If you haven't followed any of my threads recently, I've been losing weight, getting back into shape, and training to do a super-marathon canoe race (which I've done before, but I really want to do better). I'm getting back into decent shape, doing regular aerobic exercise, and trying to figure out where to best concentrate. I'm kinda concerned about my heart rate - basically, when I use the machines and really push myself, they practically say "stop because you're about to die". I am fairly fit for super-endurance racing. I could hop on a bike tomorrow and go a hundred miles and barely feel it the next day. But at that pace (you know, I'll get on a machine in the gym and do a five hour run to get a scientifical analysis of this) my heart rate is about 155 bpm and I'm taking 16.5 breaths a minute. I can do an hour on an elliptical with pretty much identical metrics. If I push myself to a high rate that I can only sustain for a few minutes, my heart rate will go as high as 190. Nothing hurts, I have no angina (kekeke), my pulse is rock solid - no fluttering, and I'm not shaky or passing out. It just seems that it's a really high rate in the grand scheme of things. Any input?