Concerning the activity of doing kicks in slow motion....

NO NO NO NO NO! WRONG WRONG WRONG! DON'T DO IT!


Unless you're a gymnast, or want to be able to hold a kick up for a long time to impress judges while you do forms, then fine...

...but if you want to be a martial artist and throw a kick that's faster and stronger, these are then not the exercise to incorporate into your regular training. The muscles required to hold up a leg are NOT the same muscles required to throw a kick w/ more acceleration and force. You are far better off doing plyometrics or any other form of dynamic resistance (such as kicking a heavy bag or kicking w/ resistance tubing) that simulates kicking as these exercises recruit the fast twitch muscle fibers in your leg. Fast twitch muscle fibers = explosive power. Holding your leg up will not give you explosive power!

That said, they're fine to throw in every now and then for variety's sake, but not if you're goal is to throw a kick w/ speed and power. If the martial art you take is a full contact sport, you want to focus more on fast twitch explosive power strength so than slow twitch static muscle strength.