It’s hard if not impossible to continue discussion on this topic since your
mind is closed to anything different from what you believe occurs. In
addition you keep changing your opinion of the importance of ankle joint
extension and other actions such as pawback and knee drive.
I will no longer be involved in this discussion because it is fruitless. I
will however leave a few bits of proven information
for readers who want to understand what happens in running. You will
disagree mainly I believe because you are too hung up on measurement of
forces rather than understanding how forces are generated, in which
direction the forces are produced and how we get a resultant force.
First the body does not act as a spring. We can use the analogy of a spring
but that is where it ends. We deal with the body so we can only deal with
muscles and limbs and how they function. Measurement of forces does not
tell you what the muscles and limbs are doing to produce the force and its
direction. This is why I focus on running technique. Running technique
does not happen automatically as you imply. If only running were that
Your assumption that speed is constant and does not require the application
of additional force is erroneous. In fact, studies of the finalists in a
Tokyo Olympics showed that speed changed every 10 m. there was a slowdown
and then speed up to produce what can be called constant speed.
If the ankle joint extension was not important the runner would not execute
this action. If we use your explanation then a rebounder in basketball
would automatically be going up for rebounds without ever stopping or
exerting any extra force. If we apply this spring model to his actions we
would see that major loading occurs in the knee joint and returned mainly
in the knee joint extension. Why doesn’t this happen in running? Why is
the ankle joint the only one that gets loaded more than the other joints?
but now you admit that the ankle joint extension is important but you never
Do not bring paraolympians into the discussion; that is a separate
The biggest error that you commit is believing that there is 100% return and
that it is passive. This is impossible. The greatest return ever measured
was only about 90%. In running the best estimates say about 70%. Where
does the extra force come from to maintain this constant speed or is it now
variable speed ?
Michael Yessis, PhD
Professor Emeritus, CSUF
President, Sports Training Inc.