FREE YOURSELF FROM YOUR OPPONENT'S FORCE - 2nd principle of power

If our force is a kind of matter that is projected from the inside out, on the other side the opponent's strength tends to follow the opposite way, to enter into us, in our spine, our center. Therefore, these two forces going in opposite directions, mine from the inside out, the other from outside to inside.
By the term "to free", we mean in this case "avoid this force being released into our body"; it will be necessary to prevent the entry of the opponent force while continuing to project our own (to not violate the first law of force ).
However, if the two forces collide in a direct way we could hardly apply the first principle: it is as if a person wants to leave a room and the other one wants to enter, if ythey try to do both frontally and at the same time, probably none of them succeed in his goal, just they keep pushing one each other, using the raw strength - that we want to refine at least -. So it is necessary that the opponent's strength does not affect us without this being a result of a confrontation between the forces.
The possibility therefore are two:
1. The strength of the opponent does not enter, but it doesn't meet my strength (I create the vacuum);
2. The strength of the opponent does not enter, meet my strength, projected outward at an angle different from that attack.
The very existence of the third principle ("if the opponent's strength is greater, yield") suggests that the encounter may well be possible, therefore we have to consider both the possibility. The first situation occurs when my body will not be aligned with the strength of the opponent (see the footwork); while the second one when I can deflect the force of the opponent, projecting mine with a different angle, without the two colliding frontally (see the wedge or pyramid, and yang techniques).
"Get rid of your opponent's strength"for me means not being crushed, not going to apply force against force, but rather using my own where there is not the opponent's one, trying, of course, to find a gap."Get rid of your own strength", however, as we have said elsewhere, do not mean to be "inconsistent" or yielding always and anyway. The release must be through specific principles and concepts. One thing is to get rid of his strength not worrying too much about what of this force, another is to get rid of it while maintaining control and being able to use it to our advantage.
For some people, the principle we are talking about means "take out" the opponent's energy, while for others it means "not being in front of the opponent. " Many describe the Chi Sao as a technique through which the most skilful of the two creates a vacuum in relation to the push or thrust of the opponent, a sort of "dematerialization" before the attack ... Corners well prepared and well distributed pressures lead "outside" the strength of the opponent. The problem is that our level of knowledge and application often is not adequate and creates handholds which the enemy tends to stick, allowing him to find a gap in our sphere.
In some lineage is believed that in order to get rid of the opposing force is necessary a full rotation of the trunk - old memories ... -, which would allow the release of the opposing force out of our vertical midline (and, consequently, out of our center line). Well, in my experience, I can only "put aside" - to be kind - this theory, which has caused so much damage in the stability of the practitioners, who performed the rotation of 90 ° without any roots to the ground. Rotate your upper body on one leg, but in exceptional circumstances and with the necessary precautions, is like to let everyone, who knows a minimum of concepts of plyometrics, hurl you down!
Let's get back to us. The moment you want to get rid of the other external forces, remember do not get too close your elbows to the body, because you risk being crushed. This is another bad souvenir that many will carry with them, but it is also another luggage - or ballast? - we have to throw into the sea. Does it mean that the arms must not yield back? Of course not, but it is important that the angle of the elbow does not exceed the minimum threshold of 90 °, after which only elbow strikes or other type of shock can save your ass.
We assume that in order to learn the mechanics of how to unload the weight, or, better, how to get rid of the opponent's strength, we must first understand what it means to actually get rid of our own force and all those instinctive reactions leading to muscle contractions in a situation where we receive very strong stimulations on our arms or on our bodies in general. Only after understanding the first concept related to the force we can understand the second one. 
Getting rid of the strength of the opponent is an effective way to understand how to take advantage (freeing ourselves from) of the lines of force that our opponent uses (attacking us), to our full advantage.Through a structure built out correctly, our arms will be able to receive all the streams and lines of force of the opponent, unloading all the energy of the opponent to the ground, throughout the body, to be able to fight back dynamically, in the moment in which his strength, that we have unloaded, is equal to zero (thus reversing the situation in our favor and applying in this way the 4th principle of power). If I may suggest a practical thing, I suggest you first unload the opposing force at a diagonal angle: if the attack is to the right arm, get the weight (and strength) on the left heel and vice versa for an attack on your left side. With this basic exercise, you can work to unload the incoming forces. The exercise can be also executed with pushes directly on the body or on the arms. 
This principle reveals another aspect of the system, to not ever oppose resistance (composed of raw force) to the opponent. Getting rid of the strength of your opponent means to take possession of his strength for us, then to be able to use to our advantage in combat. The strength of our opponent should not be an obstacle to our action. Even with the Siu Nim Tao, we have to be able to develop the principles that allow us to convey into our body the strength of the opponent, to accumulate and turn it into explosive energy when we go into action to attack.
The application of the principle we are dealing with, is an important element of distinction between the different lineages; it is closely related to the way in which they plan to absorb the opponent's energy.
We use our principles and different strategies (Kiu Sao) to make the first contact and to absorb the force of our opponent (a fist or whichever other action), creating our bridge (Kiu) and trying to sink his (Cham Kiu). From here youwe can have various scenarios. Sometimes it is sufficient to take the weight on one foot, others to apply a small rotation of the trunk, others a step. Create distance, somehow, from the point of pressure - "deflated" - with the center of gravity down and back, so you can decide what to do. But for today I will stop here, because we are dealing with the second principle. To get rid of the attacking force, we should not stop to have pressure towards those who attack us (contact points, lines of force, etc..) how many instructors from the more different lineages explain, with only "power forward" - without saying  forward where -.Rather, we must remain stuck to the contact point and we must take care not to let the opponent's pressure or attack enter into our body structure, or we risk to lose our balance and, consequently, we will not be able to get rid of his strength. The stability is vital, remember always that.

                                   (adapted from the Riccardo Di Vito's Blog)