The complex physiology of ski mountaineering

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In July, the International Olympic Committee announcement that ski mountaineering will make its Olympic debut at the 2026 Winter Games in Milan-Cortina, Italy. The transition from a niche passion in the backcountry to a source of five Olympic medals will bring new attention to the sport, including from sports scientists. To begin with, a team of researchers led by Lorenzo Bortolan from the Italian University of Verona (with colleagues from Sweden and Slovenia) just published an introduction to what is currently known about skimo, as the sport is known to connoisseurs, in the journal Frontiers in physiology. Here are some highlights:

The basics

Skimo consists of climbing mountains, mainly on skis equipped with non-slip skins. There are also technical sections, for example along ridges and corridors, where you climb on foot with your skis strapped to your backpack. And the reward is coming back down the mountain with your skins removed.

The Olympic program includes a men’s and women’s sprint, which typically involves a single ascent of about 250 vertical feet, followed by a ski descent, lasting a total of 3 to 3.5 minutes. There is also an individual men’s and women’s event which lasts 1.5 to 2 hours and includes at least three ascents and descents, with a total vertical gain of one mile or more and ski-in-ski technical sections totaling up to ten. percent of the stroke. Finally, there is a mixed relay of about 15 minutes.

Physiology

It takes a lot longer to hurtle down a mountain than to ski down it. This means that it is above all an endurance sport. If you are a few percent better than your climbing rivals, you will save minutes on them; if you are a little better on the descent you will only gain a few seconds. Indeed, in an Austrian study Released earlier this year, the best predictor of racing performance in a group of elite and sub-elite skimo racers was their performance on a ski-specific VO2 max test. The best pros would train 16-24 hours per week during base times, about half skiing and the rest biking, running, and roller skiing. In any given year, they will accumulate 150 to 190 vertical miles.

Of course, mastery of the descent matters too. You have to be good enough to hit some pretty intimidating slopes without scooping or chasing snow the entire way. This is not trivial: another study found that the heart rate stays around 85% of maximum even during descents, in part, the authors write, due to “psycho-emotional and physical stress associated with choosing the optimal course on the difficult course with difficult conditions. variable snow ”.

Altitude is another factor to consider. While the rules for cross-country skiing at the Olympics limit altitude to just under 6,000 feet above sea level, skimo has no upper limit. Events often take place at 10,000 feet and sometimes up to 13,000 feet. For every 3,000 feet of elevation, VO2 max decreases by about six percent, and some people (especially highly trained athletes) are more affected than others – so your ability to deal with thinning mountain air could be a limiting factor.

Finally, weight matters because you have to lug it uphill, so studies have found an inverse correlation between body fat and run time. It also affects equipment choices, which we’ll see below.

Biomechanics

Climbing a mountain is a lot like classic cross-country skiing technique, the main differences being that your skins don’t really slide uphill, and if you lose your grip you’ll fall hundreds of feet to your death. (Okay, not quite, although a rule that goes into effect in 2022 says that bindings must have a safety system that automatically stops the ski if it comes loose – an innovation I would have appreciated in my own very limited experience!)

Due to the lack of glide imposed by the skins, ski mountaineers stride shorter and faster than cross-country skiers. And when the ground gets steeper, they shorten the strides even more and slow them down. In comparison, cross-country skiers tend to keep their stride frequency roughly constant and control their speed by changing only the stride length. Upper body strength and climbing hitting technique are also crucial.

On the descents, ski mountaineers don’t go as deep as downhill skiers, both because the terrain is much more rugged and unpredictable and, let’s be honest, because their legs are always pulled up from the climb.

Equipment

Weight matters: An extra kilogram (2.2 pounds) at a skier-mountaineer’s ankle burns two to three percent more energy. Safety matters too, which is why the International Ski Mountaineering Federation has a very long and detailed list of specifications for the required equipment to prevent athletes from competing wearing the lightest and most fragile equipment. In particular, there are minimum weights for ski boots (1000 grams for men, 900 for women) and skis and bindings (1500 grams for men, 1400 for women).

You must also bring an approved snow shovel, snow probe, survival blanket, whistle, crampons and avalanche detector, and have a minimum number of layers of clothing. Bortolan’s article has a beautiful infographic give details.

So what remains to be discovered by 2026? Bortolan and his colleagues point to environmental conditions as a current blind spot. How do high altitudes, cold temperatures and varying snow conditions affect the demands of a race and dictate how best to prepare for it? Wearable technology specially optimized to collect relevant data on pace and effort during ski races will provide a more detailed picture of what athletes are going through. Better gear that improves performance and simplifies the transitions between skinning, hiking and downhill skiing will undoubtedly emerge.

Yet, while Olympic glory and the rewards that come with it await, it may be worth doing away with. this video of a day of skimo that Maestro Kilian Jornet took from his home in Norway a few years ago. Every sport craves more attention and bigger crowds at some level, but for many ski mountaineers the obsessive pursuit of faster, higher, stronger is just a means to another end. less quantifiable.


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