Resistance Training-Induced Changes in Muscle Thickness: A Comparison Between Longitudinal and Transverse Ultrasound Measurements

• Grant number: 25/26016-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2026
• End date: January 31, 2027
• Field of knowledge: Health Sciences - Physical Education
• Principal Investigator: Cleiton Augusto Libardi
• Grantee: Bruno Kaique Reis Pereira
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 23/04739-2 - RESISTANCE TRAINING PROGRESSION: EFFECTS ON THE REMODELING OF THE EXTRACELLULAR MATRIX IN HUMANS, AP.R

Abstract

Muscle thickness (MT), assessed by ultrasound (US), is widely used as a morphological marker in studies investigating muscle hypertrophy induced by resistance training (RT). Although MT can be obtained with the transducer positioned longitudinally or transversely to the muscle fiber axis, it is not yet established whether these approaches provide comparable results in detecting RT-induced morphological adaptations. Therefore, the aim of this study is to compare changes in vastus lateralis MT after 12 weeks of RT using US measurements acquired in the longitudinal (MT-L) and transverse (MT-T) planes. Healthy young adults will perform 24 RT sessions consisting of three sets of 10-12 repetition maximum on the knee-extension exercise. MT measurements will be obtained before and after the intervention using both approaches. Statistical analyses will consider absolute and relative changes between time points, as well as measurement reproducibility. The findings may offer methodological insights to support the selection of the most appropriate acquisition plane in studies using US to assess muscle hypertrophy, contributing to more robust and standardized evaluation protocols across different research and applied settings. (AU)