I am about to embark on a study looking at leg stiffness pre and post fatigue.
To measure leg stiffness I will have participants performing various drop
jumps and hopping tasks on a force platform. To calculate leg stiffness I
first need to calculate the centre of mass displacement from the force
measurements recorded during each ground contact. I know the mathematical
procedure of double integration will give me the CoM displacement from the
force data. However, I have been trying to construct a spreadsheet that will
do this calculation for me so all I need to do is simply paste in force data
and the CoM displacement will be automatically calculated. Unfortunately I
have not been able to get my commands quite right in excel so my calculations
are not working. Has anyone out there got a spreadsheet (or name of a
program) that would do these calculations for me?

I would like to calculate the CoM displacement throughout the entire ground
contact phase so I can also check for spring like behaviour as well as
measuring leg stiffness (which only requires the maximum CoM displacement).

Thanks for your time,

Jon Oliver