This is another time that I did two sketches of the same pose during the same sitting. It was a habit I was in at the time, I was in a rush and the first sketch would be out of proportion or the stance was all wrong so I'd start another one. I don't really do that much better now, I'm just more inclined to wipe out and re-draw on the same sheet of paper. At any rate these two similar sketches (this one and the one I'll post tomorrow) give me an opportunity to go with different ideas on each drawing. So I double my mileage.
Many times the coolest looking poses were what we call gesture sketches. They're 3 minute poses which should be a bit physically challenging or at least something the model couldn't maintain for a twenty minute stretch. So we end up with a lot of very rough sketches that would be the coolest art we've ever done if we could finish it.
Sometimes the model allows photographs to be taken which could help with that and sometimes you can find anatomy books or similar photos on the internet which you could use to guide you in working out the musculature of those figures. Often it's a lost cause. Whenever I do find photos on the web it's never really right, it's an arm here or a leg there and the head posture in a third place. it's actually kind of a pain and sometimes doesn't really seem to match. Getting a model to pose like you want is immeasurably better no matter what your model looks like. A fat old woman posing as a muscular young man is going to assemble better than a hodgepodge of unrelated photo references in terms of form and shadow and where all the parts connect.
I based this costume in part on traditional Mongolian wrestling harness