Lately my favourite running spots have been in a conservation area close to where I live. I can run there from my house and the distance is less than 8k. It is a perfect run for me right now. And what I love about running in this place is that it is outside, not too crowded and the terrain makes for some pretty interesting challenges. It is amazing to me how running on uneven ground works your core. Did I mention the views were spectacular??
Regardless whether you run or walk the surface you choose makes a huge difference. Outside sidewalks are the hardest surface causing your body to absorb more of the impact when your foot hits the ground. Asphalt roads are slightly less impactful. Trails and 'natural' surfaces carry the least impact. Treadmills also absorb a great deal of the impact from your foot stroke compared to paved surfaces. If I have a choice of where I will run, inside or out, I will always try to choose outdoors. Not only is it better for you mentally and emotionally to be outside, the way your body moves running on the ground is much different than a treadmill.
When you run on the treadmill, you are keeping up with the speed the belt is moving at. Your hip flexors work pretty hard to power your legs through this repetitive movements. Compare that type of work to either running or walking outside, the ground beneath you is not moving, you are. In outside running, you are propelling yourself forward using the muscles in the back of your legs. This movement targets your glutes, hamstrings and calves more than your hip flexors. This isn't to say your hip flexors won't get tight while running outside, just not as tight compared to strictly treadmill running. When you add in uneven terrain and rises in elevation, you add an additional core component to your run or walk.
That being said, there are times when running on a treadmill is better than not running at all. But during those workouts it is important to pay extra attention to stretching those hip flexors, increasing the treadmill's incline to 1.0 and adding a couple sets of squats to the end of your workout to balance the work done by the front of your legs. I know in the winter I will be back on my treadmill a bit more and posting some indoor workouts but for now I'm hitting the trail!