Can AI-based methods help you get better glide on your cross-country skis? Now researchers at Luleå University of Technology have developed a method that can help skiers at – eventually all levels: “This will be able to streamline the method of finding the “right pair of skis,” says researcher Kalle Kalliorinne.

Kalle Kalliorinne is a researcher at Luleå University of Technology. He is now defending his research on the glide of cross-country skis. 

“We have been interested in the friction between the ski and the snow, and this from two different scales: the camber of the ski and the structure of the skis. The structure can be “affected” in many ways,” says Kalliorinne to Langd.se.

The tests have been done during “early spring” in Luleå, a time of year when the sun does not rise. This is because the temperature is stable for a more extended period (not as later in the spring when the temperature, with the help of the sun, rises relatively quickly). 

“We have run the tests with skate skis in classic hard tracks at three different temperatures: -3, -9, and -13 °C, and we have tested three different grinds.”

And what differences did you find?

“In our tests, the ski itself was considerably more important than the grind. It doesn’t necessarily mean that this is always the case, but in the results we obtained in our tests, the ski and the ski’s camber were the most crucial part of how the ski glide,” says Kalliorinne.

“Then you generally say you want ‘longer contact zones’ in the snow when it’s cold. Then you might ask what cold is, but we saw some kind of ‘switch’ between minus nine and minus thirteen. In simple terms, you could say that it was advantageous to have a short contact zone at minus nine, and at minus thirteen, it was advantageous to have a longer contact zone,” says researcher Kalliorinne.

Friction is significant in skiing, and everyone wants to find the best solution to minimize it. At the elite level, a minimal reduction in the resistance between the ski and the snow can significantly impact race results. Selecting and preparing cross-country skis to minimize friction requires careful control of various details regarding the ski’s tension, material, grinding structure, and waxing methods. These choices must be adapted to the prevailing snow and weather conditions to ensure optimal performance, of which minimal friction is crucial.

To better understand the complex nature of friction between skis and snow, the researchers have developed a multi-scale AI-based modeling approach that relies on coupling the macro and microscopic properties of the ski. Field tests in ski tracks show that the calculation method works in practice, now attracting significant interest in the ski world. Using the method, the researchers have determined and minimized friction in certain typical weather conditions. The researchers have measured the entire geometry of the ski with varying loads and created AI that generates input to a computational model used to study the contact between the ski and the snow. The computational model can be used to characterize the mechanical properties of the ski in terms of how it distributes the skier’s weight across the front and rear glide zones.

How will the results you have obtained affect the national teams’ work on optimizing ski glide?

“I would say that the next step will be to select the skis using the calculation model. This means going to the manufacturer and picking out skis based on the calculation model, thereby getting skis suitable for different snow and weather conditions, thereby picking up a more ‘diverse fleet’ of skis, and not coming home with many similar skis.”

But will this also facilitate the work of optimizing the glide even out in the competition arena an hour before the start?

“What we have found so far does not mean you do not need to test skis before races. However, it may mean that you will find more ‘good pairs’ and thus have a larger proportion of good skis in your ski fleet. For the national teams, it means that they have a better idea of how different skis in the truck perform in different conditions. Combining the right ski, structure, and waxing method for different weather conditions is crucial for elite skiers’ success. Cooperation on implementing the methods at the national team level is underway,” says Kalliorinne.

“Our research results help to select optimal combinations of ski type and grinding structure that provide the best glide on racing skis for different snow and weather conditions. The results are already being used in the development of new ski bindings together with the Swedish Olympic Committee,” says Kalle Kalliorinne.

When will the findings you have now come up with be implemented at the training level?

“I think the national teams will want to do this for a few years. So, I don’t think it will happen before the Olympics (2026).”

But as a Vasaloppet skier, how should you think about buying a pair of skis?

“I would say anyone with ambitions and opportunities should have two pairs of skis. One pair is for colder temperatures, and one is for warmer temperatures. Because as I said, there is a big difference in what works best in different temperatures. When choosing skis for Vasaloppet, I think you should not emphasize the temperature at the start but instead check what temperature it is on the day. You want to ski for as long as possible with skis that glide as easily as possible for most of the race,” says Kalliorinne.