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A sedentary lifestyle due to the lack of physical activity has come to characterize a large swath of contemporary society, posing great health risks and becoming a major public health issue. Masamitsu Kamada is an associate professor in the Department of Health Education and Health Sociology at the Graduate School of Medicine whose mission is to drive progress toward a world free of physical inactivity. The public health expert shared his thoughts on how we can create an environment in which anyone can lead an active lifestyle.

The science of spreading the gospel of physical activity

── What does research tell us about the current state of physical activity in our society?

Research on people’s lifestyle and health has shown that a lack of sufficient physical activity increases the risk of various diseases and other health issues. Here, “physical activity” refers not just to sports and exercise per se, but also other sorts of activity in our daily lives, including household chores, farmwork, moving to and fro between places, as well as taking care of children. When we look at the risk factors associated with causes of death among Japanese people today, the third leading factor is lack of sufficient physical activity. Physical activity is recommended for all people, regardless of ability, but becoming and staying engaged in it can be challenging for a variety of reasons.

There have been reports showing that the problem of insufficient physical activity is worsening in Japan and many other countries. In Japan, the intensity level of occupational physical activity has decreased by an average of 10% over the past 50-60 years. Although some reports indicate that the average number of steps that Japanese people walk per day is among the highest in the world, that number has been declining over time. Furthermore, various surveys show that a significant portion of people in Japan simply do not do enough physical activity.

For this reason, I am involved in various activities and carry out research with the mission of driving progress toward a world free of physical inactivity and creating a society in which each person can lead an active lifestyle that suits them. One of my specialties is dissemination and implementation science, which I’ve employed to spread (i.e., disseminate) physically active behavior and to identify the keys necessary to realize (i.e., implement) projects and initiatives for that purpose. Our behavior patterns are influenced not only by individual factors such as knowledge, but also our physical and social environment and public policy. Therefore, we need to examine how the national and local governments and the private sector can intervene effectively to promote behavioral change in individuals. In order to implement societal initiatives that promote physical activity, we need to start by having discussions with people from throughout society, strategize with them, and then carry out initiatives and projects with the multiple perspectives we have gained.

── What kind of data do you analyze, and what do you learn from them?

First, studies looking at the relationship between step count, health and mortality risk have shown that people who take more steps per day live longer. In terms of the actual number of steps, however, even . The accumulation of daily steps can also make a big difference in the long run. Based on such findings, the World Health Organization has shifted its guidelines in recent years to place more emphasis on the message that when it comes to one’s health, any physical activity is better than none.

In order to gain an in-depth understanding of current physical activity levels in Japan, we have been working with a company to analyze the number of daily steps recorded with a smartphone app that allows users to accumulate points based on distance traveled, among other factors. An analysis of the data of approximately 1.2 million app users throughout the country has revealed regional differences at the municipal level that were not apparent in the national-level data acquired in the (Japanese only). For example, the highest average number of daily steps for people aged 20-64 is in large urban areas, such as the 23 special wards district of metropolitan Tokyo where the average is approximately 7,500 steps per day. In places like Tokyo, people frequently use public transportation as their main means of travel, and walking to, say, the nearest station understandably increases the number of daily steps. On the other hand, the average number of steps is naturally lower in smaller, regional cities, where people are more dependent on automobiles and the impact of car culture is much stronger. The average number of daily steps is approximately 4,000 in the municipality that logged the lowest number, and the difference among municipalities is significant, even when comparing the same age groups. This result reinforces the need for measures, including urban planning and transportation policies, that focus on the daily living environment to address physical inactivity, and that these measures should take a variety of approaches, especially in rural areas.

A project that moves you

── What are some effective ways to increase physical activity in the population?

It is a very difficult problem to tackle, but we have discovered that there are a number of effective approaches with a scientific basis. This is an issue that needs to be approached from multiple perspectives, including by building and expanding the availability of walkable communities. For example, our project in the city of Unnan in Shimane Prefecture in western Japan is considered the first in the world to demonstrate, through a rigorous method known as a cluster randomized controlled trial, that . Unnan has a population of 40,000 people, but in 2006, under the leadership of then-Mayor Yuichi Hayami, the city established the Physical Education and Medicine Research Center Unnan. I myself was involved in the establishment of this research center as a researcher, and I also worked on various local health initiatives as a city official. The research center is engaged in various activities related to health promotion, evaluation and research, in collaboration with sectors both within and outside the municipal government. Part of these activities involved conducting a communitywide intervention study like the one I mentioned earlier, where we see by how much we can actually increase the number of people who engage in habitual exercise. The first few years of the study did not yield population-level behavior change, but after five years, we were finally able to see some success.

One particular approach we used was social marketing, which applies a marketing technique used by companies to change people’s behaviors. This included developing an information dissemination strategy with a clear priority target audience. We worked to ensure that exercise-related information spread throughout the community using not only flyers, posters and audio broadcasts, but also through word of mouth and by providing educational opportunities. For the word-of-mouth strategy, we found residents who could take on core roles in their communities as “influencers” (where they adopted familiar and approachable names like X Community Movement Awareness Team). In each community, residents worked together with the local government to co-create activities, which were initiated by residents and supported by the government. Some residents even volunteered to walk around the neighborhood wearing sashes to raise awareness. Thanks to activities like these, information and physical activity spread by word of mouth throughout town.

As a result, we saw that even in sparsely populated mountainous areas, continuing to carry out strategic grassroots activities throughout the community with residents and various other organizations could increase population-level physical activity, regardless of age or gender. Currently, under the leadership of Unnan’s Mayor Atsushi Ishitobi, multiple municipal departments, other organizations and residents are working together to expand this program to the entire city, along with other health initiatives. The study has been recognized for its research quality (namely, its low bias risk) and careful application of social marketing. It has even and has been mentioned in the as the world’s first rigorous evidence of successful physical activity improvement at the community level. The city of Fujisawa in Kanagawa Prefecture, just south of Tokyo, which has a larger population of approximately 400,000 people, also implemented its own communitywide intervention. A five-year evaluation confirmed that here, too, they are seeing improved population-level physical activity.

── What other initiatives are you working on?

We have also been working with Nippon Professional Baseball’s Pacific League (Pa League) on a smartphone app that utilizes gamification, which employs elements of gaming to encourage some behavioral change. The Pa-League Walk app, officially sanctioned by the six-team Pacific League, has various functions designed to help baseball fans naturally become more active. So far, it has surpassed 70,000 downloads nationwide, across all 47 prefectures in Japan.

The app includes an illustrated players directory function, which provides users with images of randomly selected players from their favorite baseball club on days they reach 10,000 steps. And on game days, fans of the opposing teams compete against each other and the team that has accumulated the most steps, by adding up the number of steps that each user on their side has walked, is crowned the victor. The design draws on the psychology and sense of camaraderie and belonging among fans who value their connection to the club and players they support. An analysis of de-identified data (from which information that can be used to identify someone has been removed) confirmed that .

Our survey also revealed that about 1 in 4 users had not contemplated starting to exercise in the near future at the time they downloaded the app. It is noteworthy then that the app, by way of professional baseball, was able to effectively reach out to people who otherwise would have been difficult to reach through such conventional means as exercise classes, and encourage them to change their behavior. The study also found that the number of daily steps taken increased regardless of gender, age, education, income and body mass index. Since the launch of Pa-League Walk, a similar project was launched with the J. League professional soccer league. In the future, we intend to initiate collaborations beyond the sports business and seek to tie up with entertainment domains like the music industry, in order to encourage people to naturally start moving their bodies while also enjoying what they love.

Fostering a lifetime of activity

── What about activity among children? How does Japan compare on an international scale?

In the country-by-country report cards released by the , which assess the level of physical activity of children in 57 countries around the world, Japan has received among the best marks in the world. In addition to compulsory physical education classes, Japan has the highest percentage of elementary and junior high school students who commute to school by active means of transportation, such as walking or bicycling. Japan has long made various efforts to ensure that children can walk to school safely. For example, many safety considerations are made at the administrative level. This includes guidelines for the placement of schools put forth by the Japanese Central Council for Education, which factor in commuting distance. Local residents are also involved in ensuring traffic safety, and school zones have been established in accordance with the Road Traffic Act. In addition, in many areas of Japan, students have long walked to school in neighborhood groups. In the U.S. and other countries, so-called walking school buses, in which schoolchildren walk to and from school accompanied by volunteer adults, have been gaining attention as a means of encouraging active school travel.

Japan’s multilayered approach that centers on collaboration between the community and schools, along with road traffic regulations is not something that comes about automatically. In recent years, school districts have expanded due to school closures and consolidation caused by declining birthrates and rural depopulation, which have resulted in more and more schools having to operate school buses. Parents and community members often serve as crossing guards in the morning to protect children traveling to school on foot; in some areas, these, too, are being cut back or eliminated altogether in order to reduce the burden on parents and other volunteers. Experts in various fields such as education, public health, traffic safety, crime prevention and urban planning, are watching this situation vigilantly with a sense of urgency, myself included.

When people from different backgrounds come together and pool their knowledge, there is so much that can be accomplished. For example, an elementary school in Unnan has set the school bus drop-off 500 meters from the school gate, so that students who ride the bus and those who walk share part of the same walking route to school. (In some English-speaking countries, this initiative is known as remote drop-off or park and walk.) Some communities also encourage “watch and walk” as a health promotion measure, in which local residents, including older adults, walk to and from school with the kids while also monitoring them.

Because the school commute cannot be managed by schools alone, handling it as a community matter is critical. This approach also generates benefits for the adults in the community. I believe that we experts must continue to widely disseminate good examples of this partnership between schools and their surrounding communities to society at large. It is becoming increasingly important that this kind of co-creation by people in various positions will be the key to realizing a society in which all people, both young and old, can easily lead more active, healthier lives.

References
1 Lee IM, Shiroma EJ, Kamada M, Bassett DR, Matthews CE, Buring JE. “Association of Step Volume and Intensity With All-Cause Mortality in Older Women.” JAMA Intern Med. 2019 Aug 1;179(8):1105-1112.
2 Kamada M, Kitayuguchi J, Abe T, Taguri M, Inoue S, Ishikawa Y, Bauman A, Lee IM, Miyachi M, Kawachi I. “Community-wide intervention and population-level physical activity: a 5-year cluster randomized trial.” Int J Epidemiol. 2018 Apr 1;47(2):642-653.
3 Kamada M, Hayashi H, Shiba K, Taguri M, Kondo N, Lee IM, Kawachi I. “Large-Scale Fandom-based Gamification Intervention to Increase Physical Activity: A Quasi-experimental Study.” Med Sci Sports Exerc. 2022 Jan 1;54(1):181-188.
4 Abe T., Kamada M., Kitayuguchi J., Yamakita M., Hanazato M., and Hino K. “Implementation of a section allowing children to walk to elementary school from remote school bus drop-off sites: A qualitative study based on the Consolidated Framework for Implementation Research (CFIR).” Japan J. Phys. Educ. Hlth. Sport Sci. 2025 Apr 15; 40:329-343.

Masamitsu Kamada
Associate Professor, Graduate School of Medicine

Native of Miyazaki Prefecture in southwestern Japan. Prior to obtaining a Ph.D. from the Graduate School of Medical Research at Shimane University, Shimane Prefecture, in 2013, received a bachelor’s degree from the University of Tokyo’s Faculty of Education in 2005 and a master’s degree from the Graduate School of Education in 2007. Has been engaged in community health projects as a researcher at the Physical Education and Medicine Research Center Unnan in Unnan, Shimane Prefecture, since 2006. Assumed current role in 2025 after working as a research fellow at Japan’s National Institute of Health and Nutrition, a research fellow at Harvard University in the U.S., and an assistant professor, then lecturer in the Graduate School of Medicine at the University of Tokyo. Also works as a policy counselor for the city of Miyazaki (sports and health sector), an adviser for Kagawa Prefecture’s health promotion policy and a technical review expert for the Japan Sports Agency. Co-author of numerous journal articles, including “” (Lancet, 2021).

Interview date: Sept. 9, 2024
Interview: Yuki Terada, Hannah Dahlberg-Dodd