And then you’re at sea level. Almost 8 years in Arizona has acclamated me to a higher elevation. In Phoenix, 2 miles is a good run for me. The 2 mile distance around Fremont’s Lake Elizabeth barely prompted a sweat. This also included dodging nasty geese and their nasty poop, groups of people doing Tai Chi, and other people on the trail. I even tried to do lunges and felt superhuman for the lack of pain and resistance.
It was awesome! On one hand, it feels good to feel in shape. One the other, my workouts this weekend were less than strenuous.
So, if you want encouragement, try a lower elevation. If you want to stay strong, keep training at a high one.