Past reports have reinforced global public health concerns related to physical inactivity. Recent global efforts to increase physical activity and decrease sedentary behaviors have been underway. The development and release of Report Cards on physical activity for children and youth have in many countries improved advocacy and social mobilization with the intent of increasing young people’s activity by influencing perceptions, priorities, policies, and practices. In 2016, 38 countries including Japan produced a cross-country comparison finding that showed higher physical activity and lower sedentary behavior in countries that reported poorer infrastructure, and lower physical activity and higher sedentary behavior in countries that reported better infrastructure. This suggests that autonomy to play, travel, chore requirements and/or fewer attractive sedentary pursuits, rather than infrastructure and structured activities, may facilitate higher levels of physical activity. Future nationally representative surveys on overall physical activity, active play, and community and the built environment are needed. The establishment of evaluation methods for the international comparison of daily physical activity and its factors in Japanese children and youth are needed.

Pedometers are frequently used to measure habitual physical activity (PA). However, non-locomotive PA may constitute a substantial part of total PA in workers engaged in certain occupations. The purpose of the present study was to examine the relative contribution of non-locomotive PA to total habitual PA in Japanese workers. Subjects were 177 Japanese males and females. Occupations of the subjects were preschool (kindergarten and nursery school) teachers, salespersons, drivers, licensed cooks, security guards, housewives, garbage collectors and office workers. Light PA, moderate-to-vigorous PA (MVPA) and step counts were assessed using a triaxial accelerometer (Active style Pro HJA-350IT, Omron Healthcare Co., Ltd), which allowed for an accurate discrimination between locomotive and non-locomotive PA. The non-locomotive component of MVPA predominated in licensed cooks and garbage collectors, while security guards displayed more locomotive MVPA. The non-locomotive component of light PA predominated in preschool teachers, salespersons, licensed cooks and housewives, while security guards displayed more locomotive light PA. Relative contributions of non-locomotive PA were different among occupations. The present study suggests that locomotor measurements alone might substantially underestimate habitual PA in workers engaged in certain occupations (e.g., licensed cooks and garbage collectors).

The aims of the present study were to examine the role of epoch length (time sampling interval) on locomotive and non-locomotive physical activity (PA) estimates and the relationships with obesity in healthy adults in each sex. Subjects were 308 Japanese women and 183 men aged 20-to-64years old. Time in locomotive and non-locomotive light PA (2.0 ~ 2.9METs; metabolic equivalents) and moderate-to-vigorous PA (MVPA, 3 METs or more) and step counts were assessed using a triaxial accelerometer (Active style Pro HJA-350IT, Omron Healthcare Co., Ltd) presented in 60s and 10s epochs. Body mass index (BMI) by height and body weight was calculated. There were significant differences between results by epoch lengths in both locomotive and non-locomotive PA. In particular, the difference was remarkable for non-locomotive PA. Time in each MVPA for women and men when presented in 10s epochs were significantly higher. Time in total MVPA was different by nearly 30min for women and nearly 20min for men. Moreover, time in non-locomotive light PA when presented as 60s epochs was significantly higher in both women and men than that when presented as 10s epochs, and time in total light PA showed an obvious difference of nearly 50min higher in 60s epochs for women. Conversely, the relationships between PA with 60sec and 10sec estimates and BMI were weak, even though over half of PA variables showed significant correlations. These findings suggest that non-locomotive PA evaluated by the triaxial accelerometer was obviously affected by epoch length. The finding also showed gender differences.

Most Japanese preschool children attend either kindergartens or nursery schools, each providing a distinct environment for children, and the difference between these may be associated with varying patterns of physical activity (PA). The purpose of the present study is to compare the levels of PA in Japanese preschool children enrolled in kindergartens to those enrolled in nursery schools by using triaxial accelerometry (ActivTracer, GMS). PA was assessed using a triaxial accelerometer and daily steps were captured using a uniaxial accelerometer for 6 consecutive days, including weekdays and weekends. Subjects were 157 four- to six-year-old Japanese children attending kindergartens or nursery schools. Moderate-to-vigorous physical activity (MVPA) and step counts were 107 (±34) min/day and 13,567 (±2,725) steps/day respectively for kindergartens, and 97 (±30) min/day and 12,526 (±2,884) steps/day respectively for nursery schools. MVPA and step counts were significantly higher for children enrolled in kindergartens than those enrolled in nursery schools. Although PA on weekdays did not differ significantly, physical activity level, MVPA, and step counts on weekends were significantly higher for children enrolled in kindergartens than those enrolled in nursery schools. In addition, we observed large variability in PA among children enrolled in kindergartens, and relatively little variability among children enrolled in nursery schools. The results suggest that children in nursery schools exhibit less engagement in moderate PA than children in kindergartens, and the difference is more pronounced on weekends. Additionally, we found that PA patterns in young children enrolled in kindergartens may vary greatly.

This study examined the physiological response to different water depths in recreational synchronized swimming. Nine middle-aged, female, recreational swimmers carried out the same team free routines in deep water (deep-water synchronized swimming: DWS) and shallow water (shallow-water synchronized swimming: SWS). Heart rate (HR) was measured continuously during each performance, combined with estimation of metabolic equivalent (MET) values using individual linear regression equations of HR-oxygen uptake. These equations were created using the results of 12 water activities. Blood lactate concentration and systolic blood pressure were measured at the 1/3 and 2/3 stages and immediately after each performance period. HR and estimated METs during DWS (mean±SD, 152.9±7.5 beats·min^-1 and 7.3±1.2) were significantly higher than those measured during SWS (131.8±11.3 beats·min^-1 and 5.7±0.8). Blood lactate concentration and systolic blood pressure measured immediately after DWS were significantly higher than those measured after SWS. With DWS, blood lactate concentration at the 2/3 stage and immediately after the performance were significantly higher than those measured at the 1/3 stage, whereas in SWS no significant difference was found in these values at any time period. In conclusion, the exercise intensity of DWS was high and SWS moderate. The predominant sources of energy may be phosphocreatine stores and aerobic metabolism during these performances. It is possible that glycolysis may also play an important role in energy requirements during the 2/3 stage and immediately after a DWS performance.

The accuracy of a uniaxial accelerometer for assessing physical activity in preschool-aged children was assessed by using an indirect calorimeter which provides the physical activity ratio (PAR) for free living activities. Subjects were 5- to 6-yr-old Japanese girls and boys (n=24, 6.1±0.3 years). PAR was assessed for nine activities (lying down, watching a video while sitting and standing, line drawing for coloring-in, playing with blocks, walking, stair climbing, ball toss, and running) using the Douglas bag method. “Exercise intensities” were recorded with the uniaxial accelerometer (Lifecorder EX ; Suzuken Co. Ltd, Nagoya, Japan). PARs were also predicted by using the equations presented by Higuchi et al. (2003) and Kumahara et al. (2004). Significant correlation was observed between “exercise intensities” as measured by the uniaxial accelerometer and PAR for all activities (r=0.827). Predicted PAR values for walking and running were overestimated according to the equations. On the other hand, PAR values for stair climbing and ball toss were underestimated. These findings indicate that although the uniaxial accelerometer may help in evaluating daily physical activity in preschool-aged children, its use as a proxy measure of PAR based on the above equations may be limited.

This study aimed to examine the relationship between daily outdoor playing time assessed using questionnaires for parents and daily moderate-to-vigorous physical activity (MVPA) using triaxial accelerometers for young children (213 boys: 5.8±0.6years and 193 girls: 5.9±0.6years). The study also examined the potential relationships between daily MVPA and exercise habits or familial and preschool factors which were assessed using questionnaires for parents. Daily MVPA was assessed using a triaxial accelerometer (ActivTracer, GMS) for 6 consecutive days, including weekdays and weekends. Outdoor playing time and percentage of outdoor playing time more than 60 min/day were 81±62 min/day and 64% for boys and 78±61 min/day and 62% for girls, respectively. Outdoor playing time was not significantly correlated with MVPA. The study found that no factors for MVPA, including exercise habits, were correlated with MVPA when adjusted for age, body height and log-body weight, except that MVPA for girls in kindergartens was higher than that in nursery schools. These findings suggest that the percentage of outdoor playing time more than 60 min/day was about 2/3 in young children. The questionnaire didn't reflect their MVPA. The factors used in the present study except for the preschool type for girls may not contribute to the time spent in MVPA in preschool children.

This study sought to examine the potential relationships of physical education (PE) participation at preschool and sports club (SC) participation out of school and daily physical activity (PA) measured objectively using a triaxial accelerometer, with physical fitness in preschool children. Physical fitness testing was used to measure both health-related and skill-related parameters of fitness in 191 Japanese preschoolers in the Kanto region (94 boys and 97 girls, 5.6 ± 0.6 years). Daily PA was assessed using a triaxial accelerometer (ActivTracer, GMS) for 6 consecutive days, including weekdays and weekend days. PE and SC participation was assessed using questionnaires for preschool teachers or parents of subjects, respectively. All health-related and skill-related physical fitness and total Z-score were correlated with time spent with physical activity ratio (PAR)≧4 when adjusted for age, sex, body height and weight. In addition, greater grip strength was associated with PE participation at preschool, and 25 m run speed was associated with SC participation, also. However, 25 m run speed was negatively associated with PE participation. These findings suggest that daily PA may contribute to the development of both health-related and skill-related fitness in preschool children, although further research on the cause-effect relationship is needed. Moreover, participation in a SC may contribute to the development of running speed.

Moderate to vigorous physical activity is associated with improving insulin resistance in overweight and obese adults. However, effect of light physical activity on insulin resistance remains to be fully elucidated. The purpose of this study was to investigate the effect of light physical activity on insulin resistance in overweight and obese men. Thirty-seven overweight and obese middle-aged men (28.9 ± 1.8 kg/m², 51.0 ± 8.8 years) participated in this study. They took part in the lifestyle intervention (calorie restricted diet and exercise) for 12 weeks. Anthropometric parameters, fasting glucose, HbA1c, fasting insulin, and HOMA-IR were assessed at baseline and post intervention. Physical activity was objectively measured using a triaxial accelerometer at baseline and during intervention. Light physical activity (+17.7 min/day) and moderate-vigorous physical activity (+33.2 min/day) increased significantly, while body weight (-12.4 kg), fasting glucose (-9.5 mg/ml), fasting insulin (-4.2 μU/ml), and HOMA-IR (-1.1) decreased significantly. The change in light physical activity from baseline to during intervention were inversely related to change in fasting insulin (r = 0.18, P = 0.02) and change in HOMA-IR (r = -0.16, P = 0.03), after adjustment for several confounders. These results suggest that an increase of light physical activity improves insulin resistance in overweight and obese men.

Forearm bone mineral content for adult white elite synchronized swimmers is lower than that of normative data (Roby et al. 1988). However, bone mineral density (BMD) in local body regions and the body as a whole are unclear in adolescent synchronized swimmers. The purpose of this study was to examine BMD of adolescent synchronized swimmers. This study also examined the relationship between BMD for young athletes and biological (e. g. morphological and functional aspects) and habitual (e. g. physical activity and nutritional state in daily living) variables. Subjects were nine females selected nationwide out of a large number of synchronized swimmers of fourth to sixth grade in elementary school, who participated in an audition with the committee of synchronized swimming in the Japan Swimming Federation. Chronological and bone age were 13.4±1.0 years and 12.7±0.9 years (n=8), respectively. BMD was evaluated in local regions and the body as a whole by dual X-ray absorbtiometry (DXA). Walking was measured by pedometer, and physical activity and nutritional status were analyzed by activity diary and food weighing method, respectively. As a result, mean BMD in athletes tended to be lower than in normal Japanese girls for lower limbs and lumbar vertebra (L2-L4), while it was almost the same between the two groups for whole body, upper limbs, thoracic vertebrae and pelvis. The correlations between BMD for whole body and bone age, the number of years since menarche, body mass, lean body mass and physical activity in leisure time of daily life were significant. An analysis using a general linear model indicated that bone age and active leisure activity together explained 94.6% of the variance of the BMD. These findings indicate that BMD of adolescent synchronized swimmers tended to be unique in local regions. Furthermore, BMD in athletes was affected by the biological maturation level and physical activity in leisure time of daily life.