was v interested to read the piece in the latest Fellrunner and it got me to thinking about taking a two week holiday next year in the Pyrenees, with the aim of taking in three races if possible: The Nuria, the Dent D'Orlu and Bonascre.

I'd obviously have to make sure I was in shape, but I was wondering whether there are likely to be any altitude effects at these races.

I've always worked on the belief that altitude only becomes a factor once you get above about 2,500m. Is this correct, or will you feel it before then if you're trying to run up a mountain? (I know some people get it worse than others, but as a rule ...)