Final answer:
Protein synthesis in muscles can be affected by growth hormone, insulin-like growth factor 1 (IGF-1), and ß-hydroxy ß-methylbutyrate (HMB) supplementation.
Step-by-step explanation:
Protein synthesis refers to the process of creating new proteins in the body. In the context of muscle protein synthesis, there are several factors that can affect its rate. One important factor is the activation of growth hormone and insulin-like growth factor 1 (IGF-1), which directly accelerates protein synthesis in skeletal muscles and bones.
Another factor is the supplementation of ß-hydroxy ß-methylbutyrate (HMB) combined with an appropriate exercise program. HMB has been shown to increase muscle protein synthesis and decrease muscle protein breakdown, leading to gains in muscle hypertrophy, strength, and lean body mass.
Overall, the activation of growth hormone and IGF-1 and the supplementation of HMB are likely to have the greatest effect on muscle protein synthesis.