does having a lagging bodypart mean that...?

[newahnald]

...you are born with fewer muscle fibers in that area?

For instance, if you have a gentically lagging chest, does this mean that your genetics simply provided you with fewer muscle fibers in this area in proportion to the amount of muscle fibers you have in other muscle groups?

[Ronnie Rowland]

...you are born with fewer muscle fibers in that area?

For instance, if you have a gentically lagging chest, does this mean that your genetics simply provided you with fewer muscle fibers in this area in proportion to the amount of muscle fibers you have in other muscle groups?

ABSOLUTELY!