Effect of Brief Breathwork and Mindfulness Interventions on Anxiety, Psychological Flexibility and Physiological Variables in Spanish-Speaking University Students: a Four-Arm Randomized Controlled Trial
| Registry | NCT07621042, acronym BREATH-4 |
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| Status | Not yet recruiting |
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| Phase | Not applicable |
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| Study type | Interventional; randomized, parallel, masking: single, basic science |
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| Enrollment | 240 (Estimated) |
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| Sponsor | Valencian International University (VIU) (Other) |
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| Conditions | Anxiety, Psychological Flexibility, Stress |
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| Interventions | Box Breathing, Cyclic Sighing, Mindfulness AH Exhalation, Mindful Cyclic Sighing (Behavioral) |
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| Dates | start 2027-01-01 (estimated), primary completion 2027-03-01 (estimated), completion 2027-05-01 (estimated), first posted 2026-06-02, last updated 2026-06-04 |
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Related Papers Related Patents Related Grants Related Experts
All trials for Anxiety All trials for Psychological Flexibility All trials of Box Breathing All trials of Cyclic Sighing
-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.
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+Arms and interventions
| Arm | Type | Interventions | Description |
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| Box Breathing | Experimental | Behavioral: Box Breathing | 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. |
| Cyclic Sighing | Experimental | Behavioral: Cyclic Sighing | 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. |
| Mindfulness AH Exhalation | Experimental | Behavioral: Mindfulness AH Exhalation | 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. |
| Mindful Cyclic Sighing | Experimental | Behavioral: Mindful Cyclic Sighing | 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. |
- 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.
- 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.
- 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.
- 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.
+Outcome measures
Primary outcomes
- State Anxiety (STAI-E) [Baseline (Day 0), daily pre- and post-practice (Days 1-28), post-intervention (Day 31), and 2-month follow-up]: 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).
Secondary outcomes
- 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]: Positive and negative affect measured with the Positive and Negative Affect Schedule (PANAS). 20 items rated on a 5-point Likert scale. Two subscales: Positive Affect (PA) and Negative Affect (NA). Spanish validated version (Lopez-Gomez et al., 2015).
- Psychological Flexibility (MPFI-24) [Baseline (Day 0), post-intervention (Day 31), and 2-month follow-up]: Multidimensional psychological flexibility and inflexibility measured with the Multidimensional Psychological Flexibility Inventory short form (MPFI-24). 24 items rated on a 6-point Likert scale assessing 12 Hexaflex processes. Spanish validated version (Navarrete et al., 2024).
- Psychological Flexibility (Psy-Flex) [Baseline (Day 0), daily (Days 1-28), post-intervention (Day 31), and 2-month follow-up]: Unified psychological flexibility measured with the Psy-Flex scale. 6 items rated on a 5-point Likert scale. A modified daily version will be used during the intervention period. Spanish validated version (Navarrete et al., 2024).
- Trait Anxiety (STAI-R) [Baseline (Day 0), post-intervention (Day 31), and 2-month follow-up]: Trait anxiety measured with the State-Trait Anxiety Inventory - Trait subscale (STAI-R). 20 items rated on a 4-point Likert scale (0-3). Higher scores indicate greater trait anxiety. Spanish validated version (Guillen-Riquelme \& Buela-Casal, 2011).
Other outcomes
- Resting Heart Rate (RHR) [Daily (Days 1-28)]: Resting heart rate in beats per minute (bpm) obtained from participants' personal wearable devices (smartwatch/fitness tracker). Change calculated as the slope of a linear regression fitted to daily values over the 28-day period.
- Heart Rate Variability (HRV) [Daily (Days 1-28)]: Heart rate variability obtained from participants' personal wearable devices during deep sleep. Change calculated as the slope of a linear regression fitted to daily values over the 28-day period. Only available for participants with compatible devices.
- Respiratory Rate (RR) [Daily (Days 1-28)]: Respiratory rate in breaths per minute obtained from participants' personal wearable devices. Change calculated as the slope of a linear regression fitted to daily values over the 28-day period. Only available for participants with compatible devices.
+Eligibility
Sex: All, ages: 18 Years to 65 Years, accepts healthy volunteers
Inclusion Criteria:
* 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
Exclusion Criteria:
* 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
+Publications
- 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
- 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
+Investigators
- Isaac Carmona-Rincón, PhD, Principal investigator, Valencian International University (VIU)