As people age, their skeletal muscle mass starts to deteriorate. Your skeletal muscles (also known as lean muscle) are the muscles that attach to your bones and are under voluntary control.
As a result of deterioration, people begin to look, well, flabby as they get older. You may see these changes start as early as your 30s, but most people see the biggest changes between their 40s and 50s.
A recent study concluded that total muscle mass decreases by nearly 50 percent for people between the ages of 20 and 90. On average, people lose about 30 percent of their strength between ages 50 and 70, and another 30 percent of what's left per decade after that. Generally, people lose about 1 percent of their lean muscle mass per year after age 40.
The following four types of muscle weakening (called atrophy) become more common as people age, and each type responds differently to strength training.
- Sedentary: Muscle deterioration is a natural process, but a sedentary lifestyle can accelerate it. You can rebuild muscle mass lost from a sedentary lifestyle — all you have to do is get off the couch and do something physical! Some sedentary people include those who are bedridden, astronauts, and people with minimal physical activity.
- Statistics show that people confined to bed can lose around 1 percent of muscle strength for each day in bed. Physical therapy is often prescribed as treatment for people who are bedridden so that they don't have muscle loss. A person's recovery time from being bedridden can be improved if the proper actions are taken to prevent muscle loss. Interestingly, muscle loss also affects astronauts, who spend much time in a weightless state!
- Age-related: Age-related muscle loss is also called sarcopenia, which means "vanishing flesh." Sarcopenia isn't an inevitable part of aging; it's the result of the loss of around ten ounces of muscle a year that isn't replaced due to a sedentary lifestyle. You can win this muscle back with a strength-training program.
- Medication-related: Certain medications, such as systemic corticosteroids (often prescribed for people with asthma or inflammatory conditions such as rheumatoid arthritis or lupus), can result in muscle weakness.
- Disease-related: Muscle atrophy from disease can be more difficult to overcome, especially when it involves nerve damage or disease of the muscle itself. The muscle loss in these situations is more damaging because you have almost no use of the diseased muscles. With the other types of muscle loss, you have at least some use of the muscle groups. Cancer can also result in a muscle wasting syndrome called cachexia. Diseases that cause cachexia often progress rapidly; many have no cure and are progressively disabling. Work closely with your doctor to prevent muscle loss if you have any of these conditions:
• Nerve diseases affecting muscles, including polio (poliomyelitis)
• Lou Gehrig's disease (amyotrophic lateral sclerosis or ALS)
• Guillain-Barre syndrome (self-limiting demyelinating polyradiculoneuropathy), which can cause short-term muscle weakness or paralysis
- Other diseases affecting muscles include muscular dystrophy, congestive heart disease, liver disease, and AIDS. If you have any of these illnesses, talk to your doctor about setting up a physical therapy program to help you retain as much muscle mass as possible.
In addition to general skeletal muscle loss, the following changes occur as you age:
- Muscles take longer to respond to brain signals in your 50s than they did in your 20s. As a normal course of aging, you begin to lose the muscle fibers that are responsible for making you move quickly. The speed of transmission of impulses from the brain to the muscles also slows down, so it takes longer to get the signal, "Hey! Move it!" Your muscles also can't repair themselves as quickly as they used to, due to a decrease in enzyme activities and protein turnover.
- The water content of tendons (the cord-like tissues that attach muscles to bones) decreases as you age. This change makes the tissues stiffer and less able to tolerate stress.
- Your heart muscle becomes less able to propel large quantities of blood quickly through your body. As a result, you tire more quickly and take longer to recover.
