Bioelectrical impedance vector in pre- and post-menarcheal females

OBJECTIVE: To present what is to our knowledge the first study of the effects of puberty on the distribution of bioimpedance vectors. METHODS: Resistance and reactance (standard, tetrapolar analysis at 50-kHz frequency) were measured in 143 pre- and postmenarcheal Sardinian girls aged 10 to 15 y. RESULTS: The data agreed well with the reference values proposed for the Italian population. Bioelectrical impedance vector analysis showed a clear differentiation between pre- and postmenarcheal girls, whereas no significant age-related differences were observed within groups. Postmenarcheal girls had a shorter impedance vector (reduced R/H and Xc/H) and a greater phase angle than did premenarcheal girls. CONCLUSIONS: Sexual maturity is the major cause of differentiation in the body composition of adolescent females. We recommend that this source of variation be considered in clinical and anthropologic analyses of bioelectrical variables.