Is it true that your body will only grow in proportion? Meaning your upper body will stop getting bigger if your lower body isnt getting bigger (ie. only doing upper body workouts)
Technically, no. But your body has its limits, you can't reach your maximum growth potential for your chest for example if you never EVER workout your legs. Your body just won't let you. And it's not so much that your body doesn't want to grow in proportion, it has to do with the fact that some of the muscle fibers you are using to do a exercise aren't always going to come from just that primary muscle that you're training.