Kinematic Comparison of Successful Split Jerk and Unsuccessful Frontward Barbell Drop Among Japanese National-Level Male Weightlifters

This study aimed to investigate the success factors of split jerks from a kinematic perspective among Japanese national-level male weightlifters by analyzing barbell trajectories and lifter's motion.

Among the participants of the all Japan weightlifting championships, 13 athletes were selected for analysis. Each met the criteria of successfully performing a jerk attempt after a failed attempt due to a frontward barbell drop with the same weight. Using motion analysis of recorded videos, the kinematics of the barbell, angles of the lower-limb joints, and trunk during the jerk were calculated and compared between successful and unsuccessful lifts.

No significant differences were observed in the vertical and horizontal velocity of the barbell. However, the backward displacement in the catch phase and throughout the jerk was significantly greater for successful lifts than for unsuccessful lifts (P < .05, Cohen's d > 0.50). Furthermore, the range of motion of the trunk and the peak extension velocity of the hip and trunk in the drive phase were significantly greater in successful lifts than in unsuccessful lifts. By contrast, the peak knee flexion angular velocity in the dip phase was significantly greater in unsuccessful lifts compared with successful ones (P < .05, Cohen's d > 0.50).

These results suggest that moving the barbell backward widely is one of success factors of the split jerk, which may have been influenced by the trunk movement associated with the hip extension motion. In addition, rapid knee flexion during the dip phase may reduce the likelihood of a successful split jerk.