Below are a couple of interesting studies on running and ground reaction forces. The SMU study presents some interesting thinking on a "Two-Mass System" of examining vertical ground reaction forces involved in running. The French study looks at a contrasting idea, that of horizontal impulse forces during acceleration.
Ground reaction force is somewhat minimally mentioned when talking about the average, mass-produced speed program other than pushing a sled or towing a parachute. Rather, we should probably be focusing thinking on the dynamic health and function of the ankle joint in terms of producing/dealing with horizontal and vertical forces and reaction forces, stabilization and health of the knee joint, and the ability of the core muscles to stabilize the mid-section as force is applied to the ground and reaction force is channeled upward while simultaneous arm motor action occurs. This does not include cerebral activities involved such as running and tracking, running and reacting, running and problem-solving. In addition, how well can the body cumulatively execute running in sterile and competitive environments? How about the effect of fatigue on sports outside of track and field? What is the impact of conditioning level and the ability to produce force and run fast over and over again? What if I am niche-fit and competition takes me out of my niche, how does that impact running?