Sam Mangum called in after the team took a rest day at Camp 2, letting their bodies further acclimatize to the thin air of the upper reaches of Aconcagua.  At 18,000′, there is one half of the oxygen in any given volume of air as there is as sea level.  Our bodies need oxygen to create energy to do work, and when each breath has only half as much O2, everything is harder!

They went for a hike partway up to High Camp today, as moving around and partaking in gentle exercise can help you acclimate better than just lounging in your tent, due to the increased respiration rate that results from hiking at altitude.  They are eager to move up to their next camp, because that means the summit is just a few thousand feet away!

Here is Sam:

An Overview of their route up the mountain.