Leg sweeps are a great setup to a string of offensive techniques. If your opponent has poor stances, a foot sweep can make them stumble. This atemi causes the opponent to briefly take their mind off of the fight as they scramble to keep themselves upright. The opponent is completely vulnerable to attack in that moment. This is why stancework is so important -- because the punishment for a poor stance is a leg sweep. A well-timed leg sweep can literally sweep your opponent off of their feet, dumping them onto the ground.
[Successful leg sweep from the side, with no part of the uke touching the ground.]
There was nothing special about that technique you just saw; in the martial arts, and in life, there is nothing more spectacular than simple things done extremely well. The secret is in the timing -- when the opponent steps forward, sweep his leg just before they set in their stance (i.e., before they shift their weight onto that leg). Leg sweeps can be effective without being full takedowns, they only need to disrupt the opponent's balance. The takedown is a 1-in-100 bonus.
To perform a leg sweep, first notice your opponent’s stance. If their stance is wider or narrower than the width of their shoulders, or if they are in the middle of transitioning to some other stance, then you can proceed. If your opponent is in a solid stance, do not attempt a leg sweep; your foot will just awkwardly bounce off your opponent just like a tree, or a load-bearing column.
To sweep your opponent, step your rear leg up to (but not past) your front leg, just like in a step-up front kick. The sweep itself takes a J-shaped path. First, swing your foot diagonally out to the side a little bit, and then quickly snap your foot in a straight line across your body, until it is directly in front of your rear leg. When done properly, the knife-edge of your foot sweeps the floor like a broom. The ball of your foot pushes the opponent’s ankle. Do not stop when you feel your foot make contact; there is no polite way to foot sweep someone.
After a foot sweep, you will be awkwardly standing on one foot, so you'll need to recover quickly. Immediately pull your knee up to your chest, entering a fighting crane stance. A foot sweep followed with a front kick makes an excellent combination, just like peanut butter and French toast. (No seriously, it’s amazing.) This way, you instantly strike your stunned opponent if you sweep succeeds -- and if the sweep fails, the kick will keep your opponent on defense while you recover.
[Leg sweeps In the air from the front and the side, in the air, fast and slow.]
Leg sweeps should always be directed at the opponent’s front leg. If you can reach the opponent’s rear leg, then you are also close enough to be punching, kicking, etc., and should concentrate on those things instead. It doesn’t matter if you sweep the inside or the outside of an opponent’s leg, as both will disrupt their balance. Leg sweeps should never contact higher than the opponent's ankle. There are two reasons for this:
- High foot sweeps can injure your training partners, and if you break your partner, you do not receive a new one. The difference between a very high foot sweep and an inside crescent kick to the side of the knee is purely semantic.
- Foot sweeps use the opponent's leg as a lever to rotate their body. Sweeping as far down the leg as possible will maximize your leverage, and thus maximize the power of your foot sweep.