Aging muscles
One of the inescapable facts of life is that muscle mass and function decline as we age. Dr. Russ Hepple, a physiologist at the University of Calgary, wants to know why. "I've always been an athlete, and that has influenced my work as a physiologist. I'm interested in what limits human performance. The fact that exercise capacity declines as we get older intrigues me. I want to know if there's anything we can do about it."
In past work, Dr. Hepple showed that long-term caloric restriction can forestall the age-related decline of muscle mass and function. Rats fed a calorie-restricted diet from a very early age experienced only a 20% drop in muscle mass and no loss of muscle function at old age, compared to rats fed a normal diet that lost 50% of their muscle mass and 50% of muscle function. He has also looked at the benefits of exercise training in rats. While exercise training slows muscle wasting and decline in muscle strength for rats in late middle age, the muscles of older rats—comparable to 80 years and older in humans—do not benefit from exercise training. Dr. Hepple notes that these results should not overshadow the other benefits of exercise training, such as lower body fat and improved longevity.
To find out what is going on in the muscles, Dr. Hepple has turned his attention to the mitochondria. These structures generate energy for the cell and also help regulate cell death. His team is looking at how mitochondrial function changes in aging muscles and whether these changes relate to the decline in muscle mass and function.
Dr. Hepple is also working to validate his animal studies in humans. He recently began a study of elderly athletes to see what their muscles look like. "I'm wondering what is unique about these people," he says. "Is it the mitochondria or something else? By studying people who have aged extremely well by anyone's measure, I hope to gain insights that can be used to help prevent frailty in the elderly. Perhaps we could protect their muscle mass and strength and maybe even rebuild muscle in those who have already experienced significant declines."