How does muscle tissue grow?

[fantastical]

Re the recent discussion in 'body and soul,' how does human muscle tissue grow - i.e. get bigger? It starts with transmission of ATP at the cellular level, right...energy for growth?

[Calvesy]

I used to be a bodybuilder, and I learned that you never lose or gain numbers of cells, but that as you get stronger the supply networks of capillaries, nerves and lymph grow to meet the new demand. Tendons do thicken, but at one sixth the rate of muscle. It is the tendons that lengthen as you demand more flexibility. Bones also thicken with regular loading. Working against the contraction of the muscle is the part of the lift that creates most benefit.