Muscle building question

[tgw85]

I'm a 19 year old college student who loves bodybuilding, but I'm being hindered by a negative mental perception and attitude because of a question on how a muscle grows.
I've seen pictures of Arnold Schwarzenegger around age 20, and in some pictures the very bottom of his chest looks thicker then compared to some pictures of him in his prime years, age 27,28. My question is as the chest grows bigger and longer does the very bottom of the chest grow in such a way that after some point it starts getting thinner?
Thank you.

 

[LAM]

muscles either contract as a whole or not at all, that being the case technically you can't effectively "target" part of a muscle that has multiple heads and attachment points. all you can do is to hit each muscle from multiple angles which changes the pattern of muscle fiber recruitment. along with varying the load, rep scheme and tempo that's all you can do.

in regards to your question about the pecs since you can't change were a muscle attaches to tendon or tendon length it's physiologically impossible to change the shape of a muscle through exercise as myocytes either hypertrophy or atrophy in response to that type of stimulation.