I love this! But I'd agree with Chip that the upper body anatomy, especially, looks a little skewumpus; his left arm looks a big long-ish and awkward and his right arm looks like it's made of silly putty - the elbow isn't distinct and it looks like it has no bones. But I also love seeing the little details like his boxers!
Also, I literally thought he was holding a dumbbell in his right hand - I didn't realize it's a bag, so be sure that your details are simple to read so that the story doesn't get lost.
I look forward to seeing more of your work here - welcome!