Inspiratory muscle warm-up (IMW) is a specific pre-exercise breathing intervention designed to prepare the respiratory muscles before physical activity and potentially enhance exercise performance. Previous research suggests that IMW may acutely improve inspiratory muscle function; however, the duration of these effects during exercise and their responses under different exercise intensities remain unclear. Furthermore, placebo-controlled comparisons are limited in the current literature.

The purpose of this study is to investigate the acute effects of inspiratory muscle warm-up on inspiratory muscle strength during aerobic and anaerobic exercise in trained athletes. The study will compare three experimental conditions: a standardized inspiratory muscle warm-up protocol, a placebo breathing warm-up, and a control condition without respiratory warm-up.

In this repeated-measures interventional study, trained athletes aged 14-30 years will complete three experimental sessions in randomized order. The active intervention consists of inspiratory muscle warm-up performed at 40% of maximal inspiratory pressure (MIP). The placebo condition includes a low-resistance breathing protocol designed to mimic the intervention without providing a meaningful training stimulus. The control condition involves exercise performed without respiratory warm-up.

Participants will perform treadmill exercise at intensity levels representing aerobic and anaerobic workloads, defined according to percentage of maximal heart rate. Inspiratory muscle strength (MIP) will be assessed at baseline, immediately after the warm-up protocols, and periodically during exercise to evaluate time-dependent changes.

The primary objective is to determine how long the acute increase in inspiratory muscle strength is maintained during exercise and to compare responses between aerobic and anaerobic athletes across the three conditions. The findings may provide evidence-based guidance for integrating respiratory muscle warm-up strategies into sport-specific preparation routines.

Inspiratory muscle warm-up (IMW) has emerged as a non-pharmacological pre-exercise strategy aimed at enhancing respiratory muscle readiness prior to physical activity. The inspiratory muscles, particularly the diaphragm and accessory respiratory muscles, play a critical role in meeting increased ventilatory demands during exercise. Acute respiratory muscle fatigue has been associated with reduced performance through mechanisms such as altered ventilatory efficiency and activation of the respiratory muscle metaboreflex, which may redistribute blood flow away from locomotor muscles. While previous studies have reported beneficial acute effects of IMW on respiratory and performance parameters, the temporal characteristics of these effects during ongoing exercise remain insufficiently understood.

Existing research has primarily focused on pre- and post-intervention comparisons, often evaluating inspiratory muscle strength immediately following IMW without assessing how long these acute improvements persist during exercise. Furthermore, the influence of exercise intensity domains and athlete specialization (aerobic vs. anaerobic disciplines) on the duration of IMW-induced effects has not been systematically investigated. Another limitation of prior studies is the limited use of placebo-controlled designs, which are important for distinguishing physiological effects from expectancy or psychological influences associated with warm-up interventions.

The present study is designed as a repeated-measures interventional investigation to evaluate the acute time course of inspiratory muscle strength responses following inspiratory muscle warm-up under different exercise conditions. Each participant will complete three experimental sessions, including: (1) an active inspiratory muscle warm-up protocol performed at a standardized relative intensity, (2) a placebo breathing warm-up designed to mimic the intervention without providing a meaningful physiological load, and (3) a control condition without respiratory warm-up. The order of conditions will be counterbalanced to minimize order effects.

Exercise trials will involve treadmill running performed at predefined intensity domains representing aerobic and anaerobic workloads based on individual maximal heart rate. Inspiratory muscle strength will be measured repeatedly throughout exercise to identify the time-dependent decline relative to baseline and post-warm-up levels. This design allows examination of both immediate and sustained effects of respiratory muscle preparation strategies.

By comparing responses between athletes from predominantly aerobic and anaerobic sports backgrounds, the study seeks to explore whether differences in energy system utilization, muscle fiber composition, and ventilatory demands influence the effectiveness and duration of inspiratory muscle warm-up. The findings may contribute to a more precise understanding of respiratory muscle preparation and support evidence-based integration of breathing-specific warm-up strategies into athletic training and competition routines.

Inclusion Criteria:

• Age between 14 and 30 years.
• Regular participation in organized sports training for at least 4 years.
• Engaged in predominantly aerobic or anaerobic sports disciplines.
• Training frequency of at least 3 sessions per week.
• No known cardiopulmonary disease affecting respiratory function.
• Ability to safely perform maximal effort treadmill exercise.
• No respiratory illness within the last 12 weeks.
• Willingness to comply with study procedures.
• Provision of written informed consent (and parental consent for minors where applicable).

Exclusion Criteria:

• History of asthma, chronic obstructive pulmonary disease (COPD), or other respiratory disorders.
• Age below 14 years or above 30 years.
• Orthopedic injury or condition limiting running ability.
• Participation in inspiratory muscle training within the last 12 months.
• Use of medications affecting respiratory or cardiovascular function.
• Active smoking.
• Failure to provide informed consent.

De-identified individual participant data (IPD) underlying the results reported in publications, including maximal inspiratory pressure (MIP) measurements, demographic variables, exercise responses, and related outcome variables, will be made available upon reasonable request. Data will be shared after publication of the main study results and in accordance with institutional ethics approval and applicable data protection regulations. A data dictionary and relevant methodological documentation will be provided to allow appropriate interpretation of the dataset. Requests for data access will be evaluated by the principal investigator to ensure scientific validity and compliance with ethical standards.

De-identified individual participant data will be available beginning 6 months after publication of the primary results and will remain accessible for up to 5 years, subject to reasonable request and ethical approval requirements.

De-identified individual participant data and supporting documents will be available to qualified researchers upon reasonable request. Researchers must submit a proposal outlining the research objectives, analysis plan, and intended use of the data. Requests will be reviewed by the principal investigator to ensure scientific validity, ethical compliance, and alignment with the original informed consent and institutional policies. Data sharing will require the signing of a data use agreement, and access will be provided for non-commercial scientific research purposes only. Data will be shared in anonymized form through secure electronic transfer.

Participants and study staff are blinded to whether the breathing warm-up is performed at 40% MIP (active IMW) or as a placebo/sham protocol. Warm-up loads are pre-set by an independent staff member not involved in testing, and conditions are labeled with neutral codes (e.g., A/B/C). The intervention administrator and outcome assessor record and analyze outcomes using coded conditions. Unblinding occurs only after data collection is completed. (If a no-warm-up control session is included, it is described separately and may not be fully blind unless a sham breathing routine is used.)