1) Enzymes in the stomach break proteins apart to become peptides.
2) These peptides are chains of amino acids and are used by your body as the bricks and mortar to rebuild muscles and cells. The harder you train, the more you need.
3) The amino acids are transported straight to your liver which sends them into your bloodstream.
4) Your blood stream delvers the amino acids to the various muscles around your body.
5) Your muscles are basically long fibres and training creates small tears in these fibres, these occurrences stimulate your immune system to supply stem cells and growth hormones to the muscles.
6) The hormones and stem cells then use the amino acids as the repair foundations for the damaged muscle fibres.
7) Your DNA acts like the boss, directing their deployment. The Hormones and stem cells use the supplied amino acids to weave myofibrils, critical to muscle contraction.
8) The myofibrils then fuse with the damaged muscle fibres making the muscle bigger and stronger.