In my best Seinfeld voice, "What's up with aging?!"
I don't know if it's because: 1) my body isn't used to running a lot of miles anymore, 2) I ran for too many years with terrible form, 3) my running shoes are worn out, or 4) I'm just getting older, but during my 4.75 mile run last night my feet, knees and hips were all protesting.
I'm not even 30 yet.
I'm going with options 1-3. I'm sure that's it.