Comparative Effects of Four Brief Breathwork and Mindfulness Interventions on Anxiety and Psychological Flexibility: A 4-Arm RCT

NCT07621042 | Not Yet Recruiting

• 1 other identifier: VIU-BREATH-RCT-2026
• Study Type: interventional
• Target: 240
• Locations: 0 countries
• Sites: N/A

Brief Summary

This four-arm, single-blind randomized controlled trial examines the effects of four brief daily 5-minute practices over 28 days on psychological flexibility and physiological variables in Spanish-speaking adults. Participants will be randomly assigned to one of four groups: Box Breathing, Cyclic Sighing, Mindfulness focused on exhalation with the syllable "AH", or Conscious Cyclic Sighing. Outcomes include state and trait anxiety (STAI), positive and negative affect (PANAS), psychological flexibility (MPFI-24, Psy-Flex), and physiological variables (heart rate, respiratory rate, heart rate variability). Assessments are conducted at baseline, daily during the 28-day intervention, at post-intervention (day 31), and at 2-month follow-up.

Conditions

Anxiety; Psychological Flexibility; Stress

Keywords

breathworks; mindfulness; box breathing; cyclic sighing; heart rate variability; randomized controlled trial; Spanish-speaking

Outcome Measures

Primary Outcomes (1)

• State Anxiety (STAI-E)

  State anxiety measured with the State-Trait Anxiety Inventory - State subscale (STAI-E). 20 items rated on a 4-point Likert scale (0-3). Higher scores indicate greater anxiety. Spanish validated version (Guillen-Riquelme \& Buela-Casal, 2011).

  Baseline (Day 0), daily pre- and post-practice (Days 1-28), post-intervention (Day 31), and 2-month follow-up

Secondary Outcomes (4)

• Positive and Negative Affect (PANAS)

  Baseline (Day 0), daily pre- and post-practice (Days 1-28), post-intervention (Day 31), and 2-month follow-up

• Psychological Flexibility (MPFI-24)

  Baseline (Day 0), post-intervention (Day 31), and 2-month follow-up

• Psychological Flexibility (Psy-Flex)

  Baseline (Day 0), daily (Days 1-28), post-intervention (Day 31), and 2-month follow-up

• Trait Anxiety (STAI-R)

  Baseline (Day 0), post-intervention (Day 31), and 2-month follow-up

Other Outcomes (3)

• Resting Heart Rate (RHR)

  Daily (Days 1-28)

• Heart Rate Variability (HRV)

  Daily (Days 1-28)

• Respiratory Rate (RR)

  Daily (Days 1-28)

Study Arms (4)

Box Breathing

EXPERIMENTAL

Daily 5-minute box breathing with individualized timing based on a CO2 tolerance test. Participants perform a maximal exhale and record the duration; this determines their personal inhale/hold/exhale/hold intervals (3-4s, 5-6s, or 8-10s). Equal-phase cyclic breathing with exclusive focus on mechanical control and counting.

Behavioral: Box Breathing

Cyclic Sighing

EXPERIMENTAL

Daily 5-minute cyclic sighing. Participants inhale slowly through the nose, then take a second shorter nasal inhale to maximally fill the lungs, followed by a slow, complete oral exhalation. This double-inhale/long-exhale pattern is repeated continuously for 5 minutes. No mindfulness or attentional instructions are given.

Behavioral: Cyclic Sighing

Mindfulness AH Exhalation

EXPERIMENTAL

Daily 5-minute focused-attention mindfulness practice. Participants sit or lie down, close their eyes, and direct attention to the forehead region between the eyes. On each exhale, they softly vocalize the syllable "AH" aloud (gentle, unforced audible sound). When distracted, they use the internal label "thinking-thinking" and redirect attention to the breath and then to the forehead region. Practice continues for 5 minutes.

Behavioral: Mindfulness AH Exhalation

Mindful Cyclic Sighing

EXPERIMENTAL

Daily 5-minute hybrid practice combining cyclic sighing mechanics with mindfulness instructions. Participants inhale slowly through the nose, take a second shorter nasal inhale to maximally fill the lungs, then exhale slowly while softly vocalizing the syllable "AH" aloud (gentle, unforced). Attention is directed to the breath and the sensation of release during exhalation. When distracted, participants use the internal label "thinking-thinking" and redirect attention back to the breath. Practice continues for 5 minutes.

Behavioral: Mindful Cyclic Sighing

Interventions

Box Breathing BEHAVIORAL

Individualized box breathing based on CO2 tolerance test. Participants perform a maximal exhale and record the duration (CO2 discard time) to determine their personal cycle interval: 3-4s (0-20s discard), 5-6s (25-45s discard), or 8-10s (50-75s+ discard). Equal-phase cycles of inhale/hold/exhale/hold repeated for 5 minutes daily. Focus on mechanical breath control only.

Box Breathing

Cyclic Sighing BEHAVIORAL

Double nasal inhalation (slow deep inhale + short top-up inhale to maximal lung capacity) followed by slow complete oral exhalation. Repeated continuously for 5 minutes daily. No attentional instructions.

Cyclic Sighing

Mindfulness AH Exhalation BEHAVIORAL

Focused-attention practice with eyes closed. Attention directed to forehead region between the eyes. Each exhalation accompanied by soft audible vocalization of syllable "AH". Distractions managed with internal label "thinking-thinking" followed by attention redirection. Practiced daily for 5 minutes.

Mindfulness AH Exhalation

Mindful Cyclic Sighing BEHAVIORAL

Hybrid practice: double nasal inhalation (cyclic sighing mechanics) combined with slow exhalation vocalized as soft audible "AH". Mindfulness instructions include attention to breath sensations and use of "thinking-thinking" label upon distraction. Practiced daily for 5 minutes.

Mindful Cyclic Sighing

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age between 18 and 65 years (inclusive)
• Native Spanish speaker or fluent in Spanish (sufficient to understand audio instructions and complete psychometric questionnaires)
• Stable internet access and an electronic device (smartphone, tablet, or computer)
• Ability to provide informed consent and commitment to the 31-day protocol and 2-month follow-up

You may not qualify if:

• Active diagnosis of severe or chronic respiratory disease that prevents safe performance of breathing exercises (e.g., advanced COPD, severe uncontrolled asthma, cystic fibrosis)
• Current diagnosis of severe psychiatric disorder (e.g., psychotic spectrum disorders, acute-phase bipolar disorder, severe major depression with suicidal risk)
• Any acute medical condition contraindicated for voluntary alteration of breathing patterns

Sponsors & Collaborators

• Valencian International University (VIU): lead

Related Publications (2)

• Chan AW, Boutron I, Hopewell S, Moher D, Schulz KF, Collins GS, Tunn R, Aggarwal R, Berkwits M, Berlin JA, Bhandari N, Butcher NJ, Campbell MK, Chidebe RCW, Elbourne DR, Farmer AJ, Fergusson DA, Golub RM, Goodman SN, Hoffmann TC, Ioannidis JPA, Kahan BC, Knowles RL, Lamb SE, Lewis S, Loder E, Offringa M, Ravaud P, Richards DP, Rockhold FW, Schriger DL, Siegfried NL, Staniszewska S, Taylor RS, Thabane L, Torgerson DJ, Vohra S, White IR, Hrobjartsson A. SPIRIT 2025 statement: updated guideline for protocols of randomized trials. Nat Med. 2025 Jun;31(6):1784-1792. doi: 10.1038/s41591-025-03668-w. Epub 2025 Apr 29.

  PMID: 40295741 BACKGROUND

• Balban MY, Neri E, Kogon MM, Weed L, Nouriani B, Jo B, Holl G, Zeitzer JM, Spiegel D, Huberman AD. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Rep Med. 2023 Jan 17;4(1):100895. doi: 10.1016/j.xcrm.2022.100895. Epub 2023 Jan 10.

  PMID: 36630953 BACKGROUND

MeSH Terms

Conditions

Anxiety Disorders

Condition Hierarchy (Ancestors)

Mental Disorders

Study Officials

• Isaac Carmona-Rincón, PhD

  Valencian International University (VIU)

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Isaac Carmona-Rincón, PhD

CONTACT

+34 618 187 325; isaac.carmona@professor.universidadviu.com

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Masking Details: Participants are blinded to study hypotheses and group comparisons. All interventions are presented as equally valid wellness practices. Investigators and outcome assessors are not masked.
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Researcher, PROCESS Lab

Model Details: Four-arm parallel-group RCT. Participants are randomly assigned 1:1:1:1 to one of four daily 5-minute breath-based practices for 28 days.

Study Record Dates

• First Submitted: May 27, 2026
• First Posted: June 2, 2026
• Study Start (Estimated): January 1, 2027
• Primary Completion (Estimated): March 1, 2027
• Study Completion (Estimated): May 1, 2027
• Last Updated: June 4, 2026

Record last verified: 2026-06

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Beginning 6 months after publication of primary results, available for 5 years
• Access Criteria: Researchers who provide a methodologically sound proposal. Data shared under a data sharing agreement ensuring confidentiality and appropriate use.