Why does my HR go up, why does run form go bad for so many?

BIKE indoors 60 mins, 16 miles?
RUN outdoors! 31 mins and 2.8 total. Ran 16-17 mins and 1.8 miles
BIKE COMMUTE 3.5 miles

I made a point to get to bed earlier last night, to help recover from Sunday. I woke up feeling good and kept to schedule. Yesterday Bob and I planned to ride in TGP this morning, but he had a family emergency so it was just me. The sun was up but it was chilly, so I stayed indoors. WU then 8' pushed intervals with 2' rest, until 1 hour.

The run felt good, I left the Blerch behind so no pod or music. Just the breeze, my foot falls, my rambling mind. Felt great, extended out again to 3-4 min run intervals. No major pains or issues. My feet and ankles seem to have good and bad days as they adapt to running and they new form. Today, not so bad. But I really gotta buy new shoes.

Lab for a short hour, then out to PT. No "warm up" like we normally do, jumped right into the yoga ball. Some of that, then up to the single leg squats. Last week he pushed me lower so that my unweighted leg shin bone was near parallel to the floor. In that low of a crouch, the left hip flexors struggled and squawked. Today all the more, in fact, I had trouble pushing to stand back up! Had to abort a few of the squats. It was fatigue, but also some guarding I think. It hurt to push them, but I think I could have done it fine with just a few more grams of confidence that I wouldn't do damage. This was left side only, right side just fine. We discussed maybe changing my schedule to NOT brick before these sessions. I'm both ways about it, I like finding that fatigue threshold.

I asked a few questions. And as I love, he had answers.

Why, if I'm running with a better form, does my HR go up? Because I'm using upper back and arm muscles now (that's definitely new for me) so I'm recruiting more muscles and that requires higher demand of cardio vascular system.

My form falls apart around 3.5 mins. (This was less a question). I need to stop sooner, not later. I was pushing just 15 seconds more. Nope Nope. STOP at 2.5 mins before the form falls apart.

Whether or not running is considered "natural" for humans, why do so many runners end up with bad form? Long answer that I'll do no justice for here, but in short because they don't realize it's going wrong, the cardio vascular fitness can cover for it, and it's just a blind spot that degrades over time. Yup, that's me.

Other things today: JH's prev client bumped the truck in the parking lot and came back inside with her info. How'd she know it was my truck? The tattoo, the bike, the stickers :)  Minor damage, unlikely to follow up with insurance.

Much better energy today. Was it just post-ride fatigue yesterday? Find out tomorrow, will I swim?

haha, Will It Swim?