Whole-body angular momentum regulation during Tai Chi stepping: Task- and experience-related differences

Tai Chi stepping involves slow progression, prolonged weight transfer, and coordinated trunk-limb rotation, but its whole-body angular momentum regulation remains poorly understood.

How do whole-body angular momentum regulation patterns differ across the tested movement conditions of normal gait (NG), Brush Knee Twist Step (BKT), and Repulse Monkey (RM) at self-selected speeds, and between experienced and novice-level practitioners?

Seventeen experienced and 14 novice-level Tai Chi practitioners performed NG, BKT, and RM. In each anatomical plane, whole-body angular momentum excursion and intersegmental cancellation were quantified over the movement cycle, and bilateral external-moment cancellation during the double-support phases. Outcomes were analyzed using linear mixed-effects models.

BKT and RM were slower than NG (0.14-0.23 vs. 1.28-1.29 m/s) and had longer total double-support duration (approximately 69% vs. 23% of the cycle). Relative to NG, both showed greater transverse-plane angular momentum excursion (6.5-10.4 × 10^-3 vs. 1.9-2.2 × 10^-3), higher frontal-plane intersegmental cancellation (46-55% vs. 39-41%) but lower sagittal- and transverse-plane intersegmental cancellation (19-38% vs. 76-82%), and higher sagittal-plane bilateral external-moment cancellation (87-90% vs. 29%). During RM, experienced practitioners had smaller angular momentum excursion in all planes and higher transverse-plane bilateral external-moment cancellation (50.1% vs. 30.5%); a wider step width was also observed in the experienced group (0.109 vs. 0.061 m).

Relative to NG, Tai Chi stepping showed movement- and plane-specific patterns of angular momentum regulation, with experience-related differences clearest during RM. These findings indicate that whole-body angular momentum regulation can be quantified as a biomechanical feature of Tai Chi stepping tasks.