Something that actually exists. After strenuous exercise endorphines are released creating a "high" feeling. Its not the same as a marijuana type high. Its more of a lightheaded feeling and you cant feel your body alowwing you to run even further. You wont get it if you run 5 minutes. Most feel the effect after 30-40 minutes of hard running.
Joe: Dude runner's high doesnt exist.
Bob: Thats because you only run a lap then give up you fucking pussy.
The time right before a race that your nerves outweigh your anticipation. No matter what, you have to race somewhere first to blast your load before they fire the gun.
Also, this applies to the general fruity, aromatic smell that wafts from the porto-s & alleys throughout the rest of the racing audience.
When running long distances, you all of a sudden feel an extreme urge to poop and if you don't get to a toilet fast, you're probably going to poop your pants...bad! Runner's trots usually are a precursor to some nasty diarrhea.
When finishing a run, usually that of distance, it is common for a runner to cough. This may be due to a dry throat and dehydration. Gets it's name from "Smoker's cough" although they aren't usually related.