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.
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.
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.
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”.
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.”
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”.
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.
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