For studying anatomy you should focus on the length ratio ie how long is the leg vs the arm (see spoiler on head to body ratio image). You should also pay attention to how the muscles overlap, and consider how they would be shaded under different light sources. The Skeleton is good to know if you like fleshing up a skeleton, but not as useful as knowing how muscles work/look!
I like the top image; think they would look great with lines. The full body needs some work.
Bring in those armpits - that gap is too huge on the left and looks dislocated.
Tighten those hips - His hips should be narrow and not round. Women have round hips, men have diminishing hips.
Bring in those knees - The knees should not both be pointed that direction unless it's a profile or he is "walking like an egyptian."
The wrong foot - the foot that is currently larger should be smaller, the foot that is smaller should be larger. This will help make it look like he is stepping forward.
If the line art was firm over the sketch, and you made those few changes, I think it would pretty good actually.
I think the "Stop" is 'cause the second image is striking the Drawn Together character Zander "gay" pose