Abstract: Miyaguchi, K, Demura, S, and Omoya, M. Relationship between jump rope double unders and sprint performance in elementary schoolchildren. J Strength Cond Res 29(11): 3229–3233, 2015—According to dynamic analyses of muscle contraction, jump rope is a typical stretch-shortening cycle (SSC) movement. It has been reported that the relationship with SSC is higher in double unders than in single unders (basic jumps); however, the relationship between jump rope and sprint performances has not been extensively studied. To clarify this relationship in elementary schoolchildren, we compared the sprint speed and SSC ability of children who were grouped according to gender and ability. The subjects were 143 elementary fifth and sixth graders (78 boys, 65 girls). The consecutive maximal number of double unders, reactivity index (index of SSC ability) by Myotest, and 20-m sprint time were measured. According to the mean of jump rope records, the children were divided into a superior ability group (more than average + 0.5 SD) and an inferior ability group (less than average − 0.5 SD) for each gender. In both genders, a significant difference was found in the 20-m sprint time between the inferior and superior ability groups. The times for the superior ability groups (boys, 3.75 ± 0.23 seconds; girls, 4.02 ± 0.24 seconds) were excellent compared with the inferior ability groups (boys, 4.17 ± 0.32 seconds; girls, 4.23 ± 0.21 seconds). This effect size was higher in boys (1.44) than in girls (0.93). The reactivity index in the superior ability group was excellent compared with that in the inferior ability group. In conclusion, children who perform better in double unders are also faster during a 20-m sprint run. This tendency may be higher in boys. Classic jump rope training, such as double unders, should be effective as elementary plyometrics for improving the sprint ability of children.