The purpose of this study was to examine the characteristics of ground contact patterns and running step variables during barefoot running in young children. The subjects were 111 preschool children aged 4-6 years (59 boys, 52 girls). The subjects ran a 10 meter sprint under two conditions: with shoes (shoed condition) and barefoot (barefoot condition). Measurements were conducted in a playroom in the kindergarten, with wooden flooring. OptoJump Next (Microgate) was used to analyze running step variables. Eleven variables, including ground contact time and flight time were used as running step variables. A digital camera (Lumix dc-fz85, Panasonic) was used to distinguish ground contact patterns during running. Ground contact patterns were classified into three types: forefoot strike (FFS), where the forefoot strikes the ground first, midfoot strike (MFS), where the forefoot and rearfoot strike almost simultaneously, and rearfoot strike (RFS), where the rearfoot strikes the ground first. As a result, for running step variables, the flight time, step and stride length, step angle, and heel contact time were significantly higher under the shoed condition than the barefoot condition, while the ground contact time, speed, pitch, and push-off time were significantly higher under the barefoot condition than the shoed condition. Regarding ground contact patterns, FFS and MFS showed significantly higher values under the barefoot condition and significantly lower values under the shoed condition. For RFS, the values were significantly higher under the shoed condition and significantly lower under the barefoot condition. The characteristics of barefoot running in young children suggest a forward contact, with shorter steps and a higher pitch.

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[Purpose] This study aimed to investigate the impact of the long-term implementation of the Active Child Program (ACP) as a warm-up exercise on the physical fitness development of first-grade elementary school students during physical education classes. [Methods] The study involved 93 first-grade elementary school students (49 boys and 44 girls). Baseline physical fitness was measured using three tests: 50-meter sprint, standing long jump, and championship softball throw. These assessments served as pre-tests. After six months of participating in ACP warm-up exercises, the same tests were conducted as post-tests. To assess the effectiveness of the ACP, physical fitness improvements over six months in the ACP implementation group were compared by sex to the national average gains (national average group). Additionally, to examine differences based on initial fitness levels, the participants were divided into three subgroups according to sex and their pre-test performance levels. A two-way ANOVA with repeated measures on one factor was conducted, followed by Bonferroni multiple comparisons when significant main effects were identified. Effect sizes (Hedges’ g) were calculated to evaluate the magnitude of observed differences. [Results and Discussion] The ACP implementation group exhibited greater improvements across all fitness measures compared to the national average group, indicating that the ACP warm-up exercises significantly enhanced first-grade children’s basic physical fitness. Significant effects were observed for all the fitness tests, with particularly large effect sizes noted in the lower performance subgroup. This suggests that ACP warm-up exercises are especially beneficial for children with lower initial fitness levels. These findings demonstrate the value of structured physical education programs, such as ACP warm-ups, in improving overall fitness, particularly amid concerns about declining fitness levels and widening disparities in physical abilities. Therefore, ACP warm-ups present an effective approach to enhancing foundational physical development, especially for younger children.

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