BRIEF RESEARCH REPORT article
Front. Nutr.
Sec. Sport and Exercise Nutrition
Volume 12 - 2025 | doi: 10.3389/fnut.2025.1595259
This article is part of the Research TopicSports, Nutrition and Public Health: Analyzing their Interconnected ImpactsView all 12 articles
Skeletal Muscle Mass Estimation in Brazilian Jiu-Jitsu Athletes: Validation of Predictive Equations
Provisionally accepted
Alex Ojeda-Aravena1*
Eduardo Báez2,3
Xurxo Dopico4
Mauricio Cresp-Barría5
Jorge Olivares-Arancibia6
Jairo Azócar-Gallardo7,8- 1Universidad de Los Lagos, Osorno, Chile
- 2Escuela de Educación, Carrera de Entrenador Deportivo, Universidad Viña del Mar, Viña del Mar 2520000, Chile, Viña del Mar, V Valparaíso Region, Chile
- 3Laboratorio de Evaluación y Prescripción de Ejercicio, Facultad de Ciencias de la Actividad Física y del Deporte, Universidad de Playa Ancha, Valparaíso, Chile
- 4Performance and Health Group, Department of Physical Education and Sport, Universidade da Coruña, A Coruña, Spain
- 5Department of Innovation and Education, Faculty of Education, Catholic University of Temuco Chile,, Temuco, Chile
- 6AFySE Group, Research in Physical Activity and School Health, School of Physical Education, Faculty of Education, Universidad de las Américas, Santiago, Chile
- 7Departamento de Ciencias de la Actividad Física, Universidad de Los Lagos, Puerto Montt, Chile
- 8Programa de Investigación en Deporte, Sociedad y Buen Vivir (DSBv), Universidad de Los Lagos, Osorno, Chile
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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 repeatedmeasures 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, p < 0.0001), while Sagayama and McCarthy did not differ significantly. Stepwise regression identified the Kim equation as a strong predictor of Sagayama SMM values (R = 0.851; R² = 0.724; RMSE = 2.0 kg; F1,20 = 52.369; p < 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.
Keywords: Skeletal muscle mass, Brazilian Jiu-Jitsu, Predictive equations, Body composition assessment, dual-energy x-ray absorptiometry
Received: 17 Mar 2025; Accepted: 28 May 2025.
Copyright: © 2025 Ojeda-Aravena, Báez, Dopico, Cresp-Barría, Olivares-Arancibia and Azócar-Gallardo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Alex Ojeda-Aravena, Universidad de Los Lagos, Osorno, Chile
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