This past week, my cousin Jenny and I have been doing some great LSD in Yellowstone and Grand Teton National Parks. There are gazillions of trails right outside our government cabin door...it is very fun and a new adventure happens every day. We noticed that we feel more tired and sluggish at higher altitudes even when maintaining the same paces. We went from 8,000 to 5500 yesterday and I felt speedy and "turbo" at the lower elevation. It's pretty fun to just start running on some random trail, not knowing if it will lead to the boiling geothermal, turquoise-colored, hot stream or if we will run into a bear or even a grumpy old man on his cabin porch....(quickly leave if you encounter the last two items). Anyway somehow I still enjoy running. Like Bill said, Keep it a game, not a job!