Whats up with the title?

I have been enjoying the story of 'American Muscle' in the title 'Creator Owned Heroes'. My one request is that they explain the title. Creator Steve Niles mentioned that it had to do with the cars they drive in some way but it has not been any important part of the story. It is a post-apocalyptic zombie tale and has little to do with any kind of muscle or American. I just don't think the title fits...yet.