the max power output during 2nd pull and the support reaction force during receiving are a different thing.
Exactly My Point
The amount of force generated for Pulls is completely different from the force in receiving the bar in a Power Clean.
Research Data On Olympic Power Output Pulls
During Entire Snatch or Clean Pull Movements:
34.3 w/kg Men
21.8 w/kg Women
Second Pulls:
52.6 w/kg Men
39.2 w/kg Women
Squat and Deadlift:
12 w/kg Men
For female powerlifters, “estimates indicate that the corresponding values
for women are 60-70% as great”.
With this basic breakdown in mind, the power output comparisons of a
100-kilo male lifter in the clean, second pull and deadlift would be as follows.
Clean————-3430 watts
Second Pull—-5260 watts
Deadlift———-1200 watts
Obviously, there is a huge difference in power outputs. The
power output of clean pulls is 2.85 time greater than a deadlift. Second pulls are even higher with power outputs 4.38 times larger than deadlifts. Garhammer’s research showed that even when dropping the training poundage down to lower percentages for Olympic pulls and deadlifts, outputs for Olympic pulls were still almost twice as great.
Source: The No Deadlift Program to Improve Your Deadlift
[
The No Deadlift Program to Improve Your Deadlift]
“A Review of Power Output Studies of Olympic and Powerlifting: Methodology, Performance, Prediction and Evaluation Test”. Dr John Garhammer, National Strength and Conditioning Research Journal
Top Part of The Olympic Power Clean
The Second Pull is where the greatest amount of Power is displayed.
However, in a heavy Power Clean, bar Power Output and Velocity dramatically drop just above the waste. At some point, a Heavy Power Clean turns into a fairly Heavy Olympic High Pull. That due to the fact that the bar stops ascending.
That leave you with...
Two Options
1) Drop into Partial Squat to catch the bar.
2) Note that Set in your Training Log as a Olympic High Pull; due to the fact you didn't Power Clean it.
The receiving support force always is much more greater than pulling...
This takes up back to your...
Force = Mass X Acceleration
The receiving force is no where near the amount of force generated in the Second Pull.
To reiterate, that due to the decrease the Power Output and Velocity of the bar in top part of a Heavy Power Clean. At the apex of the Power Clean, the bar will stall; that's where you want to catch it.
If you allow the bar drop, then catch it, the Velocity of the bar is going to magnify the true weight on the bar.
As someone once said, "Jumping out of a 5 story building won't kill you. It's the sudden stop (Impact Force) that you need to worry about.
Take Home Message
Catching the Power Clean at the Apex of the Pull produces little stress on the knees; providing you have preformed the movement correctly.
Anyone who's preforming Power Cleans and having knee problem is doing something wrong or has some knee issues.
Show Me The Bodies
Power Cleans are a staple movement for the majority of athletes in High Schools, Universities, Professional Sports, etc.
If Power Cleans were as destructive as you have stated, there'd be, metaphorically speaking, a "Grave Yard" full of people. It would be constantly reported in research journals; very easy to find.
The Clean High Pull Solution
For anyone who for any reason believe the Power Clean Catch stresses and harm the knees, the simple solution it it to simply perform the Clean High Pulls and avoid the Clean.
This is where that greatest Power Output is achieved and developed. The movement is simpler and easier to learn and preform.
The Clean High Pull | T Nation
1) The athlete doesn't have to catch the bar.
2) Use heavier loads. This is especially true for athletes with technique issues in the catch phase where a lighter than optimal load must be used...
3) This heavy load, combined with the fast bar velocity seen in this movement, is responsible for the high power outputs that occur when performing this exercise (an average of 52 watts per kilogram for male athletes).
My work is done on this topic.
Kenny Croxdale
