Posted by: ray porco () on Wed Aug 31 18:18:15 2005

Jim,


Some definitions:

The centre of mass of a body is the single point about which every particle of its mass is equally distributed. If the body were suspended or supported at this point, it would be perfectly balanced (eg, balance a pen or pencil on your finger). Each body behaves as if its entire mass were acting or being acted upon at its centre of mass. The centre of gravity refers to the centre of mass in one direction only, that defined by the direction of gravity - it is the net location of the centre of mass in the vertical direction. For the human body, of course, the location of the centre of gravity changes with the body configuration or posture. In the anatomical position, the centre of gravity of adult humans has been found to be slightly anterior to the second sacral vertebra (Braune and Fischer 1984) or approximately 55% of a person's height (Hellebrandt et al 1938).]

The line of gravity is the line which passes from the centre of gravity of the mass toward the centre of the earth.

The centre of pressure is the location of the vertical ground reaction vector from a force platform. It is equal and opposite to a weighted average of the location of all downward (action) forces acting on the force plate

http://www.hkin.educ.ubc.ca/biomech/labtour/forcep.htm.

http://www.amtiweb.com/bio/force_platform_sys.htm






>>>“So, what is the evident why?”<<<





As Major Dan said, “Simply pushing with the front leg is not as strong as loading the front leg, then pushing the load back.”





We shift weight to LOAD the front leg, but that’s not all.
What we are talking about, (actually not talking about enough) is not JUST a mere SHIFT in WEIGHT, but a CONVEYANCE OF PRESSURE. A TRANSFER of FORCE.
And that conveyance DOES NOT STOP at “heel plant”, rather it stops AT CONTACT.
My proof?
Well force plates can scientifically confirm, but all you really have to look at, is the rear foot off the ground (or barely on the toe) at contact. Where is the “Center of Pressure” at contact?
Quoting Major Dan, “The front leg is not just used to bounce off of, but to catch the body weight and redirect it.”