The purpose of this study was to assess the validity of activity record (AR), accelerometer (AC) and heart rate (HR) methods in comparison with the doubly-labeled water (DLW) method as the criterion measure of total energy expenditure (TEE) in high school students undergoing vigorous activities. Twelve baseball players in Japanese high school (16.5±0.5 yrs) were monitored for seven consecutive days. TEE values obtained over a 3-day-period by AR, AC and HR were simultaneously validated against TEE measured by DLW over a 7-day-period. TEE value measured by DLW was 4922±391 kcal/day. The Physical activity level (PAL=TEE/BMR (basal metabolic rate)) was 2.66±0.14. TEE estimated by AR, AC and HR was significantly different from DLW, with mean differences of -13.9±6.5%, 35.3±3.6% and 31.6±23.9%, respectively. However, TEE estimated by AC and AR significantly correlated with that measured by DLW (r=0.73, r=0.70, p<0.05, respectively). The limits of agreement between DLW and AR, AC and HR were from -1350 kcal/d to -21 kcal/d, -2293 kcal/d to -1192 kcal/d, and 3875 kcal/d to -797 kcal/d respectively. AC was superior to the other methods. However, the limits of agreement in AR were similar to AC. These data suggest that on accuracy and precision, AR would be superior to the other two for predicting TEE in high school students undergoing vigorous activities. However, AC has the advantages being able to examine patterns of activity over long periods of time without interfering with normal movement and the ability to store data continuously over long periods of time. Therefore, it was suggested that, simultaneously, the AR and AC methods are accurate predictors of TEE and patterns of activity while undergoing sports vigorous activities.

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.

The International Physical Activity Questionnaire (IPAQ) is a self-reported questionnaire for assessment of physical activity and has been validated in many countries among adults. However, there are few studies about the validity of IPAQ for children. The purpose of this study was to investigate the validity of moderate to vigorous physical activity according to the modified version the IPAQ for Japanese Early Adolescents (IPAQ-JEA). Ninety-two adolescents aged 10-13 years participated in this study. The validity of the IPAQ-JEA criteria was tested using an activity monitor (Active style Pro, HJA-350IT; ASP). Daily physical activity was continuously monitored for one week by ASP. The participants were asked to complete the IPAQ-JEA after wearing the ASP. The epoch length of ASP was set at 1-min in this study (ASP_1-min). According to the minute by minute METs values, time spent on moderate intensity physical activity (MPA, 3 to 6 METs), vigorous intensity PA (VPA, > 6 METs), and moderate to vigorous intensity PA (MVPA, > 3 METs) was calculated. In addition, we also calculated bout physical activity maintained for 10 minutes or longer (ASP_bout). Weekly time spent on MVPA assessed by IPAQ-JEA (MVPA_IPAQ-JEA) was significantly correlated with that assessed by ASP_bout (MVPA_ASP_bout) (ρ=0.359, p<0.01) and ASP_1-min (MVPA_ASP_1-min) (ρ=0.399, p<0.01). However, MVPA_IPAQ-JEA was significantly higher than that of MVPA_ASP_bout and MVPA_ASP_1-min (p<0.001). Although time spent on VPA assessed by IPAQ-JEA (VPA_IPAQ-JEA) was also significantly correlated with that assessed by ASP_bout (VPA_ASP_bout) (ρ=254, p<0.05) and ASP_1-min (VPA_ASP_1-min) (ρ=438, p<0.01), time spent on VPA_IPAQ-JEA was significantly higher than that for VPA_ASP_bout and VPA_ASP_1-min (p<0.001). These results support the use of the IPAQ-JEA as a relative measure of physical activity among 10-13-year-old 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.

The purpose of this study was to examine the effects of long-term habitual exercise on daily total energy expenditure (TEE) and its components, body composition and maximal oxygen uptake (VO₂max) in middle-aged Japanese women. Twenty-eight subjects aged 39 to 58 years were assigned either to a nonhabitual exercise group (Control ; n=12) or a habitual exercise group (Exercise ; n=16). TEE, physical activity level (PAL) and the daily physical activity energy expenditure (PAEE) were assessed by doubly labeled water (DLW) method. The exercise-induced energy expenditure (ExEE) and nonexercise-induced energy expenditure (NExEE) were evaluated based on the activity record investigation conducted simultaneously during the DLW measurement period. The result follows that TEE was significantly (p<0.01) higher in the Exercise group (2520 kcal · day^-1) than in the Control group (1921 kcal · day^-1). There was no significant difference in basal metabolic rate between the groups. PAEE and ExEE were significantly higher in the Exercise group than in the Control group (p<0.01). Habitual exercise induced an increase in TEE without resulting in a compensatory reduction of NExEE. The percentage body fat (fat%) was significantly lower in the Exercise group (25.5%) than in the Control group (30.9%). VO₂max was higher in the Exercise group (1788 ml · min^-1) than in the Control group (1417 ml. min^-1). After correction for body weight, fat% was negatively associated with TEE (p<0.01), PAEE (p<0.01) and ExEE (p=0.05), while VO₂max was positively associated with TEE (p<0.05), PAL (p<0.05), PAEE (p<0.05) and ExEE (p<0.01). These results suggest that habitual exercise is associated with the increase of TEE, the improvement of body composition and VO₂max. The improvement of VO₂max was mainly caused by the increase in ExEE, indicating that the exercise intensity is important to the improvement of cardiorespiratory endurance fitness.

The purposes of this study were to investigate the relationships between physical activity variables and physical fitness, and between amount and intensity of physical activity in children and adolescents. Subjects were divided into two groups : 178 children (99 boys aged 9.8±0.6 and 79 girls aged 9.7±0.6) who had not reached the age of peak height velocity (PHV), and 336 adolescents (141 boys aged 15.0±1.1 and 195 girls aged 15.3±1.2) who had reached the age of PHV. Physical activity level (PAL : total energy expenditure/basal metabolic rate) which indicates the amount of physical activity, and time engaged in each of physical activity intensity (light, moderate and vigorous), which indicates the intensity of physical activity were estimated from uni-axial accelerometer. Physical activity was monitored for 3 consecutives days : 2 weekday and 1 weekend day. Moreover, physical fitness test suggested by the Ministry of Education, Culture, Sports, Science and Technology was applied. Results of this study showed that PAL was closely related to physical fitness in children, while time engaged in vigorous activity was more related to physical fitness in adolescents. On the other hand, time engaged in light and moderate activity was closely associated with PAL in younger girls, whereas in younger boys, PAL was closely related to time engaged in moderate and vigorous activity. However, time engaged in moderate activity was more related to PAL in the adolescent group. These results suggest that the relationship between physical activity variables and physical fitness and between amount and intensity of physical activity might vary according to the growth development of boys and girls respectively.

The purpose of this study was to determine daily steps corresponding to the reference value for the quantity of Physical Activity and Exercise for Health Promotion 2006 (23 METs·h/wk) considering non-locomotive activities. Two hundred and thirty one men and 224 women wore a tri-axial accelerometer for two weeks. We analyzed the data in each age group (young (less than 40 years), middle-aged (40 to 59 years), and elderly (60 years or more) groups), also. There were significant relationships between daily steps and locomotive activity (r = 0.762 to 0.820, p < 0.001) and total (locomotive and non-locomotive) physical activity (r = 0.706 to 0.824, p < 0.001) with intensity of 3 METs or more in all groups. The daily steps corresponding to 23 METs·h/wk, calculated using regression lines between the daily steps and total physical activities with intensity of 3 METs or more in men and women were 6,534 steps/d and 6,119 steps/d. On the other hand, the daily steps corresponding to 23 METs·h/wk, calculated using regression lines between the daily steps and locomotive activities with intensity of 3 METs or more in men and women were 7,888 steps/d and 8,584 steps/d. These results suggest that non-locomotive activity should also be taken into consideration in the case of assessment of a daily physical activity.

The purpose of present study was to examine validity of accelerometer (Lifecorder ; LC) and to assess the free-living physical activity (PA) in Japanese elementary school students used by LC method. Firstly, to examine validity of LC, twelve children, aged 11.2±1.0 years, were measured total energy expenditure (TEE) by doubly labeled water method and resting energy expenditure (REE) by the expired gas analysis. Physical activity energy expenditure (PAEE) is calculated as 0.9 TEE minus REE. At the same time, PA was evaluated by both daily walk count (WC) and vigorous activity time (LC7-9) using LC method. PAEE per 1 kg body weight significantly correlated with WC (r=0.785, p<0.005) and LC7-9 (r=0.828, p<0.001). Secondly, 140 boys and 167 girls, aged 8-11 years were measured PA by LC method. WC and LC7-9 each were 13000-18000 counts and 16-32 minutes in week-day, and 8000-12500 counts and 8-18 minutes in week-end. PA analyzed by MANOVA were significantly higher in boys than in girls, and lower in week-end than in week-day, and decreased in proportion as grade. Present study suggests that LC method is a good measure of PA in free-living condition for elementary school students.

This report provides an overview of the effectiveness of objectively measured physical activity, sports participation, and outdoor play on outcomes related to mental health and social skills in children and adolescents. Findings based on observation studies of longitudinal and cross-sectional design are inconsistent. On the other hand, several intervention studies with high intensity exercise programs indicated that intensity and amount of physical activity might provide a short-term benefit against depressive symptoms and anxiety. However, there are reports that psychosocial approaches confer effects similar to exercise programs. The effects of participation in organized sports clubs on mental health conditions such as depression, anxiety, self-esteem, self-efficacy, health-related quality of life, social skills (e.g., relationship skills), and coping ability were diverse. Notably, there could be unfavorable relationships in athletes exhibiting a higher performance. Meanwhile, participation in sports could represent a predictor of escalation in alcohol use as evidenced by longitudinal observation studies in adolescent, although there could also be effectiveness in terms of preventing use of illicit drugs. Lastly, active outdoor play under natural conditions without supervision also represented an effective approach to promote mental health (e.g., reducing depressive symptoms and building social skills such as self-regulation and coping skills in the face of difficult human relationships). We recognize that not only sports participation but also outdoor play under abundant nature environment could represent a significant physical activity to maintain mental and social health from childhood to adolescence.

The primary aim of this study was to examine moderate-to-vigorous physical activity (MVPA) levels in preschool children during indoor and outdoor free playing time and during preschool physical education (PE) classes. The secondary aim was to determine which types of PE lessons are the best for increasing the percentage of MVPA. Physical activity during free playing time and in lessons was objectively evaluated with a triaxial accelerometer in preschool boys and girls (n = 281). Minutes of physical activity were categorized into physical activity ratios (PAR). MVPA was defined as PAR ≥3.0. Time tables and PE lesson types were recorded using logs kept by class teachers. The percentage of MVPA in outdoor free playing time (38.9±16.3%) was significantly higher than that of indoor free playing time (12.6±10.1%, p<0.001). On the other hand, there was no significant difference between the percentage in MVPA in outdoor free playing time and the percentage in PE lessons (n=94: 38.0±19.4%vs. 34.9±15.8%, ns). After adjustment for gender, age, body height and weight and preschool, there were not significantly different the percentage of MVPA among contents of PE lessons. In conclusion, children engaged in almost 30~40% MVPA during outdoor free playing time or PE. The children also engaged MVPA during indoor free playing time.