Does it happen to you? Do you ever find yourself in the middle of a game and notice that your heart is racing and your palms are sweaty? It happens to me every now and then ... especially in games that are really important to me.
I've noticed that the last couple of games I've played, that when I spot a tactic, my heart rate jumps up considerably. I find myself having to control my breathing. Only recently have I began to concentrate on my breathing during chess games ... whenever I begin to feel nervous or feel my heart rate increase, I take several controlled deep breaths until my heart rate is back to normal. Although I appreciate the workout my heart is getting, I find that unless I get it under control, I am more prone to blunder. Therefore, I take my time to calm down and cooly assess the situation before moving.
There have been plenty of times where I did not try to calm my nerves down (or couldn't because it was a blitz game) and I blundered horribly.
Interestingly enough, I found an article about a research that was performed on chess players with regard to heart rate. The summary simply states, "Hopelessness is associated with decreased heart rate variability during championship chess games." You can read the entire article here.