Compare the different styles of mawashigeri from two diferent JKA instructors.
Kagawa sensei - Mawashi Geri (JKA shotokan)
Tanaka sensei - mawashigeri (JKA shotokan)
http://www.youtube.com/watch?v=3QUZ7DuGAbQ
Mawashigeri or (roundhouse kick) in traditional karate the ball of the foot is extensively used, although the shin and instep are also used to attack softer meatier targets.
We have all seen muay thai kicks in action and the conditioning of the shins on professional muay thai fighters is something to behold, because these athletes have spent countless hours in their training conditioning their shins to be able to absorb so much punishment in that area.
The section of the shin that is used to strike out at their opponents is the bottom third of the shin just on top of the ankle. A well conditioned shin is a formidable weapon but at what cost to the athlete?. Unless you have a professional instructor that knows what he is doing you could be headed for a very uncomfortable middle to old age suffering from arthiritis and the ability to walk normally.
You hear some really grazy things about how to condition the shins, things like kicking bannana trees (ala Van Dam in the movie kickboxer) or rolling bottles or rolling pins on your shins, or hitting your shins with a piece of wood etc etc. all so you can deaden the nerves and not feel any pain.
You should never kick at or hit your shins with anything that is harder than the human bone.
All the above would definetly be bad for your shins/body in general and will have a very big impact on you in latter life, the people that advocate such training methods are silly / crazy, actually if you come across someone like that just get out of his gym because he doesn't have a clue on the subject matter and in the end you will be the one to pay the price.
Using such silly and brutal methods to condition your shins might actually have the opposite effect and weaken your shins not strengthen them.
The best way to condition your shins is on a heavy bag or focus thai pads held by a partner, or actually sparring and subjecting your shins to dishing out on your sparring partner while learning to block them as well, also you might get a partner to kick at your thighs and then return the favour, make sure you both wear shin pads and go easy at first, then work up the intensity but it shoul never be full contact round kicks.
Ten minutes a day (five minutes each leg) conditioning your shins in this manner should be enough to make them very strong over a period of time maybe six months, but if you stop the conditioning then you will lose it, it has to be maintained.
Muay Thai round kick
Like i mentioned earlier traditional martial arts use the ball of the foot, and they do so for a reason the ball of the foot is naturally conditioned every day of your life every time you walk, run, jump you are conditioning the ball of your foot so in a way your every day activities are already condtioning the ball of the foot.
The ball of the foot might not be as effective as the shin but if you put your hips into / behind it coupled with the smaller area the ball naturally uses it wouldn't be too far away from the force generation of the shin per square area.
Also the skill required in delivering a traditonal mawashigeri with the ball of the foot is greater than the skill required to deliver a muay thai round kick, this means it will take you longer to become effective with the traditional mawashigeri kick than with the muay thai round kick.
The other advantage of using the ball or the foot for effective roundhouse kicks is that you have less chance of hurt yourself in the execution, most people that condition their shins still hurt themselves when they strike with the shin especially if they spike themselves on a elbow or another bone of the body.
Once you have learned to deliver a mawashigeri with the ball of the foot effectively in the traditional karate manner, the execution and mechanics of all other types of round kicks will come more easier to you than someone who is from a muay thai background and tries to learn mawashigeri with the ball of the foot.
That is if you can deliver effective round kicks with the ball of your foot converting to shin or instep is made easier, just ask people who never kick with the ball, and you will see that they have real problems converting to the ball.
I think the shin along with the ball should be further conditioned if you are parcticing a traditional martial art, but not so you can mindlessly and continuously deliver round kick after round kick not worrying about where it lands and which part of the body your attacking.
Hope some of the information has been useful and good training to you all.
Ramon Dekkers Muay Thai