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Published online: 21 February 2017
© Springer International Publishing Switzerland 2017
Abstract Chronic increases in testosterone levels can significantly increase hypertrophy and strength, as has been demonstrated by pharmacological intervention. However, decreases in basal testosterone levels can have the opposite result, as has been seen in hypogonadal populations. Because of these profound effects on hypertrophy and strength, testosterone has often been studied in conjunction with resistance exercise to examine whether the endocrine system plays a role in adaptations to the stimulus. Whereas some studies have demonstrated a chronic increase in basal testosterone, others have failed to find an adaptation to regular resistance exercise. However, improvements in strength and hypertrophy appear to be possible regardless of the presence of this adaptation. Testosterone has also been shown to acutely rise immediately following an acute resistance exercise bout. While this substantial mobilization of testosterone is brief, its effects are seen for several hours through the upregulation of the androgen receptor. The role of this acute response at present is unknown, but further study of the non-genomic action and possible intracrinological processes is warranted. This response does not seem to be necessary for resistance training adaptations to occur either, but whether this response optimizes such adaptations has not yet been determined.
1Introduction
The development of strength and hypertrophy is sought by a wide range of populations, spanning those experiencing a muscle-wasting disease to elite athletes aiming to optimize human performance. One such means to develop strength and hypertrophy is that of resistance exercise, where careful manipulation of the acute program variables can lead to substantial improvements [1]. In addition, strength and hypertrophy can be gained through the use of testosterone supplementation, even in the absence of resistance exercise, in both young [2] and older men [3]. Owing to the anabolic nature of the testosterone hormone, its concentration in human blood has often been measured in conjunction with resistance exercise, either during or immediately after individual bouts of resistance exercise, or to assess whether changes in basal levels exist following several weeks or months of regular training. Such studies have been conducted to assess whether this increased exposure to testosterone is playing a role in the adaptations of strength and hypertrophy to resistance exercise. If these adaptations are indeed...