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In this study, we assessed the factor structure and construct validity of the parent-reported Inventory of Callous-Unemotional Traits (ICU) among school-aged children and adolescents, aged 6 to 15 years, in a community setting in Japan (n = 10,936). We investigated 15 models that have been reported in previous studies and used confirmatory factor analyses to determine a model that might actually be the best-fit among these. We then examined the correlations between the score of ICU and the Strengths and Difficulties Questionnaire (SDQ) in the best fit model and the three-factor bifactor (3FBF) model with the original ICU through cross-sectional and longitudinal analysis to determine the concurrent and predictive validity of the ICU. The results showed that the best-fit model was the two-factor bifactor (2FBF) model with a revised version of the ICU with 12 items, excluding all but one item of unemotional factors. The cross-sectional and longitudinal analysis showed that higher general callous-unemotional factor scores, callousness and uncaring specific factor scores were significantly associated with a higher level of conduct problems and a lower level of prosocial behaviors in the SDQ. These tendencies were shown both in the 2FBF model with the revised version of the ICU and the 3FBF model with the original ICU. We conclude that the 2FBF model was useful for school-aged community samples, as it predicts increases in conduct problems and decreases in prosocial behavior with fewer items than the 3FBF model. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the running pace and step characteristics among various competitive-level 400-m hurdlers through inter-group and intra-athlete comparisons. We analysed spatiotemporal data involving the split time, mean step length (SL) and mean step frequency (SF) for 13 male world-class and 14 male national-level 400-m hurdlers. We analysed 16.5 ± 3.9 races for each world-class hurdler and 19.8 ± 6.0 races for each national-level hurdler (the total number of analysed runs was 491) using publicly available television and internet broadcasts. Inter-group comparisons showed that both first- and latter-halves split times of the world-class hurdlers were significantly shorter than those of the national-level hurdlers. In the latter-half phase, no significant differences of SL and SF were observed between the world-class and national level hurdlers. Intra-athlete comparisons showed that no athletes favoured only first-half phase in terms of running speed in short finish times. In contrast, finish times of all hurdlers were sensitive to running speed in the latter-half phase. In the latter half of the race, 18 of the 27 hurdlers were identified as being SF reliant during speed enhancements; running speed of the other 9 hurdlers were also sensitive to high SF. In conclusions, important findings regarding high performance in inter-group comparisons do not always corresponded with those in intra-athlete comparisons. All athletes and coaches should first prioritize maintaining high running speeds in the latter half of 400-m hurdles rather than in the first half of the race. [ABSTRACT FROM AUTHOR]