Time was of the essence, so after picking up 'Z' from cross country (his first hard run in a while with so much soccer), I got home and hit the the 'cross at school next door (not my school). It's a bitch of a course with a bit of flat on top, a middle portion with a stair-step descent, a divebomb descent down to the creek, a rooty trail across the backside leading up to another grassy run. From there it's uphill time before a run-up with stairs and then back around school while gasping.
I used the HRM again. Once I saw low 170s while I was about to lose my stomach through my nose, I figured I should probably slow down. I used that general benchmark the rest of the way, putting in (most of) a 'hot lap' until I approached the upper-160's and slowed down until I settled down into a more normal pace. Two more observations: