>>8712923You need the foot you're putting power behind to be on your toes so you can get the maximum hip snap behind it. You can't accomplish this with both heels on the ground and it stifles your hip twist. In fact you need to be on your toes to move around in boxing for that matter otherwise you're flat footed. If you're flat footed you're slow. Same with kickboxing.
Overextension has nothing to be with proper foot movement. In fact it would happen more often from being flat footed due to an inability to get your feet moving quick enough to step in on the punch. Instead you'd be reaching.
Watch any boxing fight, training, video or anything. I know Tyson is the meme to go to but every shot he throws is with proper balance. If Tyson misses he will not lose his center of balance, and surprisingly his heel is always up on one foot.
https://youtu.be/z5rtp8guIZoYou wind up flat on your back from being squared up and flat footed.
