after setting a personal best on firday i took a few days rest due to an injury in my knee, when i started running again on wednesday i had to stop because of a strained feeling in my shins. similar to the feeling you get in your thighs after standing in a squat position for a while, when i ran again today the same thing occured. this has never happened before, and i have the correct shoes, does anyone know why this might happen, and how to prevent it?