High-Intensity Functional Concurrent Training for Physical Fitness, Body Composition, and Psychological Outcomes in Schoolchildren: Protocol for a Randomized Controlled Trial.

High-intensity functional concurrent training (HIFCT) has emerged as a form of training characterized by constantly varied functional movements adapted to individual fitness levels. Previous studies have reported positive effects on muscular strength, cardiorespiratory fitness, body composition, and psychological well-being; however, evidence regarding HIFCT interventions in school-aged children remains limited. Therefore, the aim of the present study protocol is to evaluate the effects of an 8-week HIFCT programme on muscular strength, cardiorespiratory fitness, body composition, anxiety, stress, and self-esteem in children aged 10-12 years. Physical fitness, anthropometric variables, and psychological outcomes will be assessed before and after the intervention using validated field-based tests and questionnaires. This study may provide novel evidence regarding the feasibility, safety, and potential effects of HIFCT programmes in the school setting. The study protocol was registered at ClinicalTrials.gov (NCT07552844) and approved by the Córdoba Research Ethics Committee (IMIBIC, Córdoba, Spain; protocol code SICEIA-2025-000408).