Protein synthesis

Finally, the message filters down to alter the pattern of protein expression. It can take as long as two months for actual hypertrophy to begin.^{[citation needed]} The additional contractile proteins appear to be incorporated into existing myofibrils (the chains of sarcomeres within a muscle cell). There appears to be some limit to how large a myofibril can become: at some point, they split. These events appear to occur within each muscle fiber. That is, hypertrophy results primarily from the growth of each muscle cell, rather than an increase in the number of cells.