How Different Breathing Methods Affect Brain Activity in Young Adults With Chronic Ankle Instability (BRAIN-CAI)

Comparative Analysis of Breathing Intervention Types on Neural Activation in Young Adults With Chronic Ankle Instability: An fNIRS-EEG Randomized Controlled Trial

Chronic ankle instability is a common condition that can affect balance, movement control, and daily activities in young adults. Breathing exercises may influence brain function and attention, but their immediate effects on brain activity in individuals with chronic ankle instability are not well understood.

This randomized controlled trial aims to investigate the immediate effects of different breathing interventions on brain activity in young adults with chronic ankle instability. Participants will be randomly assigned to different breathing intervention groups. Brain activity will be assessed before and after the intervention using functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG). The findings may improve understanding of the relationship between breathing exercises and brain function and support the development of rehabilitation strategies for individuals with chronic ankle instability.

Study Overview

• Status: Recruiting
• Conditions: Young Adult; Chronic Ankle Instability, CAI
• Intervention / Treatment: Behavioral: Diaphragmatic Breathing Training; Behavioral: VR-based Breathing Meditation; Behavioral: Neurofeedback Brain Relaxation Training

Detailed Description

Background and Rationale Chronic ankle instability (CAI) is a common sequela of lateral ankle sprain, characterized by recurrent giving way, perceived instability, and impaired dynamic balance. Growing evidence suggests that CAI involves not only peripheral deficits but also altered central nervous system processing, including changes in prefrontal cortical activity. Breathing-based interventions may influence postural control as well as cortical and autonomic regulation. However, it remains unclear how different types of breathing interventions compare in their immediate effects on brain activity in individuals with CAI. This study compared three breathing interventions: diaphragmatic breathing training, VR-based breathing meditation, and neurofeedback-based brain relaxation training.

Study Design This was a parallel-group, assessor-blinded randomized controlled trial. Thirty-three young adults with CAI were randomly allocated to one of three groups (n = 11 per group): the Diaphragmatic Breathing Group (DBG), the VR-based Breathing Meditation Group (VMG), or the Neurofeedback Brain Relaxation Training Group (NRG). Outcome assessors were blinded to group allocation. Each participant received a single intervention session according to group assignment, and outcomes were assessed before and immediately after the intervention. The study was designed and reported in accordance with the CONSORT guidelines.

Interventions The DBG performed diaphragmatic breathing training. The VMG performed breathing meditation delivered through a virtual reality environment. The NRG performed brain relaxation training based on EEG neurofeedback. The three groups differed in the type of breathing intervention while all received a single session. Detailed intervention procedures are described in the Arms and Interventions section.

Outcome Assessment The primary outcomes were cortical activity and EEG-based self-regulation indices. Cortical activity was measured by functional near-infrared spectroscopy (fNIRS) as oxygenated hemoglobin (HbO2) concentration in prefrontal regions of interest, including the dorsolateral prefrontal cortex, frontopolar cortex, orbitofrontal cortex, and medial prefrontal cortex. Neural self-regulation was evaluated using indices derived from EEG neurofeedback. The secondary outcomes were diaphragm contractility, measured as diaphragm thickening fraction using ultrasound; dynamic balance, measured by the Star Excursion Balance Test (SEBT); and ankle instability. Detailed outcome definitions and time frames are described in the Outcome Measures section.

Statistical Analysis Between-group differences were analyzed using analysis of variance (ANOVA), and within-group changes from pre- to post-intervention were analyzed using paired t-tests. Associations among fNIRS, EEG, and balance variables were examined using Pearson correlation analysis. Effect sizes were reported as Cohen's d. Bonferroni correction was applied where multiple comparisons were made. The significance level was set at 0.05.

Significance The findings of this study are expected to clarify how different types of breathing interventions immediately modulate prefrontal cortical activity and neural self-regulation in individuals with CAI, and to provide a basis for neuroscience-informed rehabilitation strategies for CAI.

• Study Type: Interventional
• Enrollment (Estimated): 33
• Phase: Not Applicable

Contacts and Locations

Study Locations

• South Korea
  • Gwangju, South Korea, 62287
    • Recruiting
    • Gwangju Health University
    • Contact: Hyeongju Yoon Yoon; Phone Number: +82-10-5920-1504; Email: hyungju504506@naver.com
    • Contact: Seungwoo Shin Shin, Ph.D.; Phone Number: =82-10-9820-2382; Email: ptssw94@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 34 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Young adults
• CAIT-K score of ≤24
• A history of at least one ankle sprain occurring at least 12 months prior to study enrollment
• At least two episodes of ankle "giving way" within the 6months precending study enrollment

Exclusion Criteria:

• A sprain of the involved ankle within 3 months prior to study enrollment
• A History of lower-extremity surgery or fracture
• A history of neurological disorder
• The presence of cardiopulmonary disorder
• Self-reported symptoms of cybersickness
• Left-handedness

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Diaphragmatic brathing Training group; Participants in this group received diaphragmatic breathing training in a single session. Outcomes, including cortical activity, EEG indices, diaphragm contractility, dynamic balance, and ankle instability, were assessed before and immediately after the session.	Behavioral: Diaphragmatic Breathing Training; Participants assigned to this intervention will perform diaphragmatic breathing training in a single session. Participants will be guided to breathe using the diaphragm, and the training will be delivered under the supervision of a trained researcher.
Experimental: VR-based breathing meditation group; Participants in this group received breathing meditation delivered through a virtual reality environment in a single session. Outcomes, including cortical activity, EEG indices, diaphragm contractility, dynamic balance, and ankle instability, were assessed before and immediately after the session.	Behavioral: VR-based Breathing Meditation; Participants assigned to this intervention will perform breathing meditation delivered through a virtual reality environment in a single session. Participants will wear a VR headset and follow the breathing meditation content presented in the virtual environment.
Experimental: Neurofeedback relaxation training group; Participants in this group received brain relaxation training based on EEG neurofeedback in a single session. Outcomes, including cortical activity, EEG indices, diaphragm contractility, dynamic balance, and ankle instability, were assessed before and immediately after the session.	Behavioral: Neurofeedback Brain Relaxation Training; Participants assigned to this intervention will perform brain relaxation training based on EEG neurofeedback in a single session. Participants will receive real-time feedback on their EEG activity and will be trained to achieve a relaxed brain state.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in dorsolateral prefrontal cortex oxygenated hemoglobin (HbO2) concentration measured by fNIRS	Oxygenated hemoglobin (HbO2) concentration was measured by functional near-infrared spectroscopy (fNIRS) in the dorsolateral prefrontal cortex. Change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in frontopolar cortex oxygenated hemoglobin (HbO2) concentration measured by fNIRS	Oxygenated hemoglobin (HbO2) concentration was measured by functional near-infrared spectroscopy (fNIRS) in the frontopolar cortex. Change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in orbitofrontal cortex oxygenated hemoglobin (HbO2) concentration measured by fNIRS	Oxygenated hemoglobin (HbO2) concentration was measured by functional near-infrared spectroscopy (fNIRS) in the orbitofrontal cortex. Change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in medial prefrontal cortex oxygenated hemoglobin (HbO2) concentration measured by fNIRS	Oxygenated hemoglobin (HbO2) concentration was measured by functional near-infrared spectroscopy (fNIRS) in the medial prefrontal cortex. Change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in EEG delta band power	Delta band (0.5-4 Hz) power was measured by electroencephalography (EEG) at [electrode site(s)]. Change was calculated as the difference between pre- and post-intervention values. Unit: [µV²].	Baseline (before the intervention) and immediately after the single intervention session
Change in EEG theta band power	Theta band (4-8 Hz) power was measured by electroencephalography (EEG) at [electrode site(s)]. Change was calculated as the difference between pre- and post-intervention values. Unit: [µV²].	Baseline (before the intervention) and immediately after the single intervention session
Change in EEG alpha band power	Alpha band (8-12 Hz) power was measured by electroencephalography (EEG) at [electrode site(s)]. Change was calculated as the difference between pre- and post-intervention values. Unit: [µV²].	Baseline (before the intervention) and immediately after the single intervention session
Change in EEG sensorimotor rhythm (SMR) band power	Sensorimotor rhythm (SMR) band (12-15 Hz) power was measured by electroencephalography (EEG) at [electrode site(s)]. Change was calculated as the difference between pre- and post-intervention values. Unit: [µV²].	Baseline (before the intervention) and immediately after the single intervention session
Change in EEG beta band power	Beta band (15-30 Hz) power was measured by electroencephalography (EEG) at [electrode site(s)]. Change was calculated as the difference between pre- and post-intervention values. Unit: [µV²].	Baseline (before the intervention) and immediately after the single intervention session

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in diaphragm thickening fraction measured by ultrasound	Diaphragm thickness was measured by ultrasound at end-inspiration and end-expiration, and the diaphragm thickening fraction was calculated as (end-inspiration thickness - end-expiration thickness) / end-expiration thickness × 100 (%). Change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in dynamic balance measured by the Star Excursion Balance Test (SEBT)	Dynamic balance was assessed by the Star Excursion Balance Test (SEBT), in which participants reached as far as possible with the free limb while standing on the affected limb. Reach distance was measured in each direction, and change was calculated as the difference between pre- and post-intervention values.	Baseline (before the intervention) and immediately after the single intervention session
Change in ankle instability measured by CAIT-K	Ankle instability was assessed using [instrument name]. Change was calculated as the difference between pre- and post-intervention scores.	Baseline (before the intervention) and immediately after the single intervention session

Collaborators and Investigators

• Sponsor: Gwangju Health University

Study record dates

Study Major Dates

• Study Start (Estimated): December 14, 2026
• Primary Completion (Estimated): February 14, 2027
• Study Completion (Estimated): March 30, 2027

Study Registration Dates

• First Submitted: November 4, 2026
• First Submitted That Met QC Criteria: November 11, 2026
• First Posted (Actual): November 13, 2026

Study Record Updates

• Last Update Posted (Actual): November 13, 2026
• Last Update Submitted That Met QC Criteria: November 11, 2026
• Last Verified: November 1, 2026

More Information

Terms related to this study

• Keywords: Randomized controlled trial; Breathing exercise; Virtual reality; Neurofeedback; Electroencephalography; Dynamic balance; Functional near-infrared spectroscopy; Diaphragmatic breathing; Chronic ankle instability; Breathing meditation; Brain relaxation training
• Other Study ID Numbers: P01-202610-01-075

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

De-identified individual participant data underlying the results reported in the publication will be shared with qualified researchers upon reasonable request to the corresponding author. Data will be available after publication of the main results.

IPD Sharing Time Frame

Data will be available beginning 6 months after publication of the main results

IPD Sharing Access Criteria

Qualified researchers may request access to de-identified individual participant data by contacting the corresponding author. Requests will be reviewed by the research team, and data will be shared for academic research purposes.

• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

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