If a man suddenly rushes at me, how do I push him away fast and hard?
I will present a frame challenge here. Why push them at all?
As someone who is fairly light - it is very unlikely I could shove an attacker very far, even with perfect technique. And it is also unlikely to dissuade them from attacking me further (I have probably just made them angry/angrier).
So I present my alternative:
- COVER - hands on head, elbows tight
- MOVE - if someone is rushing at me - I only need to get out of their path - a couple of feet to the side is usually plenty.
They will end up at least as far away as a decent shove would manage, you haven't laid a hand on them, if they had braced for contact they will likely be off balance and may fall.
Obviously the follow up is now the same as the shove would have been - make sure you are safe before you switch off
The first step is readiness. It's sometimes half-joked that the most effective way to win a fight is for the other person to not know that it's a fight (knives, specifically, when analyzed, show that there's usually several stabs before the other person realizes there is a knife involved). And once you realize there is an attack, you need to act immediately and not freeze up. Second, for an effective push, you generally need to drop your center of gravity, get your arms free and clear, and push off the axis of the attacker so that you're not putting force directly against force. Other than the first step of being aware of your surroundings, and training yourself to act calmly and reflexively in the face of a threat (which generally does require a degree of live training), you're going to want to do the following:
- Bend your knees and drop your weight an inch or two to lower your center of balance.
- Bring your hands up to at least shoulder height with bent elbows so that you are ready to shove or block
- Step off axis and move into the attacker at an angle, putting your body weight behind the shove, keeping your arms a bit flexed so that you can absorb the impact enough to not injure your arms. I've seen some people argue that pushing on two different levels (one hand higher than the other) makes it harder for the other person to push back against you without putting themselves off-balance, but it will also likely reduce your own force.
- Take steps to either finish the fight (attacking the hopefully off-balance attacker, or start your retreat)
The push kick technique is specifically for this purpose. You bring up your knee (either one) as high as you can, and push out with your foot when the opponent is in proper range. The act of doing so may even intimidate the opponent to aborting the attack.
If you are smaller, actually executing the push kick may push you away instead of pushing your opponent away. This is fine, if you have balance, as you are still increasing the distance between you.