Not enough people talk about this, I feel. Thanks for shedding some light on the animation techniques used in such an old gem. Very informative and interesting.

I just came. Awesome.

Yeah this show is full of that but the manga is even more detailed while the posing seems even unrealistic at times but the supernatural realism is quite exceptional

Interesting topic. The scene you discuss is of course your own favourite, to each his own, and it is in fact a good scene. I do want to point out though some things. Not to denunciate you but rather more share some more thoughts about that scene, making it even more interesting:
- It is not gravity which is moving his arms outwards again (and of course, gravity would move them downwards, not upwards), but rather more the uncontrolled retracting power after overstretching his muscles. Enhancing what you correctly identified as being helpless/powerless in that very instant.
- The force/strength of the punch is indicated/enhanced by another thing: The camera can not keep up when he was hit.
- Everything what comes after the first few frames gives us more clues about how the protagonist in this scene experiences the "flight": The way upwards has been elongated compared to the downfall. Which already now indicates that he is aware that he had been hit and he will inevitably crash into something, waiting for it in powerless tragedy, knowing it will hurt. But already now, he is in control of his thoughts again. Not of his body, though.
- When he finally hit the lamp, it does in fact hurt and you feel his pain by seeing him suffer for some frames. But this also indicates one rather important thing: A normal human being would have been knocked out. Not the protagonist. He feels the pain and reacts to it, even fights it: His eyes are closed and he even seems to find the strength to shout by forcefully contracting his lungs. A normal human would have had his eyes open, gasp devious and not a single frame would be wasted on showing him "fight" the impact. If that would be the case, we as viewers would immediately think that the person is knocked out, or even dead. This not only is used in animation, but in gaming as well: People turn into ragdolls. The protagonist has the strength to fight the impregnable forces time and gravity itself, indicating that he is not only merely surviving such a beating, but stands (or will stand, in the course of the show) above such puny things.
- Crashing into the lamp gives the protagonist his awareness back, both mind and body. This also explaines why the downfall is rather short compared to the uprise. It felt like he was catapulted 10 meters hight where in fact, it was a maybe 3 meters. This pulls us viewers out of the subjective view of the protagonist back into reality.
- One rather large animation flaw you did not mention, but which is fairly common in eastern animation: The clothing does bump on the floor together with the movement of the body when he hits the ground. This is not how clothing behaves. But it enhances the feeling, that the protagonist is whole and in full control now again, even his clothes stick to his movements. He has survived the attack and is now rigid and strong.
Just some points. It's interesting to discuss.

Informative and funny. Loved it!