We moved from 7500 ft elevation in New Mexico to 800 ft in Kentucky. Along the way, I quit trail running. Next week I start 10 hour works days at Amazon. I need stamina. Just did Week 1, Day 1. Tomorrow I'll do it again and hope I can finish it.
I'm a believer in the barefoot running technique, which has you land on your forefoot. Of course, this is somewhat difficult to do with most shoes that have an elevated heel. It's much easier with a zero drop (flat) shoe. If you can find a place to run barefoot on a smooth concrete or tile surface, you will soon find out how much force is generated through heel striking, and you will naturally start running with a forefoot strike. This technique does use different muscles, and requires some transition time.