VO₂ vs V2: why form beats fitness for amateur skiers

I first started working on what would become Kiqwax based on a common frustration: I was a good athlete, but not a good skier. As it turns out, I'm not alone. During interviews with dozens of skiers and coaches, one question was repeated: am I struggling because of my form, or am I in worse shape than I thought? To answer this question, we hit this books. Here's what the science tells us.

Why am I struggling up this hill?

In 2017 Ørtenblad and Jensen took twelve recreational cross-country skiers and tested them properly: VO₂max on a treadmill, VO₂max on a double-poling ergometer, and gross efficiency — how much of the energy you burn actually becomes forward motion. Then they ran a six-minute all-out double-poling time trial and asked which measure predicted it.

Efficiency did, strongly — it was the standout predictor in the analysis, at r = 0.79. This means that the biggest driver in their performance wasn't their athleticism, but their form. In the authors' own words: "neither DP VO2 max, nor treadmill-running VO2 max, correlated with 6-min DP performance."

Anyone who's clipped in to Nordic skis can likely relate to this. We know how hard we're working, and we still see more skilled skiers fly past, barely breaking a sweat.

Roy Young, head coach of the British cross-country team, says this: "Power, speed, endurance — Cross Country is the most technically demanding endurance sport in the world. Along with having very high VO2 max, athletes have to spend a lot of time on technical accuracy." The 2017 study focused on double poling, but expert coaches will confirm weight transfer and balance are the keys for skate skiing. Until you master these, those hills are going to hurt.

How much does it matter?

The study that made the mechanism concrete for us came out in Scientific Reports in 2024. Zhu and colleagues took five experienced skiers and five novices and had them double-pole on roller skis at an identical speed — 16 km/h — measuring oxygen cost.

The experienced skiers used 21% less oxygen to travel at exactly the same speed (p = 0.016).

With oxygen use correlating directly to our cardiovascular output, this study gave a resounding answer: keeping up with a more skilled skier requires 21% better fitness or effort. Or put another way, correcting your form should reduce your load by about a fifth.

What about during a long ski?

Ohtonen and colleagues (2018) had skiers complete a simulated 20 km skate skiing race, then measured maximal-velocity biomechanics before and after. Or in other words: they got their subject tired and then checked how their performance degraded. Everything degraded — speed fell 11.6%, cadence fell 8% — but it degraded unevenly. Vertical ski force dropped 8.3%. Pole force dropped 26.0%.

Roughly three times the decline in the upper body. Your poling falls apart about three times faster than your legs do. This means that to efficiently ski longer, we have to learn to use our legs.

It also means when we look at data, an average hides what we need to know. Understanding our form in the moment is key to improving and keeping our form efficient.

What stops us from fixing it?

The obvious answer to all of this is spending more time on form. The challenge? People struggle to understand what they're doing wrong. Amri-Dardari and colleagues (2022) found that gymnastics learners couldn't accurately understand what their bodies were doing without external cues or feedback. Anyone who's ever seen a video of themselves skiing can relate: do I really look like that?

The kind of attention matters too. A meta-analysis by Chua and colleagues (2021) — 73 studies, more than 1,800 participants — found an external focus of attention beat an internal one for retention and transfer. The same movements, cued correctly, showed measurably more efficiency than without cues. And the benefit wasn't moderated by age or skill level: it works on beginners and experts alike. (In fairness, a recent preprint argues those effect sizes are inflated by publication bias. We think the direction is solid; the magnitude is debated.)

So where does that leave us? Form matters, and it's highly trainable. It's also the hardest part of skiing to improve on your own. Historically, that meant a coach standing beside the trail. Most of us don't have one.

What's changed?

In a word, smartphones. Motion sensors and the phones that carry them have improved enough that we can capture data, analyze it, and immediately provide feedback. Don't take our word for it though: Stöggl and colleagues (2014) classified skate-ski sub-techniques — which gear you're in — at 90.3% accuracy using nothing but the accelerometer in a mobile phone on the chest. Rindal and colleagues (2018) reached 93.9% on classical sub-techniques with two small sensors and a neural network.

That's the driving force behind Kiqwax: use motion-capture data to help skiers when they can't have a coach around. In our next post, we'll dive into how we can take motion data and turn it into meaningful coaching insights to help skiers improve, right now.

Sources

• Ørtenblad, N. & Jensen, K. (2017). Gross efficiency predicts a 6-min double-poling ergometer performance in recreational cross-country skiers. Sports Engineering 20(4): 329–333.
• Zhu, Y. et al. (2024). Skiing economy and kinematics during field double-poling roller skiing among novice and experienced cross-country skiers. Scientific Reports 14: 7073.
• Ohtonen, O. et al. (2018). Changes in biomechanics of skiing at maximal velocity caused by simulated 20 km skiing race using V2 skating technique. Scandinavian Journal of Medicine & Science in Sports 28(2): 479–486.
• Amri-Dardari, A. et al. (2022). Immediate effect of self-modelling with internal versus external focus of attention on teaching/learning gymnastics motor skills. Journal of Human Kinetics 84: 224–232.
• Chua, L.-K. et al. (2021). Superiority of external attentional focus for motor performance and learning: Systematic reviews and meta-analyses. Psychological Bulletin 147(6): 618–645.
• Stöggl, T. et al. (2014). Automatic classification of the sub-techniques (gears) used in cross-country ski skating employing a mobile phone. Sensors 14(11): 20589–20601.
• Rindal, O.M.H. et al. (2018). Automatic classification of sub-techniques in classical cross-country skiing using a machine learning algorithm on micro-sensor data. Sensors 18(1): 75.
• Young, R., quoted in "The Ultimate Endurance Sport: Cross-Country Skiing," Pledge Sports, May 2017.
• Doyle, C. et al. (2022). The effectiveness of gait retraining on running kinematics, kinetics, performance, pain, and injury in distance runners: a systematic review with meta-analysis. Journal of Orthopaedic & Sports Physical Therapy 52(3).

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