I recently got a question about training at altitude from one of my athletes. I hit up Google Scholar for the latest scientific thinking on the subject and found little support for any type of altitude training having benefits when returning to sea level. The doctrine of "living high and training low", for example living and resting at 2500m (~8000ft) and training at 1250m (~4000ft), has only limited support. Not forgetting the fact that it is highly impractical for your average age-grouper vacationing in the Sierras to be driving down the mountain each day to go train.
If you want to read more the well regarded British Journal of Sports Medicine presents a particularly scathing review of the research for ignoring the possible negative effects of altitude training. Also a fun article about training at altitude having more to do with the power of association that any physical benefits.
Keeping hydrated (low humidity and increased breathing rate) and being prepared to train at a lower intensity (low availability of oxygen) as at sea level are considerations when going on high altitude vacations. A final very important consideration is that training at altitude in the summer time more often than not means cycling through mountains, swimming in warm lakes and running through forest trails. A very motivating training environment that fuel a love for your sport which is far more important than small percentage increases to VO2.
The above picture and map from a great little ride I recently took in the Lake Tahoe region in California, U.S.A.
