I'm pretty new to smoking (about a year), but i think the whole pounding heart thing happens to a lot of people. I know some people who don't like smoking bc they get paranoid and feel like they are gonna die. I think it can be pretty normal for a bunch of people. so dont worry, your not alone. I never heard of any of my friends having their muscles tense up, but it might be bc your not relaxed and possibly bc you are nervous and feel like your gonna die. yeh, iduno but i wouldnt worry about it too much.