Im not sure, I would assume its about on par with MMA fighters but because it inst regulated in Japan they dont have to disclose it.
EDIT: Search for the K-1 events from Vegas cause they would have to disclose to the athletic commision...
"If you get hit and it hurts hit him back you not knocked out yet."-Joe Doerksen
The Toxic Terrors (FFL)
Demetrious Johnson*Eduardo Dantas*Emanuel Newton*Will Brooks*Michael Page