Muscle Deterioration Not Inevitable
There's a similar breakdown for both young and old men, new research finds
THURSDAY, Sept. 20, 2001 (HealthDayNews) -- Just because you're old doesn't mean your muscles have to sag.
Or so say the authors of a study published in the Sept. 12 issue of the Journal of the American Medical Association. The results of the study, the largest of its kind to date, could represent a sea change in thinking about something we had long taken for granted: that losing muscle function and strength is an inevitable part of aging.
"We were trying to establish whether the loss of muscle with age was due to an alteration of muscle protein metabolism in basal conditions [after waking up in the morning, before getting out of bed and before having breakfast], but it doesn't seem to be the case," says Dr. Elena Volpi, lead author of the study who is now assistant professor of medicine at the University of Southern California. "Other conditions, such as feeding and physical activity, need to be studied," she adds.
One indisputable, albeit unpleasant, fact of life is that people lose muscle strength and function (a condition called sarcopenia) as they get older. Muscle proteins constantly break down and rebuild as part of a natural cycle. Muscle loss of any kind results in an imbalance between muscle protein synthesis and breakdown.
"The question has been 'why,'" says Dr. Nir Barzilai, director of the Institute for Aging Research at the Albert Einstein College of Medicine in New York City.
Availing themselves of new technology to measure protein synthesis in the muscle directly, researchers at the University of Texas Medical Branch at Galveston studied protein synthesis and breakdown in 48 younger (average age 28) and older (average age 70) healthy men right after they had woken up in the morning -- in other words, without complications from eating and/or exercising.
The researchers found that synthesis and breakdown rates were similar in both groups; protein synthesis was even slightly higher among the older group.
Now Volpi and her colleagues are wondering whether muscles develop different responses to diet and exercise as they get older and if this is somehow responsible for sarcopenia.
"There may be lifestyle considerations. We cannot exclude them," says Volpi. "Exercise and diet are the most likely causes. It may be a response to food, or there may be a slight impairment in response to exercise. Other studies clearly show that exercise stimulates muscle growth in older people, but we don't know over the long term."
The good news is that it means sarcopenia -- and loss of independence in older individuals -- may be preventable. Other research is already underway to determine the effect of insulin and of nutritional supplements on muscles. "It's most likely that there are several potential causes, and all together they might each contribute a little bit and at the end give you this major problem," Volpi says.
Barzilai cautions against some possible limitations of the study. One is that the older men in the group, who had 11 percent less muscle mass than their younger counterparts, may have started out with less muscle mass.
"That's a little bit of a problem because they take two groups of people who were born 40 to 50 years apart, and we know that the [average person] is getting bigger every decade," says Barzilai. "This doesn't mean that those individuals really lost muscle. It could be that when they were 28, they had the same muscle mass."
The researchers also worked with a group of extremely healthy subjects. "They may not get much change in their muscle protein," says Barzilai. "What they're showing, in a way, is that healthy older people are healthy, but that doesn't mean that people who age and have sarcopenia will follow the same route."