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How are athletes able to improve their physical and athletic abilities? Professor Kazutoshi Kudo of the Graduate School of Arts and Sciences, who researches human perception and action, explains the latest measurement technologies and the mechanisms behind record-breaking performances at the Olympics and other elite, global sports competitions.

── What kind of field is sports science?

Sports science is an applied science that draws from various disciplines, including physiology, neuroscience, psychology, medicine, biochemistry, nutrition, biomechanics and informatics to explore research topics related to sports. The main pillars of this field relate to improving performance and promoting health. In my lab, we study how skilled individuals, such as sports athletes, dancers, musicians and actors, use their bodies and perceive their surrounding environment. How they move and perceive the environment around themselves are refined through practice, and become inseparable from one another. To give a few examples of our research, we have analyzed how dancers match their movements to music, how race car drivers perceive their surroundings, and what perceptual information is involved in pitch and stride coordination in track and field athletes.

The findings that come out of sports science also serve to benefit the general public by improving everyday life and health. We use our bodies for a variety of activities every day, and what we learn through sports science can be applied across a wide array of areas, including stress management, positive thinking and injury prevention. In my classes at the Graduate School of Arts and Sciences on the Komaba Campus, in addition to the basics of physical conditioning, I’ve also tried incorporating vocal training and posture improvement by inviting an opera singer as a guest lecturer. Methods of coping with pressure have been studied in sports science, and the findings from this research can be applied to many types of physical performance, including musical performance. Through these classes, students who struggled with public speaking were able to carry themselves well in front of an audience by the end of the semester.

Taking measure of the evolving human body

── What can we learn from measuring the body movements of track and field athletes?

One thing that we have begun to understand is that the surrounding environment, including the presence of other competitors, can bring out the abilities of track and field athletes. The Jamaican sprinter Usain Bolt set a new world record of 9.58 seconds in the finals of the men’s 100-meter race at the 2009 World Championships in Athletics in Berlin. American sprinter Tyson Gay, who finished second in the same event, set a new personal record of 9.71 seconds. Research analyzing the movements of the two sprinters revealed that when they ran in adjacent lanes in the 100-meter final, their strides were synchronized in certain segments of the race. Meanwhile, this phenomenon was not observed in the semifinals when they raced in separate heats.

At the 2021 Fuse Sprint held in Tottori Prefecture in western Japan, Ryota Yamagata broke the Japanese men’s 100-meter record with 9.95 seconds, while compatriot Shuhei Tada improved his personal record to 10.01 seconds. My lab used a video analysis tool that utilizes deep learning to extract the coordinate points of the athletes’ bodies and analyzed how the movements of the two athletes related to one another. showed that the strides of the two athletes were more in sync in the final, when they ran in adjacent lanes, than in the semifinal, when they competed in separate heats. In other words, we saw the same spontaneous phenomenon that we did with Bolt and Gay in Berlin.

These examples are both from short-distance footraces, but in sports in general, the conventional wisdom is that when someone performs well, it lifts the performance of those around them. I myself was a member of my university’s gymnastics team, and the same phenomenon has been observed in gymnastics. It might take time until someone is successful in executing a new technique, but once they do, others follow suit in quick succession after the breakthrough. Additionally, the presence or absence of spectators can also affect how athletes perform. These examples and the results of related experiments demonstrate that an individual’s abilities do not lie solely within their physical body, but rather, their abilities can be drawn out by the circumstances of the environment.

── What kind of advances have we seen in recent measurement technologies?

One recent advancement is the ability to measure heart rate from video imagery. Using this technology, it becomes possible to, for example, instantly read how tense a baseball player is when they’re at bat. Another newly developed technology involves the ability to analyze minute eye movements to provide clues as to what a person is perceiving and thinking. In particular, microsaccades, which are small, involuntary eye movements, could provide important information in a sports context. When captured with a high-speed camera at a high temporal resolution, microsaccades may be able to tell us where in space an athlete is subconsciously directing their attention. There have also been advances related to devices that measure brain activity during exercise, as improvements in signal-to-noise ratios have made it easier to obtain reliable data.

In addition to these kinds of technology, a model based on a mathematical concept known as nonlinear dynamics is gaining traction for showing relationships between complex variables with mathematical formulas and units, instead of the descriptive terms based on intuition used previously. In competitive sports, the more information one has about one’s opponent, the more advantageous and better. Currently, there are no specific regulations in international competitions related to analyzing information about athletes. So there are naturally ethical concerns about the potential ways this technology could be misappropriated and abused in assessing and analyzing athletes’ bodies. We need to discuss how to utilize this technology to improve athletic performance without compromising fairness and impartiality.

Breaking out of constraints

── The sport called breaking, a style of street dance commonly known as breakdancing, made its Olympic debut at the Paris games this year. From a sports science perspective, how does one improve at dance?

Learning how to move in varied ways in response to sound or music is thought to allow for a greater range of expression through dance, and there are several stages involved in improving one’s performance. First, a dancer learns to move rhythmically to sound, then makes the movements more complicated and sophisticated. Next comes the stage in which the dancer is able to freely combine these movements with music. Experienced dancers can insert movements at will between beats, but this is very difficult to do for beginners. There is a big difference between simply performing a certain movement and performing that movement at a specific tempo and timing, though they may seem similar at a glance. Beginners may try to imitate more experienced dancers, but they may not able to move their body as desired because they are drawn into synchronizing their movements with the timing of the beat.

, whereby movements naturally tend to synchronize with one another or with one’s surroundings, is known as entrainment. Some examples of entrainment include moving one’s body rhythmically to rhythmic music, as well as the tendency for the movements of dancers dancing next to each other to synchronize. Even the inclination of one’s left and right hands to move in sync is a kind of entrainment. If you make good use of this phenomenon and synchronize your movements with those of a skilled dancer, you can improve your performance; but you may not be able to achieve the performance you envision if you are entrained to unintended movement. For example, if you alternate between moving your left hand and right hand quickly, their movements will end up synchronizing. In this way, entrainment, which occurs unconsciously, can be considered a kind of constraint in dance. Once you overcome this constraint, you can express yourself as freely as you wish.

── What other kinds of constraints exist in sports?

Another constraint is assumption, or in more technical terms, cognitive bias. There are many types of assumptions in sports that would be considered cognitive biases. For example, when you serve in tennis, if you aim for an ace by trying to land the ball at the very edge of your opponent’s service box, you are more likely to fail and commit an error. On the other hand, if you hit an easy, reliable serve in order to avoid errors, your opponent will have the advantage. Some players aim too close to the edge and rack up errors, while others aim where it’s safe too often, making it easy for their opponent to return the serve. In other words, if you can overcome the cognitive biases that lead you to serve to the wrong place, under the mistaken assumption that it’s the best option, you take the first step toward improving your performance.

Where a player chooses to aim and land their serve on the court from an infinite number of possibilities reflects their ability, as where you aim will naturally vary depending on your skill level. If a beginner tries to imitate a skilled player and aims for the very edge of the line, they will fail. Where you aim also depends on where you are on the timescale of the progression of your ability; what may not be the optimal choice in the short term may end up being optimal in the long term, and indeed, a beginner who makes a lot of errors on their service by aiming near the line may find that same spot becoming the best place to aim as they improve. This scenario applies in many sports where skilled play and risk are involved. The secret to improvement is breaking free from the shackles of cognitive bias.

── How does a person overcome such constraints?

Overcoming constraints means first identifying the variables associated with those constraints. In the case of dance, we know that the speed of the movement has a significant impact on entrainment. When your body does not move the way you desire, it is helpful to practice changing the speed and tempo, as when practicing piano. Additionally, overcoming cognitive biases requires rethinking the assumptions we take for granted. This process involves a great deal of effort and may result in a temporary decrease in performance. You have to confront yourself with patience and perseverance to overcome constraints.

In general, the process of motor learning involves both exploration, which entails trying many different kinds of movement, and exploitation, which involves learning how to utilize one movement effectively through repetition. Rethinking what we take for granted is one example of exploration, and practicing a single skill repeatedly is a type of exploitation. Balanced repetition of these two activities helps refine movement and improve your abilities.

Understanding human movement

── Although computer analysis technologies continue to improve, are there any characteristics of the human body that are uniquely difficult to capture even with these advanced technologies?

There have been attempts to simulate the human body and brain using computers, but even if we seem to be able to replicate them perfectly, we cannot actually predict how they will behave. This is because the human brain and body as a whole are inseparable from the surrounding environment. And unless we can recreate this condition in its entirety, environment included, we cannot predict human behavior. To put this into perspective, it is also difficult to predict how global warming will change the environment in the future as it continues to progress; but predicting how the human body will behave is even harder. The phenomenon observed in the track and field sprint races that I cited earlier is one such example of this difficulty. In addition to the athlete’s physical condition, the weather conditions on the day, the runner in the next lane, the cheering of the spectators and other factors converging, all interact in complex ways to bring out an outstanding performance from the athlete. On the other hand, it is important to keep in mind that what can be learned from computer analysis is the behavior of the body in a very limited environment, not the behavior of the body in diverse environments.

My lab investigates minute fluctuations in body movement. Movement fluctuations can be caused by changes in the internal state of the body or by external forces, such as changes in the environment. As a result, when internal and external environmental variations overlap and interact, it becomes theoretically impossible to reproduce any movement perfectly. For example, even if a person appears to be repeating the same movement, precise measurements always reveal that the movement is slightly different. It is a miracle that the human body, which is constantly undergoing changes, is able to repeatedly reproduce complex movements. This is perhaps one of the reasons why sports and art performed with the human body are so impressive to audiences. In our research, we have found that skilled people do not try to eliminate natural variability between movements, but rather adopt a flexible strategy that achieves accuracy while maintaining some of the variability. I personally believe that our research on how humans cope with natural human variability is one way of understanding human nature itself.

References
Furukawa, H., Miyata, K., Richardson, M. J., Varlet, M., & Kudo, K. (2024). Could spontaneous interpersonal synchronization enhance athletes’ performance? A case report on the Japanese 100-m record race. Research Square.
Editor’s note: This paper is a preprint, a preliminary version of a manuscript that has not completed peer review by a journal.
Kudo, K., Okano, M., & Kurebayashi, W. (2023). Hisenkei rikigakukei toshite no shintai [“Human Body as a Nonlinear Dynamical System”]. Butsuri, 78 (7), pp. 390-398.

Kazutoshi Kudo
Professor, Graduate School of Arts and Sciences

Obtained his Ph.D. in 1998 from the Department of Life Sciences in the Graduate School of Arts and Sciences at the University of Tokyo. Before assuming current role in 2022, served as an assistant professor in the Graduate School of Arts and Sciences and associate professor in the Interfaculty Initiative in Information Studies, both at the University of Tokyo, and spent time as a visiting researcher at the Center for the Ecological Study of Perception & Action at the University of Connecticut in the U.S. Contributing author to several books, including Arts-Based Methods in Education Research in Japan (Brill Sense, 2022).

Interview date: July 4, 2024
Interview: Yuki Terada, Hannah Dahlberg-Dodd