The reason it looks so fast is that you are using less frames than needed, so, it seems he is kicking instead of walking. Also, arms do not bend like that when they are in the back... some people do that when their arms are in front, but not it the back. Stand up and try it, it' s fairly unnatural.
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I come here humble, trying not to repeat the mistakes of the past, for improving my art and try to help the others improving their own when I can...