system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening internally when a boxer 'loses his feet' ?

When a boxer has the difficulty to move around, what exactly happened inside his body and where did he need to get hit in order to 'lose his feet' ?

Clarification: I don't mean a knock out. I mean not being able to move around freely; it's like like your legs are resisting.

(edit: word stuff)
gpt
Well aside from the whole "O shit that hurt!" part of the brain when you take a massive body shot. It's also a biological reaction. When you receive that kind of trauma to the internal organs. You're body reflexively goes into survival mode. As it's not sure exactly what the hell just happened. So it ramps up blood production to start healing or clotting blood if it needs to and it's starts loading those new blood cells with more O2 to aide in this process. It also starts to constrict the blood vessels of the extremities to increase blood flow to the torso and the vital organs of the body. A similar process to that of hypothermia. It then decides that the "pain" is to distracting so it starts shutting down nerve function and your receptors. So fundamentally, your legs and arms lose circulation briefly, reducing the O2 to those cells and nerves and then the nerves that are really important to, you know muscles movement and stuff are turned off. You body doesn't know your a dumb ass boxer. It's just knows, "Holy flippin' hell something just hit the crap outta us! Save all the inside stuff, toes are for CHUMPS!" Is basically what happens.