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

NCT07717801 | Recruiting

• 1 other identifier: NCKU_Combat_Diaphragm
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Respiratory Muscle Function; Athletic Performance; Postural Balance

Keywords

Combat sport athletes; Dysfunctional breathing; Diaphragmatic function; Diaphragmatic breathing retraining; Core stability; Postural control

Outcome Measures

Primary Outcomes (24)

• 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)

Study Arms (2)

Diaphragmatic Breathing Retraining Group

EXPERIMENTAL

Combat sport athletes with dysfunctional breathing patterns will receive supervised diaphragmatic breathing training.

Other: Diaphragmatic breathing training exercise

Usual Training Control Group

OTHER

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

Interventions

Diaphragmatic breathing training exercise OTHER

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.

Diaphragmatic Breathing Retraining Group

Usual training OTHER

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.

Usual Training Control Group

Eligibility Criteria

• Age: 18 Years - 50 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• National Cheng Kung University: lead

Study Sites (1)

Department of Physical Therapy, National Cheng Kung University,

Tainan, 701, Taiwan

RECRUITING

Central Study Contacts

Yi-Ju Tsai

CONTACT

+886-6-2353535; lulilutsai@gmail.com

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: July 2, 2026
• First Posted: July 21, 2026
• Study Start: May 1, 2026
• Primary Completion (Estimated): July 1, 2029
• Study Completion (Estimated): July 1, 2029
• Last Updated: July 21, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will not share

Locations

TW (1)