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.
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
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
60
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.
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.
Department of Physical Therapy, National Cheng Kung University,
Tainan, Taiwan
RECRUITINGBreathing 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).
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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.
Time frame: 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
Time frame: 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
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
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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: Baseline (Day 1), Week 8 (post-intervention), Week 16 (8 weeks after intervention completion)
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