The exercise of running backwards helps the runner fix quite a few of the most common biomechanical problems, such as lateral knee pain, certain kinds of lower back pain, and plantar fasciitis. It does this by correcting the location of your center of gravity (CoG).
The CoG is importantly related to the body’s “mechanical solution,” the algorithm of muscle contractions that maintains the body erect and stable throughout the course of activity. Because the CoG is defined as the place where there are no forces acting on the body, any shifts or changes in the muscle firings that the body interacts with mechanical energy—any change in the mechanical solution—will necessarily alter the location of the center of gravity.
Strengthening a muscle that was previously too weak to be used in strenuous exercise will change the body’s mechanical solution: for any particular action, employing more muscles instead of less facilitates the body’s movement through space, since the brain is better able to correct for a center of gravity that moves due to change of direction, change of speed, or variable terrain.