What Happens To Muscles When We Age?
Aging is an inevitable part of life. Hopefully, we’re around long enough to experience the aging process. However, the slow decline of our bodies is not usually a welcome change. We might feel stiffer, slower, or less balanced as we get into our older years. But what’s actually happening to our muscles and bones when we experience these age-related changes? In a two-part series, we’ll take a closer look at what happens to our body structures as we get older. In this first article, we’ll look at what happens to our muscles as we age.
What is a muscle?
Remember that at the micro level, skeletal muscle cells are composed of two proteins, actin and myosin. Those individual cells are wrapped in layers of fascia, which are bundled together and wrapped in fascia again. Those bundles are grouped again and bundled in fascia. When those two proteins in a muscle cell are chemically stimulated to move towards each other, that cell contracts. When a bunch of muscle cells contract, we have the kind of muscle activity that we’re familiar with.
What do our muscles do?
Muscle contraction has critically important functions in our body in addition to the obvious one of moving us around. Muscle activation shapes and stabilizes our static body posture and is part of what drives our respiratory function. Skeletal muscle contractions also produce heat and have a role in regulating our body temperature, especially in response to cold. Muscle activity contributes to maintaining a healthy metabolism of the food we take in and to balancing our protein synthesis with protein breakdown. Skeletal muscle activity is even involved in our immune system response.
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How do muscles change as we age?
We experience changes in multiple body systems that affect our muscles as we age. Our tissue itself changes, and we also experience metabolic and nervous system changes that affect our muscles. Changes happen at the cellular level that result in both structural and functional changes we experience at the macro level.
Because increasing inactivity often goes along with unavoidable age-related changes, researchers have difficulty separating the specific effects of aging from those of inactivity. What does seem clear is that as we age, we experience a decline in skeletal muscle mass, strength, and tone.
When we lose muscle mass, either due to the aging process or to reduced activity levels, it is replaced more slowly as we get older. The quality of our tissue also changes. It becomes more fibrous. Additionally, as lean muscle mass decreases, it is often replaced with more fat tissue. However, when it comes to muscle strength, some amount of that loss may be related to the decrease in activity that often happens along with aging.
Muscle tissue changes
Specifically, during the aging process, the number of our individual muscle fibers decreases, and these fibers also get smaller. Our muscle tissue also tends to lose what are called type 2, or fast twitch fibers. Aging affects our ability to both synthesize and break down protein, which may be part of what causes the reduction in muscle mass and increase in weakness. Hormone levels also affect muscle synthesis and metabolism which causes some of the changes that we experience as we age. Additionally, the contractibility of our muscle tissue decreases as a result of changes in our nervous system.
Research differs on exactly when age-related changes start occurring in muscle tissue, but an estimate is possibly as early as after age 30, likely after 40, and at a higher rate of decline after 60. If age-related muscle atrophy becomes very significant and impairs our ability to function, it’s called sarcopenia. However, researchers and medical professionals differ in their opinions of what is officially considered sarcopenia, and when the changes are simply considered age-related decline.
Why do age-related muscular changes matter?
Reduced function in our muscle tissue can have many consequential effects. Less muscle tone, strength, and contractibility can increase the likelihood of falling as well as other kinds of injuries. Additionally, changes to the muscular system can result in declining balance. Muscle health is also related to bone health. We need healthy muscle tone and activation in order to do the kinds of weight-bearing activities that help us maintain bone density as we age. Changes in muscular system function can negatively affect our breathing, proprioception, strength, and endurance. Ultimately, reduced muscle function can reduce our quality of life by limiting the kinds of activities we can do and how independent we can be in our later years.
What can you do to slow muscle decline?
The good news is that lifestyle interventions seem to have a positive effect on slowing muscle decline. We all have to get older, but we have some control over how fast we get there. Muscle mass and strength are faster and easier to lose than they are to build and maintain. Therefore, consistency of different types of exercise and movement activities is key.
Both resistance exercises and aerobic exercise affect protein synthesis, and therefore affect muscle mass. However, the specific effects of each are different. A variety of exercise types seems to address the widest array of age-related changes to our muscular system. Including strength-building exercises, resistance training, aerobic exercise, and mobility exercises will go a long way toward slowing the process of age-related decline in our muscular system if no other disease or other contextual factors are present.
Conclusion
The inevitable aging process results in a decline in skeletal muscle mass, muscle strength, and muscle tone. This can have negative consequences like decreased balance and an increased likelihood of falling. However, we can slow the age-related decline of our muscle tissue by staying consistent with a variety of types of exercise, including resistance training, aerobic exercise, and mobility exercises.
References
Nair, K.S. Aging muscle. 2005. American Journal of Clinical Nutrition. 81(5):953–963.