Heart Rate Variability Biofeedback in Security Forces (GNR-HRVB)

February 4, 2026 updated by: Egas Moniz - Cooperativa de Ensino Superior, CRL

Heart Rate Variability Biofeedback in Distress Regulation and Burnout Prevention Among Security Forces

This exploratory study evaluates the effectiveness of a 12-session Heart Rate Variability Biofeedback (HRV-BFB) protocol in reducing distress and burnout while promoting psychological well-being among Portuguese National Republican Guard (GNR) professionals. Exposed to high occupational stress from unpredictable risks, shift work, and limited resources, these individuals face elevated vulnerability to chronic stress outcomes. The intervention leverages real-time HRV feedback to enhance autonomic regulation, breathing techniques, and emotional self-regulation.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Security forces like the GNR play a critical role in public safety but endure chronic stress from violence exposure, rapid decisions, shift rotations, and institutional resource shortages, heightening risks of distress, burnout, and impaired well-being. Distress arises when perceived threats exceed coping resources, leading to persistent negative emotions and health disruptions. Burnout manifests as exhaustion, mental distancing, and reduced efficacy from unmanaged chronic stress, with organizational impacts including absenteeism and eroded public trust. Psychological well-being encompasses multidimensional aspects like autonomy, relationships, and purpose beyond mere absence of illness. Traditional interventions face barriers such as stigma and access issues in rural GNR contexts, necessitating flexible, self-administered tools.

Intervention: HRV-BFB Protocol HRV-BFB trains participants to consciously modulate physiological responses via real-time monitoring of heart rate variability (HRV), reflecting sympathetic-parasympathetic balance. Low HRV links to mental health risks, while training targets resonance frequency breathing (~6 breaths/min or 0.1 Hz) to boost HRV amplitude, cardiac coherence, and baroreflex strength. Delivered autonomously via app post-initial guidance, the 12-session protocol requires no daily clinician oversight, enhancing accessibility for dispersed GNR personnel. Evidence shows HRV-BFB reduces stress, anxiety, depression, and burnout while fostering well-being in high-stress groups like emergency workers.

Study Objectives This exploratory trial tests whether HRV-BFB significantly lowers distress (multidimensional: physical, cognitive, emotional, behavioral), burnout levels, and boosts psychological well-being in GNR professionals. It aims to inform scalable interventions tailored to Portuguese police realities, addressing gaps in institutional support.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Portugal
      • Setúbal, Portugal
        • Recruiting
        • GNR - Comando Terrritorial de Setúbal (GNR - Setubal Territorial Command Centre)
        • Contact:
        • Sub-Investigator:
          • Clauda Carrilho

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  1. Operational military personnel of the Guarda Nacional Republicana (GNR) performing security, patrol, criminal investigation, or road safety duties
  2. Any military rank or professional category within operational roles
  3. Age between 18 and 55 years, inclusive
  4. Both males and females
  5. Capable of providing informed consent in Portuguese language

Exclusion Criteria:

  1. Extended sick leave or medical absence
  2. Currently involved in serious disciplinary proceedings
  3. Use, modification, or initiation of psychotropic medication (including antidepressants, anti-anxiety medications, antipsychotics, mood stabilizers) within the past 6 months

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: HRV Biofeedback Training
Participants receive 12 individual sessions of heart rate variability biofeedback (HRV-BFB) over 4 weeks (one 12-minute session every 2 days). Training is delivered using a chest-worn ECG sensor (eSense Pulse) connected to a mobile application that provides real-time visual feedback.
Behavioral: Heart Rate Variability Biofeedback (HRV-BFB) Training
Participants receive a structured heart rate variability biofeedback (HRV-BFB) training protocol delivered over 4 weeks. The intervention uses a portable chest-worn ECG sensor (eSense Pulse) connected via Bluetooth to a mobile application that provides real-time visual feedback of heart rate variability. Each participant completes 12 individual sessions of 12 minutes each (one session every 2 days). Sessions take place in a quiet room and follow a standardized format: a brief preparation phase, followed by approximately 10 minutes of guided breathing at resonance frequency (around 6 breaths per minute) using a visual breathing guide. The application displays color-coded feedback indicating how closely the participant's physiological response matches the target HRV pattern, and participants are instructed to adjust their breathing and recall positive memories to maximize time in the desired state. The aim is to increase HRV, strengthen parasympathetic activation, and improve stress and
Other Names:
  • HRV biofeedback
  • Resonance frequency breathing training
No Intervention: Control: No Intervention
Participants receive no active intervention during the 4-week study intervention period and continue their usual duties and routines. They complete the same assessment schedule as the experimental group at baseline, 4 weeks, and 10 weeks. After completion of the final follow-up assessment, they are offered the opportunity to receive the HRV biofeedback training protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Psychological Distress (Kessler Psychological Distress Scale - K10)
Time Frame: Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)
The Kessler Psychological Distress Scale (K-10) is a 10-item self-report measure assessing psychological distress over the past 30 days. Items measure anxiety and depressive symptoms on a 5-point Likert scale (1=never to 5=always). Total score range: 10-50 (higher scores indicate greater distress). Portuguese validation: α=0.91. Primary outcome is change from baseline to post-intervention (week 4) and follow-up (week 10).
Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)
Change in Occupational Burnout (Burnout Assessment Tool - BAT-12)
Time Frame: Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)
The Burnout Assessment Tool Short Form (BAT-12) is a 12-item self-report measure of occupational burnout across 4 dimensions: exhaustion (3 items), mental distance (3 items), cognitive impairment (3 items), emotional impairment (3 items). 5-point Likert scale (1=never to 5=always). Total score range: 12-60. Portuguese validation: α=0.85. Primary outcome is change from baseline to post-intervention and follow-up.
Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)
Change in Psychological Well-Being (WHO-5 Well-Being Index)
Time Frame: Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)
The WHO-5 Well-Being Index is a 5-item self-report measure of psychological well-being over the past 2 weeks. Items assess positive mood, vitality, sleep, daily functioning, and life satisfaction on a 0-5 scale. Total score range: 0-25 (higher=higher well-being). Primary outcome is change from baseline to post-intervention and follow-up.
Baseline (Week 0), Post-intervention (Week 4), Follow-up (Week 10)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
SDNN (Standard Deviation of NN Intervals) - Heart Rate Variability
Time Frame: Baseline (Week 0), after each of 12 training sessions
SDNN measures the standard deviation of the average NN (R-R) intervals in milliseconds during a recording period. It is a general indicator of overall heart rate variability and reflects the body's overall capacity for physiological adaptation and autonomic flexibility. Higher SDNN values indicate better autonomic regulation.
Baseline (Week 0), after each of 12 training sessions
RMSSD (Root Mean Square of Successive Differences) - Parasympathetic Activity
Time Frame: Baseline (Week 0), after each of 12 training sessions
RMSSD measures the root mean square of successive differences between adjacent NN (R-R) intervals in milliseconds. It is a primary time-domain measure of high-frequency heart rate variability and specifically reflects parasympathetic (vagal) nervous system activity and the body's recovery capacity. Higher RMSSD indicates stronger parasympathetic tone.
Baseline (Week 0), after each of 12 training sessions
Stress Index - Autonomic Balance Indicator
Time Frame: Baseline (Week 0), after each of 12 training sessions
The Stress Index is a proprietary metric derived from heart rate variability analysis that quantifies autonomic nervous system balance. Lower values indicate better autonomic regulation and lower physiological stress levels. Higher values reflect sympathetic dominance and poorer stress adaptation.
Baseline (Week 0), after each of 12 training sessions

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Egas Moniz - Cooperativa de Ensino Superior, CRL

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 28, 2026

Primary Completion (Estimated)

April 1, 2026

Study Completion (Estimated)

August 1, 2026

Study Registration Dates

First Submitted

January 28, 2026

First Submitted That Met QC Criteria

January 28, 2026

First Posted (Actual)

February 4, 2026

Study Record Updates

Last Update Posted (Actual)

February 6, 2026

Last Update Submitted That Met QC Criteria

February 4, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PT-214/25

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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