Skip to main content
OpenTrials
Recruiting

NCT Number: NCT07717801

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

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.

Recruiting

Interested in participating?

Request Info

Key information

Conditions

Respiratory Muscle Function Athletic Performance Postural Balance

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Department of Physical Therapy, National Cheng Kung University,

Tainan, 701, Taiwan

Location status: Recruiting

Location contact

Chiao-Yun Lin

CONTACT

[email protected]

+886-6-2353535 ext. 5930

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

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.

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.

Primary outcomes

  1. Breathing Pattern_ Total Faulty Breathing Scale (TFBS) Score

    Time frame: Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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).

  2. Trunk Flexor Endurance _ McGill Curl-Up Hold Test

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  3. Back Extensor Endurance _Biering-Sørensen Test

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    Isometric back extensor endurance measured as hold time during the Biering-Sørensen Test. A longer time indicates greater endurance.

    Unit of Measure: seconds

  4. Movement Speed_10-Meter Sprint Time

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  5. Agility _ T-Test Time

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  6. Visual Motor Reaction Time _ BlazePod System

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  7. Dynamic Balance _ Y Balance Test Composite Score

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  8. Reactive Postural Control - Time to Stabilization

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  9. Reactive Postural Control - Trunk/Pelvis Angular Displacement

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  10. Reactive Postural Control - Trunk/Pelvis Angular Velocity

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  11. Reactive Postural Control - Peak Ground Reaction Force

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  12. Reactive Postural Control - COP Path Length

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  13. Reactive Postural Control - Trunk Muscle Onset Latency

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    EMG onset latency of trunk muscles relative to perturbation onset, measured via surface electromyography. Unit of Measure: milliseconds

  14. Reactive Postural Control - Trunk Muscle EMG Amplitude

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    Normalized EMG amplitude of trunk muscles during the early stabilization phase following an unexpected anterior pulling perturbation. Unit of Measure: percent of MVIC

  15. Maximal Inspiratory Pressure (MIP)

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion) Secondary

    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.

  16. Maximal Expiratory Pressure (MEP)

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  17. Diaphragmatic Excursion

    Time frame: Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  18. Diaphragmatic Thickening Fraction

    Time frame: Baseline (Day 1), Day 1 (immediately after first session), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  19. Proactive Core Stability - Time to Stabilization

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  20. Proactive Core Stability - Trunk/Pelvis Angular Displacement

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  21. Proactive Core Stability - Trunk/Pelvis Angular Velocity

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  22. Proactive Core Stability - Peak Ground Reaction Force

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    Peak ground reaction force during the stabilization phase following single-leg drop landing, measured via force plate. Unit of Measure: percent of body weight

  23. Proactive Core Stability - COP Path Length

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    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

  24. Proactive Core Stability - Trunk Muscle EMG Amplitude

    Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)

    Normalized EMG amplitude of trunk muscles during the early stabilization phase following single-leg drop landing. Unit of Measure: percent of MVIC

Study contacts

Contact information is provided by the study sponsor or research team.

Yi-Ju Tsai

CONTACT

[email protected]

+886-6-2353535 ext. 5021

Sponsors and collaborators

Lead sponsor

National Cheng Kung University

Other

Registry information

Official study title

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

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Jul 21, 2026
Registry last updated
Jul 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.