This is right, I started working for my uncle and had to shift bags of peat at a plant nursery at around 14, because of it I over developed chest muscles that caused me to have my first of about 4 'heart attacks' at around 17. It was caused by the muscles in my chest squeezing the heart and forcing it to stop briefly. Kinda puts me on my ass, but I can feel is still to this day and now understand how to relax when i feel it begin to come on (I'm 31 now and still kicking)