The Japanese really have the best stuff.  There was a Zenra series from the publisher Soft on Demand which featured totally naked women doing sports or other things.  There was a naked ballet, naked judo, naked gymnastics, naked swimming, and a whole bunch of others.  And for those most part these were actual high level athletes, and some of them wore masks to hide their identities because they were semi-famous or up-and-coming or something.  Unfortunately (for at least a number of us), the back end of the DVD had hardcore sex.  But the beginning parts were often training montages and a mini-performance, both clothed and naked. 

Having said that, I'm not even sure if this one is from Soft on Demand.  But in any case, it is a well trained fighter.  Completely naked of course. 

[Permission to view this media is denied]

Another naked workout/stretching clip.  I guess this overlaps with cam girls maybe?

She seems to be a fitness model type who might actually be somewhat mainstream now.  She still does nudity, but her Instagram looks like she's a serious glamour model.  I think this is one of her early videos before she made it big (she has since gained muscle and maybe had some aftermarket parts installed, although I'm not sure.  She looks really good today).  

AND, we get to see her pussy.[Permission to view this media is denied]