This article focuses on Jerk technique, the second part of the competition movement known as the Clean and Jerk. In particular, the article discusses the conventional technique of the ‘Split Jerk’ which is employed by the vast majority of Weightlifters worldwide. While the author acknowledges that World Champions have used the ‘Power Jerk’ or ‘Squat Jerk’ techniques, the Split Jerk technique is recommended as the most effective and the safest.
From this point on, the Split Jerk technique will be referred to simply as “The Jerk”
Key Issues of Jerk Technique
The Jerk is a highly complex movement that many athletes in Weightlifting find harder to master than the Snatch. In the Jerk, athletes must overcome several key issues if they are to become good exponents of the lift. These key issues are:
- The extreme heaviness of the barbell. Although Weightlifters are masters of ‘heaviness’, an exceptional performer in the Clean and Jerk will lift in excess of 80% of their best Back Squat. In addition to excellence of Jerk technique, the athlete will need great courage, will power and tenacity to complete a Clean and Jerk that is near to the limit of their strength capacity.
- Achieving and maintaining a lockout of the elbows with the weight overhead. If an athlete, for anatomical reasons, has a difficulty in maintaining an elbow lockout, then the likelihood of reduced performance potential in the Jerk increases significantly.
- Even when both elbows are locked out, the athlete will experience significant difficulty in maintaining balance and control of the weight overhead. This is a matter of physics. In the situation where the athlete has a barbell of twice bodyweight overhead, the combined centre of mass (of the barbell and lifter) will be situated at approximately neck height or higher (see figure 2 below). The higher the combined centre of mass, the greater the balance problem.
Learning Jerk Technique
It is important to take a long-term approach, from the very first moment that training begins, toward achieving total confidence and positional correctness in Jerk technique. Coaches should understand that the skill learning process should not be rushed. Errors that accumulate early in the learning process are hard to correct later. It is unfortunate that beginning athletes can often succeed with Jerks despite poor technique but as the athlete progresses to higher levels of qualification, the special issues described above will undoubtedly diminish the athlete’s performance potential unless appropriate attention is given to the following key learning objectives:
- A smooth and purposeful ‘dip and drive’
- Rapid and efficient movement under the bar
- Positional correctness of the body in the receiving position
- Controlled recovery to the finish position
The Dip Phase of the Jerk
Not all aspects of the Dip and Drive are well understood. Easy to understand, but not easily achieved, is the need to elevate the bar in one direction only – vertically upwards. This directional control requires an absolute avoidance of any rotation of the upper body during the dip, in other words the body must stay totally vertical as displayed in Figure 5. It is critical for the athlete to ‘bear down’ through the heels in the Dip to prevent forward movement of weight distribution to the front of the foot.
A common fault in the dip is an inability to “dip straight” (keep the torso vertical). This incorrect action, displayed in Figure 6, will send the barbell forwards. Even a slight rotation of the body will have an undesirable effect. Once the barbell is moving forwards it gains momentum and becomes very hard, and often impossible, to stop. In Figure 6 it can also be seen that the forward movement of barbell is so dramatic that even at the bottom of the dip the barbell is no longer over the base of support.
Another common fault in Jerk technique is forward movement of the ‘centre of pressure’ during the dip. The ‘centre of pressure’ is the effective point of application of force through the foot into the floor. Figure 7 portrays the common fault where the athlete starts the dip with the centre of pressure toward the heel but as the bottom of the dip is reached, the centre of pressure has moved forwards to the ball of the foot. The probable effect of this is forward movement of the body during the dip and as a consequence the bar gains forward momentum. This issue is also the root cause of the problem depicted in Figure 6 above.
Other aspects of the Dip and Drive for the Jerk are not well understood. In particular, the velocity of the dip is critical to success. The higher the downward velocity of the bar, the greater ‘impact’ of the bar at the bottom of the dip. The impact, that is the abrupt stopping of the bar and changing its direction to upwards, must be absorbed by the body. The effect of this impact can be seen in slow-motion video and is typically manifest in the ‘buckling’ (loss of rigidity) of the torso, that is bending of the spine, dropping of elbows and partial collapse of chest. On the other hand, there are also beneficial effects of absorbing the kinetic energy of the barbell in the dip. To some extent, the body acts like a spring and the ‘recoil’ is the upward movement of the bar (The Drive). Therefore, if the velocity of the dip is too slow, the athlete looses some of the beneficial spring effect. Furthermore, there is also the complicated issue of the spring in the bar, which increases in magnitude the greater the weight. It is important to control the dip velocity. If it is too rapid or too slow, there can negative consequences.
In Figure 8 below, X is the start of the Dip and Z is the bottom of the Dip. Y is an arbitrary point at which barbell downward velocity begins to slow. The distance between X and Y (marked in Figure 8 as the distance d1) is the “fall” distance. This is not a free fall as the athlete is resisting the downward movement of the bar. However during the “fall”, the bar will be accelerating. The distance between Y and Z (marked in Figure 8 as d2) is the “impact” distance and is characterised by deceleration of the bar until it comes to a stop at Z. During the “impact” distance, the athlete is exerting great force to decelerate the barbell to zero and change its direction to upward.
The following spreadsheet illustrates that the consequence of a more rapid dip during the fall distance (in the Jerk) is that more force is required to decelerate and change the direction of the bar. The difference between Case 1 and Case 2, is that in Case 2 the fall time is 0.25 sec or 25% longer duration than Case 1 which is 0.20 sec. Therefore the downward velocity over the “fall distance” is faster in Case 1 (1.18 m/sec) than in Case 2 (0.944 m/sec). The result of the slow dip speed in Case 2, is that force required to turn the bar around is 717 Newtons, and this is significantly less than the force required in Case 1 (897 Newtons).
There may be a limit to which each athlete can produce sufficient force at the bottom of the Dip without significant “buckling” of the body. The issue is that coaches and athletes are not aware that a fast Dip can be problematic. The incorrect assumption made is that a faster Dip stores more kinetic energy, and therefore a more ballistic Dip and Drive gives the athlete a better chance of elevating the bar to the height needed. However this assumption does not take account of the athlete’s limited ability to avoid “buckling” which causes the kinetic energy to be absorbed in body position changes rather than transmitted to the barbell.
Jerk Receiving Position with Straight Back Leg
It is unfortunately common to see weightlifters with significant deficiencies in the Jerk receiving position. The Jerk receiving position is not easily mastered and for many, problems tend to be ongoing throughout the lifting career.
Of particular concern, athletes can easily acquire a “straight back leg” receiving position (see illustration on right) and, as a result, a problematic tilt of the pelvis caused by tight hip flexors. This pelvic tilt (illustrated and explained above) is problematic because it increases the lordotic curve of the lumber region of the spine. Any abnormal curvature of the spine increases the risk of injury.
Moreover, the “straight back leg” receiving position in the Jerk is often accompanied by a forward lean of the trunk and a greatly uneven distribution of weight on the feet. As a result, the athlete will suffer instability as the weight will move towards the front of the base and will likely continue moving forward. In the above illustration the stripes on the athlete’s uniform provide an excellent guide to the degree of pelvic tilt, and lumber curvature. You can see that there is a significant change in angle between the upper and lower torso.