Respiratory Muscle Strength and Jiu-Jitsu-Specific Performance in Male Brazilian Jiu-Jitsu Athletes

This is an analytical cross-sectional observational study involving 40 male Brazilian Jiu-Jitsu athletes aged 18 to 40 years. Assessments will be completed during three visits separated by 48 to 72 hours. At Visit 1, eligibility will be assessed and written informed consent will be obtained. Demographic and sport-related information, including self-reported height, body weight, and Brazilian Jiu-Jitsu experience, will be recorded. Spirometry will be performed using acceptable and repeatable forced expiratory maneuvers in accordance with current ATS/ERS technical standards. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, and peak expiratory flow (PEF) will be recorded; percent-predicted and z-score values will also be documented when available. Respiratory muscle strength will be assessed as maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP). Participants will perform at least five acceptable maneuvers for each pressure measurement, with up to eight attempts when necessary. The highest acceptable value meeting reproducibility criteria will be recorded in cmH2O. At Visits 2 and 3, participants will complete the Jiu-Jitsu Anaerobic Performance Test (JJAPT) and the Maximum Static Kimono Grip Test on separate days in randomized order. Before each performance test, participants will complete a standardized sport-specific warm-up. The JJAPT consists of five 60-second work bouts separated by 45 seconds of passive recovery. A partner whose body weight is within 5% of the participant's self-reported body weight will be used, and the total number of valid butterfly-guard lifting repetitions will be recorded. For the static kimono grip test, a kimono is wrapped around a horizontal bar and the participant maintains a suspended position with maximal elbow flexion for as long as possible; performance is recorded in seconds. The primary analysis will assess the relationship between MIP and JJAPT total valid repetitions. Secondary analyses will assess MEP in relation to JJAPT performance and MIP and MEP in relation to static kimono grip endurance. Spirometric indices will be summarized descriptively and examined in exploratory secondary analyses in relation to the performance outcomes. Self-reported body weight and Brazilian Jiu-Jitsu experience in months will be considered as prespecified covariates.