I've always had a racing heart rate, and I have no idea why. Even at my peak of fitness it was high. I'm now 40 and I strapped my wife's HRM on. We were both just standing here. Hers was around 73, and when she sat down it dropped to 63. For me, standing was 120-125, and sitting was like 100-110. The lowest I could get it, trying to sit back and relax was like 85. I think it's like 75 in my sleep.
The thing is, I've been riding consistently for over 20 years, while my wife has never done anything aerobic, other than the past year of cycling. Is it genetics? Bad luck? Does it even make a difference?