Also try leaning him forward a bit, basic rule of thumb is the more lean, the harder he is running and also fron foot position will shift backward as he leans more. Picture an olympic sprinter vs a marathon runner for a visual.
That's an incorrect assumption. A slight lean is fine because you let gravity aid more in the running process. However to much of a lean will attribute negatively towards running efficiency and technique. I'm a longer distances runner, and I would say the difference between an elite marathon runner and an elite sprinter is economy and efficiency over their distance (Not the lean). Sprinters use longer levers and more energy over a short distance, compared to a long distance runners shorter more energy efficient levers over long distances ( levers being arms and leg movements).
When it comes to animation though, having an understanding of proper technique is great to have, but use it as a guide. The last thing I'd want from someone is to create the perfect running technique animations all the time.
Art is freedom of creativity and something creative is more often more fun to view. At this size, we don't have the space to show complex muscle movements, with only a few pixels at our disposal. So what we do is exaggerate the movement, and let the brain interpret what's in between.
You have improved over your first iteration, but you have a bit more to do to get it just that bit better. When the back leg drives through going forward, try to get the foot closer to the bum rather than close to the floor.
