I did a 4 mile trail run and it was hard the entire time. I went on a different trail than usual; it's part of the national park, so no roots or rock gardens. I just struggled, don't know what else to say, except I kept at it, took lots of walk breaks for about 10 seconds on the way out, which was a small uphill most of the way. Felt better on the way back, but still my leg were like lead.