Having correct defensive movements as a fighter is very important. When someone throws one of their techniques at you, you must be able to read that technique and then respond with a defensive movement that ensures you are not hit. This is one step on its own, and it is at the basic or foundation level of learning martial arts. You learn techniques you can throw at an opponent, and you learn defensive movements to block those techniques.
At a higher level you must then be able to read tendencies of your opponent and exploit those tendencies, possibly even drawing them out. So if you notice a fighter consistently using the exact same defensive movement to one of your techniques, you know that they are also an opening. Even though a defensive movement may be correct in the moment, it can be incorrect in the bigger picture as you are consistently creating the same opening.
In this next video we look at an opponent who consistently parrys the jab. In a break down of what is happening during a parry, you are temporarily moving your hand away from your face to block a weapon your opponent throws, and then bringing your hand back to your face. This temporary movement away from the face is exactly what we are now trying to exploit. We do this by again throwing the jab, knowing the parry is coming, while simultaneously sliding our rear foot up to bring our lead head kick into range. From there we bring our lead foot straight up and turn your hip over to add power onto the kick.
This is a technique that is aiming to catch your opponent off guard and not one aimed at throwing as hard as you can. It is going to be hard to generate maximum power on this because your hip is already turned due to the stance you are in. To add power the hip should turn slightly and you should whip your kick over from the knee so that the foot or shin bone connects.
If done correctly you will time the exact moment the hand is away from the face and land your foot/shin bone on the exposes side of their face. Your jab is a 'throw away jab' as it is used as a set up aimed to mask the slide of your back foot. Try to avoid doing a full 'switch kick' when doing this technique as it will throw off the timing and you will most likely miss your opening to land the high kick.
Edmen Shahbazyan recently used this technique to knock out Brad Tavares and Stephen "Wonderboy" Thompson used a variation of this kick off of a cross and rear leg swing kick to knock out Dan Stittgen.
For more in depth analysis check out The Ultimate Guide to Striking for MMA, Muay Thai and Kickboxing.