Racing at altitude
Racing at altitude is profoundly different from racing at sea level, especially for those not fully acclimatized. Because of the lower oxygen content per breath, muscles receive less oxygen per breath, reducing their power output.
According to Carmichael Training Systems, riders tend to have a 10% decline in their lactate threshold at 8,000 feet compared to sea level and a 20-30% decline at elevations around 12,000 feet, the elevation of Columbine Mine.
High altitude racing also makes it difficult to recover from hard efforts, such as those required to get over a steep section of a hill. Efforts that generally take only a handful of seconds to recover from at sea level can have minute-long recoveries at high altitudes.
Thus, the most efficient way to ride at altitude is to keep effort levels steady and to try not to cross over the lactate threshold line whenever possible.