Effectiveness of Inspiratory Muscle Training on Respiratory Muscle Strength and Physical Performance in Amateur CrossFit® Athletes: A Randomized Controlled Trial

Study design: This is a prospective randomized controlled trial with two arms. The study was registered with the Research Ethics Committee of the Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM): 81443024.9.0000.5108. Procedures and data collection: Participants who seek the CrossFit® service and enroll, as well as those who are already enrolled, will be invited to participate in this study. All eligible participants will receive information about the study and must sign an informed consent form before participating. The initial assessment and reassessment of the participant will take place at Academia Compasso Sete Lagoas (Boa Vista Unit and/or Centro Unit). The data collected will be: age, height, weight, body mass (BM), Body Mass Index (BMI), heart rate, blood pressure, gender, smoking history (yes/no), medications in use, time practicing the sport and the presence of any comorbidities. All outcomes of interest (respiratory muscle strength, subjective perception of fatigue and results obtained in CrossFit® exercises) will be collected at baseline and reassessed at the following time points: medium term (8 weeks after allocation) and long term (12 weeks after allocation), in an assessment room at the gym. The collected data will initially be entered into a standardized data collection form and then transferred to an Excel table.

The evaluation process will be divided as follows: first, the participant will complete the evaluation form, and then their MIP and MEP values will be collected. Next, the first evaluation test will be performed: "Air Bike" (25 calories); then the evaluation sequence will be performed: Sit-up, Pistol, Burpee, Box Jump, 6MWT, Thruster, and Single-Under. Additionally, after completing all the exercises on the second day of evaluation, the Borg Scale will be administered.

The randomization sequence for the experimental and control groups, with an allocation ratio of 1:1, will be generated by a computer program by one of the researchers who will not be involved in the recruitment of participants. The groups will be coded and the allocation will be transferred to a series of sealed and sequentially numbered opaque envelopes. Two evaluators participated in this stage of the research: researcher 1 will be responsible for the evaluations; and researcher 2 for randomization and distribution of equipment.

Group with TMI: CrossFit® training: participants will be guided and encouraged to attend at least 5 days of training. TMI: the device used for the intervention will be the POWERbreathe®. The load used will be 50% of MIP. The TMI will be performed in two series of 30 breaths through the mouth through the mouthpiece connected to the POWERbreathe®, with a 1-minute interval between series.

Group without TMI: participants allocated to the "No TMI Group" will receive the same interventions as the "Group with TMI", but without the respiratory training included. In addition, they will also perform the TMI in a simulated manner.