Assessment of muscle quality by phase angle and body physique in nonathlete students and trained/developmental...

Phase angle (PhA), measured using bioelectrical impedance analysis, has recently gained attention as an indicator of muscle quality. This study investigates the relationship between PhA and body mass index (BMI) in nonathletic students and trained/developmental athletes. Seventy-one male and 83 female students participated in the Normal group, while 159 male and 95 female students participated in the Sports group. Each group was further divided into two subgroups: those with a BMI higher (L-Normal and L-Sports) and lower (S-Normal and S-Sports) than the median BMI. Although fat-free mass (FFM) did not differ significantly between the S-Sports and L-Normal groups, PhA was significantly higher in the S-Sports group with a large effect size. While FFM was significantly higher in the L-Sports group than in the S-Sports group, PhA did not differ significantly with a small effect size. PhA and BMI showed no significant relationship in the Sports group, whereas a positive correlation was observed in the Normal group. These results suggest that PhA can be used to assess differences in competition and activity levels that are not represented by BMI or FFM. Furthermore, although PhA is related to BMI in the nonathletic populations, this relationship is not observed in trained/developmental-level athletes.