Hello, I have no physics education at all, so this might come off a little vague. The scenario: During a sustained jumping resonance, On a pogo-stick or trampoline, the user's downward mass is storing energy in the springs which eventually will try to force the user back up. But due to the dampening of gravity, the spring back up will not be as high as the one before. So the user has to press down at the right time to efficiently add force to the jump and thus achieve a sustained jumping resonance. the Question: How much is this extra force? I guess I am interested in how much this extra force, at the most efficient time, is compared to the force from a stand-still, without the added momentum of the stored spring energy, to reach the same height? would there be a big difference? would the well timed jump added to the spring force be that much more efficient than a jump from stand still? Thanks for any help.