Inspiratory Muscle Training in Amateur CrossFit® Athletes

The aim of this randomized controlled trial is to investigate the effectiveness of inspiratory muscle training (IMT) on the performance of athletes in CrossFit® activities, respiratory muscle strength, and perceived post-training fatigue. This study follows a two-arm randomized controlled trial protocol. Ninety-four volunteers aged between 18 and 60 years, enrolled in CrossFit® training, will be randomly allocated to the IMT Group, which involves respiratory training using a linear load device (Powerbreathe®) in conjunction with CrossFit® training; or the Non-IMT Group, which undergoes the same training as the intervention group but uses a device without a valve that ensures resistance. The primary outcome is to investigate the efficacy of IMT on physical performance in the test: burning 25 calories on the "Air Bike" measured by the time taken to reach the 25-calorie mark on this equipment. The secondary outcomes include performance in the six-minute walk test, Pistol, Burpee, Sit-up, Box Jump, Thruster, and Single-Under, as well as the assessment of subjective fatigue perception. All outcomes of interest will be collected at baseline and reassessed at the following time points: mid-term (8 weeks post-allocation) and long-term (12 weeks post-allocation). The analyses will follow the intention-to-treat principle. Treatment effects will be evaluated using Mixed Linear Models. The results of this study may help clarify the effects of IMT on CrossFit® athletes.

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: initially, the participant will answer the evaluation form and then their MIP and MEP values will be collected. Then, the first evaluation test will be performed: "Air Bike" (25 calories). On the following day, the evaluation sequence will be: 6MWT, Pistol, Burpee, Sit up, Box Jump, Thruster and Single-Under. In addition, after all the exercises on the second evaluation day have been performed, the Borg Scale will be applied.

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.

Eligibility Criteria:
Inclusion Criteria:

* Age between 18 and 60 years;
* Be enrolled in a CrossFit® program;
* Be available to perform TMI at home 5 days a week.

Exclusion Criteria:

* Have any musculoskeletal, cardiovascular and/or neurological condition that prevents CrossFit® and/or IMT from being performed;
* Be a smoker;
* Not sign the Termo de Consentimento Livre Esclarecido (TCLE);
* Be performing or have performed IMT using linear load equipment in the last month.