Hormonal Mechanisms in Muscle Remodeling

Hormonal Mechanisms in Muscle Remodeling

• Hormonal mechanisms are part of an integrated signaling system that mediates changes in metabolic and cellular processes in muscle after resistance exercise and training
• Muscle remodeling involves disrupting and damaging muscle fibers, an inflammatory response, degradation of damaged proteins, and synthesis of new proteins

The Inflammatory Process

• Involves the immune system and various immune cells (e.g., T and B cells), which are influenced by the endocrine system
• The study of the connection between the neural, endocrine, and immune systems is called neuroendocrine immunology

Hormones and Protein Synthesis

• Hormones are intimately involved with protein synthesis and degradation mechanisms in muscle adaptations to resistance exercise
• Anabolic hormones (e.g., insulin, IGFs, testosterone, and growth hormone) contribute to various aspects of protein synthesis
• Thyroid hormones act as permissive hormones that allow the actions of other hormones to take place
• Anabolic hormones block the negative effects on protein metabolism of catabolic hormones (e.g., cortisol and progesterone)

Effects of Cortisol

• Cortisol has negative effects on skeletal muscle, including:
  • Inactivating immune cells
  • Blocking other signaling pathways (e.g., Akt/mTOR pathway involved in mRNA translation initiation)

Adaptive Influence of Hormones

• The interrelatedness of hormones, muscle fibers, and changes in functional capabilities of muscle fibers provides the basis for the adaptive influence of hormones in hypertrophy
• Hormones represent only one of the possible mechanisms for skeletal muscle adaptation to resistance training