The Oly Encyclopedia 22
January 11, 2022•1,232 words
An Analysis of the Six Phases of the Snatch and Clean Pull
A detailed analysis of the snatch and clean is presented in this section. This analysis includes a number of technique metrics. The figures provided for those metrics are representative of an athlete with an average, mesomorphic physique who is 170 cm tall (approximately 5' 7"). Athletes who are significantly taller or shorter will generate different numbers. For example, athletes who are taller will tend to move the body and bar greater distances and will tend to move the bar at higher speeds.
It should also be noted that in many areas of the analysis differences are noted in the patterns of movement that occur in the snatch and the clean. These differences are believed to exist primarily because of the differences in the grip widths and weights that are used in the snatch and the clean. A narrower grip (as is used in the clean) places the shoulders at a greater distance from the bar than does a wider grip, generally resulting in the torso being held more upright during the pull for the clean than in the pull for the snatch. This grip also produces in a greater deformation (bending) of the bar during the pull for the clean because the force applied during the pull is applied more toward the center of the bar. The heavier weights used in the clean also contribute to the greater deformation of the bar.
Some interesting trade-offs occur in the clean as opposed to the snatch. For example, the amortization phase is longer in the clean than in the snatch because of the heavier weights lifted in the clean. However, the final acceleration phase in the clean is shorter than in the snatch because the torso is straighter at the beginning of that phase.
Before we begin our analysis, the reader should have at least a basic understanding of the concepts of the line of gravity (LOG) and center of gravity (COG). It is important to understand these basic concepts of mechanics because they are used in the analysis of technique that follows. In the simplest terms, an object's line of gravity (when it is viewed from a given perspective) is the point at which the object would balance if a straight edge were placed under the object. For example, if we were trying to balance a ball on the edge of a steel ruler, we would have to place the ball in such a way that the ruler was under the exact center of the ball (i.e., under an imaginary vertical line that divided the ball into two halves). Alternatively, if we were trying to balance a flat wooden map of the United States that was 1" thick in a upright position, we would place the ruler near the center (east/west), but the point of balance would be unlikely to fall in the exact center measured from side to side, because the map is not perfectly symmetrical. Since the eastern and western parts of the country do not have the same shape, the left and right halves of the map would not weigh the same and would not balance along a line in the exact center. The line would be somewhat off to one side. In contrast, if we viewed such a map from the side, the line of gravity would be 1/2" from the front of the map or 1/2" from the back because the map is flat and made of wood that is 1" thick. Finally, if we laid the map down flat and then found the balance point between the western and eastern sides, a line drawn through the map at that point would represent its third line of gravity. The point at which all three lines of gravity intersect is the map's center of gravity.
Finding the center of gravity of the human body is much more difficult than finding the center of gravity of a ball or a map of the United States, because the human body can change its shape at any time by simply moving a part of the body, such a movement will change its balance points. For example, when a body is viewed from the side (the perspective that is used for much of the analysis of lifting technique that follows), the center of gravity runs approximately along a line that divides the body in half from front to back. However, if the body bends forward from the waist, the center of gravity will shift forward. If one leg is then lifted to the rear, the center of gravity will shift back toward the middle of the body. In contrast, the center of gravity of the bar is always at its exact center (as measured from all directions) since the bar is symmetrical. When two objects are connected to one another, a combined center of gravity is created. For instance, if a lifter who weighs 100 kg. holds a 100 kg, bar at waist height, the combined center of gravity of the two objects will be toward the front of the lifter's body and the rear of the bar.
The concept of the center of gravity has a number of implications for the weightlifter, and it is discussed in greater detail in Appendix 2. It should be noted that while from the technical standpoint the line of gravity concept is appropriate only for discussions of a single dimension, and the center of gravity is appropriate for discussions of three dimensions, the term center of gravity is used for single and multiple dimensions throughout this chapter, both for simplicity and because in the contexts in which it is used the difference in the terms is not material.
Its primary importance in the discussion that follows is in describing the general motion of the athlete and the bar during the performance of the snatch and C&J. For instance, during the second phase of the pull, the lifter's center of gravity shifts toward the rear, but during the fourth phase of the pull, it moves forward.
The lifter's center of gravity can be thought of as his or her balance point. When the center of gravity shifts back, so does the lifter's balance and vice versa. An important principle of mechanics is that at no time may the center of gravity go outside the base of support of an object in the case of the weightlifter the base of support is the athlete's feet). If the center of gravity of the lifter does go forward or to the rear of the furthest edge of the foot (the toes or heels, respectively), the lifter will topple over. Since the athlete's feet represent the base of support of both athlete and bar once the bar leaves the platform, the combined center of gravity of bar and lifter may not exceed the limits of the lifter's feet or the entire system will fall over (with the lifter going one way and the bar the other). In the analysis that follows, the centers of gravity of the lifter and bar and their combined center of gravity are often referred to in order to convey a sense of how these objects are moving and interacting and where the lifter's balance is at various points during the lift.
Now let's look at the six stages of the snatch and clean.