Muscle atrophy can take several months or years before setting in and eating away at the muscle tissue, according to The Free Resource. Atrophy is the wasting and deterioration of muscle tissue.
Muscle atrophy comes in two forms: disuse and neurogenic muscle atrophy. Disuse atrophy is the result of a lack of physical exercise or activity. Muscles will appear thinner if they are not being used, explains The Free Resource. For example, astronauts experience muscle atrophy after a few days in zero gravity.
Neurogenic atrophy, as defined by The Free Resource, is a more severe case of muscle wasting as the result of damage to the nerve or by disease. Neurogenic atrophy is associated with diseases such as Polio and Lou Gehrig's Disease. Once neurogenic atrophy takes hold, it is difficult to reverse.