The aim of the randomized controlled study is to investigate the effects of high-intensity inspiratory muscle training on respiratory strength, balance, and core endurance in American Football (Tackle Football) athletes.

After completing baseline assessments, participants will be randomly assigned to either the High-Intensity Inspiratory Muscle Training group (IMT Group) or the Control Group (CG) using simple randomization procedures.

All athletes in both groups will continue their regular team-based strength and conditioning routines throughout the 8-week study period. Participants in the IMT Group will additionally perform a high-intensity inspiratory muscle training protocol three times per week, with training loads set at approximately 80% of each athlete's measured maximal inspiratory pressure (MIP). Training intensity will be reassessed bi-weekly and adjusted according to updated MIP values to ensure that the prescribed load is maintained throughout the intervention. The Control Group will not receive inspiratory muscle training and will perform only their routine training program.

All athletes will be evaluated at baseline and at the end of the 8-week intervention. Outcome measures will include respiratory muscle strength (MIP/MEP), dynamic and static balance performance, core muscle endurance (McGill core endurance tests), and sport-specific performance parameters relevant to American football. Assessments will be carried out by the same researcher to minimize inter-rater variability, and all training sessions will be supervised to ensure protocol adherence.

Data will be collected and recorded systematically at both time points, and all procedures will follow established ATS/ERS guidelines for respiratory muscle testing and standard sports science assessment protocols.

Inclusion Criteria:

• Self-identified male American football athletes
• Ages 18 to 35 years
• Actively participating in team-based training at the time of study enrollment
• Minimum 1 year of organized American football training experience
• Able to perform high-intensity inspiratory muscle training (IMT)
• No history of acute respiratory infection in the past 4 weeks
• Voluntary agreement to participate and ability to provide informed consent

Exclusion Criteria:

• Acute or chronic respiratory disease (e.g., uncontrolled asthma, COPD)
• History of major cardiovascular, neurological, or musculoskeletal disorders affecting performance
• Current rib, spine, abdominal, or core muscle injury
• Diagnosed pulmonary hypertension or unstable cardiac conditions
• Recent surgery (within the past 3 months)
• Inability to correctly perform inspiratory muscle training (IMT) device technique
• Participation in another interventional study within the last 30 days

Participants must be self-identified male American football athletes actively participating in team training.

Individual participant data (IPD) will not be shared because this study is a graduate thesis project involving a limited sample of athletes, and data cannot be publicly released to protect participant privacy.