I am able to exercise very intensely for long periods of time with no discomfort. I participate in this kind of activity 4-5 x/week regularly, and have been for years. Recently, I've had three instances where I was at a resting state (at work, etc.), but then had to jump up and run up the steps. At the top of the steps, I got a very brief, sharp pain in the upper chest region. I literally goes away within 5-10 seconds, and my increased heart rate returns to normal as well. Is this trapped gas or what?