Why does higher calorie intake lead to muscle gain?

CrusaderSam

Muscles are made by the breaking down of myofibrils and their rebuilding. They are entirely made of protein (amino acids, whatever) and so adequate protein intake is essential to allow muscles to grow.

This is true but not the full story when it comes to building muscle.

Muscle cells have more then one nucleus. When myofibrils break down they are repaired with in the nucleus. They are then added back with maybe some extra myofibrils in to the contractile units of the cell. This is called protein synthesis and it takes very little energy. Taking anabolic steroids will cause the nucleus to do this even with no exercise.

Muscle cells can also get larger by adding extra nuclei. When a muscle nuclei can not repair the damage, cells called myoblasts will join with the cell to help repair the damage. The myoblasts can permanently fuse with the muscle cell or dedifferentiate back into satellite cells. Hormones like insulin and growth factor and inflammatory response will have a large roll in this.

Now I will probably get attacked for this but...the reason why people do the whole bulking thing is to get that hormonal response naturally, just its so small its not going to do much(if anything). Now the reason the pros(bodybuilders, powerlifters and strongmen) do it is because they are shooting up very large amounts of the hormones and dont want to die from low blood sugar.