It's not just because of a doughnut that air pumping isn't as good as water pumping, it's because water pumping will expand you faster a.k.a. more gains.
Wow, I am the Physics expert and I did not think of this, I am humbled! Thanks for a very important and overlooked benefit of the [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98]BathMate[/words].