Explain how "elastic potential energy" dramatically changed the sport of pole vaulting when flexible fiberglass poles replaced stiffer wooden poles.
can anyone answer this question in a physics mind-set?

when the old wooden stiff poles were being used, none of the kinetic energy during the run-up was stored in the pole.  With the new fiber glass flexible pole, some of that energy is stored in the flexing of the pole and then released as the pole straightens out at the top of its arc.  Where 13 ft was considered an excellent competition vault with the stiff pole, the additional boost from the stored energy in the flex pole has made 17 ft vaults the winning heights.

Explanation:

when the old wooden stiff poles were being used, none of the kinetic energy during the run-up was stored in the pole.  With the new fiber glass flexible pole, some of that energy is stored in the flexing of the pole and then released as the pole straightens out at the top of its arc.  Where 13 ft was considered an excellent competition vault with the stiff pole, the additional boost from the stored energy in the flex pole has made 17 ft vaults the winning heights.

The flexible fiberglass poles can bend more than wooden ones, before breaking. This meant that fiberglass poles are able to store more energy than wooden ones, and provide an additional increase in height to the vaulter, when the pole straightens out near the top of the vault.