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

Sponsor
Valencian International University (VIU)
Study ID
NCT07621042
Status
Not Yet Recruiting

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Conditions

  • Anxiety
  • Psychological Flexibility
  • Stress

Eligibility Criteria

Sex
ALL
Age
18 Years - 65 Years
Healthy Volunteers
Accepted

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.
  • 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.

Study Details

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.

Key Dates

First listed
Jun 2, 2026
Start date
Jan 31, 2027
Status verified
Jun 2026
Primary completion
Mar 31, 2027
Completion
May 31, 2027

Study Design

Enrollment
240 participants (estimated)
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE

Arms

  • Experimental: 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.
  • Experimental: 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.
  • Experimental: 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.
  • Experimental: 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.

Primary Outcome Measure

State Anxiety (STAI-E) [ Time Frame: Baseline (Day 0), daily pre- and post-practice (Days 1-28), post-intervention (Day 31), and 2-month follow-up ]

Central Contacts

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