I can comfortably run about 13-14 miles on a trail without any problems whatsoever. However, yesterday I ran on a paved surface, and after about 1 mile, I started feeling a lot of pain in my shins. I didn't want to exacerbate the problem, so I stopped at 2 miles.
Why am I experiencing such a big difference when running on pavement? About two months ago, I could run 5-6 on pavement without issue, but now it's just pain, pain, pain.