does anyone have any advice on how to prevent pain when running. i stretch, warmup and keep my running to four days per week alternating low impact activities the rest, yet lately one of my knees starts hurting about the last mile or so of my run and lasts for the quite a few hours after that. hurts like the dentist, maybe worse. its never done this and i havent injured it or anything so i fear since i recently hit 25 maybe it's just old age kickin me in the face <img alt="" class="inlineimg" src="/images/smilies/smiley.gif" style="border:0px solid;" title=""> hope not tho since i know quite a few 50+ folks that have been running all of their live long days. thx.