Red Blood Cells
water bottle belts and hydration packs when someone is doing a 5k.
people that see you coming towards them on the sidewalk and don't move an inch.
Drivers that make right turns without checking their right first.
Vibram five fingers.
The "have you done a marathon" or "whats your fastest mile" questions.
Ridiculous port-o-potty lines at races.
Being handed the chocolate flavored Gu at mile 20.