Push Jerks Enhance Vertical Jump Performance - Maybe?
For track and field, volleyball, basketball, and many other sports, jumping ability is directly related to success. Because jumping ability depends on leg drive, it seems at first glance to be closely related to the weightlifting jerk, where leg drive propels the barbell rather than the lifter’s body.
Because of their apparent similarity, coaches have often treated jumping and jerk training as complementary exercises. However, there are some obvious differences between the two. In particular, the need to control a heavy barbell imposes constraints on body movement in the jerk that are not present in jumping. In order to quantify the similarities and differences between the two, a study at Imperial College, London, used force plate and kinematic measurements to analyze the jumping, landing, and jerk movement patterns of 12 athletic men.
For the study, participants were asked to perform five maximal height jumps. Nine of the subjects had previous training in jerk technique, and these athletes were also asked to perform 40 kg (88 pounds) push jerks. As the authors pointed out, 40 kg is a relatively light load for athletic males. Further research is needed to determine whether the jerk elicits the same movement patterns at near-maximal loads. Other avenues for further study might include analyzing movement patterns in the more commonly used split jerk, and analysis of the violent hip extension observed in the weightlifting clean.
The present study found that both the jump and jerk movements followed a proximal-to-distal muscular recruitment strategy. Maximum moment arms were developed near the center of the body first, then at the extremities. In jumping, peak hip extension came first, followed by peak knee, then peak ankle extension, with the reverse pattern followed in the landing phase. In the jerk, in contrast, there was relatively little hip involvement, with peak knee extension followed by peak ankle extension. The authors attribute the lack of hip involvement to the constraint imposed by the barbell, which for maximum efficiency should remain as close to the midline of the body as possible. (Indeed, as this video explains, weightlifting coaches see excessive hip involvement as a technical flaw.)
The authors found that this recruitment strategy allowed for maximal extensions in both the jump and the jerk. For jumping, they believe this approach prevents premature takeoff, allowing the full force of the jump to transfer into lift off the ground. For the jerk, similarly, it maximizes the transfer of force to the barbell at the moment when the bar leaves the shoulders. The same pattern has been observed in runners in other studies, and appears to allow more effective energy transfer from proximal to distal joints.
Three of the jumpers were hip dominant, developing the largest contribution to the movement from the hip joint. Five were knee dominant, and the other four had a roughly balanced ratio of knee to hip torque. The authors suggested that activities, like the long jump, with a horizontal component may favor different strategies from those which require only a vertical jump.
The best jumpers were those who achieved the greatest knee and hip moments, and developed those moments the fastest. The best jumpers also developed the largest knee and ankle moments in the jerk. As noted above, however, it is not clear whether this correlation continues at maximal jerk loads.
Overall, these results suggest that vertical jump performance depends on the athlete’s ability to produce both peak knee and hip moments during the jump. The choice between knee and hip dominant jumping strategies may depend on the athlete’s relative strengths and weaknesses. Thus, training can either seek to change the strategy, or to reinforce it. For example, a coach might attempt to enhance hip drive in a knee dominant jumper, or might seek to increase knee strength.
It’s more difficult to draw firm conclusions about the usefulness of the jerk in improving jump performance. As a knee dominant exercise, the jerk may be used in developing the ability to drive with the knees, but it is not clear whether doing so will increase jump height.
1. Daniel J. Cleather, Jon E. Goodwin, and Anthony M. J. Bull, “Intersegmental Moment Analysis Characterizes The Partial Correspondence Of Jumping And Jerking,” J. Strength and Cond. Res., 27(1), 89-100 (2013).
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