I really like the picture overall. The model has such a natural look about her and a strong look (unlike a lot that I see on here). She's not too skinny which makes her look healthy and with the pose she is doing it works amazingly. I feel like the pose is kind of a typical "male" pose yet the way she does it and with the look on her face make it less manly and instead kind of gives her a "hey I'm just being me" kind of vibe. As far as the photography goes I love it. The light behind her head works great to have the focus on her face. One thing I have to say is that I don't know what is on her legs (and there seems to be something on her stomach and lower arms). It kind of looks like sand or just really dry skin. It makes her legs especially look kind of like an old lady's. However I really enjoy it overall.
This is an absolutely brilliant photograph to me. I don't know if the lighter hues of the shadows was done post-production or if you used a filter on the camera or something else but it works very well.
The color of the background is also a perfect choice; it's complimentary to the hues of the skin but with the blue hues in the shadows the subject ever so slightly merges with the background which gives the photograph a softer appearance. Speaking of color, I generally prefer greyscale photographs but this is a great exception. In fact I doubt it would work as well in greyscale, though with so many things gone right it should still guarantee a spectacular result.
The composition in my mind couldn't be more perfect and I also enjoy the model's position. ~Goddess-Loves mentioned she looks masculine but I would rather think of it as strong. Indeed it's not the most elegant pose but it's still very feminine in its own regard, not to mention quite sexy.
Regardless of the fact that I absolutely love this photograph there are still two things which I think could be improved and they both have to do with the lighting. In general the lighting and contrast is amazing but I feel like the highlight on the model's forehead is slightly too strong. I also think it's a pity that the hair on the model's leg is highlighted due to the light source. It's a bit obtrusive to me.
I suppose it's slightly odd to say something about the looks of the model given the fact you—being the photographer—had no input in that so let me just praise you on your fine choice of selecting models. If she came to you then I praise you still for presenting her beauty so well.