I remember on our former board that there used to be minor discussion regarding the look of certain wrestler's chests and then I stumbled across this video. I thought it was interesting and decided to post it, apparently that "caving" in look not only comes with age (in some cases) but also due to the trauma and stress associated with wrestling that causes the chest muscles to experience minor tears.

https://www.youtube.com/watch?v=qTmvHVFxF_c