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

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

Interventions

BEHAVIORAL

Box Breathing

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.

BEHAVIORAL

Cyclic Sighing

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.

BEHAVIORAL

Mindfulness AH Exhalation

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.

BEHAVIORAL

Mindful Cyclic Sighing

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.

Sponsors & Collaborators

• Valencian International University (VIU)

  lead OTHER

Principal Investigators

• Isaac Carmona-Rincón, PhD · Valencian International University (VIU)

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2027-01-31

Primary Completion

2027-03-31

Completion

2027-05-31