Strange...I do 6-8 mile runs 3 times a week, so I'm by no means a high-mileage runner. I find that I get a high around on around 1/4 of my runs, usually around

Strange...I do 6-8 mile runs 3 times a week, so I'm by no means a high-mileage runner. I find that I get a high around on around 1/4 of my runs, usually around the 4-5 mile mark. It starts out with a cool rush of euphoria felt in the head and behind the eyes, which quickly spreads to the extremities and blankets any perpetual pain/discomfort, replacing it with a weightlessness, like every tendon and muscle in your body has been renewed. It's a pure, cool, iron-like high that allows me to cut 30-60 seconds off the next 1-2 miles once it kicks in. I don't think it's a distance thing - it's more of a pushing yourself to the point where your brain feels the need to intervene. I expect that if I had a disciplined training schedule and ran long distances regularly, my brain would get used to the idea of running and stop getting me high. I also lift weights 3 times a week, but I never experience a high while deadlifting, bench pressing, running sleds, etc. I'm fairly certain it has to be biking/running where you have no rest in between sets in order for your brain to flip out and turn on whatever chemical switch it is that produces the effect.