I have a situation/question for you gals..

My HR is consistently high on the bike. I stopped using the strap with my PowerTap b/c I never saw changes (lowering) while training over months. I got stronger and faster, but my hr didn't go down. This first ride I did with my Garmin yesterday, I wore the HR strap. Big surprise, my HR is still high. It said my average was in zone 4-5 (aerobic/anaerobic) for most all the ride.
I was doing some reading today about calorie consumption calculations, but stumbled upon HR zone training. Now I know maybe some people just naturally exercise at a higher HR, but maybe that combined with our heat here (getting to triple digits) is taking more out of me than it should. Am I training (riding) too hard? I needed to do yardwork today, but I really didn't feel consumed by a desire to ride after yesterday's excursion (4hrs, nearly60miles, >2K climbing, 94+ by ride's end). In fact, I was watching the Tour this morning and fought it hard not to sleep through most of it. I had to MAKE myself get up and go mow the yard. Felt so tired...

I'm 38 (nearly 39) and am starting to feel hormone changes (for you ladies who know what I'm talking about). Is there more to this HR zone training stuff, or do I just need to take it easier? I can hop on the bike and I'm already at 105.

Then again - - -Maybe I just needed a lazy Sunday?