Recognizing the cause of muscle atrophy is the first step toward countacting it. The four most common causes for muscle atrophy among apparently healthy individuals are aging, injury recovery immobility, cessation of resistance exercise, and diminished resistance exercise intensity.

Defining Atrophy

As it applies to the reduction of muscle tissue mass in an apparently healthy individual, atrophy is an adaptive process that results from a diminished need for strength and or strenuous activity performance. Depending upon the cause, muscle atrophy can be localized and effect a select muscle group(s), such as limb immobilization during injury recovery, cessation of regular strenuous resistance activity for a particular muscle region) or, it can be widespread, affecting all musculature. This latter type often occurs in the case of aging, or after a complete cessation of a regularly performed overall resistance exercise program.

Aging

Of the above four major causes, aging results in the most gradual rate of atrophy, especially in the apparently healthy individual with a history of life-long strenuous activity. Various factors are involved in aging and related muscle atrophy. They include diminished hormone synthesis, a steady decrease in strenuous activity, and slowed intercellular organelle function.

Injury Recovery immobility

By limiting the use of, or completely interruptingactivity of any musculature over an exteneded period will result in diminished localized soft tissue mass. Generally, assuming normal recovery conditions, and in the absence of advanced age, illness or disease, specific strenuous activity performance can successfully restore tissue mass. In general, The longer the period of immobility, the greater the extent of tissue atrophy.

Cessation of Regular Exercise

The regular performance of strenuous muscle activity (resistance exercise) generally results in the increased size of involved muscle tissues (hypertrophy). Here, it would be accurate to think of atrophy and hypertrophy as antagonistic processes: Atrophy leads to a decrease in lean tissue due to reduced strenuous activity, while hypertrophy is enlarged lean tissue due to increased strenuous activity.

It should come as no surprise that ceasing regular strenuous resistance exercise program will result in the atrophy of trained muscle tissues. This adaptive atrophy generally stops once lean tissue mass has diminished to the approximate size that existed before the initial performance of the strenuous resistance exercise program.

Diminished Resistance Exercise Intensity

Reduced intensity of resistance exercise will result in a decrease in the muscle mass involved. This is because muscle tissue is only maintained in sufficient volume to comply with imposed strength demands placed upon the body. When these demands are decreased, muscle mass decreases. Atrophy is responsible for the decrease in muscle mass experienced by bodybuilders taking extended layoffs from intense exercise, or while "phase training" in a phase during which imposed demands are less than maximum, and sets are performed in slightly higher repetition ranges.

This adaptive atrophy generally ceases once lean tissue mass has diminished to the approximate mass required to comply with currently imposed strength demands. This type of atrophy is sometimes confused with two related phenomena: catabolism and cannibalism.

Catabolism is the stage of metabolism whereby tissue is being broken down and used for energy both during and after ongoing strenuous activity, while atrophy is attributed directly to the "shrinkage" of intercellular organelles as well as sarcoplasmic fluid reduction in the absence of adequate strenuous activity performance altogether.

In addition, cannibalism occurs during prolonged periods of extreme caloric deprivation and continued strenuous activity performance. This results in the muscle fiber actually having to break down its own internal structural tissue for survival needs.

Cannibalism therefore could be considered an extreme case of ongoing catabolism. It can be stated that put atrophy and catabolism/cannibalism, with respect to the apparently healthy individual's performance of resistance exercise, are exact opposites. Atrophy occurs as a result of under-training, while with catabolism and cannibalism occur as a direct result of overtraining.

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