I have noticed a strange phenomenon recently -- my heart rate seems to take longer to go back down after max intensity, and it seems to run up to max more quickly. I am relatively new to cycling (been riding for 11 months) and am an otherwise very fit 48 year old male, 6'1" and 168 lbs. Resting heartrate is 36 bpm, I max at 173, my delta is about 20 bpm.
I noticed this change in recovery rate after riding a metric century about a month ago. The ride was moderately hilly, I rode it on my old 28 lb steel framed bike instead of my 5200, and I had no water on my bike. The last 20 mile section I got fairly dehydrated, drank others' water.
Now when I ride steep hills, my heartrate goes up to the high 160s, but seems to take longer than before to slip back down. I noticed it yesterday, for example -- did a steep climb that was followed by an immediate descent, at the bottom of the descent (about 30 seconds, I'd guess), I was still in the low 150s. I do ultimately slow back down, but I would think that I'd be getting improved recovery, not deteriorating recovery.
Is this a recognized phenomenon that others have experienced?