Most of that kind of image is shot with fairly contrasty light. They want their muscles to show in detail. I would say a light about six-eight feet up and about 60 degrees off center. Then check and see how that balances with all the gym lights. If need be, a fill light right near the camera. You could also try some back lighting to set her off from the background. That's all for poses.

For actions use some of the weights and benches and/or machines. Maybe reduce the contrast a bit.

Just suggestions. I shoot nudes and usually do not want that much contrast. But body builders do.

I did a studio workshop with a female body builder. The key was directional light to accentuate the contours. It is really not too different than a figure study, but she'll be clothed--a little. As rmorrison stated, don't neglect to pose her in ways that allow her feminine curves to flow along with the musculature. Be subtle and remember less is more. Encourage her to have her hair done. I'm guessing this will be a set of portraits rather than an environmental workout set. But that's an idea too. Having her posing with weights doing lifts etc. would make the muscle groups flex and stand out. The ladies have longer toned shaped muscles as opposed to the Arnold large bulk.

Directional light, use a grid to focus the light. Try back lighting, and highlighting her hair. And her face is ever important, so be sure to get her expressions right. If you have fun, she'll have fun and you will be successful.Using the Gym as an "environmental" or location background can be susceptible to distracting background elements and mirrors and chrome reflecting the flash, so really watch. Shooting wide should blur out the background, but can pose pose problems with flash sync. Be sure to practice with the off camera flash(es).

Good luck and good shooting. The lady builders I've met are wonderful, confident ladies who are quite proud of their bodies and are used to posing. If you're having fun then she'll have fun. Suggest that she bring a friend to help with her outfits, makeup and hair. She will also help her relax.

The D500 really shines in the focus department if you do a lot of wildlife or other action and the faster FPS and bigger buffer are nice if you have the need. Realistically the D7100 is a very capable camera and I would think about optimising is capabilities before changing. You may consider exploring your focus system with this: http://backcountrygallery.com/secrets-nikon-autofocus-system/
This is also excellent for making your D500 walk the walk, so it may be worth your while. I do not wish to downplay the D500, but the D7100 is really decent.
Of course, if you want a new camera, go for it!

Thanks Donna,
I certainly wouldn't give up LR, or any other image editor I use (ie, On1 and others) either.
I doubt that there is much here that cannot be achieved with Lr, On1, PS, etc., in terms of general editing, such as the Lr basic panel, Tone curve, color adjustments, etc., etc., Although as you now have the program, you will be the best judge of that.

I do really like the Topaz plug ins, and I own all 17. My workflow is generally something like this: Lr>On1>Topaz (if necessary)>PS (if necessary). My concern, as I aluded to in my previous question, is this: Do the Topaz plug ins automatically load into the Studio program, and then after I do my basic editing would I then go to Studio and access the Topaz plug ins from there. If there are no dramatically new image editing features in the Studio program (which I don't know, as they do offer 10 or 24 "adjustments"), I am wondering if there is a benefit to purchasing studio, or just continuing using Topaz in my workflow, as I do now. I am also wondering if the new adjustments are different from the 17 Topaz modules I own.

Steve