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Mountaineering Training | Aerobic Deficiency Syndrome

Lost in the noise of the next great exercise fad and short cut to greatness are truths that endurance coaches and athletes have known for about a century, gained through hundreds of thousands of hours of trial and error. An important one for mountaineers to remember is that there is no substitute for aerobic base training, gained through many hours of long, slow work. The aerobic base is the key to being able to maintain activity for hour after hour, climbing stretch upon stretch to the summit and descending safely back down. When the proportion of training is off and an athlete does too much high intensity training and not enough aerobic base training, the result is a condition coined by Dr. Phil Maffetone: Aerobic Deficiency Syndrome or ADS.

How does ADS manifest itself? These athletes may feel that they are at peak fitness. During their hardest workouts, they lift more, move faster, and break their own PRs, because of the focused high intensity work that they have been doing. When they make it to the climb however, they are surprised by how quickly their heart rate rises with a relatively slow pace. A few hours into the climb, they are running out of gas, they feel the lactate building up, and they can’t keep the pace. These athletes have a well trained anaerobic system, but their aerobic system is woefully lacking.

When we don’t train the long slow miles enough, we don’t stress the slow twitch muscle fibers, the backbone of endurance. Slow twitch fibers are responsible for a cascade of physiological events that lead to endurance performance: slow twitch fibers have a remarkable ability to oxidize fat into ATP, leading to energy without the buildup of lactate, and the mitochondria they contain can metabolize the lactate that results from oxidizing glycogen (carbohydrates). Even the leanest amongst us carries hundreds of hours of fuel in our bodies in the form of fat, and have the capability to go for incredibly long distances without fuel, provided that we stay in our aerobic zone. The question, then, is how best to optimize our aerobic system.

To build aerobic base capacity, the important piece is a large distance volume, done at zone 1 and 2. These workouts may not seem exciting, they certainly aren’t sexy, but as you accumulate those miles, the aerobic system's ability to do work increases and the base expands. Elite endurance athletes can build enormous aerobic bases, such that their aerobic threshold (the intensity at which they begin to accumulate lactate and start the countdown clock to a performance decrease) is incredibly high, perhaps only 10 or 15 beats per minute below their lactate threshold. The depth of their aerobic base allows them to do more work, for much longer, at a much higher intensity. It seems to run counter, but for these athletes, their speed comes from their long, slow training, not from intervals.

Including some intensity work helps to round out the training equation and reach maximum performance. With a well established aerobic base, some intensity training helps the body to optimize the systems that remove lactate, which is an endurance athlete's performance limiter. The amount of intensity training needed is generally far less than commonly assumed, however.

Remember that there are two main physiological systems for athletic performance, defined by metabolism: aerobic and anaerobic. Both can be trained, but in peak condition, optimizing one system comes at the expense of the other. For us in the mountains, chasing long summit days and lofty goals, the aerobic system is what we rely on.


ADS, its causes, and its remedies are described well in the book Training for the Uphill Athlete, by Steve House, Scott Johnston, and Kilian Jornet. Also check out these articles from Uphill Athlete, and from the original describer of ADS, Dr. Phil Maffetone.

Questions? Comments? Share your thoughts here on the RMI Blog!

Comments (3)

Hi Jeff,
Do not forget the downhill training. On Denali (or any sled based mountain adventure), not only do you need to drag a sled up the hill, you will need to be able to support a loaded sled dragging you DOWN the hill too. I ended up at the end (top) of the down hill line and realized that I did not train enough to support 600+ pounds of loaded sleds and rope mates. This was VERY hard on my knees; to the point where I decided, to my guide’s upset, that I would be better off descending backwards to prevent further knee injury (I had trained for, and achieved, SIGNIFICANT climbing strength and endurance).

Anyway. . . great article. From this experienced endurance athlete’s point of view, this is all great advice. I may have posted this before, but it might be prudent to consider how much oxygen is needed at altitude to process food in the gut. Bypassing the food during high altitude work and utilizing fat stores instead may help climbers realize their summit aspirations. Of course one does need to train for extended periods of internal-fat-stores only based energy supply. Perhaps an article would be beneficial?

I am definitely looking forward to more adventures with RMI now that the COVID lockdowns/restrictions era is beginning to show a light at the end of the tunnel. :-)

Posted by: Keith Loritz on

So what’s a good workout to combat this. I’m currently doing a five mile loop with a 65 pound pack and a 20 pound sled on dry ground once a week over glacial terrain. Takes about 2-2.5 hours no drink or food during. This is in conjunction with 3-6 mile daily runs and a stair day once or twice a week with the pack, 1000-1500ft so far.
-Jeff, Denali June 18

Posted by: Jeffrey Burkard on

Thank you for writing such a helpful article for all the aerobics lovers. Please keep sharing such content.

Posted by: Importance of physical activity on

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