As you said, body. Read the definition of your body. What's the body? The body's the entire structure from head, toe, fingers, legs.

I'll say this, If you've an amputee and haven't got legs, then sure, just train your torso. If you've legs, train your legs.

That's a VERY nonsensical way of training. Do you ever see weightlifters, powerlifters, ask their partners or coaches to help them along while lifting?

That usually happens with guys who can't have their muscles lift, but their ego lift...