Exercise motion question 'Olympic snatch' vs 'weighted knee jump'

Youtube is a dangerous place. I found this knee jump exercise



My knees are sore just watching it.

However, it got me thinking "why would anyone do this particular variation of an exercise especially at the heavier weight? What value does it have if any?"  

I'm sure Olympic weightlifters---especially those who do the snatch movement would put similar stress on the knee ligaments, hips and thighs as the exercise above. So for those who may be experts in physiology, does this particular exercise have any value given that there are alternatives like a full snatch movement?

afulldeck wrote:Youtube is a dangerous place. I found this knee jump exercise



My knees are sore just watching it.

However, it got me thinking "why would anyone do this particular variation of an exercise especially at the heavier weight? What value does it have if any?"  

I'm sure Olympic weightlifters---especially those who do the snatch movement would put similar stress on the knee ligaments, hips and thighs as the exercise above. So for those who may be experts in physiology, does this particular exercise have any value given that there are alternatives like a full snatch movement?

Yes, the exercise predominantly has two strengths:

1. it is explosive power. Since the person is completely off the ground, the time involved is very brief, and to get off the ground with extra weight he has to apply a lot of power. In order to train explosive power the amount of weight lifted needs to be greater than 70%, usually 70-90% and the muscle contraction needs to be done at a speed of 80-100% maximum. While the weight the gentleman is lifting is not immensely high, he still reaches a total high load since he forces himself off the ground, so you need to add his own body mass to the equation.

2. Upon impact, i.e. landing, a whole number of muscles (quadrceps, gastrocnemius, popliteus, tibialis anterior, perroneus) are lengthened despite contracting. In other words, the exercise is eccentric. Eccentric training gives the greatest yield because of the enormous forces developed. It also gives the greatest muscle damage; I mean physiological muscle damage, which is not negative since it will be accompanied with muscle build. I don't think that it is really the knee joints which are that much at risk since the angle of the knee does not change that much, and a relatively save angle is used, so not hyperextension or anything.

I can see that those would be strengths for this exercise. But....(don't you just hate that word)...I just didn't think these strengths would be much greater than those of snatch or many of its assistant exercises (for example barbell jump squats) which require a jumping action landing in squated postion under heavy loads. I'm assuming your position would be that because the jumping action from the snatch or barbell jump squats is a smaller movement (? 'perhaps' there is less time in the air) than the jumping action from the knees--so the explosive power action from the snatch is much less? Or is there something else at play that I'm missing?

As you have already perceived yourself, the explosive force in the exercise shown will be different in the exercise shown for the simple reason that if it doesn't meet the threshold you will fall back on your knees with a weight on top of you. Therefore the psychological motivation is enormous. I also would surmise that the eccentric component in this exercise is proportionaly greater.

In your response you mention "I just didn't think these strengths would be much greater than ..." 'Greater' is one way to appreciate something but not the only one and also not always the most relevant one. I would hope that when someone chooses an exercise that he is driven by optimally realizing his objective. That is not simply realized by selecting the exercises that achieves the highest maximum. Other parameters, such as angle, duration, mode, number of repetitions, also play a role. I think it is also prudent to assume that someone who does an exercise this difficult or extreme, likely ALSO does snatches, so he presumably is already benefiting from what the other exercise offers. Sure, I am speculating, but if you are able to do this exercise, then you are also able to do snatches.