Hill workout. 3 miles to the bottom of the hill feeling fine. Then a quick 2min tempo just to get the legs moving and heart pumping. Apparently, I get my heart pumping too much as I felt pretty worked after just 1 quarter-mile hill. The next one felt the same as well as the final 2. Arms felt tired and I was just huffing and puffing the whole way (legs seemed fine but didn't really do enough to work them).
I started for home but had 1 more hill in the way that I thought I'd go for but gave up after just a few steps. My heart rate was through the roof and even stopping hardly helped. The "cool-down" was slow.
Not sure what triggered the struggle, might need to be more careful with my workload while summer winds down.