Fatigue of the respiratory muscles is one of the limitations of exercise at high intensity, although the mechanisms that explain it are not yet clear. This fatigue would cause a decrease in physical performance and could limit the functional capacity of the subject. In this sense, it has been shown that specific training of respiratory muscles, especially inspiratory muscles, improves their strength and resistance both in healthy people and in people with pathologies; managing to improve the quality of life and both physical and sports performance. This study, which follows the quantitative method and proposes an analytical, experimental, longitudinal and prospective design (with the aim of conducting a randomized clinical trial), proposes an intervention based on performing a specific training of inspiratory muscles for 8 weeks, taking 30 maximum inspirations at 60% of the PIM (maximum inspiratory pressure), 2 times a day for 5 days a week; with the aim of assessing the effects on inspiratory function, cardiorespiratory fitness when performing a stress test (Harvard step test) and diaphragm thickness measured by ultrasound. 40 healthy subjects between 18 and 25 years old will be recruited and divided into two groups: an experimental group (n = 20) and a control group (n = 20).

Inclusion Criteria:

• healthy university students

Exclusion Criteria:

• Suffering or having suffered aortic aneurysm; pneumothorax; rib wall or pulmonary fistulas; recent trauma or surgery to the upper airway or thoracoabdominal; recent myocardial infarction or angina; retinal detachment, glaucoma, or recent eye surgery; increased intracranial pressure (tonsillar wedge, meningocele, hydrocephalus); abdominal hernias and acute middle ear problems.