Duchamp is considered the most influential because of his radically style and actions were extremely unique and different from any other form. So much that at one point his two brothers basically had an intervention with him, telling him to calm not and to not push the boundaries of what art should be so much. Marcel Duchamp dismissed this and therefore works as Nude Descending a Staircase No. 2 (below) are displayed.
Here Duchamp is emphasizing the new movement of mechanomorphic abstraction. This is considered mechonomorphic abstract because one could not simply distinguish that this is a nude female descending stairs without the title and instead the viewer makes out what mayappear to be a machine. The mechonomorphic movement was a result of the industrial revolution in which new product, building and machines were intertwining with peoples lives. Paintings that use this technique glorify the machine and denounce the academic theology that only gods and such high pristiege could be displayed on canvas.
Also portrayed on the canvas is the essence of motion. Duchamp was interested in how the body moves and studied the movements of individual body parts while walking in order to capture the process on canvas. Etienne-Jules Mary was influential with his photography, tracking, and cinematogyaphy of motion. He performed studies, as the one shown below, tracking the movement of the heads, shoulders, hips, ect. while walking.
Interestingly this study of the body in motion is still in effect today. Recently in the news the NCAA SEC division football departments will electronically track player's speed and movement. The purpose of the study is to perhaps uncover more safety oppurtunities for the players and information and feedback to the coaches. May be a stduy in a different field, but I bet one could come up with some interesting art from the study as well.