My wakeup heart rate is down

Today is a rest day, but I checked my wakeup heart rate to see which way it is going. It was 54, down 4 points from yesterday. Two days ago I only had 4.5 hours of sleep, and I've been expecting my HR to go up. However, it was down yesterday even though I only had the 4.5 hours of sleep the night before plus an hour in two naps later in the day (after my running). It is common to have a delay between a night of insufficient sleep and a rise in my HR. Last night I had a good 7 hours sleep, and that probably accounts for the drop in my HR this morning. Sufficient sleep is critical to ones performance as an athlete and to good health for everyone.