Measurement Constructs and Inference in Skeletal Muscle Hypertrophy Research: A Systematic Methodological Review

This registration describes the protocol for a systematic methodological review examining direct and indirect methods used to quantify skeletal muscle hypertrophy in sport and exercise science research. The purpose of this review is to critically evaluate the validity, reliability, responsiveness, and interpretative limitations of commonly used imaging and proxy-based approaches, including magnetic resonance imaging (MRI), ultrasound, dual-energy X-ray absorptiometry (DXA), computed tomography (CT), and anthropometric or bioimpedance-derived measures. The review aims to: (1) Categorise measurement modalities according to anatomical resolution and construct validity; (2) Examine methodological sources of error and bias influencing hypertrophy detection; (3) Identify inconsistencies in reporting standards; and (4) Develop a translational decision framework to guide appropriate method selection in applied sport and exercise contexts. Eligibility criteria, search strategy, data extraction fields, and modality classification rules were defined a priori prior to data extraction. As the methodological framework was established before analysis but not publicly archived at the time of study commencement, this registration is retrospective.