The Kyokushin kick vs Thai kick

[Kuma]

we keep our support foot firmly on the floor!

Simple physics, the whole foot has more grip than the ball of the foot.

Sure a sweep will take out the support (back) leg, but should your opponent evade your kick and punch you (your back leg is still on its own at this time) you have a better chance of holding your position even double up the strike to the head.

This isn't across the board though, it's more up to the individual kicker. Some of the best kickers rise up slightly on the ball from what I've seen.

Watch 1:25 to see Kenji Midori in action.

[bushido_man96]

we keep our support foot firmly on the floor!

Simple physics, the whole foot has more grip than the ball of the foot.

Sure a sweep will take out the support (back) leg, but should your opponent evade your kick and punch you (your back leg is still on its own at this time) you have a better chance of holding your position even double up the strike to the head.

I have to raise up on the balls of my foot a little bit to get a good pivot going. The whole foot does have better grip, but also causes more friction, thus slowing down a kick. And me being a bit of a heavier guy anyway, I need all the speed I can facilitate. So, I'll usually pop up on the ball a bit while I turn or spin, then have the whole foot down on the ground when the kick lands.

[sensei8]

I don't think anyone can do many high kicks and/or any kick involving a turn without one not ever so slightly raising their heel. Try walking without lifting your heel, it's not conducive walking smoothly.

Most kicks, while the kick is transitioning towards a target, the heel of the supporting leg will lift. Whenever I do a roundhouse kick with my back leg, the heel of the supporting leg has to lift to complete the transition, but at impact, my heel is solidly resting firmly on the ground.

[Hawkmoon]

I don't think anyone can do many high kicks and/or any kick involving a turn without one not ever so slightly raising their heel......

....

Most kicks, while the kick is transitioning towards a target, the heel of the supporting leg will lift. Whenever I do a roundhouse kick with my back leg, the heel of the supporting leg has to lift to complete the transition, but at impact, my heel is solidly resting firmly on the ground.

Some senseis I've worked with always pick up students when this occurs, ....for as much as I brashly say 'firmly on the floor', I have to admit its appears to me to be a matter of timing.

The back foot does lift to allow the body to swivel easier, if this is when you are observed then you are said to have you heel of the floor.

If you are observed at the moment of contact....well done there is only about 6ft between the two points .....

The heel will rise when you recover!

Like I say timing; have I done this? yes, have I corrected this? I hope so, will I do this again? yes its an involuntary action IMO.

A fight is fluid your attacker will not stand and wait they will move which will in your subconscious mind have you extend to 'still' try and make contact with your target......up pops the heel for the extra 2-3 inches!