| The Role of Androgen Receptor in Resistance Training-Induced Gastrocnemius Muscle Hypertrophy |
| Paper ID : 1300-SPORTCONGRESS |
| Authors |
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Ali Nosrati Andevari * Department of Clinical Biochemistry, Afzalipour Faculty of Medicine, Kerman University of Medical Sciences, Kerman, Iran |
| Abstract |
| Introduction: The androgen receptor (AR) is a primary mediator of muscle growth regulation. Resistance training induces an increased expression of AR in muscle. The protein regulates metabolism and protein synthesis by stimulating intracellular signaling. The gastrocnemius muscle has a higher percentage of type II fibers and is thus highly suited to short-term, high-force movements. The aim of this research was to investigate the role of the AR in resistance training-induced gastrocnemius muscle hypertrophy. Methods: This review considered 40 original and review articles obtained from PubMed and Google Scholar databases using the keywords "Androgen receptor," "Resistance," "Gastrocnemius," "Hypertrophy," " Insulin-like growth factor-1 (IGF-1)," " Phosphoinositide 3-kinase (PI3K)," "Akt," and mTOR. Results: AR acts as a nuclear transcription factor. It induces IGF-1/IGF-1R. IGF-1, predominantly secreted by the liver and locally in skeletal muscle. IGF-1/IGF-1R (insulin-like growth factor 1 receptor) complex controls the activation of PI3K/Akt/mTORC1. The IGF-1/IGF-1R signaling in gastrocnemius muscle promotes protein synthesis, suppresses protein breakdown, and increases muscle hypertrophy. IGF-1/IGF-1R signaling augments the sensitivity and expression of AR and establishes a positive feedback loop that increases the anabolic response to resistance training. Resistance training, such as calf raises that activate the gastrocnemius, disrupts mechanical tension that further amplifies production of IGF-1, initiating AR-mediated hypertrophy. In males, elevated levels of testosterone maximize AR activation and IGF-1 production with augmented hypertrophy. Type II fibers, with abundant AR and maximal potential for gain in hypertrophy, are more responsive to resistance training compared to Type I fibers. The gastrocnemius is therefore able to undergo maximal growth and strength increase. Conclusion: The relationship between AR, IGF-1/IGF-1R, and PI3K/Akt/mTOR pathways is important in resistance-training-induced hypertrophy in the gastrocnemius. |
| Keywords |
| Androgen receptor, Resistance, IGF-1, Gastrocnemius |
| Status: Abstract Accepted (Poster Presentation) |
