Effects of Combined Thoracic and Diaphragmatic Breathing on Cognitive and Psycho-Physiological Functions

Assessed by the 2-back task. The outcome is calculated as the change in accuracy (percentage of correct responses) and reaction time. Accuracy range from 0% to 100%. Higher accuracy and lower reaction time indicate better working memory capacity.

Measured by the Stop-signal task (SST). The outcome is the change in Stop-Signal Reaction Time (SSRT) in milliseconds. SSRT values typically range from 100 to 500 milliseconds, with lower scores (faster reaction time) indicating better inhibitory control.

Assessed using the Wisconsin Card Sorting Test (WCST). The outcome include the number of categories achieved, perseverative errors and set-loss errors. Higher number of categories achieved, lower perseverative errors and set-loss errors indicate better cognitive flexibility and set-shifting ability.

Assessed using the Corsi Block-Tapping Task. The outcome is Corsi span score. The Corsi span is defined as the longest sequence accurately reproduced by participants. Scores range from 0 to 9 blocks, with higher scores indicating better short-term memory capacity.

HRV will be assessed as a non-invasive marker of autonomic nervous system (ANS) flexibility and neurovisceral integration, reflecting the dynamic regulation of the prefrontal-vagal pathway. Higher HRV serves as a physiological indicator of superior executive function and emotional regulation, whereas lower values are linked to autonomic dysregulation and cognitive fatigue. Data will be captured using a validated Polar H10 chest strap and the Elite HRV application for precise R-R interval detection. Outcome measurement include time-domain indices (SDNN, RMSSD), frequency-domain measures (HF, LF, and LF/HF ratio), and non-linear metrics (SD1, SD2). Increased RMSSD and HF power will be interpreted as enhanced parasympathetic modulation, providing the physiological foundation for improved attentional control and neural efficiency.

• Craniovertebral angle (CVA) Measured from a lateral-view in a relaxed standing position. Participants look forward and maintain a comfortable stance during image acquisition. The CVA is the angle between a line connecting the tragus of the ear to the C7 spinous process and a horizontal line passing through C7. A Smaller angle indicates more severe forward head posture.
• Acromion-to-table distance (ATD) While supine, the vertical distance between the posterior aspect of the acromion and the table surface is measured. A larger distance indicates increased rounded shoulder posture or thoracic kyphosis.

The Traditional Chinese version of Depression Anxiety Stress Scales-21 (DASS-21) will be used to assess negative emotional states including depression, anxiety, and stress. DASS-21 contains 21 items, with 7 items assigned to each subscale. Participants rate their symptoms over the past week on a 4-point scale ranging from 0 ("did not apply to me at all") to 3 ("applied to me very much or most of the time") in each question. Subscale scores are obtained by summing the 7 items and multiply by two within each domain, with higher scores indicating greater severity of emotional distress.

Brain activation in the prefrontal cortex, primary motor cortex, supplementary motor area, and premotor cortex during tasks is assessed using functional near-infrared spectroscopy (fNIRS). The specific metric reported is the change in the concentration of oxygenated hemoglobin (HbO). Higher HbO values indicate increased regional cerebral blood flow and higher brain activation.