when your Duration drops to 0 you fall unconscious
then (of course at this point ) Duration = Fatigue Points
a formula for Str could be
Intensity x Duration = Str x Str / 2
so a Str of 10 gives 10x10/2=50 IxD, so I=10 x D=5; or I=12 x D=4; or I=15 x D=3; or I=8 x D=6
afterwards, how do you regain Fatigue Points ?