Judd Reid says, “At the end of the day, your best kick is the leg kick. It’s very painful, easy to land and it stops your opponent moving. The less they move, the easier they are to hit.”
Pain is a profound distraction and a leg kick, especially at the heavier weights, is always effective. If you land flush on the thigh, the kick is very damaging. Even a fighter who checks most of those kicks will still suffer; they will simply suffer less.
Judd fought extensively in Kyokushin Karate, where the leg kick is a staple feature of that full-contact fighting style. Kyokushin Karate provided the training basis for Cor Hemmers, step-father and eventual trainer of Ramon Dekker. Many of the first-generation Dutch kickboxers began their training and fighting in Kyokushin Karate.
Once you remove the grapple and the elbow from the rules, the Dutch had a ready-made system which is why Dutch kickboxers dominated in both K1 and Glory, which essentially employs the K1 rule-set.
All the great K1 fighters had an outstanding low roundhouse kick and careful observation of any of those fighters will yield the parameters for outstanding execution.
The range and execution of the leg kick depend very much on the way the kick is applied. The thickest part of the lever delivers the most force, and that is the top of the shin, just under the knee.
At the top of the tibia, or shin, there is a protuberance of bone called the tibial tuberosity. You’re aiming to knock this part of the bone against the head of your opponent’s quadriceps muscle.
The muscle is at its thinnest here and the greatest amount of pain and damage is inflicted. Secondly, the impact will rock the joint, which increases the distress felt by the victim. Lastly, the nerve endings congregate at that point and are more quickly given to spasm.
You can step in and have the foot of the standing leg pointing at a 45-degree angle to the opponent, or you can twist on the ball of the foot to spin the body weight in behind the kick. Both methods seem to work equally well.
Execution
There are a few ways to go about this. As far as the kicking leg, you want right angles at the knee and hip. This is going to result in a position that makes you feel uncomfortably close to your victim, especially if you’re used to kicking with a much straighter leg, as many other styles of (combatless) traditional martial arts advocate.
Keeping the leg drastically bent allows you to get maximum transfer of power out of the hip. Your goal is to knock that tibial tuberosity against the leg of your opponent. Speed is less important than accuracy with this one.
Thai kicking is generally judged by its effectiveness on a set of Thai pads and a good kick is accompanied by a loud crack, not unlike a whip. That sound is produced by the foot when it makes contact with the leather. A good leg kick will produce a muffled thump.
As with all contact, it is best refined in terms of the impact on a partner. So go into the gym and find someone as silly as you are.
