Exploring the relationship between movement and breathing regulation in Tai Chi practice among middle-aged and older men using a three-dimensional respiratory-movement model.

Purpose: Postural control and respiration are closely integrated processes vital for stability in older adults. Although Tai Chi emphasizes coordinated breath and movement, quantitative evidence comparing neuromuscular and biomechanical adaptations between long-term and beginner practitioners remains limited. This study systematically examined differences in breathing regulation and postural control during Tai Chi movements across the two groups. Methods: A three-dimensional motion analysis system synchronized with force plates and surface electromyography was employed. Lower-limb kinematics, kinetics, muscle activity, and thoracoabdominal motion were assessed during four classical Tai Chi movements in 21 long-term and 21 beginner practitioners. Primary outcomes included respiratory parameters, joint range of motion (ROM), center of pressure (COP) displacement, and cross-correlation between respiratory volume and center of mass (COM) trajectory. Results: Compared with beginners, long-term practitioners exhibited slower, deeper breathing, greater lower-limb joint ROM, particularly in the sagittal and frontal planes, and larger anteroposterior COP displacement during single-leg stance (Kick with Heel). During Wild Horse's Mane, they showed significantly lower cross-correlation between breathing and COM displacement, indicating task-specific decoupling between respiration and posture. Conclusion: Long-term Tai Chi practice enhances motor control through optimized diaphragmatic breathing, improved joint flexibility, and adaptive coordination between respiration and posture. These findings provide systematic biomechanical and physiological evidence for the mechanisms by which Tai Chi may improve postural control and respiratory function.