Final answer:
Fibrosis and contracture in muscles are typically caused by the replacement of muscle fibers with connective tissue due to aging (sarcopenia), disease (e.g., Duchenne muscular dystrophy), overuse (e.g., tendinitis), and systemic health conditions (e.g., cirrhosis, cancer, AIDS).
Step-by-step explanation:
Fibrosis and contracture of muscle tissue can typically occur as a result of conditions that involve damage or changes to the muscular and connective tissue. This process can be associated with aging, known as sarcopenia, which involves the irreversible loss of muscle mass and strength due to the replacement of muscle fibers by connective and adipose tissue. This decline impairs the ability of muscles to produce powerful contractions. In athletes, especially those involved in sports requiring quick, powerful movements, the reduction in fast glycolytic (FG) fibers that generate rapid contractions is particularly evident.
Other conditions causing muscle fibrosis and contracture include diseases like Duchenne muscular dystrophy (DMD), characterized by progressive muscle weakness due to the absence of the dystrophin protein. Overuse and repetitive motions may lead to tendinitis, an inflammation of the tendons connecting muscle to bone, which in turn can result in fibrosis of the affected area.
Certain diseases, such as cirrhosis, which is the formation of fibrous tissue in the liver, can also indirectly contribute to muscle atrophy by affecting the overall health and functioning of the body. Similarly, systemic conditions like cancer, AIDS, and heart disease may lead to muscle wasting syndromes, further causing atrophy and possibly fibrosis over time.