high pain and tightness in lower quadriceps

recently Ive had extreme tightness in the lower portion of both of my quadriceps, this tightness is coupled with a feeling of weakness and pain. I am a competitive runner and run about 80 miles or so a week. I took about a week off from all exercise, but it does not seem like they are improving any. I cant point to an exact time when the pain started, but it came and peaked out in about 2-3 days and has been pretty steady since. The worst of the pain comes when my quadriceps get so tight that they cramp up and ache pretty bad. thanks for all the help in advance =)