Olympic weightlifting encyclopedia 26

The Fourth Phase of the Pull: Final Acceleration

The fourth phase of the pull is the one in which the athlete applies the maximum and most critical force to the bar. This is accomplished by explosively straightening the legs and torso, lifting of the shoulder girdle upward and backward and rising on the balls of the feet and toes. It should be noted that not all lifters straighten the legs fully during the explosion phase of the pull or jerk and that some high level lifters do not rise on the toes to any significant extent at all. Some coaches believe that this lesser amplitude of body straightening is an advantage.

During this fourth phase of the pull, the bar describes a forward are as the combined center of gravity of the bar and athlete shifts toward the toes of the athlete (upon which the athlete is typically balanced at this stage) until, ultimately, the bar finds a nearly vertical direction. This stage takes approximately 1 to 25 seconds to complete the clean requiring less time than the snatch). At the end of this phase, the athlete’s center of gravity has moved up and back as the bar has moved forward, and the body assumes a straightened position with the entire body generally having a slight backward lean. A straight but slightly backward leaning line passes through the bar, the lifter’s shoulders and the balls of the feet. The combined center of gravity of the bar and lifter is at approximately the same vertical line as the feet of the lifter, which are now supported on the balls of the feet on average the bar is actually of 2 to 4 cm forward of the base of the toes). The bar reaches speeds of 1.65 to 2.05 meters per second in the snatch and 12 to 16 in the clean (taller athletes tending to achieve greater speeds than shorter athletes).

The Fifth Phase of the Pull: The Unsupported Squat Under

The unsupported squat under begins with the lower limbs of the athlete at their most extended position and continues while the athlete is moving into position for the squat under. It ends when the feet make forceful contact with the platform once again. Once the final acceleration has been completed, the bar continues to rise, primarily as a result of the momentum gained during the final acceleration phase. However, the speed gained during that phase is not sufficient to account for the total height that the bar ultimately reaches (68% to 78% of the athlete’s height in the snatch and 55% to 65% in the clean). Several explanations have been offered for the extra height that the bar achieves. One is the interaction of the arms and the bar while the athlete begins to descend into the squat or split position (i.e., while the athlete’s feet still are in contact with the floor, a period of .05 to 1 second in the snatch and .1 to .15 of a second in the clean).

A second factor cited is the thrusting of the feet from the platform during the descent under the bar (because the bar’s velocity is higher after this thrust). In a way, the body collides with the bar after the maximum effort has been exerted in the explosion (the body goes up and then bounces down away from the bar), adding some impetus to the bar.

A third factor is the interaction of the arms and bar as the athlete descends in the unsupported and supported phases of the squat under. The action of the arm flexors and the muscles of the shoulder girdle (in the latter part of the snatch descent and during the jerk, the arm extensors come into play) after the feet have left and then returned to the ground can generate an upward reactive force on the bar, resulting in additional acceleration. This acceleration occurs when the force of the body returning to the platform is transmitted back to the bar thorough the arms.

During the unsupported phase the center of gravity of the lifter typically shifts forward somewhat as the athlete descends under the bar while it moves upward and then downward and backward. After the feet are thrust from the platform, they typically remain out of contact with the platform for between 15 and 33 of a second in the snatch and 1 and 2 of a second in the clean.