A biomechanical comparison of the jerk, back jerk, vertical jump and jump squat.

Although weightlifting exercises and their pulling and catching derivatives have been well studied, less is known about the group of weightlifting overhead pressing derivatives (WOPDs). There were two purposes of the present study. Above all, it was to compare WOPDs (i.e. jerk and back jerk) with jump squat in enhancing sport performance such as vertical jump in the perspective of biomechanics. Furthermore, it was to gain a better understanding of the biomechanical difference between jerk and back jerk. The study compared the kinetics, kinematics, and muscle activation of the jerk, back jerk, vertical jump and jump squat. Ground reaction forces, joint angle data and electromyography were collected from 20 track and field athletes while they performed the four movements. The joint coordination pattern and EMG characters of the jump squat were more similar to those of the vertical jump. WOPDs, especially jerk, exhibited less similarity with vertical jump in joint coordination, as well as the subsequent peak activation. The electromyography data demonstrated significant differences in rectus femoris and gluteus maximus in the relative timing of peak activations and the maximum activation. Jump squat was greater in peak force (2211N) than jerk (P < .005), greater peak power (4749W) than jerk and back jerk (P < .001) and no significant difference with WOPDs in rate of force development. Back jerk produced a greater peak force (2223 N), peak power (3767W) and eccentric RFD (15965 N{middle dot}s-1) than jerk (2061N)(P < .001) (3364W)(P < .05) (12280 N{middle dot}s-1)(P < .01)and the opposite in concentric RFD that jerk (7702 N{middle dot}s-1) was greater than back jerk (5972 N{middle dot}s-1)(P < .05). We can conclude that for runner and jumpers, jump squat was better for improving vertical jump than WOPDs and back jerk is better than jerk in power training.