The rhythmic breathing exercise group will perform 10 minutes of thoracic expansion exercises followed by 15 minutes of progressive diaphragmatic breathing (4-s inhalation/6-s exhalation) to facilitate parasympathetic dominance.

The natural breathing exercise group performed sham thoracic expansion exercises and sham slow diaphragmatic breathing

4-week supervised training program, consisting of three 30-minute sessions per week. Thoracic expansion exercises consists of chest wall stretching and mobility drills. Followed by 15 minutes of progressive slow diaphragmatic breathing (4-s inhalation/6-s exhalation).

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.