A majority of the Karate side kicks I have seen are what Taekwondo-ists call side snap kicks. These are great for practitioners who are as comfortable striking fairly deadly blows with their hands, and use their kicks in complement to their upper body weapons... or when their upper body weapons are occupied. Side snap kicks angle the body close to the kicking leg so that there is triangulation - a method to help engage the upper body to re-engage the opponent once the kick hits or misses.
In many Taekwondo schools, however you see a propensity to use the foot as the primary weapon --- or as a substitute weapon. Not to say that there are no short range kicks. But kicks are practiced and valued highly for their ability to hit the mid to long range target.
The sliding or stepping side kick (or the penetrating side kick) is a tremendous tool. Generally the exercise starts with kicking leg closer to the target. The back foot steps behind the kicking leg, with heel pointing more or less toward the target and then the knee is brought up (like for a front kick) and then piston-ed out to the target. The body is not triangulated like the Japanese or traditional yoko-geri side kick, mostly the body is aligned to the kick and together generates immense power over the distance covered.
We were practicing this sliding side kick today, and I'd like to discuss some ways to troubleshoot this weapon. Upon impact to the target:
1. If the large toe and the second or third toe is raised - you have stepped up to the target at an angle. Meaning instead of going to the target straight on, you have tended to stray toward the side of the front foot (so if your right foot is forward, you have stepped diagonally to your right). Sometimes the target shows you this by rotating around the person holding the striking pad.
2. If all your toes are raise, but your heel is still on the floor - you have not stepped and covered enough distance and have over stretched your reach.
3. If your toes are bunched up, your heel lightly lifts off the floor - this is when you have stepped either too far to the target OR you have not 'engaged' your COG over your support leg. The resultant is that you strike the target lightly and then you fall away from the target - a major problem for many beginners.
4. Your foot is flat on the floor, but you stumble forward (if your right foot is forward, you stumble to your left) after you kick - this is when you have probably leaned too far and triangulated yourself like the shotokan or karate side kick yet are trying to do a sliding side kick. In the end you trip up yourself.
5. Your heel is directly in line with the target but you spin when you try to 'recoil' your kicking leg - this is when you have not kept enough core body tension OR if you have tried to rotate your body too hard whilst doing the kick.
The best side kicks are done visualising your upper body as a bullet train that is set for the target. The kicking leg is picked up off the ground and rotates or corkscrews into the target through the second half of the kick. The basic premise of the side kick as taught to beginners (to pick up the knee and then shoot the leg straight into the target) is fine but does not allow for higher-level sparring skills to be integrated into this fine kick.
For shorter range targets (like for those in a CQ or self defence situation), the knee is not picked up off the ground, but stays close to the support knee. The heel of the kicking leg is picked off the ground, pointed to the desired target then pistoned upwards into the opponent - that's the side thrust kick. But that's another kick altogether.
taekwondo side kick defence and timing
Won-hyo: Deflection of Side Kick
Private Lessons: Toes, Turns and Twists
Snap, Cracle, Pop Go My Hips.
Won Hyo by DOnuts
The Story of Won Hyo
Tekki: Low Side Kick to Knee (More Troubleshooting)
Jumping Side Kick
Side kick and Cover
Why Yet Another Set of Side Kicks?