Age and muscle loss
No matter how many birthdays come and go, muscles perform the same type of action. But as muscle mass in the body shrinks with the passing years, strength also declines. Sarcopenia—the gradual decrease in muscle tissue—starts at around age 30. The average 30-year-old can expect to lose about 25% of muscle mass and strength by age 70 and another 25% by age 90.
Some of these changes stem from the physiological effects of aging, but disuse plays a bigger role than many people suspect. Studies of older adults consistently prove that a good deal of the decline in strength can be recouped with strength training.
Likewise, power can be regained. With age and disuse, the nerve-signaling system that recruits muscle fibers for tasks deteriorates. Fast-twitch fibers, which provide bursts of power, are lost at a greater rate than slow-twitch fibers. You might think of a nerve pathway as a set of paving stones leading to a destination. As the years pass, the path may become overgrown and disappear in spots rather than remain well traveled and clearly marked. Preliminary power training studies suggest that movements designed to restore neural pathways can reverse this effect.
Having smaller, weaker muscles doesn’t just change the way people look or move. Muscle loss affects the body in many ways. Strong muscles pluck oxygen and nutrients from the blood much more efficiently than weak ones. That means any activity requires less effort from the heart and therefore puts less strain on it. Strong muscles are also better at sopping up sugar in the blood and helping the body stay sensitive to insulin (which helps cells extract sugar from the blood). In these ways, strong muscles can help keep blood sugar levels in check—which in turn helps prevent or control type 2 diabetes. Strong muscles enhance weight control, too.
On the other hand, weak muscles hasten the loss of independence, as everyday activities—such as walking, cleaning, shopping, and even dressing—become more difficult. They also make it harder to balance your body properly when moving or even standing still, or to catch yourself if you trip. The loss of power compounds this. Perhaps it’s not so surprising that, by age 65, more than one in three people has suffered a fall. Because bones also weaken over time, one out of every 20 of these falls causes a fracture, usually of the hip, wrist, or leg. Some of these fractures can lead to serious or even fatal complications, but in general, people with greater muscle strength before a fall are less likely to sustain a serious injury.
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