[scythe]

The sixteenth notes in "Crazy Train"[1] are nominally 552 per minute, or 9.2 Hz. Moving a knife at 10 Hz is probably very difficult. I would expect 2-3 Hz is a normal pace for a skilled knife user and 4-5 Hz is showing off.

1: https://youtube.com/watch?v=tMDFv5m18Pw#t=0m32s

[superkuh]

Cerebellar oscillation (in the inferior olive) gate motor control interrupt speed and are generally limited to ~10 Hz in humans.

[john_minsk]

That escalated quickly. Thank you!

[pixelfarmer]

Which is why humans use tech and tricks to get things done. Gravity Blast is one example: https://www.youtube.com/watch?v=ir_KZNsTNiQ