This is very interesting to me as I can't stand when someone tells me they are throwing a side kick and I look at it and it is a round house kick and they don't know. But I have identified a common problem that causes this that I will get into later.
I totally agree with Mr. Billings, that there is no chamber with the lead leg side kick as in Long Two if your intent is to "jab with it. My understanding is that in the early days Kenpo guys on the circuit were known for groin kicks [i did not say or mean to imply side kicks to the groin] and for "jabbing" with their front leg side kick. [Doc, in your opinion, is this historically correct?]
As Mr. Billings pointed out, this lead leg side kick can be devestating, but after the student learns how to use proper body mechanics of pivoting, lining the hip and heel up, and thrusting. So to get to this point, I start at the begining.
I teach beginers front leg side kicks, to the height of waist level or below. For example, in a left neutral bow kicking to 12 with the left leg. [this is teaching beginers to side kick, I'm not talking about the Long 2 kick. This is how I approach getting the body mechanics down for a thrusting side kick, not snapping.]
I have my students chamber their left leg with their knee lifted and pointed to 3 o'clock. Sometimes I'll actually hold a pad at 3 and make them knee it before throwing the side kick to 12. I also have them pick their foot up and keep it flat to the ground, not toes pointed down. The supporting leg foot, r foot, will as they execute the side kick, pivot on the ball and end with their toes pointing to at least 3, but the strong kickers end up pivoting their support foot so their toes point to 6 when side kicking to 12. Again this is developing for the thrusting side kick. A snapping or jabbing front leg side kick does not need the supporting foot to pivot.
I have seen many students that will end up with a perfectly formed side kick foot and think it is a side kick, but when I watch them execute the kick, it comes out as a round house and ends up with side kick foot formation. When I futher examine their execution, the problem usually stems from their chamber. 9 times out of 10 they have chambered the leg with their kicking foot behind the supporting legs knee. From this position the leg arcs out like a round house, their is no thrust. If their is any thrusting motion from this chamber, it comes in the very last part of the kick. I am sure that there are individuals that can pull this off from this chambered position, but to eliminate my constantly correcting this, I teach chambering the foot in front of the supporting leg.
Why not with the toes pointed down? Only because in my limited opinon, it is something else the student has to remember to do, pull the toes up, straighten the foot, thrust out the heel. The foot starts from being flat on the floor, so I have my students keep their foot in that position and just lift it up. As Mr. Robertson pointed out, it can be done from this position. I can do it from this position and I originally learned from this position. But I have corrected so many errors in side kicks and a lot of them were corrected just by having the student pick the foot up flat.
Again referencing the kick in Long Two, you pick the foot up flat and snap or jab it. The ones I have seen picking their leg up with the toes pointed towards the ground in long two, again, usually [not always] end up snapping out a round house that has a the foot formed like a side kick at the end.
After they get this down with the pivots pretty good, then I will introduce rear leg side kicks. They take more time to execute, but set up correctly, they have their application and can be extremely strong.
Some of you may not agree with my methods, but my students throw side kicks that are side kick and round houses when they are suppose to throw round houses. This is my limited experience. I make no claims to "rule of thumb".
After the proper body mechanics are learned and become natural to the individual, they can execute devasting lead leg side kicks with little chambering as Mr. Billings stated. And as previously stated, the targets I also teach are the knee and shin.
Just my perspective, and I'm sticking to it.
Teej