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Background: Analyzing fat free mass (FFM) helps sport professionals during the prescription of sport training for children and adolescents in a sport initiation program. In this way, it is possible to determine fat mass (FM) (FFM subtracted from total body weight) and design interventions to increase FFM and reduce %F, making it possible to maximize performance in relation to the physical demands of sport. However, there is still no reliable anthropometric index to analyze FFM in this population. The aim the present study was to develop the Fat-Free Mass Index (FFMI) for pediatrics of both sexes., Methods: Cross-sectional study with a sample composed of 254 pediatrics (139 males [age: 13.0±2.3] and 115 females [age: 12.5±2.2]), from a sports initiation school. We divided the sample into the groups: 1) development (N.=169); and 2) cross-validation (N.=85). The body composition was analyzed by dual-energy X-ray absorptiometry (DXA), in addition we acquired anthropometric data (height, body weight and hip circumference) for the development of the FFMI - Pediatric (FFMIp). By means of linear regression we tested the predictive power of FFM using DXA as a reference method, then we developed FFMIp and tested its reliability and validity in relation to DXA., Results: FFMIp consisted of: -16.679 + (0.615 × body mass (kg)) - (2.601 × sex) + (0.618 × age(years)) - (0.332 × hip(cm)) + (0.278 × stature(cm)), where for sex 0 = male and 1 = female. For the FFM analysis, FFMIp showed no significant difference from DXA (P>0.05). It also showed significant accuracy (Cb>0.960), precision (ρ>0.990) and agreement (CCC>0.960) for both groups (development and cross-validation)., Conclusions: Pediatric FFMI proposed by this study proved to be valid for the analysis of fat-free mass in pediatric athletes of sports initiation of both sexes.

Background: The study aimed to determine the proportion of the body segments in relation to the total body mass in healthy people, as well as analyze the composition of each segment and compare these results between sexes., Methods: A total of 60 young adults (30 men and 30 women) were subjected to a full-body scan by dual energy X-rays absorptiometry (DXA) under standardized conditions. The regions of interest (ROI) were determined by a single trained evaluator. The body was divided into 16 segments to obtain values of total mass, lean mass (LM), fat mass, bone mineral content (BMC), lean mass percentage (%LM) and fat mass percentage (%FM) of each body segment represented by the 16 ROI., Results: Men presented higher absolute mass in the upper limbs (Δ=32.87%; P<0.05). The proportion of the lower limbs (Δ=6.83%; P<0.05) and trunk (Δ=5.07%; P<0.05) of men is higher than women. In addition, males have more LM in the upper limbs (Δ=42.19%; P<0.05) and trunk (Δ=26.46%; P<0.001), and more BMC in the trunk (Δ=18.78%; P<0.05) and forearms (Δ=32.21%; P<0.05). They also present higher %LM (Δ=6.48%; P<0.001) and lower %FM (Δ=54.43%; P<0.001) than women in the forearms., Conclusions: The different body segments represent a different percentage of the total body mass in men than in women, as well as men present more LM and BMC in the trunk and upper limbs.

Background: The growth and development cycle of the adult is characterized by substantial changes in physical size and maturity, and is controlled by the simultaneous influence of genetic components and the environment. Changes in the development of bones, muscles and adipose tissue are among the most important aspects of adolescent physical development. The aim of this research was to examine the correlation between bone mineral density (BMD) and neuromuscular performance in children at different stages of maturation., Methods: The study included 31 participants of both sexes (11.7±1.89 years). Body composition was assessed through bone densitometry using an energy duo X-ray source. The neuromuscular performance of the upper limbs was analyzed by the medicine ball hand grip and throwing tests. The lower limbs by the vertical counter-motion jump test, and skeletal maturation was analyzed by bone age. Maturation was used as an effect control between the association of BMD and neuromuscular performance., Results: The results demonstrated significant associations between the performance of upper (P<0.0001) and lower (P=0.01) limbs and BMD. On inter-group comparison for only the accelerated maturational stage, male participants had greater BMD than female participants (P=0.001; effect size 3.13). Regarding the maturational stages, male participants in the accelerated maturational stage demonstrated higher BMD than those in the normal and delayed maturational stages (P=0.04; effect size 3.10), whereas female participants did not demonstrate significant differences in BMD accumulation., Conclusions: BMD has a strong correlation with the neuromuscular performance of upper and lower limbs of children of both sexes.

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