[Feature: Sports and Science] Seiji Hirosawa: The Development of Figure Skating Brought About by Technology

In figure skating, performances are conducted to music within a specified time, and rankings are determined by the scores of judges. Such competitions are called scored sports (judged sports). You are likely familiar with this classification. When it comes to the use of technology in scored sports, the introduction of automated scoring systems is a topic that often generates discussion. Since it is a competitive sport, many people believe it is desirable to minimize variations in judging caused by the subjective decisions of judges as much as possible.

When thinking of automated scoring in scored sports, the case of gymnastics likely comes to mind first. Under the leadership of the International Gymnastics Federation (FIG), AI scoring systems have been introduced with the aim of achieving automated scoring to ensure accurate and fair judging, as well as to reduce the burden on judges. Development began in 2017, and since 2019, it has been used in some events at international competitions, including the World Championships. At the 52nd FIG Artistic Gymnastics World Championships held in Antwerp, Belgium, in 2023, its application to all events began. In introducing this system, the FIG worked with the development company to establish standards so that non-quantified scoring rules such as "straight" or "slightly bent" could be judged mechanically, such as "the knee angle is greater than 170 degrees." In the future, they plan to sequentially release guidelines for judging techniques more specifically using numerical values such as joint angles and limb positions, as well as provide professional commentary and video to viewers around the world.

Following these efforts in gymnastics, I feel that voices calling for the introduction of automated scoring systems in figure skating, which is also a scored sport, are growing stronger. On the other hand, I also hear opinions that "figure skating should be evaluated by humans because it competes on artistry." How should technology be utilized in the judging of figure skating?

One hint lies in the concept of a new sports genre called "Artistic Sports" proposed by Associate Professor Tatsuki Machida of Kokugakuin University *1. Mr. Machida, who was also a figure skater representing Japan at the Sochi Olympics, proposed subdividing scored sports to include a new category of "Artistic Sports" for competitions where "the competition rules require artistic physical expression that necessitates subjective interpretation." In the competition rules for figure skating and rhythmic gymnastics, expressive acts and originality developed alongside music are required. On the other hand, what is required in men's artistic gymnastics is the "difficulty and quality of techniques," and since scoring is based on a comparison with an ideal form defined by the competition rules, the originality of the competitor is not required.

In this way, it can be said that Artistic Sports, which require subjective interpretation and artistry, and Formalistic Sports, which seek the ideal form defined by competition rules, have different characteristics despite both being scored sports.

Therefore, the scoring rules for Artistic Sports that require artistry must separate "Technical Scores" for evaluating technical aspects and "Artistic Scores" for evaluating artistic aspects. Regarding technical evaluation, it is necessary to make objective evaluations without leaving room for interpretation. On the other hand, for artistic evaluation, it is said that room for interpretation should be allowed for both the competitor and the evaluator.

In other words, in the case of figure skating, there may be room for the introduction of technology for objective evaluation regarding the difficulty certification and execution evaluation of technical elements such as jumps, spins, and steps. However, if technology is introduced to perform objective evaluations of artistic aspects such as musical expression, there is a possibility of undermining the unique competitive characteristics of Artistic Sports.

Recently, tracking systems have been introduced at various sports competitions, making it possible to obtain athlete data without experimental intervention.

In figure skating, which is highly popular as a spectator sport, although an automated scoring system like that in artistic gymnastics has not been introduced, tracking systems have been implemented for the purpose of enhancing the viewing experience for spectators. Fuji Television Network, Inc., which holds the broadcasting rights, and Qoncept, Inc., which specializes in image processing, have developed two systems to date. One is "I-Scope" *2 for visualizing jumps, and the other is "Ice-Stats," which visualizes the trajectory of an athlete's skating during a performance. The introduction of these systems has made it possible to visualize the performance of figure skaters during competition, which was previously difficult to understand quantitatively (Figure 1).

I focused on I-Scope. In current figure skating scoring rules, the weight of jumps is very high. To win in competitions, it is important to successfully execute high-quality, high-difficulty jumps, and athletes do not simply try to avoid falling; they go through trial and error to perform jumps that judges will consider high quality. I-Scope uses two 4K cameras to film the entire rink and calculates the height, distance, and skating speed after landing. The takeoff and landing points of the jump are defined by the operator. Since the actual size of one pixel on the filmed screen can be calculated from the information in the skating rink's blueprints, the values can be measured. In broadcasts, a separate video with the trajectory of the jump's parabola is prepared to display the measurement results. The measurement and creation of the trajectory video are completed in about one and a half minutes and delivered to the viewers. After the competition, rankings for distance and height are released, providing a different way to enjoy the sport than the competition scoring itself. It might be interesting to have a formalistic competition where only such numerical values of jumps are contested.

I entered the Faculty of Environment and Information Studies in 2010 and joined the figure skating division of the Keio University Athletic Association Skating Team to begin competing in figure skating. While competing, I wanted to research the question of "what is necessary to jump better," but obtaining figure skating data in an experimental environment was difficult in many ways. In such circumstances, "real-world" jump measurement data during competitions was very attractive to me. Rather than letting the data end with its use as media content, I wondered if it could be used for research to support the improvement of competitive ability. After consulting with Professor Yoshimitsu Aoki, my supervisor in the Ph.D. program at the Keio University Graduate School of Science and Technology, I entered into a joint research agreement with Qoncept, Inc., the developer of the system, and began my research. My focus was on the "Grade of Execution (GOE) of jumps" within the technical score, where objective evaluation is required. The score for a figure skating jump is determined by the sum of the "Base Value," which is determined by the type and number of rotations, and the "Grade of Execution," which represents the quality of the executed technique. Unlike the E-score in artistic gymnastics, a characteristic of figure skating is that the GOE is not a deduction from a perfect score but includes positive evaluations. Judges watch the jump and immediately evaluate it on an 11-point scale from -5 to +5, including 0. Evaluations regarding the base value, such as under-rotation or edge use at takeoff, are determined by integrating the opinions of multiple judges (technical officials). On the other hand, for the GOE, a trimmed mean is adopted, which averages the scores after excluding the highest and lowest scores from the nine judges. Because of this, a certain amount of variation among judges is permitted. It can be said that the judging criteria also leave room for interpretation. Table 1 shows the evaluation criteria for positive aspects. For example, regarding height and distance, it is written as "very good," rather than "the value is large."

To examine "what characteristics of jumps receive high GOE evaluations from judges," I analyzed jump data obtained from the 2019 World Championships (Saitama) and the 2023 World Championships (Saitama). Figure 2 shows data for a total of 66 double Axel jumps performed by female athletes at both competitions that were judged to have a GOE of 0 or higher by all nine judges. The horizontal axis of each graph shows the values obtained from I-Scope, and the vertical axis shows the GOE after the trimmed mean (out of 5 points). The gray dots and dash-dotted lines represent 2019 data, the black dots and dash-dotted lines represent 2023 data, and the black solid line represents the overall trend. Looking at this, it can be seen that jump height has almost no relationship with the GOE evaluation. On the other hand, for distance, there seems to be a tendency (positive correlation) where the larger the value, the higher the GOE. Both the 2019 and 2023 competitions showed similar trends, and a characteristic is that the relationship between distance and GOE does not change significantly depending on the match. Regarding skating speed after landing, a positive correlation is seen in both 2019 and 2023, although it is not as large as that for distance. In other words, although the criteria for evaluating jump execution include the item "very good height and distance," it can be said that judges tend to give higher GOE scores to jumps with a large distance that flow smoothly after landing—that is, jumps with a large horizontal component.

The fact that data acquisition during competitions has become possible in this way has provided a sign that we can quantitatively understand the tendencies of judges' subjective evaluations. However, there are few competitions where the system is introduced, and because the sample size is small depending on the type of jump and number of rotations, quantitative evaluation is difficult. Furthermore, because takeoff methods differ, it is unknown whether the same trend would be seen for different types of jumps. If such systems are continuously introduced and analysis continues, it will serve as a benchmark for quantitatively determining "what constitutes the best jump for the sport" when digitalizing judging criteria in the future, as in gymnastics. To introduce a system at sports competitions held with various stakeholders involved, many challenges beyond technical aspects such as measurement accuracy must be overcome, but for the development of the sport, it is strongly desired that data acquisition be conducted continuously in more matches.

For previous related results using tracking data, please refer to published papers *3.

In addition to those related to scoring, I will briefly introduce the use of technology in coaching, primarily in Europe and the United States. One is the introduction of wearable devices worn around the waist. Many skaters do not know how many jumps they have performed during practice. In modern figure skating, where higher-difficulty jumps are required, the impact on athletes when landing jumps is also large, and it has been reported that cases of stress fractures are increasing due to athletes over-practicing. The U.S. Figure Skating Association reportedly uses devices to manage practice volume and provide guidance based on quantitative jump data. This is expected to contribute to injury prevention and performance improvement.

Another is the emergence of analysts. Recently, the placement of staff specializing in information analysis has been progressing in various sports. The Japan Sports Analysts Association defines an analyst as a "specialist who supports athletes and teams with a high level of expertise in terms of information strategy to lead them to achieve their goals." In figure skating, Mr. Arnaud Muccini of France is a representative figure. He uses the image processing technology of Dartfish, a dedicated software used by sports analysts for analysis, to quantify jump data from video and use it for coaching. For the 2022 Beijing Olympics, he served as an analyst for the Chinese national team and led the athletes to a gold medal in the pairs event. His skills are highly evaluated by Dartfish, and he has been awarded the title of certified expert, making him one of the world's leading analysts across sporting boundaries.

The development of technology can protect the health of athletes and contribute to the improvement of performance. In Japan as well, there will be a need to develop human resources and environments where guidance can be provided using the latest technologies mentioned above.

Figure skating is a sport where both artistry and technique are emphasized, and by utilizing technology after identifying the points for introduction, its appeal can be further enhanced. Along with the evolution of technology, I will keep an eye on how figure skating develops in the future, and as a researcher, I hope to contribute to the development of the sport as much as possible.

*1 Tatsuki Machida (2020) "Introduction to Artistic Sports Research: A Cultural Theory of Creation and Enjoyment Centered on Figure Skating" (Hakusuisha)

*2 "Figure Skating Life Extra Professionals: The People Who Support Figure Skating" (2020, Fusosha Mook)

*3 Hirosawa, S., Watanabe, M., & Aoki, Y. (2022). Determinant analysis and developing evaluation indicators of grade of execution score of double axel jump in figure skating. Journal of sports sciences, 40(4), 470-481.