I'm A 68 Year Old Male In Pretty Good Shape.

I'm a 68 year old male in pretty good shape. I do my 10,000 steps or more daily and my last physical was the best I have ever had. My question is this. I have been shoveling snow for the past two days do to the storm on the east coast (NJ). After I complete shoveling and come inside my heart rate is about 110. The problem is I have a headache. After sitting or resting for a while my heart rate goes back to normal and the headache goes away.