why do freedivers not experience reverse squeeze while ascending?

[christoph1]

hey everyone,

i was wondering this for a while and cant seem to really figure it out.
when descending during a freedive, of course, divers need to equalize according to the surrounding pressure at the give depth they are.
while ascending than the air in their body expands again and should push the eardrum outwards causing a reverse squeeze.

Obviously as we know it doesnt but can anyone explain why?

Thanks already

[Doppler]

Eustachian tubes


and you're welcome, already :)

[NetDoc]

They say nature abhors a vacuum, but she seems to tolerate it in the human body. The Eustachian tubes in our bodies seem to be better at venting pressure, then at equalizing when in a vacuum. Stretching your neck will help open them up as you descend, but there is usually no need to do the same as you ascend.

[doctormike]

Think about it this way. It's easier for toothpaste to get out of a tube, than it is for it to get back in. Reverse squeezes are less common than the regular type for this reason, but not impossible.

The reason that a reverse squeeze would be especially rare in free divers is that they usually happen to scuba divers who have poor ET function to begin with. These are the people who take a long time to descend, slowly equalizing their ears, and are eventually able to make it to depth. Then they may have the same problem on the way up, but by then, they may not have the option for lots of extra ascent time due to gas, NDL, etc.... so it becomes a real issue.

Since a very slow descent is not an option for a free diver, they would rarely be in that situation...

[christoph1]

super, thanks to everyone for the explanations!