Just got back from a run on a section of trail I had not been on before. The many road crossings got me to thinking.
I hate running on pavement. It just hurts. But the trails are just as hard sometimes.
What makes the difference?
My theory is the lack of friction on the trail allows more give. The sticky shoe to road grip jars to body and doesnt allow for as much give and absorption.
What are your thoughts?

Related topic. Was talking to some AT through hikers the other day. They were rattling off the friends who had gotten hurt on the road sections. Knees, ankles, trips, bruises, stress fractures. They were saying that the PA trail is better than the road sections, even with all of its rocks and ruts. For those not initiated, PA is notorious for it's rugged trail conditions. Notably the rocks. Hikers have been known to go through a pair of boots in PA alone.

Just got back from a run on a section of trail I had not been on before. The many road crossings got me to thinking.
I hate running on pavement. It just hurts. But the trails are just as hard sometimes What makes the difference?

Me too. I agree whole-heartedly, and I have put a lot of thought into this.

My theory is the lack of friction on the trail allows more give. The sticky shoe to road grip jars to body and doesnt allow for as much give and absorption.

Yes even when that motion is not perpendicular to the surface.

What are your thoughts?

At least as important is that level surfaces result in repetitive motion wearing joints etc in the exact same places. All it takes is a few degrees of ankle rotation in any direction to change internal "contact areas.

the PA trail is better than the road sections, even with all of its rocks and ruts. For those not initiated, PA is notorious for it's rugged trail conditions. Notably the rocks.

Lots better. Rocky surfaces mean relatively non-repetitive motion even thought he surface is hard. The instability of rock forces you to run "lightly" too. I think this is why Tico insisted that running before was great training. That reduces joint damage too. I am very sensitive to running on pavement, and I recently came to realize that even an outdoor rubber track doesn't help me nearly as much as I expected.

What are your thoughts?

At least as important is that level surfaces result in repetitive motion wearing joints etc in the exact same places. All it takes is a few degrees of ankle rotation in any direction to change internal "contact areas.

Amen. This makes all the difference in the world. Got some nasty IT band issues from running a marathon yearsd back. Now, all trails, all the time.

Lots better. Rocky surfaces mean relatively non-repetitive motion even thought he surface is hard. The instability of rock forces you to run "lightly" too. I think this is why Tico insisted that running before was great training. That reduces joint damage too. I am very sensitive to running on pavement, and I recently came to realize that even an outdoor rubber track doesn't help me nearly as much as I expected.

Ooops, it's a little late now but that should have read "I think this is why Tico insisted that running barefoot was great training. "

Guess my spell checker got me.

Running during and after is also good, if you have the time.