How far does your center of mass move from stance to stance?
You can find the relevant math here:

http://hypertextbook.com/facts/2006/centerofmass.shtml

The key factors are the body mass distribution, height, standing center of mass, heartbeat, clothing, etc. You can approximate the center of mass for a given stance as:


  In order to determine the center of mass of a person, we used the formula for torque:


$\Sigma\tau = r \times F$


  The torques due to the weight on each end of the person were set equal to each other. The displayed weight on the scale was the force, and there are two different radii. The first radius is the distance to the center of mass from the person's feet, and the second radius is the length of the board minus the distance to the center of mass from the person's feet. The net torque of the system is zero and therefore the torques on the opposite sides of the boards must be equal:


$w_1\times x = w_2\times (l~-~x)$


  where w1 is equal to the weight at the person's feet, x is equal to the distance from the person's feet to his/her center of mass, w2is equal to the weight at the head, and l is equal to the length of the beams. The resulting formula, when solved for the distance to the center of mass from the person's feet (radius one) is:


$x = \underline {~~~w_2\times l~~~}$

$\hspace {11mm}w_1~+~w_2$


  After determining the location of each person's center of mass, the ratio of the center of mass to the height of each person was calculated using the formula:


$x/h$


  where x is the location of the person's center of mass and h is the person's height.