The Barinatxe (La Salvaje) beach in Sopela (Vizcaya) will host the 20th of July of 2014 at 10:30AM the most famous Nudist sport event being held in Spain: the XIV edition of the Nudist Run of Sopela, Patxi Ros Trophy.
They expect the attendance of a large number of participants, not just for running, but also for having a good time. Over the past years, there were runners from Spain, France, Germany and the UK.
More info in NudeInSpain:
http://nudeinspain.com/blog/nudist-events/nudist-run-sopela-2014
