Final answer:
Atrophied muscles have become weaker due to a reduction in muscle fiber size, often caused by decreased use or aging (sarcopenia). While disuse-related atrophy can be reversed with exercise, age-related atrophy is generally irreversible. Exercises or physical therapy can help maintain muscle function and prevent complete muscle loss.
Step-by-step explanation:
If a muscle has atrophied, it means that the muscle fibers have become narrower and the muscle itself has become weaker. Muscle atrophy can be the result of decreased use or due to aging, a process known as sarcopenia, which is generally irreversible. Sarcopenia leads to muscle fibers dying and being replaced by connective tissue and adipose tissue, which lack the contractile ability of muscle tissue. As a result, muscles lose the ability to produce powerful contractions, leading to reduced muscle mass and strength.
In contrast to atrophy, muscle hypertrophy occurs when structural proteins are added to muscle fibers, causing the diameter of the cells to increase and resulting in greater muscle mass and strength. However, when muscle atrophy happens, the number of sarcomeres and myofibrils within the muscle fibers decreases, leading to a reduction in muscle size. Atrophy is often noticeable when a limb emerges from a cast or in those with certain diseases like polio. Proper exercise or physical therapy can help in preventing or reversing atrophy due to disuse, but it may not fully counteract age-related atrophy.