An interventional study of Breathing MR in Healthy Adolescents, sponsored by Riga Stradins University. Active, not recruiting at 2 sites in Latvia. Open to participants aged 14 Years to 17 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by Riga Stradins University · Not applicable, Interventional, and Other
This randomised controlled trial will evaluate the effects of integrating a standalone mixed-reality (MR) breathing and eye-gaze training intervention (EyeBreathe) into regular basketball practice for adolescent athletes in Latvia. Participants will be individually randomised to either a six-week MR intervention (two sessions per week) or to continue usual training. Assessments before and after the intervention will measure heart rate and heart rate variability, CO₂ tolerance, breathing pattern, reactive stress tolerance, and pre-competition anxiety. Sessions will be supervised at first, then completed independently via password-protected headset profiles. Intervention adherence will be monitored. The primary efficacy analysis will use a prespecified per-protocol population, defined as intervention participants who complete at least four of the twelve scheduled sessions.
The study will use a two-arm group design. Participants will be randomly assigned to either the Mixed Reality (MR) intervention group (Breathing MR) or to a control group. Randomisation will be performed at the individual level. The intervention period is planned for six weeks, with two sessions per week for the experimental group. Control participants will continue their regular basketball training without any additional intervention.
This is a follow-up, two-arm parallel-group randomised controlled trial of Breathing MR versus usual basketball training. The study is designed to recruit an anticipated 40-50 participants (45 participants were recruited). Subject to confirmation of comparability of eligibility criteria, intervention delivery, outcome procedures, and data quality, data from this cohort may be combined with the Breathing MR and usual-training control groups from the completed feasibility RCT (ClinicalTrials.gov NCT07869446; Organisation's Unique Protocol ID: 2-PĒK-4/1205/2025-Feasibility) in prespecified exploratory pooled analyses. Models will include cohort as a fixed effect and assess the intervention-by-cohort interaction. Cohort-specific and pooled estimates with 95% confidence intervals will be reported.
In-person study activities will be conducted at participants' usual basketball training venues in Salaspils and Rīga, Latvia. Home-based HRV recordings will be completed by participants using loaned Polar H10 chest straps and the Kubios HRV application.
Interventions will be delivered using the HTC VIVE Focus Vision standalone head-mounted display, requiring no external equipment or PC connection.
Assessments will be conducted at two time points: at baseline (before the intervention period) and post-intervention (within one or two weeks of the final session). The assessment battery includes resting heart rate and heart rate variability (Polar H10 chest strap with KubiosHRV), CO₂ tolerance (CO2TT), breathing pattern (Hi-Lo test), reactive stress tolerance (Vienna Test System - Determination Test), and pre-competition anxiety (CSAI-2R-LV).
Research staff will supervise the pre-intervention assessment phase and the first intervention sessions in person. From week two onward, participants will access sessions independently using individual password-protected profiles on the headset. A midpoint visit will be conducted at week three.
To evaluate the physiological and cognitive efficacy of the standalone MR breathing biofeedback intervention across varying exposure levels, analyses will be structured around pre-specified exposure tiers and continuous dose-response modeling:
The study was approved by the Riga Stradiņš University Ethics Committee (original approval: 2-PĒK-4/610/2024; additional approvals covering extended details: 2-PĒK-4/814/2025 and 2-PĒK-4/1205/2025). Individual participant data, analytical code, and study documentation will be archived in the repository upon study completion.
Riga Stradins University is the lead sponsor of 19 studies on the registry; 10 are open to participants now.
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Exclusion criteria
Participants receive a 6-week MR breathing and gaze-control training program in addition to their usual basketball training. They complete two 7-minute sessions per week, for a maximum of 12 sessions and 84 minutes of total exposure. Sessions are delivered at the participant's usual basketball-training venue.
Behavioral: Breathing MR
Participants continue their usual basketball training routine at their respective clubs. They complete baseline and post-intervention assessments on the same schedule as the intervention groups but receive no study-provided MR breathing training during the 6-week study period.
Participants complete two 7-minute sessions weekly for 6 weeks (maximum 12 sessions; 84 minutes total exposure) using an HTC VIVE Focus Vision standalone head-mounted display. Seated within an approximately 1 × 1 m area, participants perform slow diaphragmatic breathing while completing a gaze-controlled virtual basketball-tracking task. Breathing pace progresses from 7 breaths/min in minute 1, to 6.5 breaths/min in minute 2, and 6 breaths/min during minutes 3-7, using a 40:60 inhalation-to-exhalation ratio. A handheld controller placed horizontally on the upper abdomen detects abdominal movement to estimate breathing phase and adherence. Accurate breathing increases virtual-player responsiveness and speed, whereas departures from the prescribed pattern reduce performance. Research staff supervise baseline testing and the first two sessions; from week 2, participants use password-protected individual profiles independently.
Reactive stress tolerance
Reactive stress tolerance will be assessed using the Vienna Test System (VTS) Determination Test, Form S1, in adaptive presentation mode (approximately 6-10 minutes). The primary measure will be the number of correct reactions, as defined by the VTS. This variable provides information on the participant's ability to respond under stress conditions. The corresponding VTS percentile rank will also be reported; a higher percentile rank indicates greater reactive stress tolerance relative to the applicable normative reference group.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Intervention adherence
Attendance among participants allocated to MR intervention arm. Reported as the number of intervention sessions completed out of 12 scheduled sessions, expressed as a percentage.
Time frame: During the 6-week intervention period
Retention rate
Proportion of enrolled participants who complete the post-intervention assessment. Reported as the number completing follow-up divided by the number enrolled.
Time frame: Baseline through 6-week post-intervention assessment
Carbon dioxide tolerance
Exhalation duration in seconds measured using the CO₂ Tolerance Test during seated nasal breathing after a full inhalation.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Breathing pattern classification
Breathing pattern assessed using the Hi-Lo breathing assessment and classified as functional or dysfunctional.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Post intervention questionnaire
A study-specific 34-item post-intervention questionnaire assessing the acceptability, usability, engagement, perceived effects, technical performance, and tolerability of the MR intervention. Items address training integration, session duration, clarity of instructions, task difficulty, breathing-task experience, perceived effects on calmness, breathing, attention and stress, eye-gaze control, comfort, visual and audio experience, motivation, technical difficulties, and unpleasant physical symptoms. Responses include 5-point Likert-scale items (1 = completely disagree; 5 = completely agree), yes/no questions, and open-ended questions. Quantitative responses will be summarised descriptively, and open-ended responses will be analysed using qualitative content analysis.
Time frame: Immediately after the intervention period, at the post-intervention assessment within 1-2 weeks after the final session.
Cognitive response speed
Median reaction time, in milliseconds, for correct reactions on the VTS Determination Test, Form S1, in adaptive mode. Lower values indicate faster cognitive response speed under time pressure.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Incorrect reactions
Total number of incorrect reactions recorded during the VTS Determination Test, Form S1, in adaptive mode. Lower values indicate fewer response errors under adaptive time pressure.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Omitted reactions
Total number of omitted reactions, defined as stimuli for which no response is registered within the permitted response interval, during the VTS Determination Test, Form S1, in adaptive mode. Lower values indicate fewer missed responses or response lapses under time pressure.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Change from Baseline to 6 Weeks in CSAI-2R Cognitive State Anxiety Subscale Score
Cognitive state anxiety measured using the 5-item Cognitive Anxiety subscale of the Revised Competitive State Anxiety Inventory-2 (CSAI-2R). Items are rated on a 4-point Likert scale (1 = Not at all to 4 = Very much so). Higher scores indicate greater cognitive state anxiety. Subscale score is obtained by summing, dividing by number of items, and multiplying by 10. Score range is 10 to 40 for each subscale.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Change from Baseline to 6 Weeks in CSAI-2R Somatic State Anxiety Subscale Score
Somatic state anxiety measured using the 7-item Somatic Anxiety subscale of the CSAI-2R. Items are rated on a 4-point Likert scale (1 = Not at all to 4 = Very much so). Higher scores indicate greater physical/somatic anxiety symptoms. Subscale score is obtained by summing, dividing by number of items, and multiplying by 10. Score range is 10 to 40 for each subscale.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Change from Baseline to 6 Weeks in CSAI-2R Self-Confidence Subscale Score
Sport self-confidence measured using the 5-item Self-Confidence subscale of the CSAI-2R. Items are rated on a 4-point Likert scale (1 = Not at all to 4 = Very much so). Higher scores indicate greater competitive self-confidence. Subscale score is obtained by summing, dividing by number of items, and multiplying by 10. Score range is 10 to 40 for each subscale.
Time frame: Baseline, 6 weeks (immediately post-intervention)
Change from Baseline to 6 Weeks in Resting Heart Rate
Resting heart rate recorded in beats per minute (bpm) using a Polar H10 chest strap during a 3-minute supine morning recording, averaged across three consecutive days. Measured via Kubios HRV software. Lower heart rate reflects enhanced cardiovascular resting status.
Time frame: Baseline, 6 weeks (post-intervention)
Change from Baseline to 6 Weeks in Mean RR Interval
Mean duration between consecutive cardiac inter-beat intervals (RR intervals), expressed in milliseconds (ms). Recorded via a Polar H10 chest strap during a 3-minute supine resting condition and calculated via Kubios HRV software.
Time frame: Baseline, 6 weeks (post-intervention)
Change from Baseline to 6 Weeks in Resting Heart Rate Variability RMSSD
Parasympathetic autonomic activity measured as the Root Mean Square of Successive Differences (RMSSD) between normal heartbeats, expressed in milliseconds (ms). Recorded via a Polar H10 chest strap in a supine position over 3 minutes on three consecutive mornings and processed using Kubios HRV software. Higher RMSSD values indicate greater vagal tone and stress recovery capacity.
Time frame: Baseline, 6 weeks (post-intervention)
Change from Baseline to 6 Weeks in Resting Heart Rate Variability SDNN
Overall heart rate variability measured as the Standard Deviation of Normal-to-Normal RR intervals (SDNN), expressed in milliseconds (ms). Recorded via a Polar H10 chest strap during a 3-minute supine morning trial and calculated using Kubios HRV software. Higher SDNN reflects greater overall autonomic flexibility.
Time frame: Baseline, 6 weeks (post-intervention)
Change from Baseline to 6 Weeks in Resting Heart Rate Variability High-Frequency Power
Spectral parasympathetic activity measured as High-Frequency power (HF: 0.15-0.40 Hz) in absolute units (ms²). Recorded via a Polar H10 chest strap during a 3-minute supine trial and analyzed via Fast Fourier Transform in Kubios HRV software. Higher HF power indicates enhanced respiratory sinus arrhythmia and vagal modulation.
Time frame: Baseline, 6 weeks (post-intervention)
Change from Baseline to 6 Weeks in Resting Respiratory Rate
Resting breathing frequency derived from electrocardiogram (ECG)-based chest strap (Polar H10) oscillations (ECG-derived respiration) in Kubios HRV software during a 3-minute resting supine trial, expressed in breaths per minute. Lower resting respiratory rates reflect more efficient resting ventilatory patterns.
Time frame: Baseline, 6 weeks (post-intervention)
Plan to share: No
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Started Oct 2026 (actual). Primary completion is estimated for Nov 2026, 1 month after the start.
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Riga Stradins University