the first two steps can change ones life - even when they don't play trumpet. Better posture and breathing bring a lot of advantages - like more oxygen for the brain, better concentration, less susceptibility to back problems. In lessons I even have my students "practice" entering a room for auditions. All of us take notice when a person enters a room and they are physically and mentally "centered".
The first impression someone new has of us - even before we have opened our mouths is if we are in control of our bodies - or even aware that they exist. There is a fine line between posture that lets others take notice or posture that causes others to put a stamp "stuck up" on us.
All of this stuff is also good for the trumpet but never addressed outside of lessons. I consider body use and breathing as so vital that it should be a required course in school, university and at the workplace!
I need to add something here:
How many times have we been disappointed in powerpoint presentations given? How many times was that related to lousy reading of the slides? Why does that happen? same as the trumpet - no strategic use of BREATHING!