High accuracy in estimating energy expenditure is essential for enhancing sports performance. The resting metabolic rate (RMR), as a primary component of total energy expenditure (TEE), is commonly estimated using predictive equations. However, these references may not be applicable to adolescent athletes. The purpose of this cross-sectional study was to analyse the differences between predicted RMR in relation to energy expenditure measured by indirect calorimetry (IC) among 45 Brazilian male adolescent football athletes. Indirect calorimetry (IC) and anthropometric (bioimpedance) measurements were recorded at a single visit to the laboratory after fasting overnight. The mean age was 15.6 ± 1.14 years, body mass was 63.05 ± 7.8 kg, and height was 172 ± 7.5 cm. The RMR values predicted by equations proposed by the Food and Agriculture Organization (FAO) (United Nations), Henry and Rees (HR), Harris Benedict (HB), and Cunningham (CUN) were compared with IC RMR values, by correlation analysis. The FAO and HR predictive equations yielded different values from IC (IC: 1716.26 ± 202.58, HR: 1864.87 ± 147.78, FAO: 1854.28 ± 130.19, p = 0.001). A moderate correlation of 0.504 was found between the results of HB and IC. In the survival-agreement model, the CUN equation showed low disagreement with the IC RMR, with error values between 200 and 300 kcal/day. The results showed that HB and CUN yielded similar values as IC, with the CUN equation showing low disagreement with IC; hence, adolescent athletes should undergo evaluation with precise laboratory methods to ensure that accurate information about RMR is recorded.

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Body composition evaluation is used in different hypotheses to measure the body fat percentage (%BF). Dual-energy X-ray absorptiometry (DXA) is the gold standard method, but it is not affordable and portable. As an alternative, bioelectrical impedance (BIA) scales to be easier to use. Another portable and easy-to-use system is the Bodymetrix (BM) (Intelametrix®, CA, USA) which uses ultrasound (US) to assess body composition. PURPOSE: To evaluate the agreement between BIA, US, and DXA methods for the quantification of %BF in a Brazilian sample of adults. METHODS: The %BF was calculated on 28 adults (14 women, 14 men, mean BMI 26.1 ± 5.5 kg/m 2 , with no differences between men and women, P=0.615). In the US analysis with BM system, Jackson and Pollock 7 sites equation was used. BIA (InBody ® 270) was also performed on volunteers, with all the prior preparation required by the method. A DXA (GE ® , Madison, USA) was also used as a reference to measure %BF in the same volunteers. The Bland e Altman (1986) statistical method was used to determine the agreement between methods. RESULTS: Analysis using the Bland and Altman method and linear regression showed an agreement between US and DXA (P=0.85), but not between BIA and DXA (P=0.02). The BIA also showed proportion bias in the linear regression. Figure 1 shows the Bland and Altman plots. The BIAS and the confidence interval are represented in the Figure 1 by dotted lines. Regression analysis between US and DXA showed a significant correlation (r=0.890, P<0.001) with an SEE of ±4.63%BF. CONCLUSIONS: Ultrasound has good agreement with DXA and can be used in an adult population with a %BF range between 15 and 47%. Data obtained from a limited number of subjects (n = 28) showed good agreement and the US underestimates by 3.62% on average when compared to DXA.