<<< 4) If your heart tends to beat faster, does that then become the maximum heart rate you should use? (Mine tends to race).>>>

Sounds to me like Atrial Tachycardia.



[...]

"The name may escape you, but it's a condition that's estimated to affect as much as 40 percent of the U.S. population. And if you're among them, its an experience you'll never forget: Your heart rate suddenly shoots upward to 220 beats a minute, and it feels like it won't slow down. You feel flushed and have body chills. You may also feel nauseated and dizzy and be almost overwhelmed by a sense of panic and doom."

[...]

" Take it easy. "if you can control the stress and anxiety in your life, you're drastically cutting your risk of suffering an attack," according to Michael Crawford, M.D., chief of cardiology at the University of New Mexico School of Medicine in Albuquerque and former chairman of the American Heart Association's council on clinical cardiology. Not surprisingly, studies show that PAT strikes hard-driving, Type A personalities who are easily touched off. So if that's your style, try taking things a bit slower."

So, take it easy. It seems to be related to anxiety.

There's lots of links out there, but here's the one the above quotes are from:

[link|http://www.mothernature.com/Library/Bookshelf/Books/48/154.cfm|http://www.mothernat.../Books/48/154.cfm]