He's really not asking how to do a roundhouse, he's asking how to pivot
. The pain that he notices after throwing the kicks is from not pivoting on the ball of his supporting foot when he throws the kicks. He's probably flat-footed (all of his weight is distributed through the sole of his foot from his toes to his heels), which causes his leg to stay in the same position while his body torques over. The repetative snapping over has stressed his knee a little. In fact, I mention that can happen while addressing footwork in this thread here
. In essence, you're putting the same type of torque on your knee and ankle as you would in a heelhook
, but just for a brief moment.
Truthfully, the pivot is one of the "finer points" of throwing a round kick (and most kicks in general). It's a learned, co-ordinated movement of the whole body (you can't pivot without moving your hips and upperbody, it doesn't happen). It's one of those things that, like good, technical footwork, comes to you with repetition and drilling over and over again. That isn't to say there isn't a tip I could give you beyond that, or provide you with a few exercises that will help you develope thos movements.
First thing first: Practice good form
. Don't worry about power, and don't worry about the level of your kicks. Start out slow and break the movements down in links. Concentrate on form, and then add a little speed. When you can throw a quick, clean kick that is when you will then try to kick through your target with power. If you go for the highest, hardest kick possible without good form you are probably looking at falling on your ass (at least) or blowing out your knee (at worst).
Exercise #1: Hip Turn-Overs (With Partner)
- This will require a partner to do, but is a great way to warm up before drilling. To do this:
1) Stand in front of your partner and raise one leg up around waist height.
2) Your partner will grab your leg in a loose grip at your ankle. This is a loose grip, because you want room for their leg to rotate. One of the best ways to do this is rest one hand in the palm of the other, hold your hands at the closest hip to their leg (usually the mirror side: your left hip to their right leg and your right hip to their left leg), bend your knees a little to lower your base, and rest the top of your hands on your thigh. This will create a loop between your hip and your elbow, providing more than enough room for your partner's leg to rotate.
3) Once your partner is settled in, with a hopping motion, turn your hip over toward your partner (if your right leg is up, your hip will turn in to the left, and vice-versa). You should finish in a position where your extended foot is pointing down, the heel of your supporting leg is facing your partner, and you have to look over your shoulder to see your partner. Do that for about 20 to 30 times for each leg (20 if you are just starting out).
When doing this, make sure to keep your hands up (start building that habit now). Remember to turn your hip all the way over (it should be like flashing your buttcheek to your partner). This will help teach you how to pivot and turn your hips completely over, and help you learn what part of your foot you are pivoting on.
Exercise #2: Dead-Leg Swings
- This can be done on your own, but it is very effective if you are in front of a MT heavy bag. To do this:
1) Stand in front of the heavy bag an arm's length away in a squared stance, feet in line, shoulder-width apart with your hands up in an en garde position.
2) Raise one leg up to side about 6 to 8 inches off the ground in a relaxed position. Your knee should have slight bend to it.
3) With your leg off the ground, pivot on the ball of your supporting foot and turn your hip and shoulders in. This movement should swing your leg into the heavy bag. When you finish, the heel of your supporting foot should be facing toward the bag, the backside of your hip should be facing the bag, and your body should be turned a full 90 degrees from where it started. Do at least a dozen on each side.
When you do this, do not keep your shoulders square to the bag as it will prevent your hips from turning over. Do not stiffen your leg or kick into the bag. You are using the torque created by your body to swing your leg. Do not sweep your leg inward like you are doing a judo foot sweep. Keep your hands up. This will help teach you pivot without someone supporting your weight, and also help coordinate the movement of your upper body into a round kick.
You see, most new trainees think that punches are done solely with the arms or that kicks are done solely with the legs. The truth is that in order to punch or kick with power, you have are actually throwing each punch and kick with your whole body. You easily generate 30% to 50% of your power just off of your core movements alone. Those the fine-tuned actions of turning your shoulders, rotating your hips, and pivoting on your feet that are involded in that. So remember, form and technique first
. Power will follow after that.