Langer Raquel D, Matias Catarina N, Borges Juliano H, Cirolini Vagner X, Páscoa Mauro A, Guerra-Júnior Gil, Gonçalves Ezequiel M
Laboratory of Growth and Development - Center for Investigation in Pediatrics (CIPED), University of Campinas, Campinas, Brazil.
Laboratory of Physiology and Biochemistry of Exercise, University of Lisbon, Cruz Quebrada, Portugal.
Mil Med. 2018 Jul 1;183(7-8):e324-e331. doi: 10.1093/milmed/usx223.
Bioelectrical impedance analysis (BIA) is a practical and rapid method for making a longitudinal analysis of changes in body composition. However, most BIA validation studies have been performed in a clinical population and only at one moment, or point in time (cross-sectional study). The aim of this study is to investigate the accuracy of predictive equations based on BIA with regard to the changes in fat-free mass (FFM) in Brazilian male army cadets after 7 mo of military training. The values used were determined using dual-energy X-ray absorptiometry (DXA) as a reference method.
The study included 310 male Brazilian Army cadets (aged 17-24 yr). FFM was measured using eight general predictive BIA equations, with one equation specifically applied to this population sample, and the values were compared with results obtained using DXA. The student's t-test, adjusted coefficient of determination (R2), standard error of estimation (SEE), Lin's approach, and the Bland-Altman test were used to determine the accuracy of the predictive BIA equations used to estimate FFM in this population and between the two moments (pre- and post-moment).
The FFM measured using the nine predictive BIA equations, and determined using DXA at the post-moment, showed a significant increase when compared with the pre-moment (p < 0.05). All nine predictive BIA equations were able to detect FFM changes in the army cadets between the two moments in a very similar way to the reference method (DXA). However, only the one BIA equation specific to this population showed no significant differences in the FFM estimation between DXA at pre- and post-moment of military routine. All predictive BIA equations showed large limits of agreement using the Bland-Altman approach.
The eight general predictive BIA equations used in this study were not found to be valid for analyzing the FFM changes in the Brazilian male army cadets, after a period of approximately 7 mo of military training. Although the BIA equation specific to this population is dependent on the amount of FFM, it appears to be a good alternative to DXA for assessing FFM in Brazilian male army cadets.
生物电阻抗分析（BIA）是一种用于对身体成分变化进行纵向分析的实用且快速的方法。然而，大多数BIA验证研究是在临床人群中进行的，且仅在某一时刻（横断面研究）。本研究的目的是调查基于BIA的预测方程在巴西男性军校学员经过7个月军事训练后去脂体重（FFM）变化方面的准确性。所使用的值是通过双能X线吸收法（DXA）作为参考方法确定的。
该研究纳入了310名巴西陆军男性军校学员（年龄17 - 24岁）。使用八个通用的预测BIA方程测量FFM，其中一个方程专门应用于该人群样本，并将这些值与使用DXA获得的结果进行比较。使用学生t检验、调整决定系数（R2）、估计标准误差（SEE）、林氏方法和布兰德 - 奥特曼检验来确定用于估计该人群FFM以及两个时刻（训练前和训练后）之间的预测BIA方程的准确性。
使用九个预测BIA方程测量并在训练后用DXA确定的FFM与训练前相比有显著增加（p < 0.05）。所有九个预测BIA方程都能够以与参考方法（DXA）非常相似的方式检测军校学员在两个时刻之间的FFM变化。然而，只有特定于该人群的一个BIA方程在军事训练前和后的DXA之间的FFM估计中没有显著差异。使用布兰德 - 奥特曼方法，所有预测BIA方程都显示出较大的一致性界限。
本研究中使用的八个通用预测BIA方程在经过约7个月军事训练后，未被发现对分析巴西男性军校学员的FFM变化有效。尽管特定于该人群的BIA方程依赖于FFM的量，但它似乎是用于评估巴西男性军校学员FFM的DXA的一个良好替代方法。
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