, e.g. amino acids and
insulin”, the authors wrote. “Omega-3 fatty acids stimulate muscle protein
synthesis in older adults and may be useful for the prevention and treatment of
sarcopenia”.
Creatine
The muscle atrophy
found in older adults comes predominantly from a loss of fast twitch (FT) type
II fibers which are recruited during high-intensity, anaerobic movements (e.g.,
weight lifting, sprinting, etc.). Interestingly, these are exactly the fibers
creatine has the most profound effects on. Various studies find creatine given
to older adults increases strength and lean body mass (Chrusch et al., 2001;
Gotshalk et al., 2002; Brose et al., 2003). One group concluded: “Creatine supplementation may be a useful
therapeutic strategy for older adults to attenuate loss in muscle strength and
performance of functional living tasks.”
Vitamin D
It’s well
established that vitamin D plays an essential role in bone health. However,
recent studies suggest it’s also essential for maintaining muscle mass in aging
populations. In muscle, vitamin D is essential for preserving type II muscle
fibers, which are the very muscle fibers that atrophy most in aging people.
Adequate vitamin D intakes could help reduce the rates of both osteoporosis and
sarcopenia found in aging people (Montero-Odasso et al., 2005) leading the
author of one recent review on the topic of vitamin D’s effects on bone and
muscle to conclude: “In both
cases (muscle and bone tissue) vitamin D plays an important role since the low
levels of this vitamin seen in senior people may be associated to a deficit in
bone formation and muscle function”.
New Research
Exciting new
research released August 2011 by doctors at Columbia University Medical Center
may have found a novel new way to prevent age-related muscle weakness. Dr.
Andrew Marks has been targeting something called the “ryanodine receptor” in
muscle cells. Without getting too complicated, muscle cells use calcium to
contract. Each cell has a little “gas tank” of calcium in it. When the brain
sends a signal to the muscle to contract, the ryanodine receptor acts like a fuel
pump and releases calcium into the cell, where it’s used to pull muscle fibers
together. When the brain tells the muscle to relax, the receptor pumps calcium
back into the tank, and the fibers separate.
As we age, the
mechanism becomes damaged from stress and allows an unusual amount of calcium
to leak out of the cell. Think of it in terms of a rusty old gas tank
developing a small leak. Eventually enough calcium (gasoline) leaks out that
the muscle (car) can’t function properly.
Using a new drug
(s107) developed by pharmaceutical startup ARMGO Pharma, Marks treated mice
that were 24 months old – the equivalent of 70 in human years. The mice, which
were becoming weak and sedentary could spend 50 percent more time on the
exercise wheel than before. The drug had slowed the calcium leak in their
muscles and improved muscle function.
The drug is
currently in Phase II trials for treatment of heart failure. Dr. Marks says he
hopes to begin Phase II trials among people of advanced age for
muscle-weakness/loss within a year.
Sources and Additional Information:
