Mindfulness-Based Stress Reduction (MBSR) integrates various meditation practices, including focused attention on breathing, open-monitoring, body scanning, walking meditation, and mindful yoga. Attention to diaphragmatic breathing is a key element, and some researchers theorize it may be critical to MBSR’s efficacy in alleviating symptoms. Deep breathing has a direct physiological effect on emotions by regulating vagal tone and sympathetic-parasympathetic balance. Perhaps breathing alone can explain much of the effect of meditation.  

Wu et al. [Mindfulness] compared the diaphragmatic and core muscle changes among meditators in a standard MBSR program with those in an alternative form of MBSR that did not instruct on mindful breathing.

The researchers randomly assigned 48 meditation-naïve Chinese college students (average age = 20 years old;  71% female) to either standard MBSR or a MBSR without mindful breathing instruction. Both groups were taught in 8 weekly 2.5 hour sessions with a full-day retreat and daily homework. Both groups were taught by the same instructor, but one group was not directed to observe abdominal movement or concentrate on their breath. For example, during the body scan, control participants were simply told to focus on sensations in their fingers rather than to “maintain awareness of the breath, feeling it move in and out of your nose, concentrate on the breath, and visualize the airflow reaching your fingers.”

Ultrasound measures assessed the range of diaphragmatic movement and the thickness and elasticity of two core muscles: the transversus abdominis involved in abdominal expansion and contraction, and the multifidus involved in aligning the spine. Participants completed a survey before and after the intervention on mindfulness (the Five Facet Mindfulness Questionnaire), depression, anxiety, stress, and perceived self-efficacy in managing emotions. 

Ultrasound results showed the standard MBSR group significantly increased their diaphragmatic range of movement and multifidus thickness in the contracted state compared to controls. Transversus abdominis elasticity during contraction decreased in both groups, while multifidus elasticity increased in both groups, but there were no between-group differences. The researchers suggested such changes represent greater muscle activation, strength, and control.

Both MBSR groups significantly increased their mindfulness and total self-efficacy scores without significant between-group differences  There were no significant between-group differences in depression, anxiety, or stress scores.

The study reveals that instructions to focus attention on abdominal breathing in MBSR can increase ultrasound-assessed physiological changes in breathing anatomy while not necessarily resulting in different psychological outcomes. Interestingly, psychological benefits appear to be roughly equal in both standard MBSR and an alternative version of MBSR without a focus on attention to breath. However, the the study was not powered to test non-equivalence. The study is limited by its small sample size and the lack of detailed procedures regarding the ultrasound assessment.

Reference:

Wu, M., Fan, C., Zhao, X., Zhou, J., Liu, H., Li, H., Zhan, X., & Jiang, Z. (2024). The Effects of Mindfulness-Based Stress Reduction in Mental and Physical Health: Is Mindful Breathing Key? Mindfulness, 15(10), 2582–2594.

Link to study