Anatomy of a Stride
Remember from "Running Form: Distilled (Part 3a)" that from the running Pose you stand on the precipice, ready to give yourself to gravity, and...
Immediately following mid stance, your compressed biomechanical spring is quickly uncoiling and pushing you up slightly as you are now falling forward like a felled tree through a speed-appropriate range. Instead of pawing or pushing, your muscles simply hold your Pose position as you rotate from the ball of your foot which takes your center of mass along a horizontal plane, from point A to point B. Happily, rather than hitting the ground like the tree, you just change support and fall again, and again.
*Experience it yourself: Run in place. Notice how you're interacting with the ground. Find to the differences between naturally running in place, landing flatfooted, and landing on the heel. Which feels right? Are you pushing into the ground, or are you pulling each foot from the ground. Now, keep running in place and let yourself fall forward...
End of Fall
* Also: From the running Pose stand maybe 12 inches from a wall. Now, let your whole body fall forward as a single unit, toward the wall, while holding your Pose position. Make sure to pivot on the ball of the foot instead of leaning from the ankle. (Please catch yourself with your hands before bumping your nose, okay?) Push yourself back to the vertical and repeat several times. Then, step back six inches and Fall again. Finally, step back another six inches and Fall once more. Switch support legs and repeat.
Notice how different it feels to Fall from 12 inches, 18 inches, and 24 inches away from the wall. This is an easy way to begin understanding gravitational acceleration, and the difference between a narrow and wider range of Fall.
* And, now: Put your back against a wall and your feet a few inches from the wall and try running by using your powerful leg and hip muscles. Go ahead, try harder.
Bottom line, no one runs until they Fall. Again, Nature sets the standard.
Range of Fall Determines Pace
In the Pose Method, the concept of gravity plays a prime role to make us run fast. It works just through different angles of deviation of the general center of mass from the point of support. If we want to run faster, the first thing we have to do is to [fall] forward more in each step ... At this point we are talking about high perception of the athlete allowing him to recognize all these nuances of the body [falling] forward ... and its timing happening in a fraction of a second.
Your usable range of Fall, by the way, is narrow. From 0 degree to 22.5 degree from the vertical. Imagine falling from 12:00 to 12:04 on a clock face as the full extent of horizontal displacement. What's more, most runners will access only a fraction of this available Fall. Slower runners necessarily Fall through an attenuated range, whether they are holding themselves back, or because they inadvertently arrive late to the running Pose. Dispense with the description "Speed = Stride Rate x Stride Length" and know now that it's range of Fall and a complimentary cadence -- a more specific rate of foot turnover -- that are the real arbiters of pace.
Range of Fall | 12-Oh-4
Usain Bolt is a good example of a runner giving himself to gravity, as he Falls here from the vertical to more than 20 degrees. See how he's maintaining the Pose position? His knee is still bent, and his ankle is neutral as he hinges over the ball of his foot. Here, he's accelerated and ready to release the ground.
Romanov explains 22.5 degree...
The forward displacement of the runner's body is determined by the geometry of the falling body on support. The horizontal movement (acceleration) of the body is a function of the angle of deviation of the body from its vertical position that is a function of the vector of gravity and ground reaction force ... Of most interest was the dynamics of correlation between the horizontal and vertical components of [the] resultant vector between gravity and ground reaction, for every angle of deviation. The maximal prevalence of the horizontal component occurs at 22.5 degree angle, after which the vertical component starts dominating.
Whew! Now that's a lot to think about, right? Happily, the less you think about it, the better it all works. Most, however, do need to be more conscious of one last element in running to ensure running farther, running faster and running with less chance of injury. Learn what that is in "Running Form: Distilled (Part 3c)."