For a variety of reasons, I ran my usual distance running pace today, so I did the 1.3 miles in a little under 13 minutes.
My knee twinged the whole time, but it also felt noticeably better at the end than at the beginning.
One of the reasons I ran slowly was because I had a meeting at 8 and didn't have time for a long cooldown run, so I had to not run fast enough to need a long cooldown to fend off a post-run crash.
Speaking of which, I googled post-run crashes quickly yesterday when I was writing my update, and I found "postural hypotension." Apparently your blood pools in your legs, and while your heart rate is high, that's fine because it's working hard enough to pump blood into your brain. If your heart rate drops while your blood is still pooled--boom!--dizziness and nausea, risk of fainting. That's why a cooldown run helps: it keeps your heart pumping at a rate that can get blood to your brain while your blood distribution slowly equalizes across your body.
This makes so much sense! It feels exactly like the postural hypotension I've had since about age 10. The number of times I have either fainted, greyed out and had to sit or lie down quickly, or just felt alarmingly and miserably like I was going to faint or grey out, are beyond what I can count. Dozens, and maybe hundreds. It was bad enough that I had my doctor investigate at one point. She found nothing wrong, said it was benign, and I should just be careful and avoid my triggers. Of which apparently running is one, as it is for many runners.
So I guess a good cooldown run is, in fact, the way to go, as well as maybe investigating sports drinks (and better hydration in general) for longer runs.
landofnowhere, this is presumably why you're able to end your runs at home: you're not getting your heart rate up to a point where you need an additional 15-20 minutes of gradual renormalization of blood pressure just to not pass out.