Background：In recent Japan, the sleep situations of children are worried about. As one background of such a problem, the screen thyme of children increase is regarded as uneasiness. Therefore, the practices of “no media” which limits screen time are spreading all over the country.

Objective：The purpose of this study was to inspect the effects of the “no-media” practice in junior high school.

Methods：Subjects were 672 children at a public junior high school in Shizuoka. All investigations were carried out on control day and practice period in October 2014. The sleep situation and subjective symptoms of fatigue were measured in this survey.

Results：Subjects were early to bed and early to rise. There were also few shortage and issues of sleep. Additionally, they had few subjective symptoms of fatigue and Internet addiction tendency. Furthermore, as a result of having inspected the “no media” practice, the bed duration was significantly earlier and sleep time was also significantly longer in practice period. The subjective symptoms of fatigue in practice period were decreased. In this study, the sleep situations and subjective symptoms of fatigue by the difference of the challenge item in this practice were also analyzed. As a result, in the group which challenged the practice of “no media”, it was shown that the sleep situation was improved and tiredness was decreased.

Conclusion：From the above facts, we reached the conclusion that the “no media” practice analyzed in this study is effective in children's health.

Purpose：The purpose of this study was to compare the difference of characteristics of sprinting between barefoot and shod conditions, in relation to jumping abilities in children.

Method：94 children aged 6-12 years performed short sprints (30 m), counter movement jumping (CMJ) as a non-ballistic jumping and five repeated-rebound jumping (RJ) as a ballistic jumping. Sprinting conditions were randomized for each child in order to compare barefoot sprinting with shod conditions. High speed camera with 1/1000 second shutter speed was used to record calibration marks and performances of the children at a frame rate of 300 frame/second. The cameras were placed 20 m apart from the motion plane. Besides 5 video cameras from 5 angles obtained images of entire stance phase (right before foot strike to taking the toe off). Foot strikes were classified into 3 patterns：rear-foot strike (RFS) that land on the heel, mid-foot strike (MFS) that land with a flat foot, and fore-foot strike (FFS) that land on the fore-foot before bringing down the heel. Jumping abilities were assessed using CMJ jumping height and the value obtained by dividing jumping height by the ground contact time in 5RJ (RJ-index).

Results and Discussion：Under barefoot condition children significantly sprinted with lower velocity (p<0.05), higher step frequency (p<0.01), shorter step length (p<0.01) and shorter contact time (p<0.01). Additionally, barefoot condition induced the shift of ground contact manner from RFS to FFS and MFS. Children who sprinted faster with barefoot had higher jumping abilities than children who sprinted faster with shoes. Increased percentage of FFS and MFS in barefoot sprinting appears to enhance the utilization of elasticity produced in arches and Achilles tendon, which may affect positively to sprint performance for children who sprinted faster with barefoot. The result also indicated that jumping ability is higher in children who sprinted faster with barefoot. Our finding suggested that common factor could have effect on the ability of barefoot sprinting and jumping in children.

This study aimed to determine the difference between today's young children (2013) and those of 1985 in terms of physique and fundamental motor abilities (running, jumping, and throwing). The participants included 2,329 healthy children aged 3 to 6 years in Ishikawa Prefecture. They performed three motor ability tests (20 m sprint, standing broad jump, and tennis ball throw). The representative values (mean and standard deviation) of data on 32,538 children studied in the same manner in 1985 were utilized for comparison. A two-way analysis of variance was performed to reveal the mean differences between children from both periods (1985 and 2013) and genders (boys and girls) on physique and fundamental motor abilities. In addition, the data of 2013 was judged by five-grade evaluation based on data of 1985. The results revealed that today's children had a slightly smaller physique (height：0.5%, weight：2.2-4.3%) than those of 1985. The average 20 m sprint time was unchanged at age 3；however, a decline of more than 5% was found for ages 4, 5, and 6. In the standing broad jump, a decline of 5-6% was found in both sexes； however, there were no age differences regarding the extent of the decline. An age-related decline in the tennis ball throw was considerable in both sexes and was even greater in boys than in girls. The data suggest that children's fundamental motor abilities have decreased when compared with children of 30 years ago. Parents and caregivers should be aware of this situation and should positively introduce various forms of active play to encourage motor ability development.