I have several options for single tracking real close to my home. Today, I chose one about three miles away which eventually follows a pretty steep power line trail. I had not done this for a couple of years, and each time in the past, I had struggled with the steep hill, while dodging rocks and staying on the narrow trail, arriving finally at the top pretty tired. Today, I went up so easily, with lots of energy and reaching the top without even breathing hard.
Perhaps losing 20 pounds the last year has helped
Anyone who thinks single-tracking doesn't keep the mind active and stress the brain has never really done it IMHO. I love it!