Health promotion for workers focusing on physical activity and sedentary behavior: Epidemiological studies in occupational health at the Physical Fitness Research Institute / 体力科学

Health issues with workers include many aspects that scientific research in physical fitness and sports medicine can contribute to. Nevertheless, in Japan, there are few studies on the health problems in workers reported in the field of physical fitness and sports medicine. One reason could be the difficulty of obtaining cooperation in research from companies. This paper introduces results of epidemiological studies on health problems in workers by the Physical Fitness Research Institute. Our research serves as an example of physical fitness and sports medicine studies, including methods for securing fields for research. For the last decade, various epidemiological studies on worker’s mental health, sleep, non-alcoholic fatty liver disease, and labor related issues have been conducted in our research institute. Most of these studies indicated that lack of physical activity is associated with these indicators in Japanese workers. In recent years, we have also been conducting observational and interventional studies focusing on sedentary behavior in workers. Physical activity is deeply linked to worker’s health, therefore, the important approach to start a research in occupational health is to plan research that solves the company’s health challenges. In occupational health, the needs to promote physical activity and to reduce sitting time are growing under the movement of “Health and Productivity Management” and burden of the COVID-19 pandemic. We believe that current challenges provide an opportunity to advance physical fitness and sports medicine research in occupational health.

Isotemporal substitution of sedentary time with physical activity and its associations with mental health of Japanese office workers / 体力科学

In this study, we performed isotemporal substitution analysis to examine potential associations of sedentary time and physical activity with mental health of Japanese office workers. This study employed a cross-sectional study design. We analyzed data on 108 Japanese office workers (mean age 46.4 ± 9.8 years; 64.8% women) in the study. Sedentary behavior (SB; ≤ 1.5 metabolic equivalents [METs]), light-intensity physical activity (LPA; 1.6–2.9 METs), and moderate-to-vigorous physical activity (MVPA; ≥ 3 METs) were measured with a triaxial accelerometer. Two kinds of self-administered questionnaires, the mental stress (K6) and work engagement (Utrecht Work Engagement Scale), were used to assess negative/positive mental health. A cut-off score of 5 or higher on the K6 was used to define persons with mental stress. Logistic and multiple regression analyses using an isotemporal substitution model was applied to demonstrate the association between replacing 30 min/d of SB with an equal amount of time spent on LPA or MVPA and mental stress and work engagement; the studied covariates were age, sex, body mass index, economic status, education, and overtime hours. The results showed that replacing SB with MVPA for 30 min/d was significantly decreased odds ratio (OR) of mental stress (OR = 0.38, 95% confidence interval 0.15–0.92), whereas the replacement was not associated with work engagement (B = 0.16, P = 0.38). In contrast, substitution of SB with LPA was not associated with mental stress and work engagement. These results indicate that substituting sedentary time with MVPA could be associated with mental stress of Japanese office workers.

Relationship between mental health and exercise in adolescents / 体力科学

A number of studies have been conducted to examine the influence of physical activity on psychological well-being in young people; however, few studies have discussed the relationship between exercise and mental health. The purpose of this article was to investigate the influence of exercise on mental health in adolescents by performing a brief review. Although the studies included in this review are cross-sectional, relatively small scale and lack measurement consistency, the results show that participating in exercise and/or sports is likely to significantly improve mood. Organized sport activities contribute to the reduction of chronic stress response. On the other hand, higher levels of sedentary behavior are associated with worse mental health. These findings suggest that physical activity may enhance psychological well-being, and chronic vigorous exercise and sport activities are effective in promoting improvement of mental health in adolescents.

Pre-exercise rather than post-exerclse intake of a large meal enhances liver glycogen sparing during endurance exercise in rats / 体力科学

We investigated the effects of feeding a large meal to female rats (n = 66) just before or just after voluntary wheel running on energy metabolism during a final endurance exercise test. The rats were divided into three groups ; one fed a large meal just before exercise (BE), one fed a large meal just after exercise (AE), and one fed <I>ad libitum</I> (AD) . The rats were allowed to run voluntarily from 20 : 00 to 07 : 00 h. The BE group were given a large meal (more than 12 g) between 19 : 00 and 20: 00 h and a small meal (3 g) between 07 : 00 and 08 : 00 h. The AE group were given a large meal (more than 12 g) between 07 : 00 and 08 : 00 h and a small meal (3 g) between 19 : 00 and 20 : 00 h. After 4 weeks, 6 rats in each group were sacrificed at 22 : 00 h, and 12 rats in each group were sacrificed after 30 min starting from 22 : 00 h at 15 m/min (n=6) or 35 m/min (n=6) on a rodent treadmill (0° grade) . Four rats in each group were sacrificed after 30 min starting from 22 : 00 h at rest on the treadmill as a control. The plasma free fatty acid (FFA) and glycerol concentrations increased significantly during low-speed exercise in the AD group, and during higher-speed exercise in all groups. The liver glycogen concentration was significantly greater in the AE group than in the other groups at rest, and decreased significantly during exercise at both speeds in the AD group, but not in the BE and AE groups. The gastrocnemius muscle glycogen concentration was decreased significantly during exercise at both speeds in the AD group, and at high speed in the BE and AE groups.<BR>These results indicate that intake of a large meal just after exercise can store a high level of liver glycogen at the beginning of exercise than <I>ad libitum</I> feeding or large meal intake just before exercise, and expend plasma FFA in muscle during exercise compared with <I>ad libitum</I> feeding. This suggests that large meal intake just after exercise contributes to improvement of metabolic capacity in endurance exercise with enhanced liver glycogen sparing.