I'll focus on the second one.
You want to know about the anatomy of it, well the first thing that sticks out to me is the arm muscles. Particularly the bicep and it's connection to the elbow. The bicep looks 'boxy' when it should be more curved (even the most defined biceps are curved rather than square like this.) The elbow seems some how elongated. Try to think of the elbow as a sphere that connects the two parts of the arm, then you will see that it's not possible for it to be how you have drawn it.
The head also seems to jerk unnaturally forward.
But it's not the anatomy that really throws me off here, nor the design (The design is actually pretty cool). But the shading you've given to the chest seems bizarre to me. I don't know if that's a style thing you have created or if you've seen it in a manga style that I haven't seen but personally it confuses my eye. It makes me wonder if his chest is moving with speed and they are motion lines? It also makes me feel like he doesn't have another arm, sorta like rayman.
The hand is pretty well drawn though, seems like it would have been a tricky pose to draw the hand in too so a good job there.
Someone else should do leg anatomy because..well I don't really know!