Skiathlon Explained: Physiological Differences from Classic to Make Transition Tough

Chelsea LittleOctober 7, 20145
Don't do this: Therese Johaug (NOR) and Justyna Kowalczyk (POL) come into the transition during the skiathlon in Lahti, Finland.  Kowalczyk's fall cost her valuable seconds.  Photo: Fischer/Nordic Focus.
Don’t do this: Therese Johaug (NOR) and Justyna Kowalczyk (POL) come into the transition during the skiathlon in Lahti, Finland. Kowalczyk’s fall cost her valuable seconds. Photo: Fischer/Nordic Focus.

When you step out of your classic skis and into skate skis in a skiathlon, there’s a brief period where skiing feels very strange: the shorter skis, the lack of tracks, and the longer poles are all a distinct change from the previous style, as your body says, “what are you DOING?

This is the subject of a recent study by researchers from University of Franche-Comté in France and Mid Sweden University. One of the researchers, Sarah Willis, is an American who previously skied for Gustavus Adolphus College.

“To our knowledge, no previous researchers had examined skiathlon performance and we were intrigued by this as well as investigating the impact of an initial period of classic skiing on subsequent skate skiing,” she explained in an e-mail. “Realizing the effect of one bout on another is similar to research performed in the sport of triathlon, we used some previous triathlon studies as a ‘guide’ for an initial skiathlon study.”

Classic skiing is generally recognized to involve greater oxygen uptake and greater muscle mass involvement than skate skiing. Thus when a racer transitions to skating halfway through a skiathlon, their body is coming out of a very different physiological stress than it would have been from a skate race of the same distance.

The team worked with eight national-level Swedish skiers, who were asked to participate in two 6 k time trials on a rollerski treadmill. In one, they classic skied for 3 k, then switched gear and skated for 3 k. In the other they skated two 3 k sections, stopping for a brief time in the middle to simulate an equipment change.

Interestingly, they found that the time for the second portion of the time trial was unaffected by the previous section’s technique.

“In my opinion, it is interesting that the performance times were similar,” Willis wrote. “However, it is understandable in some ways since we, as skiers and athletes, race at race pace and alter our effort based on what we can do while giving our best in each moment. Sometimes we make alterations or changes in our technique, breathing, pacing strategy, etc., while our effort and outcome may be the same as we give all we can. We are well-trained machines and our mental approach to pacing the effort has a lot to say about our performance outcome.”

However, just because the times were more or less the same did not mean that the team didn’t find some effects of the initial classic portion of their simulated skiathlon.

For instance, in the first three minutes after the transition in the classic-to-skate time trial, VO2 and minute ventilation had higher increases than during the skate-only time trial. The cadence of the skating strides were also faster in the initial section of the skate portion of the skiathlon time trial, than in the skate-only time trial.

(What is minute ventilation? “Minute ventilation is literally the volume of gas you breathe into your lungs (inhale) in one minute, so, basically, a parameter of how much air you can move into your lungs,” Willis wrote.)

Some part of this might be fatigue. But it also seems likely that the difference in technique makes it difficult for skiers to immediately find a good and efficient rhythm when they snap into skate skis.

“Skiers may notice that it takes about 3-5minutes to get into a good rhythm, including cardiovascular and respiration (ability to increase heart rate and rhythm with breathing), and their natural technique (biomechanics of skating) before they really feel they can perform ‘normally’ in skating,” Willis wrote.

And the physiological differences, too, she chalked up to technique.

“There are alterations in the muscle requirements and biomechanics of the new technique,” she explained. “A combination of alterations in oxygenation and extraction of the blood, or simply the consumption of oxygen is most likely involved in the explanation of some factors affecting the transition from a cardiopulmonary standpoint.”

One thing is clear: skiathlons present a novel physiological challenge that athletes never encountered before the invention of the two-discipline race format.

To make the transition and subsequent skating section easier, Willis had a few suggestions: lower the pace in the final minute of the classic section to facilitate a good transition, and adjust the pace and effort during the initial phase of the skate section.

But like everything else in sport, it also simply comes down to training.

“[You can do] specific training to increase ability to perform skate after classic, at race speed or during an endurance session with higher speed before and after the transition,” she wrote.

Chelsea Little

Chelsea Little is FasterSkier's Editor-At-Large. A former racer at Ford Sayre, Dartmouth College and the Craftsbury Green Racing Project, she is a PhD candidate in aquatic ecology in the @Altermatt_lab at Eawag, the Swiss Federal Institute of Aquatic Science and Technology in Zurich, Switzerland. You can follow her on twitter @ChelskiLittle.

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  • highstream

    October 7, 2014 at 10:39 am

    Glad to see Sarah is doing well. In real races, I’ve observed that, if anything, the pace usually picks up heading toward and then in the change area, and that same feeling of the need to hurry-up through the process continues over to the skate out. Plus, there’s often a sense of needing to not let the skier(s) immediately ahead coming out, the ones who entered together, get away.

  • Martin Hall

    October 7, 2014 at 1:39 pm

    I see the study at best as a compromise in all the evaluations, because the 2 parts of the real race, classic and then skating, play very different roles in the outcome of the race, and how they are skied, and therefore a credible set of results would be hard to be realized with the actual race.
    The classic leg being the starting leg has a totally different set of criteria then the skating leg which of course is focused as the finishing leg—-demands are very different right across the scope of all considerations—tactics, strategies, speed, strength, technique and the list goes on.
    The statement—it comes down to training—really it is more likely it comes down to speed and how long you can maintain it—speed of course is trained, but a huge deciding factor, as Mr. Northug has so ably demonstrated over the years.
    That’s my take.

  • T.Eastman

    October 8, 2014 at 1:23 am

    Biathlon likely has studies that investigate similar adjustments in tasks and methods to improve transitions…

  • zachhandler

    October 13, 2014 at 11:00 am

    “Classic skiing is generally recognized to involve greater oxygen uptake and greater muscle mass involvement than skate skiing.”

    Is that true, both in terms of the physiology as well as the claim of general recognition? I am not a professional in the sport, though I have spent most my life in the racing community and never heard that. I know that there are old studies from the early 90s showing that diagonal stride consumes more O2 than skating, which in turn consumes more O2 than double pole AT A GIVEN SPEED. But my understanding was that if you let athletes go race pace with either technique, O2 consumption is the same, as in both cases it is limited by cardiac output, rather than what the muscles are doing at the periphery.

    Just curious what the science and the folklore is on this.

  • Chelsea Little

    October 15, 2014 at 11:08 am

    Hi Zach,

    it’s pretty well-known that an athlete’s VO2Max might be different depending on the activity that they are doing. For instance, doing a VO2Max test on a running treadmill vs. SkiErg vs. rollerski treadmill vs. bike would likely get slightly different results – maybe very different, depending on the athlete. So it’s not surprising that there might be slight differences between classic and skate as the muscle groups recruited are fairly different.

    Hope that helps – we should definitely do an article to follow up on this more completely. Thanks for the comment.


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