Here’s a great article on the effects of altitude, it’s well worth reading if you plan on racing or training at a higher elevation. Further into the article you’ll find some power data from cyclists and a few other interesting bits of information.
Full article on: http://www.sportsscientists.com/2010/06/altitude-arriving-and-adapting.html
There is not too much research on this question. That may be surprising, but remember that for most professional athletes, across all sports, the issue of when to arrive at altitude is one that they rarely even contemplate. In Europe, sport is rarely played at even these moderate altitudes. In the USA, it happens so infrequently as to be an inefficient way to investigate physiology. And for individual endurance athletes, like cyclists and runners, altitude training is part of the package, with a majority now spending time at some altitude before racing, even at sea-level.
However, a couple of approaches have emerged, most of them from Super Rugby (a competition involving professional teams from New Zealand, Australia and South Africa), and from the Tri-Nations, an international competition between SA, Australia and New Zealand. In these tournaments, the Australian and New Zealand teams will travel to South Africa and spend either two or three weeks here, during which time they would play one or two matches at altitude (1,500m or higher).
Read on at: http://www.sportsscientists.com/2010/06/altitude-arriving-and-adapting.html



