The animation is good. I think the shading when the extended arm is quite odd. Be careful because his pants get bigger and his shading changes drastically. The axis is wrong (I know it's just a GIF) but it might help you to see the mistakes.
I edited the axis so you can see it better (I hope you don't mind):
Spoiler, click to toggle visibilty
I think his arm should look more like this. I noticed that his right (our left) shoulder looks odd too, shading wise.
Keep it up