Can ultrasound echo intensity assess muscle quality in children aged 10-14 years? Protocol for a cross-sectional validation study in Czech children.

introductionUltrasonography is a non-invasive and safe method for assessing muscle morphology. Among its parameters, echo intensity (EI), derived from grayscale image analysis, has emerged as a promising indicator of muscle quality and intramuscular fat infiltration. This study aims to validate EI as a marker for evaluating muscle quality in a population of Czech children, through integration with gold-standard assessments of muscle strength and body composition. The primary aim of this study is to assess the reliability and construct validity of quadriceps muscle EI using ultrasound as a proxy measure of morphological muscle quality in children aged 10-14 years. METHODS AND ANALYSIS: Children aged 10-14 years will undergo ultrasound assessment of the quadriceps femoris (QF). EI will be derived from longitudinal scans of each QF head and the cross-sectional area (CSA ETHICS AND DISSEMINATION: The study will be conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of the Faculty of Physical Education and Sport, Charles University (EK 101/2024). Written parental consent and verbal assent from children will be obtained, with all data handled confidentially and anonymised. Results will be disseminated transparently to participants and their families in line with ethical principles of respect, beneficence and justice. TRIAL REGISTRATION NUMBER: NCT06792279.