2.3. Randomization and Interventions
After granting informed consent, the participants were randomized to one of the intervention groups: slow-paced breathing (SPB), mindfulness (M), or yogic breathing (SPB + M). All three conditions involved a 20-min structured introduction and detailed instructions unique to their assigned intervention, followed by a 5-min opportunity for an initial practice and questions, a 20-min formal practice opportunity with physiological recordings, and finally, corrective feedback and the opportunity to address questions or challenges regarding the practice (60-min total). The participants were provided with a 20-min audio recording to guide their home practice, comparable in format across the three conditions. Slow-paced Breathing (SPB): The participants were provided with a brief overview of the science of breathing and the benefits for autonomic regulation, then were guided via audio recording to breathe at a constant rate of 6 breaths/min (5 s inhale, 5 s exhale). The guided audio emphasized the importance of following the specific rhythm of breathing, without regard to thoughts or inner experience. A soft but firm tone of voice was employed to minimize the likelihood of relaxing effects, while maintaining similarity to the tone of voice used in the other conditions.Mindfulness (M): The procedures were broadly based on a prior study by Berghoff et al. [Yogic breathing (SPB + M): The procedures for the other two conditions were integrated with the aim of eliciting the attention to the same breathing instructions used for SPB, while also observing the quality of the experience during the practice, as conducted for M. The guided audio duration and the frequency of instructions was similar in the SPB + M condition as the other two conditions.