Influence of an Inspiratory Muscle Fatigue Protocol on Healthy Youngs on Respiratory Muscle Strength, Vertical Jump Performance and Muscle Oxygen Saturation

Respiratory muscle training represents an effective method increasingly utilized in both sports and healthcare domains, employing various devices, among which threshold devices are prominent. The aim of this study is to determine the relationship between inspiratory muscle fatigue and muscular strength in lower limbs, in both healthy and pathological subjects, as well as the association between such fatigue and other variables, including maximal inspiratory pressure and muscle tissue oxygen levels.

According to our hypothesis, the execution of a protocol inducing inspiratory muscle fatigue in healthy youngs could influence muscular strength, exercise capacity and muscle tissue oxygenation.

In this study, subjects will be divided into three groups: experimental group , activation group and control group.

Measurements of variables, such as maximal inspiratory pressure, peripheral muscle tissue oxygen levels, diaphragmatic strength (ultrasound image) and vertical jump performance, will be conducted.

This is a randomized control trial. Experimental group (EG) will perform an inspiratory muscle fatigue protocol using a specific inspiratory endurance test, in which volunteers, one-on-one, and in a single session, will breathe against submaximal inspiratory loads equivalent to 60% of their Maximum Inspiratory Pressure (MIP) through a threshold valve device. Participants will follow a free pattern of breathing until they are unable to establish flow during at least 3 maximum inspiratory efforts.

Activation group (AG) will perform a protocol of 2 sets of 30 repetitions at 40% of their MIP, one-on-one, and in a single session, using a threshold valve device.

Control group will do a seat and wait.

Interventions will be supervised by a physiotherapist. Primary outcomes will be:

Muscle oxygen saturation (SmO2) will be assessed using a near infrared spectroscopy device, immediately before intervention and immediately after intervention.

Vertical jump performance will be assessed by Counter Movement Jump (CMJ) test. CMJ test involved starting from a standing position with hands placed on hips, followed by a rapid upward jump achieved by flexing and extending knees. This plyometric action followed sequence of "eccentric - isometric - concentric" movements. CMJ measurements were taken using a force platform. This will be done immediately before intervention and immediately after intervention

Respiratory muscle strength will be assessed using a respiratory pressure meter or manometer designed, and with ultrasound image measuring cross sectional area of diaphragm at 8-9th rib level and speed of contraction with a deep and fast inspiratory manoeuver. This will be done immediately before intervention and immediately after intervention

Eligibility Criteria:
Inclusion Criteria:

* Aged between 18-45 years.
* Non-smoker.
* Engaged in sports activity at least 3 times a week for a minimum of one year.

Exclusion Criteria:

* Having a medical condition that impedes engaging in physical activity.
* Individuals with compromised cognitive capacities.
* Subjects with any chronic disease (cardiorespiratory, neurological, metabolic, oncological, etc.).
* Subjects with tympanic perforation or middle-inner ear pathology.
* Subjects who have undergone lower limb surgery within the past 12 months.
* Subjects experiencing an active episode of lower limb pain.