I'm fairly broad shouldered, with ridiculous strength in my neck and back. I genuinely think it's purely because when I was a kid I didn't sort out my backpack properly, so I always had all my stuff and my PE Kit, often on top of my ingredients for cooking class. All those folders and textbooks that I carried around all day every day had an effect. I never go the gym, but I look fit right until the moment I remove the my T-shirt. Then I look like someone with my sedentary lifestyle should look.