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Why Does It Take So Long To Climb Everest?

Text & Photos: Zeb Blais

mt everest“My heart pounded in my chest, overpowering the music blaring through my headphones.  I was skipping between large granite boulders, ascending a ridge line 3,000′ above Everest Base Camp.  I wasn’t scared.  I wasn’t moving fast.  At sea level, my heart wouldn’t have bothered itself to increase more than a few beats per minute.  At 6,000 meters (20,000′) on my first high hike above camp, it was a different story.  I could feel the thin air slowing me down and taxing my body.  If moving at 6,000 meters is this difficult, how can I expect to ascend Mount Everest’s 8,848 meters?

By scrambling up to 6,000 meters, I was forcing my body to adapt to the environmental stresses it will encounter in the days to come on this expedition.  Moving up in altitude begins a physiological process called acclimatization that helps the human body adapt to the lack of oxygen at high elevation.  The process is not fully understood, and most acclimatization schedules are based on decades of trial and error of climbing at extreme altitudes.  

It is generally accepted that acclimatization is based primarily on genetic makeup.  This means that everyone acclimatizes at different rates based on their genes.  When we subject our bodies to altitude for prolonged periods of time, we “switch on” certain genes to stimulate the production of more red blood cells.  This increase in red blood cells allows climbers to transport oxygen much more efficiently in hypoxic environments like extreme altitudes.

We force this process by doing rotations at altitude, climbing high and sleeping low.  Climbing high stresses the body and causes it to start the acclimatization process, but it takes a toll on the body.  Without the oxygen it normally has at lower elevations, the body is much slower to recover.  This means that climbers must take care to get proper rest and make sure they are recovering fully.  Sleeping low in a relatively oxygen rich environment is essential for this recovery to happen.  If a climber pushes too high too fast or too hard, it can lead to severe altitude sickness such as High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE). 

mount everestThe higher the peak, the more efficient our bodies must be at using oxygen, so the more we must acclimatize.  The highest mountains in the world are over 8,000 meters (26,400′) and the air is so thin (low in pressure), it takes weeks for our bodies to even be able to survive at the altitudes where we camp. Everyone has a slightly different philosophy to acclimatization.  Some believe that more time up high is better to expose their body to more time at altitude.  Others believe that this taxes the body too much and that it is more important to spend time low to rest and recover. A lot of this has to do with the climber’s personal physiology and they must listen to their body and remain flexible with their acclimatization schedule to ensure that they are adjusting and not wearing themselves out.  Guide services choose acclimatization schedules that work for the vast majority of people, so they are typically more conservative and slower.

In addition to these lengthy acclimatization schedules, commercial 8,000 meter expeditions use supplemental oxygen to help climbers reach the summit.  This allows climbers to have less acclimatization, to move faster and stay warmer on summit day.  Usually everyone on a commercially guided trip, including guides, Sherpa and clients, uses supplemental oxygen “Os” during the summit push.  Depending on the company, climbers and guides will start using Os as low as 7,000 meters.  Usually climbers use oxygen 24 hours a day while on their 4-day summit push above ABC.  They sleep on a low flow rate and climb on a higher flow rate, typically .5-1L per min and 2-4L per min, respectively.  Sherpa and Tibetans are genetically superior at altitude.  Their bodies have evolved over generations to process oxygen more efficiently and they typically climb on a much lower flow rate to allow them to carry less oxygen tanks during the summit push.  This also means they have to stock the camps with fewer bottles before the summit push.

Typically, teams spend between 60 to 75 days on a Mount Everest summit expedition.  This is the total length of the expedition and includes weeks of acclimatization rotations.  On the south side of Everest, teams usually fly into the Khumbu at 9,500′ and make their way to Everest Base Camp at 17,300′ over the course of two weeks.

Alpenglow Expeditions guides Mount Everest in an unconventional way.  Our total expedition length is 45 days, using what we call Rapid Ascent.  With this style, climbers “pre-acclimatize” at home by spending 8 hours a day in a hypoxic environment for weeks in advance of the trip to stimulate a physiological response to simulated altitude.  Usually our clients and guides achieve this by sleeping in a “Hypoxico” tent.  This doesn’t allow climbers to go straight up the mountain, but it does cut weeks of acclimatization off the trip by allowing team members to arrive directly at 17,200′ Base Camp instead of trekking for weeks to feel comfortable living at that altitude.  

mount everestDoes Rapid Ascent work?  So far, in our experience, the answer is yes.  Critics argue that it doesn’t work or that it changes the nature of the expedition, but we have found that it does work.  Climbers who use the “Hypoxico” system as intended, with the assistance of our doctor, are able to arrive at Base Camp and feel similar to someone who acclimatized by slowly trekking in. I’ve had three successful Rapid Ascent expeditions: Aconcagua 2016, Everest 2016 and Cho Oyu 2016.  

And yes, Rapid Ascent does change the nature of the expedition.  It removes the trekking portion of the expedition, which has pros and cons.  Many climbers feel that trekking in the Khumbu is an inextricable part of the experience.  That’s valid..  I admit that I love trekking in the Khumbu.  It’s a beautiful way to experience Sherpa culture and explore some of the most amazing peaks of the Himalaya and it means that you don’t have to sleep in a hypoxic tent.  But 75 days is a long time to spend at elevation and away from home (especially in the peak of ski mountaineering season).  Last year, conducting a shorter expedition helped keep our team strong and motivated on Everest and Cho Oyu.  Less time at altitude and less exposure to germs from trekkers and other climbers helps avoid sickness.  We had no viral sicknesses on either of those expeditions, which is huge for summit success.  Personally, I love being able to be at home, spend time with friends and tackle ski mountaineering objectives I would otherwise be hard pressed to attempt.  Last year I was able to ski the Ford-Stettner Route on the Grand Teton and this year I skied the Giant Steps Couloir on Mount Williamson while most Everest climbers were trekking in the Khumbu – can’t complain about that!

The bottom line is acclimatization is hard to understand and, therefore, hard to perfect.  Most guides and serious climbers are constantly tweaking acclimatization schedules and discussing the advantages and disadvantages of their strategy.  Knowing what’s best means learning how to listen to your body and takes years of experience and experimentation.” 

mount everest sunsetFor more information on our Mount Everest North Side Rapid Ascent expedition and other international expeditions check out our website and for any questions call the office at 877-873-5376 or send an email to