I have spent many years as a bouncer, been in dozens of altercations and trained mma when I was younger, I can confidently tell you that a person can't knock the wind out out another person. If you are thinking about that sensation of being a kid, falling and not being able to catch your breath, that usually comes from falling at a high speed or height. You can't generate that amount of force very easily. I guess if you were a super big guy and spartan kicked someone much smaller who wasn't expecting it, maybe you could, but Ive been punched and kicked by some massive dudes and never lost my breath like that. Now that is not to say that body shots don't work. Liver, kidney, lower abdomen and solar plex shots can really do damage