The Pedaling Model plots radial and tangent forces at the pedals and plots thigh and shin strength functions at points of rotation. See Figure 1 below for nomenclature.  

Forces At Pedals
Tangential and Radial Forces at the pedals result from the Shin and Thigh working together to turn the pedals (Strength Functions). In the plot below tangential forces at the pedals are in green, and radial forces are in red. They are correct as to direction and relative scale.  The solid line outside the circle is the net torque turning the pedals. 

Strength Functions
The plot below represents values for the Thigh (heavier line) and Shin (lighter line) strength functions at points in the rotation of the cranks. (For one leg.)  The direction for the thigh is the instantaneous direction in which the knee is moving; for the shin, its the instantaneous direction in which the shin is moving relative to its point of rotation at the knee. (The net of the forces are the tangential and radial forces on the pedal.) The length of the lines represent the magnitude of the respective Thigh and Shin Strength Functions. These magnitudes are shown to scale. The solid line outside the circle is the net torque turning the pedals. This plot can be used by a rider to visualize where force is generated and to visualize where to push and pull with the Thighs and Shins.

 

One can see that for the strength functions used to create the above plot, most of the force that turns the pedals comes in the down stroke, very little in the up stroke.