Glad to see I'm not the only one doing a male nude for the M&A.
You're mostly pretty perfect, anatomy wise, but there are a few problems. I'm gonna be super nitpicky with you, since you've got everything else down.
One of the key problems is that while you've done such a great job on the muscles and bones, you haven't really consider the fatty deposits in the skin much- the muscles have so much definition that the figure seems skinless.
The pectorals are a bit more like horizontal bands than they should be- you chosen to illustrate the upper striations but not the lower ones, leaving viewers with the impression that there's an additional set of muscles above the pectorals. In any case, I've never seen a living man or a photo of a man's chest where the striations are visible- the flesh should cover them up.
Next problem is the muscles on either side of the rectus abdominis muscles (six-pack). There should be two sets- the external obliques and the serratus anteriors. Your figure's side musles have either divided into several shorter muscles or you've attempted to show the ribs under the muscles- in any case it looks like there are many more sets (horizontally) than there should be.
Other problems- the ball of the tibia should a hair more to the right and a little bit bigger and rounder on the viewer's left leg. I love that you included the indentation near the upper trochanter of the femur, but in this pose I don't think it would be quite so accented.
The proportions seem pretty excellent. Might help to add some orange highlight to the rest of the piece, to make his fiery corona more believable.
