Respiratory Function and Athletic Performance in Professional Soccer Players

Association Between Respiratory Function and Athletic Performance Parameters in Professional Soccer Players: A Cross-Sectional Study

This prospective observational study aims to investigate the relationship between respiratory function and multidimensional athletic performance parameters in professional soccer players. The primary hypothesis of the study is that soccer players with enhanced respiratory function and superior respiratory muscle strength will exhibit optimized motor performance outcomes and shorter (faster) reactive reaction times. Investigators will evaluate respiratory muscle strength, spirometric pulmonary functions, dynamic balance, core and abdominal endurance, and reactive visuomotor reaction times during a single testing session within the competitive season.

Study Overview

• Status: Not yet recruiting
• Conditions: Athletic Performance; Reaction Time; Respiratory Function; Respiratory Muscle Strength
• Intervention / Treatment: Other: Respiratory and Athletic Performance Assessments

Detailed Description

Professional soccer players from Istanbulspor A.S. Football Club will be screened and enrolled based on strict eligibility criteria. Eligible athletes will undergo a comprehensive, single-session testing protocol designed to prevent fatigue-related bias. Testing will commence with a baseline pulmonary function assessment and respiratory muscle strength evaluation (maximal inspiratory pressure [MIP] and maximal expiratory pressure [MEP]). Following a standardized rest interval, dynamic balance will be quantified using the Y-Balance Test (YBT). Subsequently, reactive visuomotor reaction times will be measured using the wireless BlazePod LED system. Finally, participants will execute higher-intensity, sport-specific performance assessments, including the isometric plank test for core endurance, a 60-second timed sit-up test for abdominal muscular endurance, and the T-drill test for agility. A standardized 10-minute seated rest interval will be strictly enforced between all physical assessments to ensure full physiological recovery. Bivariate correlation models will be utilized to analyze the direct relationships between respiratory indicators and performance indices.

• Study Type: Observational
• Enrollment (Estimated): 31

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

The study population will consist of elite-level athletic professionals, specifically young adult male professional soccer players. Participants will be recruited from a licensed professional football club actively competing in national league training and competition schedules.

Description

Inclusion Criteria:

• Participants will be actively competing, licensed professional soccer players. -Participants will be engaged in regular, team-based training and competitive match schedules.
• Participants will voluntarily provide written informed consent before any study-related physical performance assessments are conducted.

Exclusion Criteria:

• Participants will be excluded if they present with an acute upper or lower respiratory tract infection that could potentially affect pulmonary function or maximal respiratory muscle performance.
• Participants will be excluded if they have a documented history of major cardiothoracic surgery.
• Participants will be excluded if they have any diagnosed respiratory and/or cardiovascular disorder associated with dyspnea or impaired pulmonary mechanics.
• Participants will be excluded if they present with any condition that elevates clinical risk during maximal inspiratory and expiratory pressure assessments.
• Participants will be excluded if they have sustained an acute musculoskeletal injury within the preceding 6 weeks that could compromise maximal physical exertion during sport-specific performance testing.

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximal Expiratory Pressure (MEP)	Description: Respiratory muscle strength will be assessed using a portable digital respiratory pressure meter. Participants will execute a maximal expiratory maneuver from total lung capacity after full inspiration while wearing a nose clip. The highest reproducible value from at least three technically acceptable trials will be recorded in centimeters of water (cmH₂O).	2 hours
Maximal Inspiratory Pressure (MIP)	Description: Respiratory muscle strength will be assessed using a portable digital respiratory pressure meter. Participants will perform a maximal inspiratory maneuver from residual volume following complete expiration while wearing a nose clip. The highest reproducible value from at least three technically acceptable trials will be recorded in centimeters of water (cmH₂O).	2 hour
Reactive Visuomotor Reaction Time	Cognitive-motor reaction speed will be quantified using a wireless LED pod system arrayed in an equidistant semi-circular matrix. Participants will utilize their dominant lower limb to deactivate randomly illuminated pods as quickly as possible across 10 sets of 22 randomized stimuli. The mean reaction time across the challenge will be recorded in milliseconds (ms).	2 hours
Dynamic Postural Stability (Y-Balance Test)	Functional reach capacity and dynamic balance will be quantified using a standardized Y-Balance Test apparatus. While maintaining a single-leg stance, participants will push indicator blocks in the anterior, posteromedial, and posterolateral directions. The maximum reach distance from three successful trials for each direction will be normalized to leg length and used to calculate a comprehensive Composite Score percentage (%) for both limbs.	2 hours
Static Core Stabilization Endurance (Prone Plank Test)	Isometric core endurance will be quantified using the isometric prone plank test on a high-density mat. Participants will support their body weight exclusively on their forearms and toes, maintaining a strict neutral horizontal alignment of the head, spine, hips, and ankles. The test will be terminated when the participant voluntarily discontinues or fails to maintain correct alignment. Total duration will be recorded in seconds (sec).	2 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Forced Vital Capacity (FVC)	Pulmonary function will be evaluated using a computerized spirometry system in accordance with ATS/ERS guidelines. Participants will perform a maximal inspiratory effort followed by a rapid and forceful expiration sustained until complete exhalation. The highest reproducible value will be expressed both as an absolute volume in liters (L) and as a percentage of predicted reference values (FVC%).	2 hours
Forced Expiratory Volume in 1 Second (FEV1%)	Pulmonary function will be evaluated using a computerized spirometry system in accordance with ATS/ERS guidelines. The volume of air exhaled during the first second of the FVC maneuver will be extracted. The highest reproducible value will be expressed both as an absolute volume in liters (L) and as a percentage of predicted reference values (FEV1%).	2 hours
Peak Expiratory Flow (PEF)	Pulmonary function will be evaluated using a computerized spirometry system in accordance with ATS/ERS guidelines. The maximum flow rate achieved during the forced expiratory maneuver will be measured. The highest reproducible value will be expressed in liters per second (L/s) and as a percentage of predicted reference values (PEF%).	2 hours
Dynamic Abdominal Endurance (60-Second Sit-Up Test)	Dynamic muscular endurance of the abdominal wall will be evaluated using a timed sit-up protocol. From a supine position with knees flexed at 90° and hands crossed over the chest, participants will flex the trunk until the elbows touch the knees, then return to the baseline position. The total number of correctly executed repetitions completed within exactly 1 minute (reps) will be recorded.	2 hours
Change-of-Direction Speed and Agility (T-Drill Test)	On-field agility and change-of-direction speed will be quantified using a standardized T-configuration cone course monitored by electronic timing gates. Participants will perform forward sprinting, lateral side-shuffling, and backpedaling maneuvers through the course. The fastest completion time out of three successful trials will be recorded in seconds (sec).	2 hours

Collaborators and Investigators

• Sponsor: Istinye University

Study record dates

Study Major Dates

• Study Start (Estimated): May 25, 2026
• Primary Completion (Estimated): July 5, 2026
• Study Completion (Estimated): July 10, 2026

Study Registration Dates

• First Submitted: May 23, 2026
• First Submitted That Met QC Criteria: May 23, 2026
• First Posted (Actual): June 1, 2026

Study Record Updates

• Last Update Posted (Actual): June 1, 2026
• Last Update Submitted That Met QC Criteria: May 23, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pathologic Processes; Respiratory Tract Diseases; Respiration Disorders; Pathological Conditions, Signs and Symptoms; Respiratory Aspiration; Diagnostic Techniques and Procedures; Diagnosis; Circulatory and Respiratory Physiological Phenomena; Respiration; Respiratory Physiological Phenomena; Physical Examination; Vital Signs; Respiratory Rate
• Other Study ID Numbers: 22

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No