The purpose of this study was to clarify the difference between the present and the 1980s by comparing the throwing performance and throwing motion for young children from the viewpoint of kinematics. There were 29 children, 14 boys and 15 girls aged five years. Their tennis ball throwing motions were videotaped with two cameras for 3‒D motion analysis (120 fps). The kinematic variables computed were the release velocity, release angle of the ball, the joint angles of the upper and lower limb joint and the segment angles of the trunk. The throw distance and release parameters were not significantly different between boys and girls. A significant positive correlation was found between the throw distance, the initial projection velocity, the projection angle, the projection height and the projection height ratio in boys and between the throw distance and the projection angle, steps and step ratios in the girls. In boys, the maximum velocity appeared in order from the shoulder to the elbow, and from the wrist to the hand to the ball, from near the trunk to the end. In girls, the maximum velocity of the elbow appeared earlier than that of the shoulder. Theses tendency were similar to the characteristics of young children about 35 years ago. There was no significant difference between boys and girls in shoulder angle, hip angle and trunk twist during maximum backswing. Comparing this study with that of about 35 years ago, the initial projection velocity and projection height were significantly decreased in boys, and no significant decrease in all items were observed in girls.

This suggested that the characteristics of throwing motions of boys and girls were similar. The values of the initial velocity and the height of the projection of boys were lower than those of about 35 years ago, suggesting that the throwing motion was poor.

The question “At what stage in their physical growth and development should youths start playing a sport?” is of considerable interest to those involved in the fields of sports, education, medicine, and health. This is because the topic is expected to provide significant information not only on when youths should start playing a sport so that it contributes to their healthy physical growth and development but also on strategies for cultivating excellent sports players, how to prevent sports‒related physical damage and disease, and how physical education should be organized. In order to benefit from such information, we need reliable statistics on the ages for starting a sport. However, the current situation is such that reliable information on this issue is not available anywhere in the world.
We conducted a literature search across various fields on “ages at which athletes start sports,” but the search did not reveal any documents containing statistical information relevant to this topic. This brief report was prepared to address this lack of information.
In an earlier study, Osawa et al. (1994) collected longitudinal data on the development of athletes for the purpose of making comparisons between male and female athletes across various sports. In that process, we investigated the “ages at which athletes start sports.” This study was limited to the collection of data from athletes confirmed to have been playing sports from a young age up to the point of investigation. The reason for this was a reflection of the fact that many investigations on this topic record the age at which target athletes began a sport and then go on to discuss those cases without confirming whether the athletes in question had continued to play the sport thereafter. For example, data in this study indicating age 10 as the start of playing a sport does not include cases wherein a youth begins the sport at age 10 but stops it at 11. In contrast to longitudinal data, cross‒sectional data showing the frequency of sports played at a certain point in time is not able to provide a substantial answer to the question of at what point in their physical developmental process did a particular group begin a sport. The data in this study on the ages at which youths started a sport enables longitudinal observation while avoiding the inclusion of such incomplete information mentioned above.
This study focused on the following three points:
1. At which ages do Japanese athletes start playing a sport?
2. Are there gender‒based differences in ages for starting a sport?
3. What are the ages for starting various kinds of sports?
Study Method
An investigation was conducted on male and female university athletes specializing in a sport at three metropolitan PE universities. The study retrospectively examined the kinds of sports they played and the ages at which they started playing.
The investigation target period was 10 years from 1980 to 1990. Longitudinal data on 5,463 male and female athletes combined was collected, from which the data serving the above‒mentioned study purpose was selected. Data on 1,627 male athletes and 1,830 female athletes (3,457 in total) was used in this study. In the case that an athlete was playing more than one sport simultaneously or changed their sports during the target period, the one sport he or she was specializing in at the point of the investigation was counted as the target sport.
The tallied figures are as shown below. With regard to the types of sports studied, some of them were excluded from the analyses due to the small number of data collected, namely, “general gymnastics,” “dance,” “kyudo,” and “other sports” for male athletes and “rugby” and “judo” for female athletes, but the numbers are included in the total figures.
Results
1. The average age at which Japanese athletes start playing a sport is 11.3 for male athletes and 11.6 for female athletes, indicating that male athletes begin a

It has been found that motor ability and motor play in early childhood are associated with the development of social skills. However, the relationships among these three factors have not yet been clarified. In this study dealt with motor skills, cooperative physical play, and social skills in early childhood and examined whether motor skills or cooperative physical play was more predictive of social skills at age 6.

A short‒term longitudinal study of 31 kindergarteners (15 male and 16 female) in Chiba Prefecture was conducted, including children between the ages of 5 and 6 years. Motor ability was measured and motor play was observed at 5 years of age, and social skills were assessed at 6 years of age.

The results of this study showed that children with high motor ability frequently engage in motor play during the year, but do not necessarily participate actively in cooperative physical play with their peers. Furthermore, participation in cooperative physical play during at 5 years of age, rather than high motor ability at 5 years of age, predicts social skills at 6 years of age. Thus, the results of this study indicate that active participation in cooperative physical play in daily life is important for the development of social skills in young children.

The aim of this study was to examine the effectiveness of a combined program for fifth‒grade elementary school students that would combine the domains of health and physical exercise in physical fitness within the physical education curriculum. This study revealed that, utilizing the “New Analysis Support System,” which analyzes the measurements obtained during physical fitness tests, clarified the goals of training for endurance running, and increased the children's attitude and cognition scores pertaining to physical education classes. Moreover, learning with the use of a teaching material called “Communication and Running” significantly improved individuals and groups of children's 5‒minute running records. Furthermore, regardless of the children's fondness for physical education classes, by recognizing the need to improve their own physical fitness and through motivated engagement in the training for endurance running, the children were able to enjoy endurance running and increase their ability of continuous movement. These results confirmed the effectiveness of the program. In addition, conducting physical fitness tests, analyzing the measurements, discovering issues by discussing the results of the analysis in health classes, and resolving the issues through physical education constitute an educational process that can be proposed as an example of “curriculum management.”