Ojeda-Aravena Alex, Báez-San Marín Eduardo, Dopico-Calvo Xurxo, Cresp-Barría Mauricio, Olivares-Arancibia Jorge, Azócar-Gallardo Jairo
Departamento de Ciencias de la Actividad Física, Universidad de Los Lagos, Osorno, Chile.
Laboratorio de Fisiología del Ejercicio y Rendimiento Deportivo, Facultad de Ciencias de la Actividad Física y del Deporte, Universidad de Playa Ancha, Valparaíso, Chile.
Front Nutr. 2025 Jul 18;12:1595259. doi: 10.3389/fnut.2025.1595259. eCollection 2025.
Accurate estimation of skeletal muscle mass (SMM) is important for body composition assessment in Brazilian Jiu-Jitsu (BJJ) athletes owing to body mass classification and force production implications. This study compared the validity, reliability, and agreement of three predictive equations-Kim, McCarthy, and Sagayama-for estimating total SMM (expressed in kilograms) in male BJJ athletes. Twenty-two male BJJ athletes (mean age: 33.1 ± 7.5 years; body mass: 78.4 ± 9.6 kg; height: 171.8 ± 6.4 cm) underwent DXA-derived body composition analysis. SMM was estimated using the Kim, McCarthy, and Sagayama equations. Statistical analyses included repeated-measures ANOVA, stepwise linear regression, Pearson's correlation, intraclass correlation coefficient (ICC), coefficient of variation (CV%), and Bland-Altman plots. The mean SMM estimated by the Kim equation was 28.95 ± 4.92 kg (95% CI: 26.89-31.00 kg), by the McCarthy equation, 27.39 ± 4.96 kg (95% CI: 25.32-29.47 kg), and by the Sagayama equation, 27.72 ± 3.71 kg (95% CI: 26.16-29.27 kg). The Kim equation yielded significantly higher SMM values than McCarthy (mean difference = 1.55 kg, < 0.0001), while Sagayama and McCarthy did not differ significantly. Stepwise regression identified the Kim equation as a strong predictor of Sagayama SMM values ( = 0.851; = 0.724; RMSE = 2.0 kg; = 52.369; < 0.001), although with proportional underestimation (slope = 0.642). Reliability was acceptable for all equations (ICC > 0.79), and the Sagayama equation demonstrated the lowest CV% (13.4%, 95% CI: 9.44%-17.36%). Bland-Altman analysis revealed systematic biases, particularly for the Kim equation. All three equations provided accurate validity and reliability for estimating absolute SMM (kg) in BJJ athletes. However, the McCarthy and Sagayama equations showed less bias and greater agreement by DXA, supporting their use for accurate quantification of SMM in this population. Their validation with magnetic resonance imaging is needed.
由于体重分类和力量产生的影响，准确估计骨骼肌质量（SMM）对于巴西柔术（BJJ）运动员的身体成分评估非常重要。本研究比较了三种预测方程——金氏方程、麦卡锡方程和佐贺山方程——在估计男性BJJ运动员总SMM（以千克为单位）方面的有效性、可靠性和一致性。22名男性BJJ运动员（平均年龄：33.1±7.5岁；体重：78.4±9.6千克；身高：171.8±6.4厘米）接受了基于双能X线吸收法（DXA）的身体成分分析。使用金氏方程、麦卡锡方程和佐贺山方程估计SMM。统计分析包括重复测量方差分析、逐步线性回归、皮尔逊相关性、组内相关系数（ICC）、变异系数（CV%）和布兰德-奥特曼图。金氏方程估计的平均SMM为28.95±4.92千克（95%置信区间：26.89-31.00千克），麦卡锡方程为27.39±4.96千克（95%置信区间：25.32-29.47千克），佐贺山方程为27.72±3.71千克（95%置信区间：26.16-29.27千克）。金氏方程得出的SMM值显著高于麦卡锡方程（平均差值=1.55千克，<0.0001），而佐贺山方程和麦卡锡方程无显著差异。逐步回归确定金氏方程是佐贺山SMM值的有力预测指标（=0.851；=0.724；均方根误差=2.0千克；=52.369；<0.001），尽管存在比例性低估（斜率=0.642）。所有方程的可靠性均可接受（ICC>0.79），且佐贺山方程的CV%最低（13.4%，95%置信区间：9.44%-17.36%）。布兰德-奥特曼分析揭示了系统偏差，尤其是金氏方程。所有三个方程在估计BJJ运动员的绝对SMM（千克）方面都具有准确的有效性和可靠性。然而，麦卡锡方程和佐贺山方程在DXA测量中显示出较小的偏差和更高的一致性，支持它们用于该人群SMM的准确量化。需要通过磁共振成像对它们进行验证。
