Swiss racer's thesis explores sensor-based penalty detection in Telemark

Fun-filled, forward-thinking and backed by a loyal community that values its tradition, technique and sense of freedom, Telemark Skiing is fast, technical and unmistakably different. With the 2025/26 FIS Telemark World Cup season already delivering close contests, rising stars and a growing fanbase, the discipline is clearly entering an exciting and decisive phase.

In competitive Telemark, athletes face the double-edged challenge of racing against the clock while also being judged on their adherence to a clearly defined technique. Penalties, particularly those linked to turn execution and transitions, are central to maintaining the integrity of the discipline, as well as playing a part in deciding in whose hands the titles - currently fiercely contested in both the Men’s and Women’s World Cup standings - will end up.

What is more, transition penalties are among the most debated aspects of Telemark racing. Judging at events relies on human observation, often under challenging conditions, and small differences in interpretation or positioning can influence outcomes. 

This has prompted ongoing discussion within the Telemark community about consistency, transparency and athlete understanding, which makes a recent Master’s thesis, conducted at the University of Lausanne and exploring whether wearable sensor technology could help support a more objective approach to detecting transition penalties, all the more relevant.

Why study using sensors?

The study, titled ‘Development and validation of a sensor-based penalty detection system in Telemark Skiing’, was motivated by well-documented difficulties in the current judging system. Transition penalties depend on assessing the fluidity between turns - a movement that can be hard to evaluate consistently from the side of the course, particularly when judges oversee multiple gates or are working on unfamiliar terrain.

Video analysis can help, but it is not always available at every level of competition and still depends on human interpretation. Sensor-based systems, already widely used in performance analysis throughout elite sport, offer an alternative way to quantify movement directly on the athlete’s person.

“As an athlete, I’ve experienced first-hand how frustrating it can be when judging feels inconsistent or opaque. The biggest challenge I wanted to tackle was subjectivity and lack of transparency in penalty decisions during Telemark competitions,” said current Telemark World Cup contender Romain Beney, who presented the study with guidance and support from Dr. Fabio Borrani and Jérôme Parent.

How does the system work?

The system uses two small wearable sensors, provided by Dr. Benedikt Fasel and his firm Archinisis GmbH, mounted above each Telemark boot. These sensors combine inertial measurement data with satellite positioning to capture detailed information about the skier’s movement, including orientation and timing.

Rather than focusing on speed or position on the course, the algorithm analyses how the skier moves through each turn transition. By comparing the motion of the left and right legs, the system can identify:

●      Telemark turns

●      Alpine turns

●      The transitions between turns

Each transition is then analyzed for smoothness. A mathematically “ideal” smooth transition is modelled, and the skier’s actual movement is compared against it. The greater the deviation from this smooth reference, the higher the likelihood that the transition includes a pause or interruption consistent with a rule breach and resulting penalty (see Figure 1 below).

“The sensor data provides feedback, showing where the technique deviates from the ideal and why a penalty might have been assigned," Beney added. "This kind of insight is invaluable for training, as it allows us athletes to target specific aspects of our skiing and track progress objectively.”

Testing times

To test the system, 14 experienced Telemark skiers completed training runs on race-standard slopes in France (Les Houches) and Switzerland (Veysonnaz). In total, more than 500 transitions were analyzed.

All runs were filmed, and three experienced former World Cup Telemark athletes independently reviewed the videos, judging for transition penalties in accordance with FIS rules. These video-based judgements were used as the reference point against which the sensor system was evaluated.

The results were encouraging, as the algorithm successfully detected all turns and transitions identified in the footage. When it came to identifying penalized transitions, the best-performing method detected the vast majority of penalties flagged by judges, while also highlighting areas where further refinement would be needed in order to reduce false positives.

What does the research show?

The study demonstrates that sensor-based analysis can reliably identify the moments in a run where penalties are assessed and can distinguish, in many cases, between clean and penalized transitions.

This is an important first step, which suggests that wearable sensors could potentially support more consistent judging, provide clearer post-run feedback and help athletes better understand how their technique is being evaluated - though limitations remain…

“While the system is promising, it’s not a complete replacement for human judgement yet,” was Beney’s verdict. “The scope of my master’s thesis was limited, and the system currently focuses on transition penalties only and requires post-run analysis, meaning it can’t provide live feedback during races."

What should athletes know?

For athletes, this research is not about introducing new rules or changing how penalties are currently applied. Instead, it offers insight into how technology might support the sport in the future, with any potential application aiming to sit alongside human judges, not replace them.

Key points for athletes include:

●      The system analyses movement patterns, not speed or style preferences.

●      It focuses on transition fluidity, a core element already defined in the rules.

●      It does not judge intent or overall performance - only whether transitions are smooth and uninterrupted.

Sensor-based feedback could, in future, help athletes review where and why penalties occur after a run.

Next steps? 

Further research is needed before any competition use could be considered. Larger datasets, more varied conditions, and continued dialogue with athletes, judges, and organisers will be essential. What this project does show is that Telemark Skiing is well placed to benefit from innovation that supports fairness, transparency, and trust - values that sit at the heart of this competitive and dynamic discipline.

"Real-time feedback could help athletes and coaches during training and competition, and a more holistic system could cover all types of penalties (Telemark step, transition, jump distance and landing). Crucially, it would act as support for judges, standardizing decisions and reducing bias, while leaving room for human oversight and interpretation. This balance would preserve the unique character of Telemark Skiing, while ensuring fairness and clarity for everyone involved,” said Beney, by way of conclusion.