I have a pretty basic HRM so I can only give you a rough idea. The highest I remember seeing it go was 183. I was doing a tough climb and was breathing hard and really felt my heart pounding in my chest. So I imagine that's a little higher than I want it to go on a regular basis.

Usually, I'm around 160-165 and then going up into the 170's on the hills. I can't say that I've seen a change in how high I can get my heart rate. It's more that, as I train, I can keep it at a training level for a longer period of time and I recover more quickly when I'm done.