for as long as i can remember when ive tried running (just normal running, medium pace for 10 minutes) i did feel my heart rate go up and breathing get heavy, but ive never felt sore at all from running...and i want to start doing HIIT but i dont feel like i will be able to go intensly enough to feel anything afterword because of my low cardio health, what i mean is i think ill be breathin too hard to continue wholeheartedly so i wont get the full benefit...any suggestions...?