The Challenges without O2 – Part 1: Energy

I thought I’d give an overview of why climbing Everest without supplemental oxygen is particularly hard. Not to scare myself (I’m already scared!) or in a “Hey y’all, watch this!” attempt to impress, but rather to educate and inform, because personally I find this fascinating.

Most climbers on Everest use bottled oxygen for their summit bid, a ‘convention’ begun in the 1950s. In 1978, two of the best climbers in history, Austrians Reinhold Messner and Peter Habeler, were the first to summit without using supplemental O2, a feat many doctors at the time thought impossible.

Why ‘impossible’? There are many reasons, all of which are shared with climbing using bottled oxygen, but exacerbated. Primarily it is about human physiology.

The first key issue is energy availability. Every person has an energy generation threshold called V02max – the maximum rate you can absorb oxygen from the air and deliver it to your cells. Beyond this rate, activity can’t be sustained for a long period. V02Max can be increased with training but there is a genetic and adaptation ceiling for each person. You obviously can’t develop infinitely big lungs or a heart, and so there is a limit to how much oxygen your blood can carry even if you are fully acclimatized.

From this maximum energy availability your body needs some of it to run your brain, to use the muscles which expand and contract your lungs, and to beat your heart, among other life-critical functions. Usually this is a small part of the available amount, so you can use the rest for sprinting, cycling uphill or swimming the last 50 meters of a race. But at the summit of Mt Everest there is only 33% of the air available at sea level, resulting in these critical activities requiring 95%+ of all your available energy at V02Max. Just breathing in and out is estimated to use 20%+ of all the energy you can generate! Only 2-5% is available for moving your body i.e. actually climbing.

What does this mean in practice? Empirical measurements show that climbers who can climb at 3,000 vertical feet per hour near sea level can manage only 50ft an hour at the summit. Climbers talk about taking a step, then having to pause and take 10 or 20 breaths before being physically able to make another. Going faster is impossible; it would use more than the 2-5% available.

Put another way, you know that out-of-breath, can’t-keep-going feeling you have at the end of a long sprint or a stair climb? That’s you at your V02Max – and how I expect to feel on Everest for 16 hours straight. Not sure I can do that.

As you can imagine, developing my V02Max towards my genetic ceiling is part of my training. Here’s a photo from the Lyon St stairs in San Francisco at dawn during my 8x 160ft stair sprint sessions intended to do just that. If you are going to suffer, suffer with a nice view!




  1. Kevin · January 16, 2017

    Great explanation. Hope you’ll carry some oxygen just in case 🙂


    • jamesrbrooman · January 16, 2017

      Yep! More posts to come on how we are dealing with the risks!


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