The Oly Encyclopedia 75

A Fast Versus A Slow Dip in the Jerk

The speed of the dip in the jerk is another area of variation among lifters. As noted above in the discussion of the dip, a faster dip will create a greater elastic contraction in the leg muscles and therefore facilitate the generation of a greater upward force. However, it is also true that, carried beyond a certain point, a fast dip will create so much downward acceleration that the muscles will actually become fatigued from the effort of stopping the downward motion of the bar, lessening the ability of the legs to generate an upward thrust. Carried to an extreme, the lifter may actually lose control of the bar if the downward speed used in the dip is too great. This can result from inadequate muscle strength, n inability to effectively coordinate the motion or loss of balance. In addition, if the lifter dips too fast, he or she can lose contact with the bar by opening a gap between the body and the bar. As a result, the bar and body will collide at some point; because the body and bar are not in contact, the collision can result in the lifter and bar traveling in different directions after contact is made. There will also be a loss of upward thrust energy; these are not desirable effects, to say the least. Even if there is no deflection of the bar and body during a collision, timing and the process of developing maximum thrust can be thrown off. Therefore, the correct balance, in terms of the depth of the dip, must be found so that the elastic properties of the muscles are activated to their maximum extent while the lifter maintains control
One additional factor that affects the determination of the optimal speed of the dip is the elastic properties of the bar itself. When a lifter dips his or her legs, he or she is effectively removing the support of the legs from the upper part of the body and the bar, allowing both objects to fall. When the lifter applies leg force once again to stop the fall, the upper body stops almost immediately, causing it, in effect, to collide with the bar. The collision occurs at the center of the bar, a point some distance from the bulk of the weight of that bar. Since the bar is constructed of a material with elastic properties (steel), the plates will continue to travel downward after the bar collides with the body, and the bar will convert the kinetic energy expended by the plates during their fall into elastic energy in the bar. Once the kinetic energy of the plates has been absorbed, the bar will release elastic energy in order to return to a straight position, driving the plates upward (and ultimately imparting more elastic energy to the bar, which is released as the bar begins to slow somewhat in its vertical rise). If this upward rebound of the plates is timed correctly and occurs at the correct position in the drive, it can help the lifter to raise the center of gravity of the bar to a height sufficient for the lifter to fix the bar overhead. If the rebound is permitted to occur too early, the bar will have a chance to spring back down on the lifter before he or she has assumed a strong position in which to catch the bar. All other things aside, a shorter stopping time will therefor elicit the greatest elastic properties of both the bar and the muscles of the leg.
Consequently, the optimal depth of the dip, the optimal speed of the dip and the speed with which the downward motion of the bar is reversed are all interrelated. If two dips are executed with the same downward acceleration, the longer dip will have a greater terminal speed. This will generate a greater elastic response in the muscles and the bar Of course, it will also place a greater force on the muscles that must stop the descent of the bar and place the joints of the leg in a weaker mechanical position from which to stop the downward acceleration of the bar and to reverse that direction. Therefore, the faster the dip, the less depth is required to activate the same elastic properties of the legs and bar and the stronger position the legs will be in order to overcome the downward force of the bar. (A faster switchover from the dip to the explosion will also more vigorously activate the elastic properties of the leg! muscles.) However, a shorter dip will give the leg muscles a shorter period in which to accelerate the bar upward. A deeper dip will give the lifter a longer period during which upward acceleration can be accomplished.
Therefore, the lifter is always better off dipping as long and as fast as is possible and reversing the direction of the dip as rapidly as possible. However, all three things cannot be achieved at once. The lifter dipping deeper will need to dip more slowly and will not be able to reverse direction as quickly, but will be able to exert muscular force on the bar over a longer period of time. The shallower dipper will be able to dip more quickly and stop more rapidly, but will not be able to exert muscular force on the bar for as long a period of time. The lifter should also be aware that regardless of the length and speed of the dip, it must be straight up and down, and the lifter's body must not sag or give in any other way as he or she reverses direction from the dip to the drive upward.
Each lifter must find his or her own balance of speed, depth and amount of time reversing the downward direction of the bar in the jerk. Regardless of the speed, depth and reversal time of the dip, the lifter must be careful to remain on the flat foot until the latter stages of the final explosio (i.e., from the start of the dip to the point where th lifter has nearly straightened the legs once again, Going on the toes too early can preclude a thrust maximum power and make the lifter subject to a loss of balance arising out of a smaller base of support. Using the arms prematurely can cause bar to separate from the shoulders during the dip or thrust or to push the lifter down against the platform before a full split position has been assumed. With respect to what the lifter thinks about during the dip, Roman advises that a slight resistance by the leg muscles during the dip will provide a correct downward speed for most lifters, while Vorobyev suggests that the lifter attempt to apply no resistance at all and simply let the bar fall to the appropriate depth. While these are starting points t may be helpful for the majority of lifters, the process must be individualized for each lifter.