Tuesday, June 20, 2023

Analysis of Weightlifting Techniques (complete) -- Ma Jianping / Manuel Buitrago


Huang Qianghui . . . 

October, 1930 - May 14, 2014

. . . and others used the 3 gravity principles for analyzing the mechanical efficacy of different weightlifting techniques and overcome historical controversies. 

The first technical issue is choosing between a low-hip position and a moderate-hip position during the start. 

Figure 2.5 [above] shows an analysis comparing hip heights and their effects on the body. (Gu 2000). 

With a moderate-hip position, the body mimics a vertical jump, and so the barbell's center of gravity is over the balance point (D). 

However, in a low start, the femur approaches a more horizontal position, which shifts more of the body's mass and balance backward. The shins incline forward to compensate for the hips, which pushes the barbell forward and creates a gap between the barbell's center of gravity and the new balance point (B). 

If the athlete uses a low-hip position, then the barbell must travel horizontally or diagonally to reach the vertical line point O which means the athlete must exert a large horizontal force backward to counter barbell (which violates the "equal magnitude" principle). 

Additionally, the torso must lean over to avoid falling, which violates the "opposite direction" principle. The knees must push forward to compensate the body's lean once the barbell clears the knees; otherwise the athlete will fall backward. This compensation imparts a deceleration in the barbell's velocity and the torso. Hence the increase in horizontal forces leads to a decrease in the vertical force component of the barbell and body and results in less end velocity during the deadlift phase of the pull (Gu 2000).

Okay, that's enough on this end for now, for a while, a short time. 

Ain't it refreshing not seeing the name "Weider" preceding every principle? 

I will be adding here, and to make it easier to find where the newer adds are will be putting Continued (1) . . . Continued (2) . . . 

Continued (1)

The moderate-hip position is more efficient because the athlete does not have to waste time, work, or energy to bring the barbell over point B. Additionally, the joint angles are greater in the ankle (L5 > L6) [I'll be using the letter L for the angle symbol instead of copy and pasting it each time]. knee (L3 > L4), and hip (L1 > L2) in the moderate hip position, which reduces the resistance torque on each joint and makes it easier to lift heavier weight. 

Some athletes will naturally be low due to a shorter femur and/or shin length, but they still balance themselves on the ball of the foot through line O. This balance is appropriate, and they should not artificially adjust their posture to achieve a moderate-hip position (and likewise, taller athletes should not artificially lower their hip positions since they will change their balance in doing so). 

Another controversy is the location of the balance point of the foot. Earlier, Chinese coaches used a range of locations, but pushing through the ball of the foot was found to significantly increase the end velocity of the barbell as it reached a finished deadlift position. Additionally, this spot created a faster initial and end velocity from the extension, which increased the barbell's height and allowed a straighter bar path. 

Figure 2-6 shows these mechanics adapted from Lu and Liang (1989) where the left panel shows how the ball of the foot acts a the fulcrum O to apply force F to the heel to lift the resistance of the body R through the tibial articulation. 

The right panel shows how a change in one's arch or a backward change in one's balance from point O1 to O2 decreases the force from F1 to F2, the speed from S1 to S2, and the height from H1 to H2 if the heel lifts at the same angle 

busy busy work shift today . . . 

Here: the whole of it for ya . . . 

Real tiresome typering with this one for me, so there it is. 
Next step, whining about popup blockers and being too cheap to put out money for Premium! 


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