25-minute (I'm not sure how long the loop is, maybe 2.5 miles) barefoot neighborhood run today after a thunderstorm blew through. Not that hot here today, but humid. I decided to wear my heart rate monitor today which I hadn't done in a while. After the first ten minutes of the run, I had a hard time keeping my heart rate out of the 180s and 190s without slowing down to a walk (which I did do on the hill that always kicks my butt). Not sure why it still tends to go so high when I've been running for as long as I have. It drops pretty quickly during the first minute after I stop, and resting it's in the low to mid 50s, so it's not like I'm out of shape. So why does it shoot sky-high while running?