... in purple lycra... Hey, at least he's keeping fit. It beats bawling under a paper bag, and - let's face it - there's worse things he could be doing in Amsterdam...

I'd no idea what a 'metamarathon' was either, but from what we can deduce without employing Lord Google is that it involves kind of a unified relay / gives people (mainly women, by the looks of things) the chance to run with a 'genius' in purple spandex.
 

And where would you be without a POV lap. Fair play to her for not snotting herself.