Students who are selected by the Japan Society for the Promotion of Science (JSPS) for a Research Fellowship for Young Scientists receive research subsidies and/or Grants-in-Aid for a period of two to three years. The research grants can be used for any purpose, and fellows can receive a maximum of 1.5 million yen per year by applying for a Grant-in-Aid. Of course, these fellowships are highly competitive, so not everyone who applies will be accepted. This time, we sat down with Teppei Matsumura, a second-year doctoral student in the Graduate School of Sport and Health Science, who earned a Research Fellowship for Young Scientists after completing a RARA Student Fellowship, having published his graduation thesis in an academic journal.

Pursuing an interest in the effects of caffeine since his days as an athlete

―― So, you ran hurdles as a member of the track and field team all through junior high school, high school, and university.

Matsumura: Yes, in junior high school, my main event was the 110m hurdles, and in high school, I primarily ran the 400m hurdles.

―― We were told that you competed in national tournaments when you were in junior high school. Why did you switch events?

Matsumura: First of all, the hurdles in high school are taller depending on the event.^*1 Since the hurdles were the same height as in junior high school^*2 if I ran the 400m, and considering that I am not that tall, I decided to try my hand at the 400m hurdles.

*1: In the men's 110m hurdles, junior high school hurdles are 91.4cm, while those for high school students and adults are 106.7cm.
*2: In the men's 400m hurdles, hurdles for high school students and adults are 91.4cm.

―― You seem to be someone who makes choices based on logic rather than intuition.

Matsumura: Now that you mention it, I was the type of person who liked to think about things while fiddling with numbers. (laughs) I would record videos of my runs and analyze them later using apps and other tools. As part of this process, I would notice a delay in a certain section and wonder why that was the case, or I would think about what I should do to run faster. Before I realized it, I had spent all my time on this analysis.

―― It seems you became interested in your current research topic of caffeine after thinking about how to run faster.

Matsumura: That's right. In high school, however, I was really only wondering if drinking energy drinks would improve my results. (laughs) Then, in a class I took as a second-year student at university, I came across some literature on the effects of caffeine on exercise performance, and I thought this would be an interesting topic to explore. The instructor of that class was Professor Takeshi Hashimoto, who is now my doctoral program advisor. When I told Professor Hashimoto that I was interested in the effects of caffeine on exercise, he invited me to do the research together with him. This was right when the COVID-19 pandemic was in full swing and more and more of my classes were getting cancelled. So, I stayed home and read every paper I could find on the topic.

Publishing his undergraduate thesis on caffeine in an academic journal

―― Had you intended to advance to graduate school when you were an undergraduate student?

Matsumura: That was not actually the case. (laughs) When I first entered university, I was not that interested in research, but around the time I was in my second year, I started to realize that going to graduate school was a possibility because I had friends who wanted to go on to graduate school. “Well, graduate school is one option,” I thought, and because I knew I liked to analyze things, I had a vague feeling that it just might suit me. At first, however, I just thought it was one of many options.

―― You said it was your experience of reading many papers during the pandemic that spurred you to advance to graduate school.

Matsumura: Perhaps it was because I read a lot of papers and wrote a lot of reports for class assignments every day at home, but when I was finally able to resume conducting experiments in my fourth year of undergraduate school, I had a good foundation for analyzing previous research and conceiving experiments. After that, I first concentrated on properly finishing my graduation thesis, while consulting with my professors about the possibility of going to graduate school. The topic of my thesis was the effect of caffeine supplementation on 100-meter sprint running performance. I finished writing it in December, but Professor Hashimoto recommended that I submit it to a scientific journal, so I fine-tuned the content and rewrote the paper in English. I submitted the paper to Medicine & Science in Sports & Exercise, the journal of the American College of Sports Medicine, and it was accepted in September after I had become a first-year master’s student. After that, we put out a press release about the paper and garnered a great response via the media coverage. On the one hand, I was happy, but on the other hand, I realized how difficult it is to accurately communicate my research to the wider world because the press and people on social media were writing things that I did not actually say in my paper.

―― Did you already have your sights set on the doctoral program in your first year of the master's program?

Matsumura: Yes, I started to think that I would like to continue my research given all the hard work I had already put into it. As I read through the papers, I found that although there were many studies on caffeine supplementation and its effects on exercise, there were many things that seemed to be known but not fully understood. So, if that was truly the case, I thought I should go ahead and do the research myself. Since I am the type of person who doesn’t commit until I’m ready to go all in, I decided that if I was going to do this, I was going to be thorough and tackle the research with everything I had. That being said, I still needed to make financial arrangements so that I could advance to the doctoral program. After entering the second year of my master's program, I applied for a JSPS fellowship but was unsuccessful, so I applied for the RARA Student Fellowship, and luckily, I was selected.

Caffeine can undermine physical training performance

―― In the doctoral program, your research has consistently focused on the effects of caffeine supplementation on exercise performance.

Matsumura: When I was in the master's program, I focused on jumping performance. According to the International Society of Sports Nutrition, caffeine intake of 3 to 6 mg per kg of body weight is considered effective to improve exercise performance. This means a person weighing 60 kg would need to ingest up to 360 mg of caffeine, or the equivalent of drinking 4 to 5 cups of coffee. Since an athlete cannot easily drink this much before a competition, I proceeded to investigate whether a smaller amount of caffeine could produce the same effect. What I found is that even at very low dose as little as one cup of coffee, caffeine has a positive effect on jumping performance.

―― I see. But it does not seem to simply be a matter of drinking a lot of coffee, right?

Matsumura: That's right. This is why I also conducted a meta-analysis in which I gathered relevant previous studies and summarized the findings from them. In doing this, I was unable to confirm a significant relationship between caffeine dose and its effect on jump performance. In other words, this result claims that increasing your caffeine intake will not make your physical performance greater. So, research into this topic is what I initially focused on for my doctoral program. After that, I started to look into the effect of caffeine on training performance and recovery.

―― Does caffeine intake also have an effect on training performance?

Matsumura: Some people actually do strength training after taking caffeine as a “pre-workout supplement”. They do this because they think it has some kind of effect (e.g., temporal performance-enhancing effect), but the extent to which caffeine intake actually impacts habitual training adaptation is not well understood. What’s more, the effects after a single exercise session (i.e., post-exercise conditioning) have not received as much attention as the effects during exercise. Even if your performance improves once, it may be a hindrance to daily training programs if your performance then temporarily decreases to a lower-than-expected level. This is the topic I am currently researching as part of my JSPS DC2 fellowship. So far, I have found that consuming caffeine before resistance exercise with a specific modality increases muscle strength during exercise, but muscle strength temporarily decreases after exercise. The question is why does this phenomenon occur, and I aim to determine the cause with my current research.

Filling in the gaps from past research is what makes research interesting

―― So, have researchers elucidated the mechanisms underlying how caffeine enhances athletic performance?

Matsumura: It is generally believed that caffeine enhances exercise performance by blocking adenosine receptors, which reduces fatigue and activates the nervous system. However, we still don’t know why caffeine might reduce post-exercise performance even further. This is what I want to find out in my research. Many papers have been published, but they have also a lot of “gaps.” Trying to fill in these gaps with my own research is something that really piques my curiosity.

―― Since you were an athlete yourself, it seems only natural that these kinds of straightforward questions would arise from your point of view.

Matsumura: Perhaps that’s my strong point. The bottom line is that if you can perform at a high level as an athlete, it will bring you joy. It sounds very simple, but if you can run fast, that alone is enough to make you happy. (laughs) I wanted to continue this research somehow, so after being selected as a RARA Student Fellow, I re-applied for a JSPS fellowship in the first year of my doctoral program and was accepted.

―― What things did you pay attention to in your application?

Matsumura: Originally, I was not good at self-promotion, and when I applied for DC1, I thought that if I wrote simply and objectively about my accomplishments, I would be accepted. As a second-year master's student, I already had two first-author papers and several conference presentations, so I mistakenly thought that was enough. In the end, my application did not fully take the reviewers’ point of view into consideration. This experience made me reflect on the need to not rely solely on my past accomplishments, but to make sure that my application conveyed the kind of research I wanted to conduct, even if someone from outside of my field was reading it. Therefore, when I applied for DC2, I carefully reviewed the information and added diagrams and other details so that the message I wanted to convey could be understood at a glance.

―― We also heard that you have given lectures to junior and senior high school students as a RARA Student Fellow.

Matsumura: Yes. As a RARA Student Fellow, I’ve had opportunities to introduce my research to junior and senior high school students in an easy-to-understand manner in the RARA Commons sessions. Caffeine tends to be a sensational topic, and I was especially mindful of how easily junior and senior high school students can be influenced, so I introduced my research with caution. I made a conscious effort to clearly communicate that caffeine has both positive and negative effects. It was a very invaluable experience for me.

―― What do you have in mind for your future career path?

Matsumura: As for the future, I still want to pursue research that interests me. For this reason, I am considering a wide range of options, both domestic and international, and I am not restricting myself to just academia or the corporate world. That being said, as I dive deeper into my research, I am exposed to more and more related areas, so I do wonder where I should focus my attention. In any case, I think it is important to maintain a strong sense of determination and pursue what genuinely interests me.