Associate Professor, Exercise Biochemistry Division, Institute of Health and Sport Sciences, University of Tsukuba.
Modern brain fatigue is an increasingly recognized challenge not only in competitive domains such as sport and esports but also in the broader context of contemporary digital society. From the tatami mats of judo to the virtual spaces of esports, Associate Professor Takashi Matsui investigates its underlying mechanisms and explores strategies for mitigation through the lens of exercise biochemistry.
Q1. What motivated you to become a researcher?
A1. From judo to brain science: discovering passion in exercise biochemistry
I never imagined I would become a scientist. From the age of five, I was immersed in judo, advancing through high school and university on sports scholarships. But during matches, I often felt a unique kind of fatigue, both mental and physical, that kept me from performing at my best, even against opponents I could easily defeat in practice.
Supplements and training could ease muscle tiredness, yet this match-specific fatigue remained a mystery well into my twenties. Then, in a university biochemistry class, I realized the true cause lay not in the muscles but in the brain.
That realization was a turning point. I became fascinated by the science of fatigue and found myself drawn toward research. Today, in the field of exercise biochemistry, I pursue my passion for understanding performance, health, and fatigue from a biochemical perspective.
Q2. Could you describe your research in more detail?
A2. Finding ways to soundly overcome cognitive fatigue
Fatigue affects both muscles and the brain, but my passion lies in uncovering the brain's side of the story. I focus on lactate, a substance produced during intense exercise. Once dismissed as a mere byproduct and a cause of tiredness, lactate is now recognized as an energy source. My research explores how lactate in the brain may serve as a safeguard by providing fuel while slowing neural activity, or act as a trigger for super-recovery, in which rest after fatigue unlocks even greater performance. We have shown that this remarkable effect occurs not only in muscles but also in the brain.
Recently, I have extended this work to esports, where players rely almost entirely on cognitive ability. Prolonged play can lead to cognitive fatigue, a decline in decision-making that arises without the sensation of being tired. Unlike in traditional sports, where fatigue serves as a warning sign, in esports that signal is absent, so mistakes creep in unnoticed.
This problem is not unique to gamers. Many modern workers spend long hours at computers and face the same risks. By developing ways to detect and alleviate cognitive fatigue, such as tracking pupil dynamics or using minimally invasive methods to measure lactate in the brain, I hope to help improve both performance and everyday well-being.
Q3. What message would you share with aspiring researchers?
A3. Science begins where passion meets curiosity
Find something you truly love, something you can be so absorbed in that fatigue fades away. When you devote yourself wholeheartedly to what fascinates you, that passion becomes the driving force of scientific inquiry and inevitably opens new doors of discovery. For me, judo was that spark, and it eventually became the pathway to my research.
Science originates from human curiosity, while sport traces back to play. When you bring these two forces together, you get sports science, a field that blends rigorous laboratory research with real-world exploration, engaging both body and mind. Because it remains closely tied to everyday life, it offers not only intellectual challenge but also a deep sense of fulfillment.
Through the perspective of scientifically studying play, I hope that many more people will discover the joy, meaning, and possibilities of sports science.
(Article: Yasuhiro Hatabe)
Profile
Takashi Matsui
Associate Professor, Exercise Biochemistry Division, Institute of Health and Sport Sciences, University of Tsukuba.
Born in Tsukuba and raised in Tokyo. Earned his Ph.D. in Health and Sport Sciences at the University of Tsukuba in 2012. After working as an Assistant Professor, he became Associate Professor in 2025. Holds a fifth-dan in judo. Member of the Japan Olympic Committee's judo staff since 2017. Selected as a JST-FOREST researcher in 2021. He continues to combine his lifelong passion for judo with his scientific curiosity, aiming to connect the world of sport with discoveries that can improve health and well-being in everyday life.
Note on Handwritten Text:
These two principles, articulated by Judo's founder Jigoro Kano, are integral to Judo's philosophy.
- Seiryoku Zen'yō (精力善用) — the principle of making the most effective use of one's energy for a constructive purpose.
- Jita Kyōei (自他共栄) — the principle of mutual welfare and benefit, emphasizing that individual progress and collective well-being go hand in hand.