I've recently purchased a chest-strap-type HRM and have had some fun logging my various activities

my average HR during sleep is 51
my average HR during work (sitting in a chair) is 65ish

so I assume that the average of the two is my natural rest rate


now, my question is.. when I come in to work after a spirited 30min bicycle ride (where I average 145 bmp), my heart rate drops to 90-ish within 5 minutes or so. However it takes it about 2-2.5 hours to get from 90 to 65... and it tends to just hang in the 85-90 zone for quite some time (maybe an hour straight)

i'm just learning about this stuff, so is this two step heart recovery normal? I guess the body "calms down" but still thinks it's about to do more work for the two hours after I got off the bike until it finally figures out that I'm not going anywere?