Purpose: To examine the relationship between the experience of movement patterns and the refinement of fundamental movements in free play in nursery schools.

Method: The subjects were 24 middle‒aged children (13 boys and 11 girls) in a nursery school. The measurement items were the acquisition status of fundamental movement and movement patterns (type/frequency) in free play. As for the fundamental movement, running, jumping, throwing, catching, ball bouncing, forward rolling, and moving on a balance beam were measured twice at 5‒month interval. For the movement patterns in free play, the types and frequencies of movement that appeared in the 30‒minute play scene were recorded twice per subject. To examine the relationship between the experience of movement patterns and the amount of change in fundamental movements, the correlation coefficient was calculated for the type and frequency of the movement pattern that appeared in free play and the amount of change in the movement score of the fundamental movement.

Result: There was no relationship between the amount of change in the movement development score and the experience of the movement pattern in free play. However, there was a relationship between the frequency of stability movements and balance beam movements in girls, and fundamental movements that had a limited but influential effect were also confirmed.

Conclusion: There was no relationship between the experience of movement patterns in free play and the transformation of fundamental movements, and it was not confirmed that the experience of various movement patterns led to the refinement of fundamental movements.

This study examined whether daily step counts under free‒living conditions differed among four types of pedometers as used by 5‒to‒6 year old children. In Study one, we compared the Kenz Lifecorder EX and Omron Active style Pro as accelerometer‒based pedometers (n=11). In Study two, we compared the Kenz Lifecorder EX (n=22) or the Omron Active style Pro (n=24) and the Yamax SW‒200 (widely used in research) and the YAMASA EX‒200 (pants pocket‒type pedometer). In Study one, the correlation was strong (r=0.825) ; the average difference between these two pedometers was -27.7％. In Study two, correlations between the Kenz Lifecorder EX and the Yamax SW‒200 or the YAMASA EX‒200 were moderate (r=0.657) or strong (r=0.817) ; the average differences between pedometers were -17.3％ and -15.6％, respectively. Correlations between the Omron Active style Pro and the Yamax SW‒200 or YAMASA EX‒200 were moderate (r=0.688) or strong (r=0.880) ; the average differences between pedometers were +28.7％ and +8.6％, respectively. In conclusion, the choice of pedometer had a substantial impact on step counts in young children.

Purpose: Childhood obesity has become a global health issue causing obesity‒related health problems in children. Sumo is a sport that requires wrestlers to increase their physique, starting from childhood, to improve performance. Herein, we aim to assess the body composition of junior sumo wrestlers who are presumed to have high fat‒free mass, and evaluate the changes associated with weight gain.

Participants and Methods: Participants included male sumo wrestlers (n=12; average age, 15.1±1.4 years) belonging to a local sumo club. We compared and examined changes in their anthropometric indices and body composition over 6 months.

Results: The average body weight was found to be 99.7±18.1 kg and the body fat percentage was 38.9± 6.6％ at the baseline. Over the six months, they gained an average weight of 2.4 kg, but their body fat percentage dropped significantly to 35.6±6.7％ (p < 0.05 each). The amount of fat‒free mass increased significantly by 3.1 kg in the trunk and 1.4 kg in the upper and lower limbs. Body fat significantly reduced by 2.6 kg in the upper and lower limbs. However, it did not decrease in the trunk. The amount of weight gain and change of trunk fat were related (r=0.949, p < 0.001).

Conclusion: Junior sumo wrestlers had a high body fat percentage with 51.5％ of the body fat mass distributed in the trunk. Despite gaining weight for over 6 months, their body fat percentage decreased. Since body fat and muscle distribution increased only in the trunk, it became clear that both fat‒free and fat were distributed in the trunk with weight gain. To continue competing while maintaining health, regular observation of body composition and nutritional education are desired for junior sumo wrestlers.

This study aimed to elucidate the characteristics for motor control ability of gripping, jumping, and throwing in late childhood. First, 10‒year‒old boys and girls were instructed to perform three movements, i.e., gripping, standing long jumping, and throwing with maximal effort (maximum task), and subsequently, with 50％ subjective effort (half task). Participants' force (gripping) and actual distances (jumping and throwing) were recorded and analyzed. The relative values of the half task were calculated based on the maximum task, and the constant and absolute errors from the target value (50％) were evaluated. We compared the movements (gripping, jumping, and throwing) and sex of the children (boys and girls).

The relative values of the half task undershot the target level in all movements regardless of sex. Absolute errors values were high for jumping, throwing, and gripping in boys; on the other hand, these values in girls were higher for jumping than for gripping and throwing. Between boys and girls, constant errors in gripping and throwing were negatively greater in girls than in boys, and absolute errors in throwing were greater in girls than in boys. Moreover, there was no relationship between the values of maximum task and errors of half task in all movements in both boys and girls. In conclusion, the motor control ability showed different characteristics in each movement and was not related to motor ability with maximal effort in 10‒year‒old boys and girls.

It is evident that differences in birth month affect various abilities and is known as relative age effect (RAE). This study aimed to clarify the RAE on the distribution of birth month, playing time, and height of mini basketball players and obtain suggestions for athlete development systems and coaching methods.

Players of a team participating in the 52nd All Japan Mini Basketball Games held in March 2021 were included in the study. We explained the purpose and content of the study to the team representatives verbally and in writing, and data were obtained from only players who provided parental consent. The number of collected questionnaires was 327, comprising 16 teams of 165 boys (42.1％) and 14 teams of 162 girls (35.9％). A total of 257 responses (126 boys and 131 girls) from the fifth and sixth grades of elementary school were analyzed.

The observations were as follows.

(1) There was a significant correlation between birth month and number of players registered on the bench, and the younger the relative age, the lower the number of registered players. However, there was no significant difference when compared to the expected frequency calculated from the percentage of births by month in Japan. (2) The existence of the RAE was suggested in the playing time of boys, and sex differences were revealed. (3) Among the boys, RAE was observed in terms of height. Additionally, there was a significant correlation between height and playing time. The results suggest that coaches should use more players with superior physique and higher relative age in games.