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

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