Hi.! I am Dr. Saddiq. I would like to respond to your query.
First of all, I should spare a moment to appreciate you. You are 22 and the kind of hobbies you are keeping are hopefully going to ensure that you will lead a healthy and cherished life ahead. I would also like to mention that you have got a keen sense of observation. You have noticed all the chain of events in your body quite convincingly, however many of them are normal physiological responses of the body towards vigorous exercises.
Now we would take your issues one by one:
1:
Adrenaline which is going to trouble your heart is by pharmacological doping or by the use of sex
steroids or adrenalines. The one produced in reponse to increased sympathetic drive is a physiological response and is not going to trouble your heart. Though if you experience exagerated symptoms or the existing symptoms worsen then you can get serum electrolytes,
thyroid profile, and if both of these are not convincing then an
ultrasound of
adrenal glands or ACTH levels along with urinary VMA levels, but at this stage you dont need such extensive workup.
2. If you are continuing strenous exercise then i would suggest you to get a 2-D Echcardiography done, to rule out any
structural heart disease like HOCM, Valvular diseases or septal defects, but after a detalied cardiac examination or discussion with a cardiologist or even your GP. That would essentially rule out any life threatening condition before continuing with such exercises.
3. Now coming to the difference in heart beats and pounding of heart sensations, i would like to summarize few facts, though going into details will be more technical and boring for you, but since you are an athletic person, your heart behaves differently from a person, who has never been through such physical stress quite often. Your cardiac output (the amount of blood pumped by your heart) is mostly driven by increased stroke volume then
increased heart rate during when you push yourself more than your routine, but since running involves an extensive bio-mechanics, it would need your heart rate to increase too to compensate for the increased oxygen demand and hence increased cardiac output.
3. Lastly i would suggest you to add other activities and increase social gatherings so that you get a good feel about yourself. Other peoples admiration would add to your confidence regarding your physique and fitness.
Hope i had been concise and clear regarding your query. Wish you a health life. Chao.