This study aimed to determine the developmental characteristics and sex differences of running performance and motions in 82 current male and female infants aged 3-5 years and compare the results with those in infants around 1980 from a kinematic point of view.
In the experiment, the time taken to run 25 m was measured, and body motions during running were videorecorded (120 fps) to analyze the step length, step frequency, and running motion factors. In both male and female participants in this study, the running velocity, step length, velocity index, step frequency index, and step length index increased with age from 3 to 5 years; however, the step frequency did not change. The non-stance time and jumping ratio also increased with age, while the stance time decreased with age from 3 to 5 years in both male and female subjects.
The running velocity in the subjects in this study did not differ clearly from that in infants around 1980, except for 5-year-old girls; however, the step frequency and step length measurements in infants aged 3-5 years indicated a larger step frequency and a smaller step length of the participants in this study than the respective values of infants around 1980. Moreover, the running motion data revealed a greater vertical movement of the body’s center of gravity in the male and female subjects in this study than in infants around 1980. Furthermore, there were no sex differences in the running motion among the male and female subjects in this study, suggesting that the running motions of boys have become similar to those of girls. No changes over time in the running motion were found in the male and female subjects in this study, suggesting that the running motions remained immature in both boys and girls.
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