On April 10 I reported on an odd pain phenomenon (Your brain on water). A terrible, horrible, no good, very bad neck pain I have …

…disappears completely and instantly when I am underwater. It resumes within seconds after getting out of the water, so it does not seem to constitute a “treatment.” It does appear to be a completely reliable mechanism of relief. But the totality of the temporary relief is fascinating.

I theorized a bit about why this might be, but more data would be nice. It would be pleasant and informative to stay in this pain-relieving situation with the aid of a snorkel! I went shopping.

Snorkel shopping

I was disappointed by my unfriendly neighbourhood gigantic sporting goods store with surly, clueless teenaged employees. They had snorkelling kits only, each one including flippers, goggles and about seven pounds of heavy plastic packaging — to protect them from what? Moisture? I could have overpaid for a crappy kid’s kit, or really overpaid for a decent one, and it occurred to me that they wouldn’t really do the job anyway: the relatively short barrel of a snorkel wouldn’t work very well with me sitting underwater and moving my neck around. Likely I’d just end up with a mouthful of water.

Then I got a storm in my brain: I decided to buy a piece of vinyl tubing at the hardware instead. $0.45 per foot! Perfect!

I chose a ¼-inch diameter, which proved to be too narrow. But it did at least provide me an odd tangent to a story that was already odd …

Breathing tube physics

Simply deep breathing while submerged to your chin is a simple way to challenge your respiratory musculature. Why you might want to exercise this way is another topic (addressed briefly below), but for now let’s just say it’s an interesting option, if a bit eccentric. If you’re really a bit of an odd duck? The exercise challenge can be made more acute — with surprising physics on display — if you add a narrow breathing tube to the equation.And if you’re really a bit of an odd duck? The exercise challenge can be made more acute — with surprising physics on display — if you add a narrow breathing tube to the equation and sink just a little further into the water.

As I discovered, it’s super difficult to breathe through a narrow tube while submerged, and the hardship spikes impressively with every inch of depth. Even modest water pressure provides substantial resistance to inhalation. The weight of the water presses relentlessly inwards on every square inch of rib cage and belly.

The narrow diameter of the tube becomes the sole pressure outlet for the weight of all that water. Air whooshes out of your lungs and through the tube, unless you stop it. Put your tongue over the tube end, and you will notice a formidable suction. When you try to inhale through that tube, you have to first match the suction and then exceed it to get any air! It becomes well nigh impossible as you descend.

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Hydraulics

Water pressure resists expansion of the rib cage and abdomen uniformly on all sides — and therefore it resists diaphragm contraction. When all of that pressure can only escape through a narrow breathing tube, the effect is startling.

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Hydraulics

Water pressure resists expansion of the rib cage and abdomen uniformly on all sides — and therefore it resists diaphragm contraction. When all of that pressure can only escape through a narrow breathing tube, the effect is startling.

This pressure differential happens with a snorkel too, and snorkelling would be indeed good respiratory exercise in itself, but there are two differences that make all the difference:

1. you’re floating horizontally and therefore much shallower
2. the tube is a fairly large diameter

So both sides of the pressure equation are smaller, resulting in a much more modest force to overcome.

(Blazingly obvious, disclaimery safety warnings: I am not responsible for you being foolish in the water. Don’t do this alone. Don’t do this in deep water. Don’t use too long/wide a tube for too long.Why?Old friend, reader, and experienced diver Jason T. explains why you shouldn’t use too big a tube: “CO2 buildup in the breathing tube. Shallow breaths won't flush the tube of CO2, and you wind up pushing spent breath a bit backwards and a bit forwards. Your lungs get that burning feeling, you get dizzy and headachy, then you pass out from the reduced oxygen if you keep it up too long. With normal snorkels, it’s really hard to get to ‘too long.’ With long snorkels, the breaths must get deeper to sweep the CO2 from the tube, and because you chest is deeper, your breaths get shallower. Whoops. The good news is that this kinda takes care of itself: most people get tired and fed up with the effort and get out of the pool before hypoxia has a chance to set in.” Don’t keep going if you feel dizzy or nauseous. Don’t inhale water. Don’t chew gum while you’re doing this. Etc.)

A helmet full of body — ewwwwww!

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The breathing tube physics described above were a matter of life and death in early diving suits — the old-timey kind with a big metal helmet and a long breathing tube to the surface. The same physics were at work, but at hyperbolic extremes, due to the depth.

The tube had to be pressurized from the surface to match the water pressure. If it wasn’t, something really horrible happened. Not only was the diver crushed, but — if the depth was great enough — he would literally be sucked into the helmet and tube, reduced to a paste of meat and bone chips. That’s the power of water pressure multiplied both by many square inches and depth! Pressure math is spooky.

The MythBusters quite reasonably wondered if such a thing is really possible. It is. And they demonstrated it. See MythBusters: A Helmet Full of Body. Tip: don’t eat first. It’s one of the most disgusting tests they’ve ever performed.

Water yoga for the lungs?

So why do this weird thing? Well, there are people who actually need inspiratory muscle training (IMT), and good evidence that it works. But that’s mostly for people with a real medical problem to solve (i.e. chronic obstructive pulmonary disease).

I have no great interest in doing respiratory exercise for its own sake, but that’s just me (I have other exercise goals). Many people who will do almost any kind of exercise it for its own sake — water yoga for your lungs, basically, just to be the proud owner of a stronger diaphragm and a greater respiratory capacity. Good for you, if you’re keen on it. And, just possibly, a stronger diaphram might be a way of relieving strain on the other (accessory) muscles of respiration … which may be overused and irritable thanks to a chronic failure to breathe “properly” with the belly … which may in turn be a common source of neck and shoulder pain (see The Respiration Connection).

This setup clearly involves a much more sharply defined and obvious challenge, for those who want that.

What an odd, interesting little detour!

I’ll continue the neck pain story once I’ve had a chance to buy and mess around with a larger breathing tube.

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See also: Water Yoga: 6 unusual ways to use a swimming pool for therapeutic exercise