This study is a randomized controlled trial on the efficacy of inspiratory muscle training on swimming performance, airway dysfunction and perceived breathlessness in elite swimmers.

Only a few studies have assessed the impact of Inspiratory Muscle Training (IMT) on swim performance with unclear and inconsistent results. This study aims to evaluate the effect of a 12-week IMT program in swimming performance, airway dysfunction and perceived breathlessness among elite swimmers. Participants will be recruited from the elite competitive Futebol Clube do Porto swimming team. After consent, individuals will be randomly allocated into the IMT or Sham-IMT group. A pressure threshold device will be used to perform the inspiratory training. The IMT group will perform 30 inspiratory efforts, 5 times a week, twice a day, against a pressure threshold load equivalent to 50% of maximal inspiratory pressure (MIP). Sham-IMT group will follow a similar protocol, except for the inspiratory effort that will be made against 15% of MIP. Measures of lung function, swimming performance, airway dysfunction, inspiratory muscle strength and perceived breathlessness will be assessed at the beginning and then in 4 weeks intervals until the end of study period. All outcome measures will be assessed by an investigator who will be not involved in the intervention process. Data will be expressed as mean ± standard deviation (SD) and respective 95% confidence interval. The significance level will be 5% (p˂0.05).

Inclusion Criteria:

• Healthy elite swimmers engaged in competitive training for a minimum period of three years;
• Individuals with no disability;
• Individuals aged between 14 and 40 years.

Exclusion Criteria:

• Individuals presenting co-morbidities or physical impairment that affects regular training;
• Smokers;
• Athletes already in a regular respiratory muscle training program
• Individuals with a predicted forced expiratory volume in the first second (FEV1) below 60%.