I'm not sure realism was ever the point of TOS. Things like the Gorn fight are absolutely fantastic because they're so absurd. They go full circle!
Actually, yes, realism was exactly the point. Roddenberry's whole goal was to create a series that treated science fiction in a serious, adult manner and brought the same naturalism to a series set in the future as you'd find on any cop, lawyer, or doctor show of the period. But realism is relative, and what constituted realism by '60s TV standards seems more staged and artificial to today's more savvy audiences. And admittedly TOS drifted somewhat away from that initial naturalism over the course of its run.
This is what a properly placed "neck chop" (commonly referred to as a ridge hand) will get you:
http://www.gorillafights.com/fightvideos/707/karate-instructor-vs.-pimp.html
Ohh, I feel a little unclean that I watched that. I only did it in the name of science. It looked like the effect was to temporarily incapacitate the opponent and leave him unable to move normally for some moments. I'd imagine it could cause some neck and spinal damage and require hospitalization. And clearly it doesn't induce unconsciousness except maybe for a few short moments; the opponent is more dazed and immobilized. I assume the mechanism of injury/incapacitation is the mechanical shock from such a sharp blow.
Plus it has to be delivered in the right place, I assume. The '60s TV-hero action chop tends to be directed all over the place, and any impact around the neck, shoulders, or upper back will cause instant and prolonged unconsciousness in the target. It's also often a very quick, down-and-up chop rather than the decisive
wham on that video -- though Kirk himself tended to go for more of a two-handed hammer strike a lot of the time, so at least it looked like it had some force to it, more than Peter Graves' technique on
Mission: Impossible, say.