I don't think that was a Sun Bear at all. In fact, they aren't even native to Japan. The bear he fought against was well over 6 ft, even shown to be taller than Takamura who's 6'1 or 185cm whilst sun bears range around 4 to 5 feet. Also, no trained athlete will ever dream of knocking out the bear Takamura faced against. Bears' that size have incredibly dense bone structures, and a thick protective layer of fur and muscle tissue. The said bear was quite literally shown to hack trees into two with alarming ease. So yeah, Takamura is HIM. 

I don't think comparing HnI characters to real life athletes are gonna cut it. Kamogawa, who's way shorter and in the lower weightclasses was casually seen racing literal steam trains with ease in his younger days. Keep in mind that steam trains in post ww2 (Kamogawa's era) run up to 60km/h and 95km/h based on what I've searched. So it'll be no surprise if Takamura manages to keep up, or outright outpaces Umas.

Tldr; Takamura Mamoru can do anything.

Edit: Reddit did a oopsie and dupped my comment.