OMG! I thought I was going to die!!

They started by taking my blood pressure then hooking up the electrodes. The nurse asked me to get on the treadmill and told me that every 3 minutes the speed would increase and the incline would raise. The first 3mins were good. I was walking and breathing. Then the first incline change and speed increase I was doing ok, no chest pains or anything..just muscles that hadn't been used in a while getting all heated up. I was okay. My target heartrate was...