Technique of the Jerk
The technique of the Jerk is considered to be as least as complex as the Snatch. Often the learning process is unstructured and key concepts are inadequately addressed.
The Dip and Drive Phase
Figure 1 has been accurately drawn from video captured at 100 frames per second. The weight of the bar is 130kg and the lifter weighs 68.5kg and therefore this lift is 1.9 x bodyweight.
Position 2 is the moment of greatest downward displacement in ‘the dip’ which occurs 0.49 sec after the start (position 1). Position 3 is the moment of maximum upward extension of the athlete which occurs at 0.88 sec. Position 4 is the moment of maximum upward displacement of the bar which occurs at 1.09 sec. Position 5 is the moment in which the athlete first achieves lockout at 1.14 sec.
Compare positions 1 and 4 and you will note that the maximum upward displacement of the bar takes it only as high as the top of the athlete’s forehead. This is by no means unusual. In fact at the limits of performance, an athlete may achieve only ‘eyebrow height’.
The actual upward displacement in this illustrated lift was measured as 25.50 cm and, as can be seen, this allows a comfortable amount of room for the athlete to achieve a receiving position with arms locked out (Position 5).
|Details||Unit||Calculation||Pos 1||Pos 2||Pos 3||Pos 4||Pos 5|
|Description||Start||Bottom of Dip||Top of Drive||Max Bar Elevation||Lockout Achieved|
|Displacement Downwards||Cm||A - B||-16.77|
|Displacement Upwards||Cm||C - B||42.27|
|Displacement Net||Cm||C - A||25.50|
It is a fact in high-performance Olympic Weightlifting, athletes must achieve low receiving positions to counter the lack of upward displacement of the bar. For example, in the Snatch, although a lifter may exert as much force as possible in the pull, the bar may rise only as high as the bottom of their rib-cage. A successful Snatch is therefore only achievable if the athlete’s receiving position is low. This concept applies equally in the Jerk. Faced with extreme heaviness of the bar, an athlete preparing for the Jerk must commit to a deep receiving position to achieve success. Using appropriate exercises and skill drills, this must be a focus of technique training from the first moment that an athlete is introduced to the Jerk.
From time to time coaches are heard to urge their athletes to ‘drive the bar to the ceiling’. This coaching cue should be reconsidered as it may incorrectly focus the athlete.
Depth of Receiving Position
The athlete in Figure 2-2 weighs 67.5kg and is lifting 180kg. This weight is 2.67 x bodyweight and, in fact, at the time it was a World Record (Yanko Rusev, 1978). The position achieved in the pressure moment is exemplary and should be a source of inspiration for all. It demonstrates the depth of receiving position required at the athlete’s limit of capability. The near horizontal angle of the rear shin is a key marker of the depth achieved. In this position, the kneecap is estimated to be 15-16cm from the ground. Compare the angle of the rear shin of the lifter in Figure 2-1 (same as Figure 1-5 above) where the angle is nowhere near horizontal. Although the depth of the Jerk receiving position displayed in Figure 2-1 may be a limit for this athlete, it should not be described as full depth.
A key issue for athletes in Weightlifting is to develop a Jerk receiving position that is low, stable and strong. The learning process takes significant time and effort, and should start from the earliest moments of training. The unfortunate fact that so many athletes have difficulty in the Jerk is testimony to an inadequacy of learning process. In Figure 2-2, the athlete’s body is perfectly positioned with the bar, shoulders, and hips in vertical alignment, and the combined centre of mass of the athlete and barbell is directly over the centre of the base. The depth achieved makes this position uncomfortable for the learner and this is a probable reason why beginner athletes are reluctant to practise it. However it is entirely necessary that that they use skill drills and light exercises to learn the position.
Speed Under the Bar
In Figure 1, the athlete moves from Position 3 (top of drive) to Position 5 (lockout in receiving position) in 0.31. It is essential that the athlete moves with great speed under the bar. If the athlete takes 1/10th sec longer, the bar will descend 10cm downwards further (from the equation d = 0.5 x g x t2).
For excellence in the Jerk, coaches must employ skill drills and exercises that help beginner athletes move fast into the Jerk receiving position. Beginners must be made aware of the need to keep feet very close to the ground during this movement. The more feet lift up in the air as they move, the greater the distance they travel as they are moving in an arc rather than a straight line.
Figure 3: Higher feet means slower movement time