The current record is 15.66, achieved in 2022 by Collin McClure. To me, it looks like he's kinda cheating - running with almost all of his weight on his feet and just slapping his hands on the ground.
The previous record, by Kenichi Ito, was 15.71, set in 2015. This looks more like truly running on all fours. He's clearly using all four extremities to generate forward motion, with all his weight transferring to all four limbs.
With good preparation, I'd imagine a professional sprinter, or someone like Mondo could crush this record. It would be interesting to see what Nick Simmonds could do - maybe too old and not enough raw speed. Hobbs Kessler with his climbing skills? Maybe too short for him. Athletes from another sport may be really good for this also. Maybe rugby, gymnastics, wrestling, martial arts.
