IT comes down to physics. Here are a few quotes that i think make it simple.
THis is a quote from Mike young over at Elite track : "Vertical forces are important for Vmax running because at maximum velocity the system acts very much like a spring or a bouncing ball. Forward momentum is developed through the acceleration / drive phase and at maximum velocity the net propulsive forces are 0. The vertical forces are what keep the system going (keep the ball bouncing). Without high vertical forces the system ceases to act as a spring-mass model and deceleration occurs.
At it’s most basic level we can think of it like this: the acceleration phase develops forward momentum—-> the body will now tend to stay at a constant velocity unless acted on by external forces (gravity, air resistance, friction, etc.). These situations of course do not occur on earth but this statement will be most relevant to the sprinter / coach if they aim to get the system to act as a perfect spring (forces in = forces out). To do this a sprinter needs high vertical forces to keep the ball bouncing. Without the high vertical forces the system becomes less and less perfectly elastic (not to be confused with the concept of the same name typically used in sprinting) and the sprinter will decelerate more and more.
You maximize vertical force output through proper sprint mechanics and force, rate of force, and power development. "
and from Tom Tellez “Tom proceeded to share the simple concept of the garden hose spraying water . When you tilt slightly back the garden hose will see the water rise, given that you are holding it parallel to the ground. The best angle is a combination of physics and anatomy, and increasing the forces on the down stroke of the stride will increase the distance, sort of like turning on the water pressure. Efforts to pull back will cause you to fall on your face. Since you are already sprinting vertical forces with trajectory angle will allow for greater levels of speed only if you can apply the forces better (power,contact time,technique).”
here is a link on maxv mechanics and it goes into the varying forces. http://www.scarboroughtrack.com/sprintingmechanics.pdf
Also, what I failed to point out in my original post comparing 40s and verts, many of the top vertical jumpers were from defensive linemen and tight ends and players who are capable of developing tons of power but there body types are nno condusive to sprinting.
Although there are many similiarities to vertical jumping, there is still a huge difference in the RFD compared to sprinting.
Let us not also forget that these players do not necasasrily have the expertise of sprint coaching avaibale, so although they maay have all of the necassary qualities to be a good sprinter, they are unable to express these qualities because they dont know how to run.