Had a 15 miler planned for yesterday and since the weather was just beautiful, I decided to go out and hit the trails for a while.
Not sure if this is normal because it's been a while since I ran the trails, but it took me a couple miles to catch my breath. I struggled for the first couple miles before I really got into any kind of groove. Granted, in that first 2 miles is where I hit my largest hills, and at one point got lost but eventually found a spot I recognized.
Also, after 13 miles of mostly trails, my quads and calves felt pretty beat up. I finished up with a nice easy 2 miles running with the kids as they train for a 5K later this month.