Validity of the relative fat mass pediatric index (RFMp) for the analysis of body composition in physically active youths at different stages of biological maturation.

BACKGROUND: The pediatric relative fat mass index (RFMp) was valid for analysis of percent body fat (BF%). However, the validation did not consider biological maturation (BM) stages.

OBJECTIVE: Verify the validity of the RFMp index in the estimation of BF% in children and adolescents of both sexes in different stages of BM.

METHODS: Cross-sectional study with a sample of 146 young (Males: 64.5%. Females: 35.5%. Age: 13.0±2.2) practicing sports modalities. We tested the validity of four RFMp equations (1: for boys 8-14-yrs; 2: for girls 8-14-yrs; 3: for both sex 8-14-yrs and 4: for both sex 15-19-yrs) to analyse BF% using dual-energy X-ray absorptiometry (DXA) as a reference method. BM was analysed by peak height velocity (PHV). Thus, we created subgroups by BM stage (pre-PHV, circum-PHV and post-PHV).

RESULTS: Analyses of agreement between methods showed that only the RFMp-3 equation was reliable to analyse BF% in subjects of both sexes aged 8-14 years at the circum-PHV BM stage (proportion bias-CI95%: -0.3; 0.5, p=0.7. CCC: 0.3; Cb : 0.9).

CONCLUSION: The RFMp equation developed for the paediatric population of both sexes aged 8-14-yrs was valid for predicting BF% in children and adolescents of both sexes at the Circum-PHV stage of the BM. This article is protected by copyright. All rights reserved.