Testosterone Use and Effect on Muscle Growth, Size & Strength.

Keywords: Sarcopenia, Low-T and Muscle Cell Loss, Muscle Cell Fiber, Muscle Hypertrophy, Testosterone and Muscle Size, Androgen and Muscle Cell, Weight Loss, Metabolism, Androgen Receptor, Muscle Growth, Low Testosterone and Muscle Wasting and Fatigue, Weight Gain, Gaining Muscle on Testosterone, Physical Function and Testosterone, SARMS



Men with low-testosterone (low-T) have decreased lean muscle mass compared to men with normal testosterone levels. The administration of testosterone to men with low-T results in an increase in lean muscle mass, muscle protein synthesis and enhanced fat cell (weight) loss.


The increase in muscle mass secondary to testosterone administration was first thought to be universal for all skeletal muscle in the human body; however, studies have found that muscles in the body respond differently to testosterone replacement (TRT). The muscles of the upper back, shoulders, head, and arms were most those most affected by testosterone and seemingly increase in size. The muscle of the thigh were not found be affected by testosterone as much. The exact mechanism why certain muscles are affected by androgen administration is unclear, but could relate to the hypothesis of different androgen receptor phenotypes in different muscle groups. Further research into this receptor variability within skeletal muscles could illicit androgens that affect and grow particular muscles more so than others.


Testosterone increases muscle mass by increasing the size of the muscle fibers (hypertrophy) and increasing muscle protein synthesis.


Muscle fibers (myofibrils) are the structural component of a muscle. Within muscle fibers are androgen receptors. Androgen receptors are stimulated by testosterone. The administration of testosterone causes myofibrils to increase in number leading to an enlargement of the muscle cell and therefore muscle mass. In men with Low-T, it has been found that lack of testosterone causes myofibril dissolution (shrinkage) and loss of muscle cells, muscle size, and muscle mass.

The mechanism by which testosterone promotes lean muscle mass and growth is by up-regulating myogenesis (muscle building). Testosterone is believed to cause nitrogen retention which may signal protein synthesis, promoting muscle and lean mass growth. An Increase in lean muscle mass will increase metabolism propagating the fat cell loss cycle.


Low-T causes muscle cell loss.


Testosterone is a necessary component for maintaining and building lean muscle mass. The actions of androgens to enhance muscle cell size is characterized as one of the anabolic components of testosterone. Testosterone has both anabolic and androgenic properties that we will now discuss. Anabolic potential refers to the ability of an androgen to increase muscle mass, decrease body fat, accelerate bone growth before epiphyseal plate closure and increase solid organ size. Androgenic potential attributes to increasing spermatogenesis, enlargement of genital size, and function, enhancing male body hair distribution, deepening of the voice and increasing sex drive. Androgenic properties of testosterone are those that boys experience during puberty and not desired by mature men on testosterone therapy.


Many men desire testosterone replacement therapy (TRT) for the anabolic component fo the medication and not the androgenic component. The ratio fo anabolic to androgenic potential is 1:1. It is an equal ration. The development of medications such as Anavar (Oxandrolone) and Nandrolone (Deca) improved upon this ration by having an anabolic to androgenic potential of 10:1. Significantly more muscle building and weight loss enhancement compared to testosterone.

May athletes and men who engage in strength-related endeavors use testosterone to increase performance and strength. A study published in the New England Journal of Medicine in 1996 by Bhasin et al. observed the effect of testosterone administration in normal men and its effect on behavior, muscle size, and strength. The study assigned 43 men to one of four groups: placebo injection with no exercise, testosterone injection with no exercise, placebo plus exercise, and testosterone injection plus exercise. The men received injections of testosterone or placebo weekly for 10 weeks. The men in the exercise groups performed standardized weight-lifting exercises three times weekly. Before and after the treatment period, fat-free mass was determined by underwater weighing, muscle size was measured by magnetic resonance imaging, and the strength of the arms and legs was assessed by bench-pressing and squatting exercises, respectively. The results of the study found that the combination of strength training and testosterone therapy produced the greatest increase in fat-free mass, muscle hypertrophy, and strength than any of the four groups studied.

Many men today administer greater than physiological dosages of testosterone to increase performance and muscle size. Whether greater dosages truly lead to a heightened athletic performance or if a saturation model exists, continues to be investigated. Still, many athletes and men admit they feel enhanced performance and endurance while on testosterone replacement therapy, each patient response can be different.


If we at look the Testosterone trials, one of the largest placebo- controlled, double blinded trials observing the effects of testosterone administration in men with low-T, men reported greater physical function.


A meta-analysis by Skinner et. al, Muscular Response to testosterone replacement vary by administration route a systematic review and meta-analysis, concluded that TRT increases fat free mass, total body strength and upper and lower extremity strength when both a topical and injectable testosterone were administered. When comparing topical testosterone (gel) vs intramuscular testosterone delivery route, there were greater strength scores and greater physical functioning scores favoring the intramuscular route of administering testosterone.

It is ideal for any man who is undertaking testosterone replacement therapy to incorporate an exercise and resistance training regimen into their everyday life, not only for the health benefits but to enhance the effects of testosterone therapy. Testosterone works synergistically with the addition of a workout regimen to provide faster results for improving strength, muscle size, and physique.


For more information how selective androgenic receptor modulators (SARMS) can increase muscle size click here.

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