Vol. I: VII. On the Proportions and on the Movements of the Human Figure: 371.
The Da Vinci Notebooks
A man when walking has his head in advance of his feet.
A man when walking across a long level plain first leans [rather] backwards and then as much forwards.
194:181 3-6: He strides forward with the air of a man going down hill; when weary, on the contrary he walks like a man going up hill.