Lately, people seem to be really excited about sealing themselves in chambers. If you want to reduce stress, ease pain or lose weight, there's a tank for that. Sensory deprivation tanks, oxygen therapy chambers, unbelievably cold saunas - you can pay someone to hang out in any of those. Most of these machines are based on real medical principles but they're generally meant to be used in very specific situations and those claims that they'll solve all your problems, that's taking things a bit too far.

One tank you might have heard of is sensory deprivation, or flotation REST. You lay in a salt water solution in a pod with limited input from the world outside. The water is dense enough that you float without having to actually try and it's kept at skin temperature so it basically feels like nothing. Usually you also wear earplugs and it's totally dark in the pod. The total lack of stimuli is supposed to be super relaxing, and the idea sounds just sciencey enough that it might seem legit.

There is some science behind flotation REST, studies have found that it can reduce stress, ease pain, and enhance creativity both during and after treatment. But there are also studies that have shown changes in hormones and neurological signals associated with relaxation, though others haven't reproduced that effect. But when I said that there were some science behind sensory deprivation, I did mean some. Most of the studies that have shown benefits from flotation REST were pretty small, and therefore statistically weak. That doesn't mean that they're wrong, it just means that anyone calling their effects miraculous is really overstating things.

So there might be some benefit from sitting in a dark watery tank and if you're willing to pay the 60 bucks an hour, or more, it probably won't do any harm. But it also will not magically transform your life. 

Then there's hyperbaric oxygen therapy which involves increasing the pressure and concentration of oxygen in a sealed chamber. Originally this technique was developed to treat divers with the bends, where nitrogen bubbles form in their bloodstream and block blood vessels. The increased pressure helps shrink the bubbles and the higher levels of oxygen push other gases out. The chamber also has other proven medical uses, especially in combination with other treatments.

But lately it's become something of a fad treatment for autism spectrum disorder. The idea is based on a tenuous claim that the brains of people with autism show inflammation. But we don't actually know what causes autism spectrum disorder, so even if people want to treat it, there's no evidence that extra oxygen will work. And a review of clinical trials testing hyperbaric oxygen therapy for autism concluded that there wasn't enough evidence to recommend using it. In other words, it's expensive and probably won't do anything. 

And for other people who feel like hopping into hyperbaric chambers, there is really no need. Healthy people usually have a blood oxygen saturation of about 99%, meaning that their blood has pretty much absorbed all of the oxygen it can. Inhaling more oxygen won't add to that and too much oxygen can even cause acute respiratory distress syndrome, where the lungs have trouble transferring oxygen into or out of the blood. So, maybe skip the oxygen chamber. 

Finally there's whole body cryotherapy, where you step inside a chamber for two or three minutes while it's cooled to -100 degrees Celsius. That's about 10 degrees colder than the lowest temperature ever recorded on Earth. The treatment is popular with athletes who say it prevents muscle soreness and speeds recovery. It sorta makes sense, cold temperatures constrict blood vessels, which slows inflammation. But there is very little scientific evidence that says that whole body cryotherapy does much to promote recovery from exercise according to a 2015 literature review. So if you are an elite athlete, enjoy the penguin experience at your own risk. 

Some people will also sell you cryotherapy to lose weight, but that is really not a thing. There's definitely a connection between cold and burning calories. Mammals, including humans, have a little bit of fatty tissue called 'brown adipose tissue' that starts to burn for heat when you get cold. So you might think that you can take advantage of this effect by chilling yourself down and forcing your body to turn that fat into heat. The idea does sound plausible but studies do not support it. Treating mice with short bursts of cold does cause them to burn more calories, but they eat more to make up for it. One study even found that mice gained weight when exposed to the cold.

Cryotherapy will set you back a good hundred bucks a session, unless you are a professional sports player and your coach had a chamber installed in the locker room. There's not enough evidence to say that it works to help you recover from exercise and there is definitely not enough evidence to say that it does anything else. So when it comes to supposedly scientific treatments that involve locking yourself in fancy tanks, it's generally not worth spending your hard-earned cash. Unless you just inherited it and are bored, I might do it. In general, if it sounds too good to be true, it probably is. 

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