Elite seoi-nage biomechanics: integration of centre-of-mass control, propulsion and rotation.

Biomechanical research on elite judo throws often focuses on the uke (receiver), leaving the tori's (thrower's) contributions underexplored. This study examined seoi-nage biomechanics in 19 elite male judoka, including world championship medallists, to identify how higher-performing (HP) tori optimise execution compared to lower-performing (LP) tori. Twelve athletes (HP, n = 6; LP, n = 6) were compared by uke angular momentum response. Three-dimensional motion and ground reaction forces were captured using an 18-camera system (250 Hz) and two force platforms (1000 Hz). The tori's centre of mass (COM) displacement, linear momentum, and angular momentum were quantified during turning and throwing phases, with group differences assessed via Mann-Whitney U tests (p < 0.05). HP tori showed greater vertical COM displacement (115-132%), increased forward linear momentum (62-142%), and higher angular momentum (62-169%) than LP tori. These traits-precise COM control, robust forward drive and early rotational force peak-enhanced uke rotation and tori stability, demonstrating efficient momentum transfer to the uke rather than the ground. Elite seoi-nage requires effective integration of COM control, propulsion and rotation. Findings inform coaching drills replicating kuzushi-tsukuri-kake sequences using uke angular momentum as a performance metric.