Effects of Diaphragmatic Breathing Retraining in Combat Sport Athletes With Dysfunctional Breathing Patterns

Dysfunctional Breathing Patterns, Diaphragmatic Function, Core Stability, and Postural Control in Combat Sport Athletes: Diaphragm-Centered Neuromuscular Control Perspective and Effects of Diaphragmatic Breathing Retraining

Combat sport athletes often need to maintain a guarded posture, stabilize the trunk, react quickly, and control balance during contact or unexpected movement. These demands may be related not only to strength and conditioning, but also to the coordination between breathing and postural control. The diaphragm is the main muscle for breathing and also contributes to trunk stability through its role in pressure regulation and deep core control. However, dysfunctional breathing patterns, such as upper-chest dominant breathing, reduced lower rib expansion, or poor coordination between the chest and abdomen, may interfere with this function.

The purpose of this study is to examine dysfunctional breathing patterns in combat sport athletes and to investigate whether diaphragmatic breathing retraining can improve breathing patterns, diaphragm function, core stability, postural control, and sport-related performance. This study will first screen athletes from combat and non-combat sports to determine the prevalence of dysfunctional breathing. Combat sport athletes will then complete laboratory tests to examine the relationship between breathing pattern, posture, diaphragm function, core stability, and postural control. In the intervention part of the study, combat sport athletes with dysfunctional breathing will be randomly assigned to diaphragmatic breathing retraining plus usual training or usual training only. The study will compare the two groups to determine whether adding diaphragmatic breathing retraining provides additional benefits. The study will also examine whether the changes are maintained after training and whether baseline measures can help identify athletes who respond better to the program.

Study Overview

• Status: Recruiting
• Conditions: Athletic Performance; Postural Balance; Respiratory Muscle Function
• Intervention / Treatment: Other: Diaphragmatic breathing training exercise; Other: Usual training

Detailed Description

Combat sports place high demands on the neuromuscular system. Athletes must generate force, absorb impact, maintain balance, and respond to an opponent under rapidly changing conditions. Many combat sport athletes also use protective or guarded postures during training and competition. These postures may help with short-term stability, but they may also be associated with altered trunk control, reduced movement adaptability, and increased loading on the spine and surrounding tissues.

Breathing mechanics may be one factor related to these movement-control demands. The diaphragm is not only the primary muscle for inspiration, but also contributes to trunk stabilization. Through its interaction with the abdominal wall, pelvic floor, and deep spinal muscles, the diaphragm helps regulate intra-abdominal pressure and support postural control. When breathing is dominated by the upper chest or accessory muscles, the coordination between breathing and trunk stabilization may be less efficient.

Dysfunctional breathing has been reported in physically active and athletic populations, but its role in combat sport athletes is still not well understood. Most sport-related breathing studies have focused on respiratory muscle strength or endurance. Less attention has been given to breathing pattern normalization and the integration of breathing with postural control. For this reason, the present study focuses on dysfunctional breathing as a possible neuromuscular control issue rather than only a respiratory problem.

This study includes three main stages. In the first stage, athletes from combat and non-combat sports will be screened for dysfunctional breathing and postural characteristics. This stage will estimate the prevalence of dysfunctional breathing and compare breathing patterns between sport types. A subgroup of combat sport athletes will also complete laboratory-based testing to examine whether breathing pattern is associated with diaphragm function, posture, core stability, and postural control.

In the second stage, combat sport athletes with dysfunctional breathing will participate in an intervention study. Participants will first complete a single-session breathing correction assessment to examine immediate changes in breathing pattern and diaphragm function. They will then be randomly assigned to either diaphragmatic breathing retraining plus usual training or usual training only. The breathing retraining program will last 8 weeks and will progress from breathing correction in supported positions to breathing control in upright and core-demanding positions.

Assessments will be performed before the intervention, after the first breathing correction session, after the 8-week intervention, and at follow-up. The assessments will include breathing pattern evaluation, ultrasound assessment of diaphragm function, respiratory muscle strength testing, movement analysis, force plate testing, muscle activity recording, and functional sport performance tests. These tests are used to examine whether changes in breathing are accompanied by changes in trunk control, balance responses, and sport-related function.

In the third stage, the study will explore why some athletes improve more than others. Athletes who receive diaphragmatic breathing retraining will be classified as responders or non-responders based on changes in breathing pattern. Baseline breathing severity, diaphragm function, posture, core stability, postural control, and low back pain status will be examined as possible factors related to training response.

Overall, this study aims to clarify the relationship between breathing pattern and movement control in combat sport athletes. The findings may help determine whether diaphragmatic breathing retraining can be used as a practical strategy to improve breathing control, trunk stability, postural control, and sport-related performance in athletes with dysfunctional breathing.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Yi-Ju Tsai; Phone Number: 5021 +886-6-2353535; Email: lulilutsai@gmail.com

Study Locations

• Taiwan
  • Tainan, Taiwan, 701
    • Recruiting
    • Department of Physical Therapy, National Cheng Kung University,
    • Contact: Chiao-Yun Lin; Phone Number: 5930 +886-6-2353535; Email: qlin0101@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Aged between 18 and 50 years.
• Currently participating regularly in combat sports, such as taekwondo, boxing, judo, karate, jiu-jitsu, or similar sports, with at least 2 years of training experience.
• Training at least 3 times per week.

Exclusion Criteria:

• Current or major musculoskeletal injury within the past year that may affect testing or training performance.
• History of major thoracic, abdominal, or spinal surgery.
• Known cardiopulmonary diseases, such as asthma, chronic obstructive pulmonary disease, or heart disease; neurological disorders; vestibular dysfunction; or other conditions that may affect balance.
• Current or recent pregnancy.
• Previous participation in breathing training or respiratory therapy, or current use of medications that may affect respiratory or neuromuscular function.
• Inability to complete ultrasound assessment, motion analysis, or exercise testing.
• Having a subordinate relationship or conflict of interest with the principal investigator or co-investigators, such as being a supervised student, research assistant, employee, or other related personnel.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Diaphragmatic Breathing Retraining Group; Combat sport athletes with dysfunctional breathing patterns will receive supervised diaphragmatic breathing training.	Other: Diaphragmatic breathing training exercise; Participants will complete one session of diaphragmatic breathing correction. During the session, verbal instruction, manual facilitation, and corrective feedback will be used to guide participants toward a more diaphragmatic breathing pattern. Participants will be instructed to breathe with relaxed shoulders and neck, increase lower rib cage and abdominal expansion, and minimize upper-chest dominant breathing. The intervention is designed to examine the immediate effects of breathing correction on breathing pattern characteristics, diaphragm function, postural alignment, and core stability-related outcomes.
Other: Usual Training Control Group; Combat sport athletes in the control group will continue their usual sport-specific training without any structured breathing intervention. They will receive non-specific limb stretching and general exercise education.	Other: Usual training; Participants continue their regular sport-specific training schedule. They receive non-specific limb stretching and general exercise education but no structured breathing exercises or breathing instruction during the study period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Breathing Pattern_ Total Faulty Breathing Scale (TFBS) Score	Breathing pattern severity assessed using the Total Faulty Breathing Scale (TFBS), a structured observational tool scored 0-12. Higher scores indicate greater breathing dysfunction. Assessed during 10 cycles of quiet and 10 cycles of deep breathing in standing. Also supported by Manual Assessment of Respiratory Motion (MARM).	Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Trunk Flexor Endurance _ McGill Curl-Up Hold Test	Description: Isometric trunk flexor endurance measured as hold time during the McGill Curl-Up Test. A longer time indicates greater endurance. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Back Extensor Endurance _Biering-Sørensen Test	Isometric back extensor endurance measured as hold time during the Biering-Sørensen Test. A longer time indicates greater endurance. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Movement Speed_10-Meter Sprint Time	Time to complete a 10-meter maximal sprint from a combat/two-point stance, measured with electronic timing gates. Lower time indicates better performance. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Agility _ T-Test Time	Time to complete the agility T-test course (sprint forward, lateral shuffles, backward run around 4 cones in a T-shape). Lower time indicates better multidirectional agility. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Visual Motor Reaction Time _ BlazePod System	Average reaction time to randomly illuminated light pods during a standardized protocol from a fighting stance, using the BlazePod system (BlazePod Ltd.). Lower time indicates faster reaction. Unit of Measure: milliseconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Dynamic Balance _ Y Balance Test Composite Score	Maximum normalized reach distance in the anterior, posteromedial, and posterolateral directions during single-leg stance on the Y-Balance Test. Unit of Measure: percent of leg length	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Time to Stabilization	Time to stabilization of center of pressure after an unexpected anterior pulling perturbation (10% body weight), measured via force plate. Lower time indicates better reactive postural control. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Trunk/Pelvis Angular Displacement	Angular displacement of the trunk and pelvis during the stabilization phase following an unexpected anterior pulling perturbation, measured via 3D motion capture. Unit of Measure: degrees	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Trunk/Pelvis Angular Velocity	Angular velocity of the trunk and pelvis during the stabilization phase following an unexpected anterior pulling perturbation, measured via 3D motion capture. Unit of Measure: degrees per second	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Peak Ground Reaction Force	Peak ground reaction force during the stabilization phase following an unexpected anterior pulling perturbation, measured via force plate. Unit of Measure: percent of body weight	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - COP Path Length	Total center-of-pressure trajectory length during the stabilization phase following an unexpected anterior pulling perturbation, measured via force plate and normalized to foot length. Unit of Measure: mm	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Trunk Muscle Onset Latency	EMG onset latency of trunk muscles relative to perturbation onset, measured via surface electromyography. Unit of Measure: milliseconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Reactive Postural Control - Trunk Muscle EMG Amplitude	Normalized EMG amplitude of trunk muscles during the early stabilization phase following an unexpected anterior pulling perturbation. Unit of Measure: percent of MVIC	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Maximal Inspiratory Pressure (MIP)	Global inspiratory muscle strength was measured in cmH₂O using a gas pressure gauge (Galemed Corporation). Participants exhale maximally, then inhale forcefully against the gauge for ≥1 second with a nose clip applied.	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion) Secondary
Maximal Expiratory Pressure (MEP)	Global expiratory muscle strength is measured using a gas pressure gauge. Participants inhale maximally, then exhale forcefully against the gauge for ≥1 second. Unit of Measure: cmH₂O	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Diaphragmatic Excursion	Maximum diaphragmatic excursion during maximal inspiration and expiration, measured by M-mode ultrasonography with a 1-5 MHz convex transducer in the right mid-clavicular subcostal region. Unit of Measure: cm	Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Diaphragmatic Thickening Fraction	Diaphragmatic thickening fraction calculated from B-mode ultrasound measurements of diaphragm thickness at end-maximal inspiration and end-maximal expiration, using a 4-12 MHz linear transducer at the zone of apposition. Unit of Measure: percent	Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - Time to Stabilization	Time to stabilization of center of pressure after single-leg drop landing, measured via force plate. Lower time indicates better proactive core stability. Unit of Measure: seconds	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - Trunk/Pelvis Angular Displacement	Angular displacement of the trunk and pelvis during the stabilization phase following single-leg drop landing, measured via 3D motion capture. Unit of Measure: degrees	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - Trunk/Pelvis Angular Velocity	Angular velocity of the trunk and pelvis during the stabilization phase following single-leg drop landing, measured via 3D motion capture. Unit of Measure: degrees per second	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - Peak Ground Reaction Force	Peak ground reaction force during the stabilization phase following single-leg drop landing, measured via force plate. Unit of Measure: percent of body weight	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - COP Path Length	Total center-of-pressure trajectory length during the stabilization phase following single-leg drop landing, measured via force plate and normalized to foot length. Unit of Measure: mm	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
Proactive Core Stability - Trunk Muscle EMG Amplitude	Normalized EMG amplitude of trunk muscles during the early stabilization phase following single-leg drop landing. Unit of Measure: percent of MVIC	Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

Collaborators and Investigators

• Sponsor: National Cheng Kung University

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2026
• Primary Completion (Estimated): July 1, 2029
• Study Completion (Estimated): July 1, 2029

Study Registration Dates

• First Submitted: July 2, 2026
• First Submitted That Met QC Criteria: July 15, 2026
• First Posted (Actual): July 21, 2026

Study Record Updates

• Last Update Posted (Actual): July 21, 2026
• Last Update Submitted That Met QC Criteria: July 15, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Core stability; Diaphragmatic breathing retraining; Dysfunctional breathing; Postural control; Diaphragmatic function; Combat sport athletes
• Other Study ID Numbers: NCKU_Combat_Diaphragm

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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