Dev you are proving that you read this stuff more thoroughly than anybody else here because that was a very unclear passage really.
The mechanical response of the SSC is described like this: Prestretch of the muscle during the eccentric phase of the movement stores elastic energy in the series elastic components of the muscle which is then released during the concentric phase of the movement.
I have changed it to keep it very simple because I want to keep this explanation as on target as possible, as far as my knowledge is concerned. So here I will respond to the question about the version you quoted and try to expand on that and explain it more.
The SSC is still subject to some controversy. Alright so most people know that if you take a squat jump, for instance, and compare it to a counter-movement jump, the force potential is much greater in the counter-movement jump. So, in other words, if you dip down first and then jump, you will jump higher than if you just jump from a already squatted position. Most people believe that this is due to recovering that elastic energy we talked about and to the action of the stretch response which increases muscle activation.
There are still many questions about this and other possible explanations as to why performance is greater. So like I said in the article, it could be that the mechanical (elastic) response and the stretch reflex are important but to what extent each are important is not clear and what other elements may be involved is not clear.
You can look at this different ways. Okay, so you can jump higher on the counter-movement jump than on the squat jump. Well, how do we jump? How often have you ever jumped from a squatting position? Maybe your just not "good" at jumping this way yet. Couldn't your neural preparation be part of this? After all it takes time for muscles to reach maximum force. This time, we know, can be shortened with training.
AND we can show this in "theory" by pre-loading a muscle isometrically, letting it come up to maximum force, and then releasing. So you end up with force potential that is comparable to the force potential you get with the SSC. Just imagine that you are in a squat, and you jump up from the squat. It's difficult to jump very high. Hell, if you haven't done this a lot you can almost "feel" the sluggish acceleration as your muscles generate force.
Now say you are squatted and you can somehow push up against something that is keeping you from going up, and you try to jump against this so that your body is isometrically pre-loaded. Right when you are exerting as much force as you possibly can, the barrier releases. You're going to jump a lot higher, aren't you?
There also may be a potentiation effect on the actual muscle contraction. Maybe the prestretch "potentiates" the resulting concentric contraction so that force is generated more quickly.
There are others such as the force time benefit and some of these have been ruled out but the contribution of but the "storage" and utilization of elastic energy can be seriously questioned. Because the muscle also changes in length so that the actual contractile elements have to work over a greater distance so it kind of cancels out any added efficiency by the storage of elastic energy in the series elastic elements (it's the musculotendinous part that is springy). Remember the further apart the myosin and actin elements are the harder it is for them to hook up.
So, we know that the SSC is very important but we do not really know for sure the biomechanical origin of these benefits. To sum up the possibilities there are 4 main ones: contractile potentiation, reflex potentiation, storage and reutilization of elastic energy, and force time benefits.
When I said the "stretch response" I left out that I meant the response of muscle to stretch due solely to it's innate mechanical characteristics. Actually this is something the Joe will probably understand, but anyway…how any of this regards to stretching a muscle as opposed to "prestretching" in during eccentric actions….
When you look at how a single piece of muscle responds to a stretch you have to realize that there is the "reflexive" response which is an electrophysiological event and what is called the "areflexive" response..meaning the response of the muscle tissues "all by themselves". If you stretch a piece of muscle that in touch with the spinal cord you would see how it responded to that stretch outside of reflex control.
Muscle is a material and like any material it responds to being stretched in some way. So obviously when you stretch a muscle there is some importance to this mechanical response as well. What I was explaining in the article is that people mix it together when they talk about the SSC.
It may well be that the reflex control of muscle in itself has a lot to do with helping to control the actual mechanical response of muscles to increases in length. What I was saying is that the mechanical response is that the early response to stretch and it is identical whether the muscle is reflexive or areflexive. In other words, at the very early stage where force is induced on a muscle, the stiffness response is identical whether the stretch reflex is "active" or not. Let me try to explain this further
Muscle has an asymmetric response to stretch. This has been studied using the soleus muscle in cats where the dorsal roots (spinal sensors) to the muscle were sectioned so that they could compare the muscles areflexively and reflexively.
What is found is that a muscle has a lot of "short range stiffness" before "muscle yield". But when and if you apply enough force to it it gets stretchy. Now, what I was getting at is that people mix up the mechanical response and the reflex response as if you can tease out the difference in active muscle between the two. So they tell you stuff like "elastic energy is stored in the muscles" and that kind of thing. But you really could only see it during the first instant and after that the stretch reflex response overlaps the intrinsic mechanical response so that you cannot "observe" the different affects of them without separating the two.
