As my kicking background is not japanese- aren’t these two completely different kicks?
Ushiro geri: (if it’s a back kick)
there’s a little trick to get the footwork & balance faster.
Basically, you perform the technique with a slight jump forward. Just an inch.
That way, your standing foot will have it a lot easier to assume the 180Â° position.
It’s difficult to explain without teaching right next to you. You shouldn’t gain height, you just use a little momentum to “fall” better into the kick’s last phase.
Try it a few times and perhaps it’ll help you.
Some beginners found this way more natural to pick up.
Stretches won’t improve your side kick force output. If you can kick at a certain height, that’s enough.
Depending on your technique, it may theoretically be better too be less flexible.