Lately I have had a sharp pain in each foot when landing on it. It tends to go away throughout the run but even today I noticed it just walking around at work (it went away after about 5 minutes of walking). Also, during my run today it sounded like I was stomping my feet when I was running. I got about 400 miles on my shoes but is it necessarily my shoes are to old? The reason I ask is I'm a high school runner with little money so if its not the shoes I will just keep wearing them. Or what signs you noticed when your shoes get to old? I just want to get the most out of my shoes thanks.