Genetics or your workout
 

I want to know if it is genetics or the workout you do that determines a muscles shape. Could it be a combo of the two?

Genetics determine the shape. Your workout decides how big the shape gets.

Exactly. Doing certain exercises to try to change the shape of a muscle is a waste of time. Just get stronger and bigger.

Very well said.

Genetics determine the individual shapes, but you can modify lifts to it different heads of the muscle groups in an attempt to even yourself out more...like you can modify a leg extension to hit your tear drops harder, etc.

Hard to argue with that logic Rich

This makes sense. I do not think you can do a whole lot to change genetics.

There is nothing outside the realm of seeking out a mad scientist that you can to do change your genetics, in a positive way at least. Gene sequencing can be damaged by many things: excessive exposure to UV spectrum and higher radiation, carcinogens, free radicals, major physical damage, and aging.

Certain things can, however, affect your gene expression, specifically steroid and steroid-like hormones. Testosterone turns on certain signals for increased synthesis of certain types of protein, leading to increased skeletal muscle, increase in male characteristics, and sometimes a poorer blood lipid profile. Cortisol, also a steroid, does the opposite in many respects, and is required for certain stages of the healing process.