A lot of people are confused on how to calculate fall arrest shock force… here’s a simple equation to determine the average impact or shock force during fall arrest:
Average impact force, F = mg(h + x) / x
m = mass
g = gravity
h = free fall distance (from initial position to just before deployment of energy absorber or other energy absorbing component)
x = stretch or extension of the fall arrest system during fall arrest
Note that there are lots of assumptions in this equation. The Canadian standards has good information on design of fall arrest systems.