Which muscle fiber type is more affected by cortisol?

Which muscle fiber type is more affected by cortisol?

• A. Fast-twitch
• B. Slow-twitch
• C. Intermediate
• D. All equally

Answer: (A)

Cortisol is a catabolic hormone that promotes muscle protein breakdown, especially in skeletal muscle. It does this by activating pathways that tag myofibrillar proteins for degradation, notably increasing components like atrogin-1 and MuRF1 in muscle cells. Fast-twitch fibers have a higher baseline rate of protein turnover and rely more on rapid, glycolytic energy processes, making them more susceptible to cortisol-driven proteolysis. Under elevated cortisol, these fibers lose protein and atrophy more noticeably than slow-twitch fibers, which are more resistant due to their oxidative metabolism and different turnover dynamics. Intermediate fibers fall between these two in terms of sensitivity. So, the muscle fiber type most affected by cortisol is the fast-twitch fibers.

Cortisol is a catabolic hormone that promotes muscle protein breakdown, especially in skeletal muscle. It does this by activating pathways that tag myofibrillar proteins for degradation, notably increasing components like atrogin-1 and MuRF1 in muscle cells.

Fast-twitch fibers have a higher baseline rate of protein turnover and rely more on rapid, glycolytic energy processes, making them more susceptible to cortisol-driven proteolysis. Under elevated cortisol, these fibers lose protein and atrophy more noticeably than slow-twitch fibers, which are more resistant due to their oxidative metabolism and different turnover dynamics. Intermediate fibers fall between these two in terms of sensitivity.

So, the muscle fiber type most affected by cortisol is the fast-twitch fibers.