PAMPLONA // For your average daredevil, risking your life once at Spain's San Fermin festival is enough. Then there are the veterans, who return year after year to run with the bulls, unable to kick their fix.
The tradition immortalised by Ernest Hemingway in The Sun Also Rises is the ultimate rush for this small club of regulars, who prepare obsessively for the electrifying and sometimes shocking dash through Pamplona's old quarter, held every year in the second week of July.
Juan Pedro Lecuana, 38, a father of four who has been coming back every year since 1989, said: "First you're hooked by the tradition, then it gets you as a fan and, finally, you get to the point where it's an extreme addiction, where you need to be running with the bulls."
At 8am from July 7 to 14, six half-ton fighting bulls are freed from a corral to rumble after thousands of runners down a fenced route of about 800 metres, ending up in a bullring where they will face matadors and certain death by afternoon.
Most runners dash through the cobblestone streets for about 50 metres before jumping out to safety behind the barriers.
For the humans, any slip-up could signal death, so preparing properly for an event that combines elements of hurdles and rugby scrum can never be taken lightly - a lesson taken to heart by the veterans but often ignored by tourists.
Fifteen people have been killed since records started in 1924, with Daniel Jimeno Romero the last in 2009.
Rick Musica, from the US, has missed only four runs over 13 years. He watches hundreds of videos throughout the year to gain better insight into surviving the obstacle course. "On one hand, you have this sheer exhilaration and on the other, sheer utter terror ... balancing those emotions is the key ... it's not always easy. Actually, it's never easy," Mr Musica, 45, said.
"To see these magical beasts thumping through the narrow streets is something that defies logic and something that is unlike anything I have ever done in my life. It is truly a celebration of life."
The do's and don'ts for the two to three-minute dash are simple: don't yell at the animals, carry a rolled-up newspaper for a handy distraction and, most importantly, if you fall, don't get up.
The American runner Matthew Tassio, 22, did just that in 1995 and was immediately killed after being charged.
Being physically fit is important, and veteran runners fine tune through various physical activities, from running to swimming in the month leading up to San Fermin.
Cesar Cruchaga, the former captain of the Osasuna football club in Spain's first division, was able only recently to return to running after ending his professional career. His first run was at age 15.
"It's a very different feeling to scoring any goal … so intense it beats any game of football I played," said Mr Cruchaga, who was born in Pamplona.
"That sensation that death is so near - there is nothing comparable to that."