The number one reason trail running is better than running on pavement is impact. Impact on your feet, knees, ankles, hips etc. Pavement is a very unforgiving surface, while a dirt trail has a little more give. Trail running also can be more scenic and more challenging.
I wouldn’t classify my knees as “bad” but I definitely notice a difference from running on pavement and running on a trail. When you run on pavement you are putting a lot of hard pressure on all your joints and muscles, every time you put a foot down. When running on a trail, not only is the impact softer but you are strengthening and engaging muscles that you might not be using on the road. You have to pay attention to where you are placing each foot. There could be roots, rocks, stumps or any other kind of surprises from animals to bikers. When I run on a trail, I sync my steps to whatever obstacle is coming up next. I like to use a little extra umph to get up and over that tree root, which in turn strengthens the muscles needed for that extra push.
Trail running is also great for your mental health. It is nice to get away from your bad day at work and just take in the view and enjoy the sounds of nature. It can be very relaxing to let your body find its own rhythm to match the elevation changes. When I run on a trail I don’t usually bring headphones. I find that I don’t need them, and instead I listen to the sounds around me. I love when I am running through the woods and I can hear a stream coming up (especially for my dog so she can get a drink), or when I’ve been running up hill for what seems like forever and I turn around to see a beautiful view.
Where I live in Colorado there are lots of trails to choose from. But if you live in a more urban area and trail options are minimal, you could try to find some other soft surfaces, like a sandy beach, dirt road or grass.
And hey, you might just get lost out there on the trail, but that is just part of the fun. (As long as you kind of know your way back, or at least the direction you need to go in). As always make sure you bring enough water and watch the weather, but mostly just have fun!
To read more, visit these two articles from Runners World where I referenced some of my ideas: