For the dankest of all memes
For anyone wondering, the answer is that exercise won't change a concave sternum, but you can make it look a little less odd with normal chest exercises (pushup, bench press, etc). If you're really thin, it can also distort lower on your body, so upper abdominal exercise (sit-ups, planks, leg lifts) can help, as well as obliques (crossing or side variants of the previous group).
Pectus excavatum. I have a (fortunately) mild case myself, not as extreme as the photo. Somewhat a source of embarrassment.
Solidarity, my friend. Exercise really can diminish the visual effect, though my familiarity with this is from discussing exercise with a close friend who has it and his general view is that the main improvement came from understanding that he had nothing to be ashamed of and I don't think I can speak to how that is accomplished since it's really a personal, internal affair.
I suppose that the pic is from 4chan and the answer seems pretty ableistic and disrespectful for me, I do not expect more from this site.
4chan really is... Let's call it... Special