Is it necessary to pivot your supporting foot or is it better to just step in and plant your foot, then kick. I know everyone always says to pivot but I’ve seen probably hundreds of kicks done with no pivot at all. They just step in and plant their feet and then power it through. It seems safer for stability since I don’t like the idea of the only contact with the ground being on the ball of my foot. It seems very easy to fall over, one little push and you’re done. And also, when you spin around like in Muay Thai, you turn your back to your opponent. This seems very risky.
Ask your teacher! 
I’m not just being facetious, but different styles do different things. Some of them have a logic behind them, some of them don’t. Personally I go with pivots, but my roundhouse kicks are crap!
BTW, since Muay Thai is one of the tried and tested badass MA do you not think it might actually not be that risky kicking the way they do if taught properly…?!
[QUOTE=hulkout;837205]Is it necessary to pivot your supporting foot or is it better to just step in and plant your foot, then kick. I know everyone always says to pivot but I’ve seen probably hundreds of kicks done with no pivot at all. They just step in and plant their feet and then power it through. It seems safer for stability since I don’t like the idea of the only contact with the ground being on the ball of my foot. It seems very easy to fall over, one little push and you’re done. And also, when you spin around like in Muay Thai, you turn your back to your opponent. This seems very risky.[/QUOTE]
I like to pivot.
Bas Rutten says it’s not necessary.
I pivot myself, it allows my kick to go alonger distance.
I pivot as well especially with a front-leg round house kick. With rear leg round-house kicks you can step into them instead of pivoting. It puts your hips in roughly the same position at the end of the kick.
Round House kick
There are basically 3 types of round house kicks and 3 different chambers.
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Japanese which strikes with the ball of the foot has a lateral chamber and the toes point toward the opponent, if the opponent is in front of you, as you progress through the kick and the culmination of the kick progresses the leg is extended perpindicular to the target. prior to contact for last amount of power the foot is pivoted so it is at a ninety degree angle to the attack much like the bottom of the letter L if it were with the left leg. After contact the upper body is reverse rotated adding snap and re-chamber.
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Korean much as above except with the Americanization of Korean arts the chamber was changed from a lateral to as in a front kick and then it rotates over and focuses past the target with full rotation of the hips and pivot foot so the toes have rotated past the point mentioned in the Japanese arts butcontinues and is pointing away from the opponent. This technique has more penetrating power but slower recovery after the attack if you miss or it is blocked. This technique has a longer lever arm but does leave you at a disadvantage if you miss.
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Mu Thai much as above but with a looser chamber and longer lever arm and more follow through very powerful but again to recover you must spin or try to reverse the motion which is very hard to do.
Biomechnically the japanese type leaves you ready to counter with a knock out punch as opposed to primary kicking styles like Mu Thai and Korean arts. The philosophy is also different thus the kicking technique is different.
Hope I wasnt too wordy BTW in all styles at the moment of impact the whole foot shoul be making contact with the ground/floor. KC 
I was taught a roundhouse very similar to the “#2” kwaichang discribed.
I pivot when being graded as my style teaches it that way. I step into it when actually using the kick. I find it easier to drop my center of gravity if it’s blocked. Dropping the center of gravity is the key to recovering from this style of round-house.
KC, I was taught a roundhouse kick very similar to # 2 as well. How do you teach it given your diverse background in MA?
[QUOTE=MasterKiller;837737]I like to pivot.
Bas Rutten says it’s not necessary.[/QUOTE]
That’s cause Bas turns his foot “out” before he throws the kick, and he’s a freak.
[QUOTE=Judge Pen;838630]KC, I was taught a roundhouse kick very similar to # 2 as well. How do you teach it given your diverse background in MA?[/QUOTE]
I was taught #2 in CMA, but now only use the Muay Thai roundhouse.
What do you mean how do I teach it ? Which one or comb of kicks do I like and why ??? KC
Both-ish for me…I was a shown to pivot on the ball but practicality kept the heel of my foot like within four centimetres of the ground. When I was done with the pivot which occured while I was still in motion (upper portion guard up) forward, I had my full foot (except for my arch) as support 180 opposite of the place that I was kicking (or directly behind me).
But in Ernie Moore Jr.‘s Kung-Fu, Squirrel; I learned from a tree to pivot on the Heel of my support leg. For me it was faster return to stability. Does other than mess with my Achilles’ tendon (badly). And I just Like it a whole-bunch. It feels super good. Also striking area on me is the meeting of leg and foot (inside) but on the outside of the upper or top foot…around where I slapped when we did crescent kicks in Kung-Fu class.
I No_Know
Tried the heel thing at one time but felt unstable, if you are pushed prior to impact during the pivot then balance will be hard to maintain. Also with a full pivot recovery is slower. All depends on how you use the RH kick and what you use it for. Also a decreased range due to the pivot place KC
[QUOTE=kwaichang;838694]What do you mean how do I teach it ? Which one or comb of kicks do I like and why ??? KC[/QUOTE]
I mean if you are teaching a begininer how to throw a “basic” RH kick, which of the ways that you describe do you teach them in the style that you train under now?
In kyokushin we have both the “MT round kick” and a more “snappier” kick to use at closer range, since we tend to kick high off the clinch and punching distance.
Can you describe the Muay Thai RH Kick?
Youtube and do a search for Muay Thai Round kick.
A video is worth 1000 words 
I pivot.
When you step into you don’t get enough rotation of the foot, unless you’re freakishly flexible in the knee. And if you don’t get enough rotation you place undue torque on your knee that can lead to problems.
My current teacher has us rotate our foot 180 degrees, which is I am not use to. I usually only turn ~135+ degrees, but I also usually pull my kick, so I don’t need full rotation in those cases.
I have never had any balance problems with that method.
I also don’t like the step in because it’s a obvious visual “tell” for what your about to do, giving a perceptive opponent more time to set their defense and counter.
One thing, if you don’t pivot, what happens to your knee/support leg, if you get counter -kicked there while your leg is in the air ( typical MT counter) ?
[QUOTE=SanHeChuan;838911]
I also don’t like the step in because it’s a obvious visual “tell” for what your about to do, giving a perceptive opponent more time to set their defense and counter.[/QUOTE]
It certainly can be. I will step in from time to time, but the step is disguised with other techniques. It’s not the usual way for me to throw the kick, but it’s in the arsenal.
I think the MT kick is easier for people with poor hip flexibility to execute than the other two methods that we’ve talked about.