How Your Muscles Age As You Get Older
Research carried out at the Stanford University Baxter Laboratory for Stem Cell Biology recently sheds new light on how muscles age. This study focused on stem cells, cells that give birth to new muscle cells. With age, researchers found some stem cells begin to produce a modified protein that blocks their ability to grow and produce new muscle stem cells. This makes it harder for new muscle tissue to form.
Researchers are experimenting with treating aging muscle stem cells with a drug that will stop the protein modification that causes them to age. After treating the cells, they want to transplant these “rejuvenated” stem cells back into the body to help rebuild aging or damaged muscle. Muscle stem cell research will hopefully yield new insights into how muscle cells age and how this aging process can be modified.
Other Factors That Contribute to Muscle Aging
Another factor that contributes to muscle aging is the loss of motor neurons, the nerve cells located in the central nervous system that tell muscles to contract. Muscle cells themselves also die over time. This leads to a reduction in the number of muscle fibers and muscle fiber size.
What role do hormones play? Muscle fibers shrink in size in response to a decrease in IGF-1 (insulin-like growth factor). IGF-1 is produced by your liver partially under the control of growth hormone and provides a stimulus for muscles to grow. Growth hormone levels decrease with age, especially in people who are inactive. Declines in growth hormone and IGF-1, both of which have anabolic effects, contribute to the loss of muscle tissue with age.
Nutritional support, especially dietary protein, is important for the preservation of muscle mass – but so are certain vitamins. Some research shows low vitamin D levels increase the loss of muscle function with age. Vitamin D appears to be important for maintenance of type 2 muscle fibers, the fast-twitch muscle fibers that are involved in strength and power moves. This is the muscle fiber type most affected by aging. People tend to retain more type 1 (slow-twitch fibers) with age relative to type 2. Type 1 fibers are those used primarily during endurance exercise.
One study involving over 400 people showed those who had higher vitamin D levels had more strength in their upper and lower body even after controlling for other variables. A number of studies have found a link between vitamin D levels and changes in strength and muscle mass in older people.
The Best Defense Against Muscle Aging
As you might already have guessed, until stem cell research makes it possible to reverse the muscle aging process, the best way to keep your muscles young is with regular resistance training. Research in nursing home residents shows even people in their nineties can increase strength and muscle mass through training. In fact, studies show older people can make similar percentage gains in muscle mass as younger people when they resistance train.
The reason older people become frail is that they lose muscle tissue and strength. Unfortunately, as people get older they walk as a form of exercise if they work out at all. Walking isn’t enough to build significant strength or muscle tissue to prevent frailty and sarcopenia. That’s why resistance training is an essential part of any fitness program regardless of age.
Nutrition is also important for preserving muscle mass as your muscles age. There’s evidence that getting adequate dietary protein helps to reduce the loss of muscle with age. The amount of protein recommended for sedentary people is 0.8 grams per kilogram of body weight, but studies suggest older adults may benefit from getting 1.0 – 1.2 grams per kilogram daily to enhance muscle protein synthesis. Some research show sedentary adults that don’t resistance train have muscles that are less responsive to dietary amino acids. This suggests that muscle tissue may be better maintained in people who do regular resistance training and consume higher amounts of protein.
The Bottom Line?
Based on the current research, the best way to slow down the loss of muscle tissue with age is to resistance train regularly, consume adequate amounts of protein and get enough vitamin D to maintain a healthy vitamin D level. Aging muscles and loss of muscle mass are a major problem that leads to frailty, disability and an increased risk of falls. As your muscles age, you lose muscle tissue and you also lose bone mass. Resistance training helps prevent both of these problems. One more reason to make sure you’re pumping iron.
References:
Eurekalert. “Turning Back the Clock on Aging Muscles”
Journal of Anatomy. “Adaptability of Elderly Human Muscles and Tendons to Increased Loading”
Circulation Research. 2005; 97: 411-414.
Mol Aspects Med. 2005 Jun;26(3):203-19.
European Journal of Clinical Nutrition 67, 1050-1055 (October 2013)
Science Daily. “Which nutritional factors help preserve muscle mass, strength and performance in seniors?”
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4 Reasons We Lose Strength as a Result of Loss of Muscle as We Age
3 Characteristics of Healthy, Youthful Muscle That Change as You Age
Lack of Exercise is More Harmful to the Muscles of Older People
Resistance Training and Testosterone: What Role Does It Play in Women?
What Role Does Mechanical Tension Play in Muscle Hypertrophy?
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