Just found a manga/anime series about female body building called How Heavy Are The Dumbbells You Lift.
The series is basically an out of shape girl who joins a gym to try and get back in shape. One of the women that she attends the gym with has a muscle fetish and although I can't see any actual FMG in it so far there is potential for it.
Plus there are plenty of actual exercises in the series that can be used to actually exercise. Although the series is comedic in nature it does have important keys for real life exercise routines for both the gym and at home.
Right now there is a manga that is currently going (and will be begin releasing in English in November) and an anime. When it comes to that there is three episodes so far in Japan with one episode dubbed into English so far. Of course more episodes will be released over time. Most likely to either 12 or 25-26 like most other anime.
Here is the link to the series on Wikipedia
https://en.wikipedia.org/wiki/How_He...ls_You_Lift%3F
And a link to the first episode dubbed
https://www.watchcartoononline.io/ho...english-dubbed
Hopefully we'll see some muscular women in the series. So far all I've seen are muscular men, but the potential is there.