It is characterized by deeper striations, increased muscle density, and a "harder" look compared to the "softer" or "puffy" appearance of newer trainees.
This development is a key reason why many professional bodybuilders don't reach their peak form until their mid-30s or early 40s. muscle mature
Muscle maturity is more dependent on (the number of years spent lifting) than chronological age. It is characterized by deeper striations, increased muscle