The benefit of physical activity in health promotion is widely accepted. Although regular aerobic physical activity is recommended by national and international guidelines, most of the guidelines also recommend regular muscle strengthening activities at moderate or greater intensity that involve all major muscle groups on 2 or more days a week for additional health benefits. Considering this trend, the epidemiological evidence on the association between muscle-strengthening exercise and health outcomes is increasing, and muscle-strengthening exercise is emerging as an important discipline in the field of physical activity epidemiology. In this narrative review, we provide an epidemiological overview of muscle-strengthening exercise. First, we define muscle-strengthening exercise. Second, we present the history of muscle-strength exercise. Third, we provide epidemiological evidence on the association between muscle-strengthening exercise and health outcomes, including the risk of mortality, cardiovascular events, cancer, and life-style related diseases. Last, we describe the prevalence of and correlates of muscle-strengthening exercise. Most of the studies included in this review were international studies, as relevant studies conducted in Japan were limited. Hence, there is a need for epidemiological studies on muscle-strengthening activity with a focus on the Japanese population.

Objective: To clarify the incidence rates of sports injuries, including those due to trauma, overuse, and diseases, a descriptive epidemiological study was conducted in players from the Keio University rugby football club.

Methods: The study participants were 368 players who belonged to the Keio University rugby football club from April 2011 through December 2018 (1,049 players year). We analyzed the incidence per practice day and game, by clinical department category and disease classification, and by unplayable period and severity of the sports injury and disease that led to leave from practice and game during the study period. In addition, we analyzed the incidence of sports injuries and diseases by body part affected, month of onset, orthopedic and neurosurgical disease statuses, and year and month of onset of internal diseases according to clinical department and disease classification.

Results: The incidence of sports injuries and diseases was 1.67 cases/player overall, 1.07 cases/player in the orthopedic diseases, 0.25 case/player in the internal diseases, and 0.24 case/player in the neurosurgical diseases (all concussions) over 8 years. The incidence rates per practice day and game were 0.41 and 1.18 cases, respectively. The conditions with the highest incidence rates were as follows: orthopedic diseases of the lower limb, 45%; ligament injuries, 46%; common cold, 40% of all internal diseases; and seasonal and annual cases of gastroenteritis, 35%.

Conclusion: This study shows that many cases of ligament injuries of the lower limb were treated as orthopedic diseases; and common cold and gastroenteritis, as internal diseases. All cases of concussion were treated as neurosurgical diseases. Given these facts, steps must be taken to secure the duration of a play.

Objective: During the coronavirus disease (COVID-19) pandemic, implementing personal protective measures is necessary for exercisers when performing exercises. However, to the best of our knowledge, no study has investigated their implementation of personal protective measures. Herein, we describe the implementation status of personal protective measures in those exercising regularly, mainly outside the home, among Japanese individuals during the COVID-19 pandemic.

Methods: This descriptive study was conducted using internet-based surveys of individuals living in the Kanto area. Of the 2400 participants in the first survey in February 2020, 2149 of those who participated in the subsequent surveys in June and July 2020 and exercised regularly and outside the home comprised the subjects. The location, sport type, and eight personal protective measures (avoiding exercise when sick, avoiding touching the face, avoiding touching the place or equipment that others could touch, maintaining hand hygiene, social distancing, wearing a face mask, exercising alone or only with family, and exercising when and where few individuals are nearby) were evaluated, and the prevalence of implementing these measures was calculated.

Results: The prevalence of those exercising regularly was 29.6% (n=636), and 431 participants exercising regularly outside the home were included. The prevalence rates of those who avoided exercise when sick were 83.3% and 91.5% among those exercising indoors and outdoors, respectively. Regardless of the location and sport type, maintaining hand hygiene after exercise revealed the highest prevalence and wearing a face mask had the lowest prevalence. Social distancing was less implemented among those exercising indoors, especially those engaging in ball games or martial arts, than among those exercising outdoors.

Conclusion: We clarified the personal protective measures that exercisers could take more strongly, such as avoiding exercise when sick and droplet precaution while exercising indoors. Awareness among exercisers should be raised regarding the necessary protective behaviors against COVID-19.

Objective: This study compared regular exercise among Japanese adults before and during the novel coronavirus (COVID-19) pandemic.

Methods: This cross-sectional study used data from an online survey conducted in July 2020. In July 2020, participants were asked if they performed 14 categories of exercises such as walking or stretching, at the time of the survey and at the same time a year earlier. Statistical analysis was conducted using the McNemar’s test to show the difference between 2019 and 2020 in the percentage of participants who performed various exercises, categorized by sex and age group.

Results: 2155 men and women in their 20s to 70s living in the Kanto region took part in this study. The proportion of participants who enjoyed at least one type of exercise was significantly higher in 2020 (78.8%) compared to the previous year (76.1%) (p<0.001). Compared to 2019, the proportion of participants engaging in walking, stretching, radio calisthenics and strength training was higher in 2020. Whereas, the proportion engaging in outdoor ball games and swimming was lower in 2020. These trends did not differ by sex or age group.

Conclusion: This study showed that during the COVID-19 pandemic, the proportion of people doing exercise seemed to have increased compared to that before the pandemic. Regarding individual activities, large increases were observed in activities which can be performed at or around the home. Whereas, reduction was observed in group activities and indoor activities at public facilities. Continued support for those who have started exercise at home may be beneficial in promoting physical activity.

Objective: Apple Inc’s iPhone Health App automatically records daily steps of the iPhone users. We developed a method to obtain the recorded step counts from the screenshot images of Health App. We examined the practicality of the method through an Internet survey by which we intended to detect regional and demographic variations in the degree of step count drop under the declaration of a state of emergency against spreading of COVID-19.

Methods: A total of 1,200 daily iPhone users aged 20-69 years living in Japan among registered monitors of an Internet survey company were surveyed, resulting in screenshot images of iPhone Health App. We developed a program to read the daily numbers of steps from the screenshot images, and confirmed the changes in the average number of steps from February 19 to May 19, 2020.

Results: About 79.9% of the collected images were able to be used for the machine reading of daily step counts without errors. The causes of errors were examined for the improvement of the proposed methods. Using a fixed effects model, it was estimated that the average number of daily steps significantly decreased after the declaration of the state of emergency, and the observed tendency was consistent with previous studies in Tokyo. We also identified significant regional and age variations of step-count decrease. Largest drops of daily step count were observed for the group of aged 20-29 year-old living in three major metropolitan areas: average decrease of daily steps of men and women in the group were 2,712 and 2,663, respectively.

Conclusion: This study indicated that the newly developed method to automatically read the number of steps from screenshot images of iPhone collected through an Internet survey is an effective way to objectively and retrospectively measure temporal changes of step counts of people.

In November 2020, the International Society for Physical Activity and Health (ISPAH) published “Eight Investments That Work for Physical Activity”. This document was updated from ISPAH’s 2011 publication: “Non Communicable Disease Prevention: Investments That Work for Physical Activity (2011)” following the “The Toronto Charter for Physical Activity: A Global Call for Action” published in 2010. Along with the “WHO Global Action Plan on Physical Activity 2018-2030”, this is useful as guidance for promoting physical activity. This document emphasized that physical activity promotion will not only improve people’s health, but also contribute to a better society and the achievement of the Sustainable Development Goals (SDGs) developed by the United Nations. The strategy to promote physical activity is based on a systems-based approach, which recommends measures in eight areas: 1) whole-of-school programmes, 2) active transport, 3) active urban design, 4) healthcare, 5) public education, including mass media, 6) sport and recreation for all, 7) workplaces, and 8) community-wide programmes. This paper outlines the document and introduces its Japanese translation version.