My sentence is simply an example of the word 'jacked' being used in a way that is synonymous with muscular. 'Jacked' is sometimes used with this meaning, regardless of your approval. Slang is often ephemeral, I would try not to get upset when it changes.
I have only given disapproval so far. Your personal approval on the other hand is pretty important to yourself. By the line of your argument, you do draw approval from others', so mine is slightly important, too, as evidenced by your attentive answers. I might just have been wrong, which is still more agreeable than accepting two concurrent opinions.
