Thanks for the feedback, everyone. It's really helpful. Here's the latest:
I don't want to create a world populated by muscle men, so I've made a character with (hopefully) more average proportions on the left.
Regarding "drag" of the feet -- I really meant let the toes lag behind the foot more in the passing positions.
I've made the toes point backwards more on the passing frames. Hopefully that seems a bit better?
The elbow could use a bit more bend, but yeah, it's tough at this scale. On the movement back, try pushing the elbow back one pixel and adjusting the rest of the arm around that to see how that works.
Here are the characters with the elbow pushed back further, and a more pronounced arm bend:
Now my concern is that perhaps the bend on the forward swing isn't pronounced enough to match the bend on the back swing - or am I just imagining that?
Regarding the "robot" feel and the shoulder [...] the number of pixels it moves is actually fine -- it's just how quickly (or gradually) you allow it to transition between those 3 pixels that defines the subtle way it comes across to the viewer [...] The major point of pain from my perspective is how the shoulders move (and how they make the hand have to "flop" forward to keep the inertia correct.) [...] I think the (ease-in and ease-out) speeds of the shoulders' movements are more to blame than the movement of the arms and elbows themselves.
I think I've cleared this up - it no longer reads to me like he's thrusting his shoulder forward. This was a tricky one because I read that the shoulder moves first, then the upper arm, lower arm, and hand. But if the shoulder is only moving one pixel, it moves the whole way immediately.
Regarding the "lean" forward -- I think it's actually fine as-is if he's walking fairly slow like an average person might walk to get something to drink or go to do some other basic task.
Yeah, I can see how there's no need to make the character on the right lean forward. I'm not so sure about the character on the left though. His head is one pixel further back relative to the shoulder than the head of the character on the right, and it reads to me like his posture is unusually straight. I've tried pushing his head forward slightly as he walks. Do you think this looks more natural?
This reference has helped me a lot in understanding what actually happens on walking and jogging, and you can vary lots of parameters.
https://www.biomotionlab.ca/demos/
This is great. What I notice immediately is that the default walk seems pretty unpronounced compared to walk cycle references and guides. If anyone is interested, I converted the side view into a (very poor) 4-frame gif:
I particularly like the way you have the hands lagging behind the forearm, looks very natural and relaxed.
Thanks. Unfortunately I've found that too difficult to include in just 8 frames now that I've extended the reach of the arms, because the arm would have to dwell at full extension for 3 frames while the hand moved out and in. For this character I want it to be as neutral as I can make it anyway, so perhaps that hand movement is too relaxed for my purposes.
We should probably see some minor changes to the silhouette of the torso as it turns. Right now it feels like the shoulders are moving but the chest isn't.
I'm not totally sure where to start with torso movement. I feel like the torso in the 1st and 5th frames would have to be different because those are the frames where the arm and legs are fully extended. I've tried modifying the thickness of the torso by one, but it just feels like it's popping in and out sporadically; it doesn't feel like movement. If I want to communicate movement rather than a binary appearance and disappearance, I feel like I'll have to move the torso by three pixels rather than two, but I'm not sure. Any suggestions on how the torso should move for these characters?