I have kind of wondered about this. When starting out, my "target HR" (or moderate intensity) Should be in the 140's... where my max is 190.(I'm 30) Well, the in the 140's I barely felt like I was exerting myself. But I hit my max easily, and stayed in my max zone while working at a high intensity. (175-185ish). I kind of just threw the heart rate "zones" out the window, and started going by how I feel. I noticed it takes a bit longer for me to get to that high intensity feeling then it did before. (I just recently got a fitbit to track my HR while I work out, so I'm curious to see what it says now.) Basically the heart is a muscle. And the more you work it, the stronger it will get. So initially you may be working at a high intensity and maxing out your heart rate with less effort. But as you keep getting in shape, you should see it come down. Or at least see it take you longer to max out. Just listen to your body. It will tell you if you are over-exerting yourself. I wouldn't be worried about it personally. Unless you feel it's doing something weird, or this is abnormal for you, you could always go talk to your doctor. But to my laymen's understanding, unless you have an underlying heart condition, you should be fine.

Crafty_camper123 wrote: »

I kind of just threw the heart rate "zones" out the window, and started going by how I feel.

Me too. Even when I was in the best shape of my life, regularly running/ weight lifting, extremely active and athletic, I have always had a high-ish resting heart rate (60-65 bpm). And I was able to get my heart rate during cardio exercise to the theoretical max very easily, and still not feel knackered. My ticker just seems to tick quickly.

My husband, on the other hand, is also extremely athletic, and his resting heart rate is in the low to mid 40s. He has to full-out sprint for many minutes (which he does during his athletic games) to get to his theoretical max heart rate.

So, anecdata says that this is a pretty individual thing. But I'm not an exercise scientist...