Lot’s of questions regarding training at sea level and racing at altitude:

Regarding sea level training and doing the Ironman Lake Tahoe, there is generally a window of 3 to 11 days upon arrival at altitude, where you will experience the following symptoms:

* higher breathing rate (approx. 8 to 12 %)

*longer recovery prior as noted by your heart rate and breathing rate when you elevate your intensity up to threshold pace

*since there are not there are not that many oxygen molecules available the feeling of heavy legs and heavy arms can come on if the intensity is too high

With that said, the advantage of doing an Ironman race as opposed to doing an Olympic distance race is that the intensity is much lower, there fore you can monitor your breathing and heart rate to maintain your aerobic pace or slightly higher, which should not be a problem at altitude.  Again this is a real plus, in that all the climbs on the bike during the Lake Tahoe race should start off slightly easier at the outset and once you feel your breathing and heart rates level off then you are good to go and maintain that pace until you reach the top of the hill.  Due to the heavy legs syndrome, you always want to stay in a slightly lower gear either seated on standing on the more difficult sections of the bike and certainly the climbs.  The outset of the swim, particularly the first 400 meters. you’ll have to start off slightly slower then your sea level pace.  Again, once you’ve established a steady state you should be fine for the remainder of the swim.  The run during Ironman Lake Tahoe, on the flat sections will be in your aerobic zone, however on any climb your heart rate again will rise at a much faster rate then at sea level.  Lastly, in Lake Tahoe the extra load on your system is about 6.5%, more difficult then a t sea level.  This translates into 3 to 4 seconds longer for every minute of exercise.  Or if you look at it an 8 minute mile at sea level translates into a 8.24 to 8.32 mile at altitude.

Good luck with your training!