Long time no post. I fixed the legs up and began work on the arms.
The arm in the foreground is well shaped but too thick (compare it to legs).
And legs themselves are realistic but very thick, almost fat: are you making an agile running and jumping ninja or a bodybuilder? In the latter case you might want to increase the width difference between shoulders and waist.
If this is the smallest figure you can draw comfortably, consider making him taller to stretch arms, legs and torso to better proportions with the same widths.