Motion Tracked Graph

Let me talk about the sample shot you provided. 

First, it's a camera pan, so AE's camera tracker will not give you any depth information. The perspective should be fairly accurate and the surface is relatively flat so selecting a bunch of trackers, scaling up the Target, establishing an Origin and Ground Plane, then adding a Solid and a Camera on the same spot should give you a fairly good surface to work with. 

You can then create a new Shape layer with a simple path, make the Shape Layer 3D, Shift + Parent it to the Solid you created, then adjust the path to get a relatively good path in just a few minutes. This path only has 5 vertices and it only took a couple of minutes to line it up fairly well with the uphill ski. Duplicate it make adjustments for the downlill ski and add trim paths and that part of the work is done.

I always use a solid instead of a null because you can see if it sticks, then I add a blend mode, sometimes a grid, and make it a guide layer so I can verify that the track sticks.

If you had an uneven surface, the shot would be much more difficult to track and it would require more than one shape layer and more than one track solids.

Regarding animating the graph, you could use Mocha AE to motion track the skier's feet and use that position data for the pressure data in your graph. You could then create an expression that would use the change in direction to detect the apex of each left and right turn. When the skier turns left, the pressure will be greater on the right ski. The opposite happens when the skier turns left. The pressure is always higher on the outside ski. When the motion is pretty much in a straight line, the pressure on both skis will be about the same. If you don't have real-time data to work with, and you don't want to try and come up with an expression (it will be recursive and slow), you could turn that position data into a differential pressure data stream that would animate a graph and give you some numbers. An easier approach might be to simply add an Expression Control/Angle Control. to a null and manually keyframe the direction the skier is traveling and turn those values into a pressure graph. Throwing a little wiggle into the result would give you some varying numbers that you could use to drive a bar graph or animate the shape and progress of a line graph as is in your example. Without some real world data, that's probably the approach I would take.

If 0º = equal pressure and + or - 90º equals maximum pressure something like this would give you some changing values fairly easily.

//apply to a text layer to get left and right foot pressure
t = effect("Angle Control")("Angle");
lFoot = linear(-t, 90, -90, 10, 100);
rFoot = linear(t, 90, -90, 10, 100);
l = lFoot.toFixed(2);
r = rFoot.toFixed(2);
"Left: " + l + "\r" +
"Right: " + r

 You'll also need to duplicate the footage layer, pre-compose the top copy moving all attributes, name. it roto, and Rotobrush or rotoscope the skier so the path stays under him. This is a rough start on the problem. I'll leave you to decide how to generate the graph.

The path needs more work,  and so does the timing.