I still haven’t gotten mine to work properly for any length of time so I can’t personally comment on its efficacy.
It seems like it should work for a newer PEer based on what I’ve read elsewhere and maybe help gains from other exercises.
Nobody has concrete results and nobody has tested it in a vacuum to see and as far as I know the only clinical studies used extenders.
That said, many big PErs use some sort of passive extender or ADS and even golf weights, and claim it contributes to success. If those work, then I would imagine the corkscrew to provide the same exercise and benefits.
