A question on senders

I just want to as a few questions regarding senders before using them for martial arts training when I find a gym with a good spring floor. When rebounding do the ankles absorb any force at all, or do they extend on impact as well for power generation? Also if rigid straight legs are the way to go, would it be appropriate to use a little knee bend on contact with the ground in hope to generate more power? Wouldn't having more knee bend on contact aid in generating more power for punching (not absorbing) through a springed floor?

the knees and ankles will bend even if you lock them out while punching the floor. sometimes this can only be seen with a camera in slow mo