Hello and thank you for using HCM. I carefully read your question and i understand you concern. I will try to explain you something and give you my opinion. According to your explanations i thing we are dealing with extrasistolic-heart beats. This are electrical impulses generating from parts of the heart different from that of normal sinus rhythm. They cause this escaped beat, this sensation of a palpitation that cause you a chest discomfort. The extra-sistolic beats might happen for different reasons. From simple emotional stress to anemia, hyperthyroidism, ischemic heart disease ect. The fact that you exercise without any problem is a very good thing. To know haw to deal with this extra-sistoles you have to do some examinations like a blood analyses, an electrocardiogram, an echo-cardiography and a holter monitoring. It can give us a better view of you heart structure and the rhythm tendency. Only then we should know if it is necessary to treat this with medication. At mean time i encourage you to keep training and avoid caffeine products because they rise extra-sistolic beats. Hope I was helpful. BEST REGARDS.