Every traditional art and combat sport will tell you that the power comes from the ground up. It’s very true. For maximum power and effectiveness, one must be balanced. In order to be balanced, you need relatively conditioned and strong legs and ankles.
One thing that can drastically alter your balance are leg injuries and also the environment. In a situation such as a slippery floor where you can’t grip the floor, your effectiveness will drastically go down. For one, you can’t exert force if the floor is slippery, and also the tripping hazard is a major concern. This can drastically alter your chances of victory since slipping can have disastrous consequences.