This study aimed to apply longitudinal data (in four waves) to examine relationships between body mass index (BMI), flexibility, muscular endurance, and explosive power, and employed a random-intercept panel model… Click to show full abstract
This study aimed to apply longitudinal data (in four waves) to examine relationships between body mass index (BMI), flexibility, muscular endurance, and explosive power, and employed a random-intercept panel model (RIPM) to divide the variations of different waves into between- and within-person variations. Furthermore, a multi-group model test was conducted to explore whether an interaction effect existed between sex and these relationships. The data were collected from a university in Taiwan between August 2009 and July 2010, and 3863 freshman and junior students were recruited. Results showed that the between- and within-person relationships between BMI and explosive power, and between BMI and muscular endurance, were negative (independent of sex). The negative between- and within-person associations between BMI and muscular endurance were both invariant with respect to sex. The negative between-person associations between BMI and explosive power were not equivalent for both sexes, yet the within-person associations between BMI and explosive power were equivalent for both sexes. The between-person associations between BMI and flexibility were positive for both sexes, but the within-person associations of these two variables were negative for both sexes. The invariance test confirmed that the positive associations of between-person BMI and between-person flexibility were invariant for both sexes, yet the negative associations of within-person BMI and within-person flexibility were not equivalent for both sexes. Between-and within-person correlations among explosive power, muscular endurance, and flexibility were significantly positive. Only the auto-regressions of BMI and muscular endurance were significant and equivalent for both sexes.
               
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