They sure do. But harder surfaces aren’t always worse. Our bodies adapt to surfaces over time and will adjust to the hardness or softness. If you are used to running on asphalt then your body will be adapted to asphalt. When you change surfaces, such as to a softer trail, your leg and foot muscles will have to work harder to adapt to that surface. This can put you at risk for injury.
Many of the runners where I live enjoy running on the Towpath Metro Park Trails, especially for their long runs. This is a recipe for disaster. Why? Because theses trails have a soft surface made of fine limestone which is very unstable and causes the foot and leg to work harder, especially during foot strike.
I have seen many achilles tendon injuries in patients as a result of running there. I’m not saying that running the Towpath trails are bad, but if your body is used to running on asphalt for your training runs of 3-5 miles, and then you run 15-20 miles on the towpath for a long run, it can lead to injury
Running in snow can also create the same types of injuries. One of my running partners routinely develops an achilles tendonitis when we run in the snow because he changes his gait to prevent slipping on the snowy surface. This activates the achilles tendon more so than it is used to.
One final thought. Many people say that concrete is harder then asphalt, so it’s safer to run on concrete. If I made a hammer out of each material and asked which would you rather be hit with over the head with – the asphalt hammer or the concrete hammer? They both would feel the same right? My point exactly. They’re both hard. What can be different though is the smoothness of the surface. A slicker surface can change your gait.
All things to think about!! Enjoy your running!