Trail running is considered any run that takes place on an unpaved path that is completed outside in nature. Ultrarunning is running a distance further than a marathon.
Women's Trail Running Shoes
What is Trail Running? - Ultra Running Magazine
What Makes Trail Running Shoes Different, Gear Guide
What Is Trail Running? Everything You Need To Know
Alpine Running Guides
The Beginner's Guide to Trail Running
5 Key Features to Look for When Choosing Trail Running Shoes - Run United
Best Trail Runs UK 2020
How to Start Trail Running: 10 Ways to Make the Most Out of Your Workout
Trail Running Shoes vs. Hiking Shoes, Running Gear Stories